• 
A Prel iminary  Ecological  Study of  Nut-Grass  (Cyperus  rotundus  L. )  
Under  Tr inidad Condi t ions  
by 
B.L.  Honess  (B.Sc. )  
1960 
D.T.A.  Repor t  
In  Par t  Fulf i lment  For  The 
Diploma in  Tropical  Agr icul ture  
of  the  Imper ial  Col lege  of  Tropical  Agr icul ture  
Tr in idad,  W.I .  
CONTENTS 
Page 
SYNOPSIS 
SECTION I  -  INTRODUCTION 1  
REVIEW OF LIT ERATURE 1  
SECTION I I  -  DESCRIPTION OF T ILE PL ANT 
(a)  Sys temat ic  Posi t ion  4  
(b)  Genera l  Morphology 4  
( i )  Main family  charac ters  4  
( i i )  Tubers  5  
( i i i )  Rhizomes 6  
Civ)  'Basal  bulb '  7  
(v)  Leaves  8  
(v i)  Inf lorescence  8  
(c )  Ecology 8  
(d)  Life  History  10 
SECTION I I I  -  DISPERSAL 
(a)  Vegeta t ive  12 
( i )  Tuber  format ion 12 
( i i )  Dis t r ibut ion of  tubers  13 
( i i i )  Shoot  format ion and the  
factor  of  apical  dominance 14 
( iv )  Tuber  dormancy 15 
(b)  Seeding 16 
( i )  Flower  product ion 16 
( i i )  Seed product ion 17 
( i i i )  Seed germinat ion 19 
( iv)  Factors  af fect ing seed product ion 22 
(v)  Shat te r ing of  seed 24 
(v i)  Seed d ispersa l  24 
SECTION I V -  COMPETITIVE EF FECT O F NUT-GRASS 
(a)  Compet i t ion  exper iment  25 
( i )  Expe r imental  des ign 25 
( i i )  S i te  26 
( i i i )  Set t ing  up exper iments  26 
( iv)  Progress  of  exper iments  27 
(v)  Resul t s  28 
(b)  Cover  Crops  30 
SECTION V -  CONTROL OF NU T-GRASS 
(a)  Peasant  methods  31 
(b)  Genera l  agr icul tural  methods  31 
( i )  Cul tural  31 
( i i )  Herb ic ida l  31 
( i i i )  Combinat ion of  cul tura l  
and herbicidal  methods  32 
(c)  Dif f icul t ies  of  e radicat ing nut-grass  32 
SECTION VI  -  CONCLUSIONS 
Summary of  conclus ions  
RECOMMENDATIONS 
ACKNOWLEDGEMENTS 
BIBLIOGRAPHY 
SECTION VII  -  APPENDIX 
I  Diagrammat ic  drawings  (F ig  
I I  Genera l  
I I I  Compet i t ion  exper iments  
SYNOPSIS 
The purpose  in  making a  de ta i led  s tudy of  Cyperus  ro tundus ,  nut -grass ,  
was  to  ascer ta in  i t s  habi t  under  Tr in idad condi t ions ,  and to  compare  such 
f indings  wi th  those  a l ready repor ted  f rom other  par t s  of  the  Tropics .  Such 
work ,  i t  was  hoped,  would  fur ther  c lar i fy  the  problem which nut -grass  presents  
as  a  pan-t ropical  weed.  
A morphological  s tudy of  the  weed i s  repor ted  wi th  de tai l s  of  the  
subterranean par ts  and a lso  of  the  inf lorescence .  No real  d i f ferences  were  
found, to  those  repor ted  e lsewhere  in  the  t ropics ,  bu t  i t  was  decided to  refer  
to  the  swel l ing  a t  the  junct ion of  the  leaves  and rhizome as  cormlike  ra ther  
than use  the  misleading term 'basal  bulb ' .  A l i fe  his tory  f rom a  s ingle  
tuber  was  s tudied and the  impor tance  of  loca l  spread by means  of  underground 
rhizomes and tubers  i s  s t ressed.  The most  encouraging methods  of  control l ing  
underground spread by cu l tura l  and herbic ida l  methods  are  summarised as  wel l  
as  the  d i f f icul t ies  involved in  a t tempt ing such contro l .  Tuber  d is t r ibu t ion 
in  the  soi l  a t  the  Col lege  compared favourably  wi th  tha t  found e lsewhere  in  
the  t ropics ,  the  major i ty  occurr ing in  the  top s ix  inches ,  and only  rare ly  
below nine  inches .  
Under  favourable  growing condi t ions  f lower ing took p lace  in  one month  
f rom a  previously  dormant  tuber .  The ra te  of  seed product ion was  low,  being 
approximate ly  one seed per  inf lorescence .  Freshly  col lected  seed could  not  
be  induced to  germinate ,bu t  v iabi l i ty  of  50-60% was  demonst ra ted  by use  of  
the  Tet razol ium sa l t  tes t .  Effor ts  to  gain  an  assessment  of  pol len  v iab i l i ty  
were  unsuccessful  and such work must  be  repeated .  
The compet i t ive  e f fec t  of  the  weed was  tes ted  agains t  radish  and mi l le t  
p lants  in  a  pot  exper iment .  The radish  appeared to  wi thstand the  compet i t ion  
bet ter ,  but  for  bo th  crops  considerable  reduct ion in  plan t  y ie ld  resul ted  wi th  
increas ing nut-grass  popula t ion .  More  fer t i le  so i l  resul ted  in  more  rapid  
product ion of  tubers  though tuber  weight  and s ize  a lways  remained fa i r ly  
constant .  
Poss ible  associat ions  of  nut -grass  wi th  o ther  p lants  (Cynodon dactyIon 
and Cleome spp. )  are  repor ted ,  but  such eco log ica l  work needs  fur ther  s tudy.  
Other  recommendat ions  for  fu ture  work a re  a lso  g iven .  
Sect ion I  
INTRODUCTION 
In  temperate  regions  much inves t igat ion has  been carr ied  out  on crop 
weeds  and the i r  cont rol .  Equivalen t  s tudies  in  the  t ropics  have t  ended to  
lag  behind and only  dur ing comparat ively  recent  years ,  par t icu lar ly  s ince  
the  advent  of  hormona l  herb ic ides ,  has  a  considerable  volume of  l i te ra ture  
appeared concerning t ropical  weed cont ro l .  Al though weed problems appear  
bas ica l ly  the  same in  the  t ropics  to  those  e lsewhere  in  the  wor ld ,  there  are  
the  specif ic  cases  which res i s t  the  usual  contro l  measures .  In  making a  
de ta i led  s tudy of  a  p lan t  i t  was  decided to  take  such a  weed,  and by making 
deta i led  observa t ions  in  associa t ion wi th  the  publ ished l i tera ture ,  to  bui ld  
up a  bet ter  unders tanding of  the  weed under  Tr in idad condi t ions .  
Cyperus  ro tundus  L. ,  commonly known a s  Nut-Grass ,  a  pan- t rop ica l  weed,  
was  se lected  for  s tudy.  I t  was  real ised  that  wi th  the  res t r ic ted  amount  of  
t ime avai lable  there  would  be  a  l imi t  to  the  amount  of  de ta i led  inves t igat ion 
that  could  be  made.  However ,  the  pr incipal  object ive  was  to  ga in  as  
thorough knowledge of  the  plant  as  poss ible  so  as  to  make recommendat ions  
for  fu r ther  s tudy.  
In i t ia l ly  i t  was  decided to  make a  more  intense  s tudy of  the  f lower ing 
and seeding habi t  of  the  p lant  but  factors  of  genera l  morphology and habi t  
were  la ter  included.  I t  was  a lso  found poss ible  to  make some s imple  
observat ions  into  the  compet i t ive  proper t ies  of  the  plant  wi thout  de t rac t ing 
f rom the  main  s tudies .  
REVIEW OF LIT ERATURE 
To give  a  concise  review of  l i t era ture  publ ished concerning the  control  
of  nut -grass  i s  beyond the  scope of  th is  repor t .  A.J .  Boyd (1921)  s ta tes :  
"To f ind  a  method of  e radicat ion of  nu t -grass  has  been the  theme of  hundreds  
of  a r t ic les  and as  many papers—but  a l l  in  va in ."  Since  h is  t ime advances  
in  agr icul tura l  prac t ices ,  and part icular ly  the  use  of  the  di f ferent  types  
of  weedki l ler ,  have led  to  a  considerable  volume of  l i te ra ture  being 
•2-
publ ished on the  subject  of  nut -grass  cont ro l .  Very l i t t l e  of  th is ,  however ,  
p resents  economic  methods  of  eradicat ion,  the  major i ty  repor t ing fa i lure  
and the  d if f icu l ty  of  ex terminat ing the  weed f rom arable  land.  Sparrow (1958)  
g ives  an  up- to-date  account  of  the  recommended methods  of  contro l  and a l so  
a  l i s t  of  the  re levant  l i te ra tu re  on the  subject .  
The f i r s t  rea l ly  comprehensive  s tudy of  Cyperus  rotundus ,  o r  nut -grass  
as  i t  wi l l  now be  refer red  to ,  was  car r ied  out  by Ranade and Burns  (1925)  
in  India .  Their  a im was  to  fu l ly  understand the  weed ' s  l i fe  cycle ,  to  f ind 
i t s  weakest  po int ,  and then to  a t tack i t  a t  that  point  to  gain  control .  
They fu l ly  apprecia ted  tha t  such a  method of  a t tack was  s low,  bu t  fe l t  a t  
the  conc lus ion of  thei r  work tha t  i t  was  jus t i f ied .  Their  very  fu l l  s tudy 
of  the  p lant ' s  l i fe  his tory  and i t s  genera l  morphology has  served as  a  
basis  for  much subsequent  work.  
Andrews (1940,  1945,  1946)  s tudied the  nut-grass  weed over  several  years  
under  the  condi t ions  found in  the  Sudan Gezira .  Cl imat ic  condi t ions  were  
obviously  d i f ferent  to  those  found by the  Indian workers ;  never theless  the  
problem presented by the  weed was  bas ica l ly  the  same.  Andrews agreed in  
the  major i ty  of  h i s  f ind ings  wi th  Ranade and Burns  and recommended s imi lar  
cul tu ra l  pract ices  of  deep ploughing in  the  dry  season to  k i l l  the  weed.  
Fol lowing the  work done by Andrews herbic ides  became more  genera l ly  used 
and rapid  development  resu l ted  as  to  thei r  mode of  ac t ion ,  potency and 
se lect iv i ty .  The res is tance  of  nut -grass  to  these  more  advanced chemicals  
caused a  group of  workers  (Muzik ,  Cruzado and Lousta lo t ,  1948-51)  in  Puer to  
Rico to  make a  deta i led  morphologica l  and physiologica l  examinat ion of  the  
p lant .  They were  par t icular ly  concerned wi th  the  plant ' s  abi l i ty  to  survive  
appl icat ions  of  hormonal  weedki l lers  and concluded (Muzik  and Cruzado,  1950)  
that  such herb icides ,  a t  the  t ime of  thei r  work,  were  t rans loca ted  too 
s lowly throughout  the  p lant  sys tem producing no more  than a  check to  growth.  
The considera t ion of  the  above three  se ts  of  work has  la rgely  governed 
the  course  of  observat ions  in  th is  repor t .  A b r ief  ment ion needs  to  be 
made of  o ther  workers  who have in terested  themselves  in  par t icu lar  aspects  
of  the  nut -grass  problem.  
Smith  and Fick (1937) ,  in  America ,  worked on the  underground habi t  of  
nu t -grass  and,  in  par t icular ,  the  fac tors  associa ted  wi th  apica l  dominance.  
I 
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Their  work concerning the  effects  of  ext remes of  tempera ture  and drying on 
tuber  viabi l i ty  encouraged Smith  and Mayton (1938)  to  t ry  a  scheduled sys tem 
of  t i l lage  on arab le  land to  exhaus t  the  nut-grass  weed.  This  they found 
could  command a  fa i r  degree  of  contro l ,  especia l ly  i f  summer  fa l lowing was  
associated  wi th  the  use  of  winte r  cover  c rops .  Recent  work (U.S .D.A. ,  1958)  
has  fur ther  subs tant ia ted  the  impor tance  of  cover  crops  in  suppressing 
nut-grass  growth when a iming a t  control  by t i l lage  methods .  
The response  of  nut -grass  to  mois ture  as  an  impor tant  fac tor  of  f i e ld  
eradica t ion has  been s tudied by severa l  workers .  Davies  (1942)  a imed a t  
determining levels  a t  which the  plant  showed d i f ferent ia l  response  to  so i l  
mois ture  under  greenhouse  condi t ions .  Du Preez  (1944) ,  in  a  genera l  s tudy,  
cons iders  the  degree  of  des iccat ion tha t  nut -grass  tubers  can wi ths tand 
before  death  and g ives  a  f igure  of  15% m oisture  as  the  average ,  below which 
shoot ing capaci ty  i s  los t .  
That  the  nut-grass  problem s t i l l  ex is ts  i s  borne  out  by Cox (1959)  in  
an  a r t ic le  on "Weed Contro l  in  West  Indian Sugar  Cane" .  The publ ica t ion of  
s tudies  made concerning the  metabol ism of  nut -grass  by Palmer  and Por ter  (1959)  
shows a  new d epar ture  in to  the  s tudy of  the  p lant .  They worked on de ta i ls  
of  enzyme ac t iv i ty  wi thin  the  p lant  and a lso  the  ef fec t  of  d i f ferent  levels  
of  carbon diox ide  and oxygen on metabol ic  react ions  and shoot  product ion.  
I t  can be  hoped tha t  such work may sugges t  new methods  of  a t tack.  Unt i l  
then the  cont inual  appearance  of  numerous  repor ts  concerning t r ia ls  of  new 
ideas ,  new techniques  and new h erb icides  a imed a t  so lving the  nut-grass  
problem can be  expected.  
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•4 
Sect ion I I  
DESCRIFHON OF T HE PL ANT 
(a)  Systemat ic  pos i t ion  
Cyperus  ro tundus  L.  ,  occurs  in  a  genus  composed of  about  400 spp.  The 
genus  i s  one of  seventy  f ive  tha t  make up the  family  Cyperaceae  in  the  
Monocotyledons .  
The de ta i led  sys temat ic  pos i t ion  of  the  family  var ies  according to  the  
major  sys temat i s ts .  That  se t  out  by Engler  and Pran t l ,  where  the  family  
Cyperaceae  a long wi th  the  Gramineae  form the  natural  order  Glumif lorae ,  i s  
used by most  workers .  Hutchinson,  whose  sys tem of  c lass i f icat ion i s  becoming 
widely  used,  p laces  the  family  under  i t s  own order  Cypera les  which with  
the  Graminales  and Junca les  form the  divis ion Glumif lorae  of  the  sub-phyl lum 
Monocotyledons .  His  sp l i t t ing  of  the  family  in to  seven t r ibes ,  of  which 
the  t r ibe  Cyperaceae  conta ins  the  genus  Cyperus ,  i s  s impler  than tha t  proposed 
by ear l ier  taxonomis ts .  
(b)  Genera l  morphology 
( i )  Main family  characte rs  
Usual ly  perennia l  grass l ike  herbs .  Stems so l id ,  not  jo inted ,  f requent ly  
t r iangular  in  c ross  sec t ion .  Leaves  wi th  a  grassl ike  b lade,  three  ranked 
and wi th  a  c losed sheath .  Flowers  smal l ,  b isexual  or  unisexual ,  general ly  
monoecious ,  a r ranged in  sp ikele ts .  The f lowers  are  so l i ta ry  wi thin  a  glume 
and are  e i ther  ar ranged in  two ranks  or  spira l ly .  Inf lorescence  subtended 
by one  or  more  involucra l  bracts .  Per ianth  reduced to  sca les ,  b r i s t les  or  
hai r s ,  of ten  absent .  Stamens  usual ly  three ,  hypogynous .  Anthers  bas i f ixed.  
Ovary superior ,  uni locular  wi th  a  so l i t ary  ovule .  S ty le  two-  three-branched.  
Fru i t  an  achene,  indehiscent .  Seed erec t ,  smal l  embryo,  abundant  mealy  
endosperm.  
Characters  such as  the  unjo inted ,  t r iangular  and sol id  s tem,  leaves  
in  three  ranks  having closed sheaths  and no l igule ,  and the  f ru i t  being an  
achene ,  which c lear ly  d is t inguish  members  of  the  Cyperaceae  (Sedges)  f rom 
the  Gramineae  (Grasses)  a re  a l l  clear ly  exhib i ted  by nu t -grass  (Cyperus  
rotundus) .  The p lant  a lso  conforms to  be ing a  perennia l ,  cons is t ing  of  an  
underground sys tem of  rh izomes which produce tubers  a t  in tervals .  These  
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tubers  produce an  extens ive  root  sys tem and a l so  give  r i se  to  the  aer ia l  
par t  of  the  p lan t .  For  the  sake  of  c lar i ty  in  repor t ing the  morphology of  
the  p lant  d iv is ion wi l l  be  made in to  i t s  var ious  components .  
Components  of  the  nut -grass  plant  
( i i )  Tubers  (see  Figs .  I  & I I )  
When m ature  tubers  vary  f rom about  I - *" ^- n  length  and 4-f"  in  d iameter .  
In i t i a l ly  they are  a lmos t  spher ica l ,  whi te-sk inned and succulent .  With  age  
they become a lmost  b lack-surfaced and hard ,  a  resul t  of  the  t i ssues  being 
packed wi th  s tarch.  Papery  brown sca le  leaves  pers is t  on the  tubers  unt i l  
a  considerable  age  and i f  they are  los t  leave  charac ter i s t ic  leaf  scars  on 
the  tuber  sk in .  Buds  on the  tuber  a re  mainly  concentra ted  a t  the  
morphological  apex ,  and f rom these  buds  rh izomes are  produced.  There  i s  a  
c lose  resemblance  in  s t ructure  between rhizome and tuber  (Muzik ,  1950) ,  the  
la t te r  conta ining more  parenchyma ce l ls  and a  more  complex network of  
vascular  t i ssues .  The tubers  are  essent ia l ly  food s torage  organs .  
( i i i )  Rhizomes 
The product ion of  a  rh izome f rom the  apical  bud of  the  tuber  does  not  
normal ly  occur  before  tuber  expans ion i s  complete .  The rh izome may e i ther  
terminate  in  another  tuber  or  produce an  aer ial  shoot .  When young the  
rhizomes bear  2-3  sca le  leaves  a t  the i r  nodes  but  these  are  s loughed off  
wi th  age  a long wi th  the  ou ter  epidermal  layer  leaving a  black thread- l ike  
rhizome.  Ranade and Burns  (1925)  refer  to  di f ferent  types  of  rh izomes which 
a re  pos i t ive ly ,  negat ively  and d ia-  geo tropic .  I t  i s  a  fac t  tha t  chains  of  
tubers  can be  found to  a  considerab le  depth  in  the  so i l ,  even in  Tr in idad,  
but  whether  such d is t inc t ions  can be  drawn be tween rhizomes must  be  ques t ioned,  
for  under  favourable  condi t ions  and adequate  aer ia l  growth i t  can be  expected 
tha t  the  subterranean sys tem wi l l  fu l ly  ramify  through the  so i l .  
Rhizomes found deeper  in  the  soi l  appear  to  be  d i f feren t  f rom those  a t  
the  surface  in  tha t  they bear  a  few advent i t ious  roots  a t  each node.  
Throughout  the  underground sys tem the  proper ty  of  ap ica l  dominance exis ts  
and i f  a  deep seated  tuber  i s  severed f rom i t s  surface  s t ructures  i t  
produces  a  rhizome which grows to  the  surface.  Such rh izomes can be  of  
considerable  length  and several  of  these  were  ex t racted  f rom sawdust  heaps .  
The sawdust  had been dumped onto  nut -grass  infes ted  land thereby ar t i f ic ia l ly  
producing the  condi t ions  of  deep-seated  tubers  unat tached to  aer ia l  growth.  
On examinat ion i t  was  found tha t  bes ides  bear ing the  occas ional  root  a t  the  
nodes ,  severa l  bud swel l ings  were  a lso  produced which were  usual ly  in te r-
nodal  ( see  Fig .HID).  Such buds  appeared to  remain  inact ive  unless  the  
apical  bud of  the  growing rh izome d ied  before  reaching the  so i l  surface  
whereupon they would  develop and cont inue  upward growth .  When such a  bud 
d id  develop ,  bes ides  the  product ion of  a  new rhizome,  a  f lush  of  advent i t ious  
roots  a lso  appeared .  This  form of  development  resul ted  in  the  surface-
-seeking rhizomes becoming cons iderably  branched.  No e quivalent  bud format ion 
has  been found on rh izomes connect ing tubers .  Ranade and Burns  (1925)  
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ment ion the  format ion of  in tercalary  tubers  on rh izomes f rom deeply  bur ied  
tubers  but  none were  found when the  observat ions  descr ibed above were  made.  
The rh izome be ing an  underground s tem has  an  equivalent  s t ruc ture  
(Muzik ,  1950)  and i s  mainly  an  organ for  the  spread and t rans locat ion of  
food mater ia l .  
( iv)  'Basal  bu lb '  (Fig.  I l l )  
At  the  junct ion of  the  shoot  leaves  and the  rhizome producing them a  
swel l ing  resul ts  which Ranada and Burns  (1925)  te rm the  'basal  bulb ' .  The 
format ion of  th is  s t ruc ture  i s  of  ex t reme impor tance  to  the  success  of  the  
p lant  because  i t  is  essent ia l  for  fu l l  aer ia l  development  and subsequent  
tuber  and root  product ion .  Du Preeze  (1944)  descr ibes  the  'basal  bulb '  as  
forming be tween 2"  to  4"  below so i l  surface.  More  commonly in  Tr in idad i t  
i s  found wi th in  the  top  2 "  of  the  soi l  and qui te  of ten  occurs  immedia tely  
below the  soi l  sur face .  Muzik  (1950)  suggests  tha t  the  format ion of  the  
swel l ing  pr ior  to  fu l l  leaf  product ion i s  dependent  on l igh t ,  which i f  not  
p resent  resul t s  in  the  format ion of  a  tuber .  I t  would  appear  that  the  
s t imulus  for  format ion of  the  organ comes f rom the  t ip  of  the  rhizome behind 
which the  swel l ing  occurs .  
The s t ruc ture  of  th is  basal  organ forms a  po int  of  d isagreement  in  the  
l i tera ture .  Ranade and Burns  (1925) ,  a l though they give  a  de ta i led  
descr ip t ion of  the  anatomy of  the  p lant ,  fa i l  to  g ive  any informat ion as  to  
i t s  s t ruc ture .  Subsequent  workers  (Andrews,  1940;  Smith  and Fick ,  1937;  e tc . )  
descr ibe  i t  as  a  tuberous  enlargement ,  whi ls t  Muzik  (1950)  regards  i t  as  
a  bulb  compar ing i t  to  the  s t ruc ture  of  an  onion.  Under  careful  s tudy i t  
appears  to  be  a  def in i te  enlargement  of  the  rhizome,  the  lower  region 
producing sca le  leaves  and roots ,  and the  upper  region g iving r i se  to  leaves .  
I t  a lso  seems that  the  swel l ing  can develop in to  a  more  mature  type  of  tuber .  
Besides  aer ia l  growth this  basal  s t ruc ture  a l so  produces  rh izomes which 
subsequent ly  produce s t r ings  of  tubers .  The naming of  th is  swol len  rhizome 
t ip  as  a  'basa l  bulb '  i s  d is t inc t ly  mis leading as  i t  i s  in  no way a  bulb  
s t ruc ture  (Fig.  I l l  A & B)  bu t  much resembles  a  corm and i t  wi l l  fur ther  be  
refer red  to  as  a  corra- l ike  s t ructure  pending fur ther  s tudy to  dec ide  i t s  
ac tual  naming.  
-8-
(  v)  Leaves  
I t  i s  the  surface  layer  of  tubers  tha t  normal ly  g ive  r i se  to  the  
aeria l  growth.  The leaves  conform to  those  of  the  family  having grass l ike  
blades  about  1 /16-1/4"  wide  and varying in  length  according to  habi t .  
Normal ly  under  f ie ld  condi t ions  in  fu l l  sunl ight  th is  var ies  between 2-8"  
when mature .  Each leaf  carr ies  a  d i s t inc t  midr ib  and i s  very  dark  green in  
co lour .  
Cvi)  Inf lorescence  (Fig .  IV)  
From the  basal  tuf t  of  leaves  a r ises  the  f lowering scape.  This  f lower  
s ta lk  is  leaf less ,  sol id  and t r iangular  in  cross  sect ion .  The inf lores­
cence  is  essent ia l ly  a  compound sp ike ,  resembling an  umbel ,  wi th  4-6  sp ikes ,  
a l l  except  the  terminal  one  be ing subtended by an  involucra l  brac t .  The 
lower  b racts  tend to  remain  green and leaf l ike  unt i l  wel l  a f ter  f lowering.  
Most  of  the  sp ikes  are  longer  than the  brac ts  which subtend them ( the  outer  
ones  not  a lways  so)  and on a  broadly  winged rach i l la  bear  f rom 2  to  9  
sp ikele ts  which are  l inear  or  s l ight ly  curved.  Spikele ts  a re  6  to  18(24)-
- f lowered,  the  f lowers  being typical  of  the  Cyperaceae .  The basal  g lumes 
on the  spike le t  are  commonly s te r i le  and of  a  more  del ica te  na ture  than the  
fer t i le  glumes which a re  boat-shaped and brown in  colour  wi th  a  prominent  
green kee l .  This  produces  a  brown compressed sp ikele t  wi th  a  green la tera l  
s t r ipe  usefu l  in  ident i f ica t ion .  The sol i tary  f lower  of  3  s tamens ,  a  
s ingle  ovary  bear ing a  s ty le  wi th  3  branches ,  and no per ian th ,  i s  car r ied  
wi thin  the  glume.  The t r igonous  achene tha t  i s  produced i s  dark  brown,  very  
thick  coated and about  ha l f  the  length  of  the  glume.  
(c)  Ecology 
Cyperus  rotundus  i s  a  widespread weed of  the  t ropics  and subtropics .  
In  dry  areas  such as  the  Sudan Gezira  (Andrews,  1945)  i t  i s  mainly  a  weed of  
i r r iga t ion channels  and i r r iga ted  f ie lds .  When there  is  a  less  in tense  dry  
season the  plant  i s  more  widespread and this  i s  the  case  in  Tr inidad.  I t  i s  
sole ly  a  weed of  cu l t ivated  land ,being unable  to  s tand up to  compet i t ion  
f rom o ther  vegeta t ion,  and grows bes t  in  fu l l  sun fa i l ing  to  thr ive  under  shady 
condi t ions .  Al though i t s  water  requirements  a re  high i t  wi l l  not  grow in  
inundated land.  Because  of  i t s  subterranean tubers  i t s  drought  res is t ing  
-9-
powers  a re  high,  though the  growth ra te  of  the  aer ia l  par ts  of  the  p lant  i s  
reduced to  a  minimum d ur ing dry  per iods .  The abi l i ty  of  the  p lant  to  grow 
in  seemingly  unsui tab le  places ,  such as  cracks  in  pavements ,  demonst rates  
i t s  audacious  and pers is tent  characte r .  
Rochecouste  (1958)  presents  an  ecological  c lass i f ica t ion of  the  major  
weeds  in  Mauri t ius .  Using Thornwaite ' s  c lass i f icat ion of  c l imate  zones  
he  d iscusses  weeds  in  re la t ion  to :  (a)  subhumid zone,  (b)  humid zone ,  
(c)  superhumid zone,  (d)  weeds  common to  a l l  zones .  He suggests  tha t  
Cyperus  ro tundus  only  a t ta ins  fu l l  development  on f ree  soi ls  in  the  humid 
zone though he  a lso  no tes  i t  under  weeds  common to  a l l  zones,  i t s  abundance 
varying accord ing to  the  annual  precipi ta t ion.  Rochecouste  a l so  presents  
a  weed success ion of  Cyperus  ro tundus  wi th  Cynodon dactyIon as  fo l lows:  
(Cul t iva ted  land indicated  by dot ted  l ine ,  abandoned land by p lain  l ine)  
Free  so i l s  Al l  so i l s  
V* 
V 
Cyperus  ro tundus  Cynodon dacty lon 
Al though the  c l imat ic  condi t ions  in  Tr in idad a re  not  ident ical  wi th  
those  in  Mauri t ius ,  i t  would  be  interes t ing to  know whether  any such 
associat ions  occur  in  Tr inidad.  In  data  made avai lab le  f rom a  weed success ion 
s tudy (Haggar ty ,  1960)  on cul t ivated  land wi th  a  high percentage  cover  of  
when 
Cype rus  ro tundus ,  /abandoned,  Cynodon dacty lon d id  increase  in  impor tance  
whi l s t  Cyperus  ro tundus  decreased.  However  i t  did  not  become the  most  
impor tan t  weed in  respect  of  ground cover ,  over  the  l imi ted  recording 
period of  f ive  months ,  hal f  of  which occurred in  the  dry  season.  In  the  
same succession a  posi t ive  associa t ion was  found between Cyperus  ro tundus  
and Cleome spp.  (C.  spinosus  and C.  c r is ta tus)  (Grime,  1960) .  Both  were  
repor ted  as  be ing underdispersed,  the  underdispersa l  be ing coincident .  
Other  species  of  the  Cyperaceae  which have occurred on nut -grass  
infes ted  land ,  and which might  poss ib ly  be  confused wi th  Cyperus  ro tundus  
in  the  vegetat ive  phase,  are :  
-10-
Kyll inga  odorata  (Vahl)  
Kyl l inga  brevi fol ia  (Rot tb . )  
Kyi l inga  monocephala  (Rot tb . )  
Torul in ium ferax (L.C.  Rich. )  
Cyperus  sphacela tus  (Rot tb . )  
The la t ter  may be  par t icular ly  confus ing ,  even in  the  f lower ing s tage,  
but  can be  dis t inguished by having green sp ikelet s ,  producing abundant  seed ,  
the  glumes being shed when r ipe ,  and having an  advent i t ious  root  sys tem.  
None of  the  above species  produce underground tubers .  
(d)  Li fe  h is to ry  
At  the  commencement  of  the  invest iga t ions  i t  was  hoped to  fo l low the  
l i fe  his tory  f rom seed to  f lower ing .  From a bout  1 ,000 seed co l lec ted  and 
put  to  germinate  no seedl ings  were  produced even af ter  prolonged a t tempts  
(see  Sect ion I l lb ) .  However  the  l i fe  his tory  f rom a  tuber  was  examined.  
Dormant  tubers  obta ined by breaking up several  tuber  sys tems were  sown about  
ha l f  an  inch deep in  pots  and genera l  observat ions  made on the  progress  of  
development  ( see  Fig .  V f or  graphical  representat ion of  th is  development) .  
Two d ays  a f ter  p lant ing the  tubers  were  throwing a  considerab le  number  
of  new roo ts  and a  fur ther  two days  la ter  the  f i rs t  shoots  broke the  sur face .  
Af ter  one week a l l  the  tubers  tha t  had been p lanted had aer ia l  shoots .  In  
the  major i ty  of  tubers  d is turbed whi ls t  making observat ions  the  rhizome 
giving r ise  to  the  f i rs t  aer ia l  shoot  was  very  shor t .  The cormlike  
swel l ing  was  f i rs t  not iced on some shoots  on the  6th  day a f ter  plant ing and 
a t  the  10th  day a l l  shoots  carr ied  th i s  basal  swel l ing.  I t  was  es t imated 
tha t  this  cormlike  format ion occurs  dur ing the  product ion of  the  th ird  and 
f i f th  leaf—though swel l ing  cont inues  whi l s t  subsequent  leaves  are  produced.  
New rhizomes produced f rom the  tubers  were  seen af ter  ten  days  and these  
resul ted  in  the  format ion of  new tubers  by the  th ird  to  four th  week.  This  
compares  favourably  wi th  Smith  and Fick 's  (1937)  f igure  of  21  days  f rom 
p lant ing .  Subsequent  tuber  format ion occurred a t  about  for tnigh t ly  in ter ­
vals  and th is  i s  suppor ted  by f igures  of  tuber  product ion in  the  two 
compet i t ion  exper iments  (Sect ion IV) .  No a ssessment  of  rh izome product ion 
f rom the  cormlike  swel l ing  was  made,  long- term observat ions  would  dete rmine 
th is .  
In  an  ef for t  to  fol low the  overground development  of  the  p lant ,  four  
-11-
quadra t  counts  were  made on a  p iece  of  ro tovated land which had a  h igh 
nut-grass  popula t ion .  A square  quadrat  (50 cm.  x  50 cm.)  was  used d ivided 
in to  twenty-f ive  10 cm.  squares .  This  was  la id  over  the  nut-grass  a t  four  
f ixed posi t ions  and p lant  counts  made.  In  assess ing the  development  i t  was  
decided to  record  the  number  of  leaves  per  p lant .  Whils t  the  nut-grass  
th in  
sward remained/ th is  was  easy,  bu t  in  the  th i rd  count  the  number  of  p lants  
were  d iv ided in to  those  wi th  0-3  leaves  and those  wi th  more  than 3  leaves .  
Counts  were  made a t  weekly  in tervals  fol lowing an in i t ia l  per iod of  e leven 
days  a f ter  ro tovat ing.  In  the  four th  week due to  the  densi ty  of  the  sward 
only  two out  of  the  four  quadrats  could  be  counted and then only  a  d is­
t inc t ion between vegeta t ive  and f lowering shoots  was  made.  
Table  I :  Development  of  nut -grass  shoots  on rotovated land 
11 days  18 days  25 days  33 days  
Tot  a l  413(145)  788(339)  1 ,260(533)  (550)  
0-3  leaves  313(113)  263(121)  246(101)  
4-5  leaves  97(31)  308(137)  1 1 
6 -8  leaves  3(1)  208(77)  890(394)  j  (410)  
9  leaves  + 9  .1 J 
Flowering 1  124(38)  314(140)  
(Figures  in  brackets  denote  counts  on only  2  quadra ts . )  
Unfor tunate ly  no counts  a f ter  33 d ays  were  made,  though i t  appears ,  
f rom the  t rend of  f igures  obta ined ,  tha t  the  overground shoot  populat ion was  
beginning to  balance  i t se l f  and f rom genera l  observat ions  l i t t l e  ext ra  
f lower ing resu l ted .  The above s tudies  demonst ra te  the  speed wi th  which the  
overground l i fe  cycle  i s  completed  under  favourable  condi t ions  of  growth .  
-12-
Sect ion I I I  
DISPERSAL 
Methods  of  d ispersa l  of  the  nut-grass  weed can be  considered under  
the  two headings:  (a)  Vegeta t ive ,  and (b)  Seeding.  
(a)  Vegeta t ive  
This  i s  the  most  s t r ik ing method of  spread by the  plan t  and i s  depend­
ent  on the  format ion of  rh izomes f rom a  tuber  or  cormlike  s t ruc ture  which 
ramify  through the  so i l  forming new tubers  a t  in tervals .  The format ion of  
a  tuber  f rom a  rhizome was  s impl if ied  in to  four  s tages  by Muzik  (1950) .  
1 .  Development  of  a  rhizome f rom a  bud,  
2 .  Cessa t ion of  growth of  the  rh izome,  
3 .  Expansion of  the  region jus t  behind the  rhizome apex 
resul t ing  in  a  tuber ,  
4 .  New g rowth of  rh izome and repet i t ion  of  the  process  
g iv ing a  s t r ing  of  tubers .  
( i )  Tuber  format ion 
The ra te  a t  which new t ubers  are  formed f rom the  mother  tuber  can be  
cons iderable .  Smith  and Fick (1937)  repor t  tha t  they obtained a  sys tem of  
146 tubers  in  3 j  months  f rom a  s ingle  tuber .  I f  th is  was  the  case ,  growth 
must  have  been under  very  ar t i f ic ia l  condi t ions .  In  two pot  exper iments  
where  a  constant  number  of  crop p lants  were  grown wi th  a  varying number  of  
nut -grass  tubers  (Sect ion IV)  perhaps  a  more  na tural  increase  of  tubers  
resul ted .  In  Table  2  i s  indicated  tuber  numbers  obta ined for  each exper iment  
a t  d i f ferent  da tes  f rom plant ing.  (For  fu l l  exper imenta l  da ta  see  Appendix  I I I ) .  
Table  2 :  Numbers  of  tubers  per  tuber  p lanted  (neares t  0 .5)  
Fer t i l i sed  Soi l  Unfer t i l i sed  Soi l  
No.  of  tubers  p lanted  7  14 28 7  14 28 
Exper iment  I  
a t  5  weeks  3 .5  2 .5  2 .5  2 .0  2 .5  2 .0  
a t  8  weeks  6 .0  4.0  4 .5  5 .0  4 .0  4 .0  
Exper iment  I I  
a t  7  weeks  5 .0  3 .5  3 .0  3 .5  3 .0  2 .5  
a t  12 weeks  7 .0  6 .0  5 .0  6 .0  5 .5  4 .5 .  
-13-
CI3 
H  
CO 
>-
cc: 
-a ;  
o r  
CO 
I t  must  be  remembered tha t  these  f igures  were  ob ta ined wi th  the  nut -grass  
growing in  compet i t ion  wi th  another  p lant .  They however  indica te  the  ra te  
of  tuber  product ion over  a  re la t ively  shor t  per iod ,  and show tha t  th is  i s  
accele rated  under  more  fer t i le  condi t ions .  Compet i t ion  resul t ing  from 
high popula t ions  of  tubers  tends  to  retard  the  format ion of  new tubers .  
In  harves t ing p lants  of  Exper iment  I I  a t  12 weeks ,  counts  were  made 
of  the  tubers  produced f rom the  or ig inals .  In  genera l  the  numbers  of  tubers  
per  chain  c losely  agreed wi th  the  f igures  shown in  Table  2  ( i . e .  pot  of  
28  tubers  in  fer t i l i sed  soi l  mainly  car r ied  chains  of  4 ,  5  & 6  tubers ,  e tc . ) ;  
for  a  fu l l  l i s t  of  the  counts  made,  see  Appendix  I I I .  Occas ional ly  a  tuber  
chain  would  seem to  develop a t  the  expense  of  o thers ,  a  s t r ing  of  14 tubers  
being the  maximum, found in  a  fer t i l i sed  pot  p lanted  wi th  14 tubers .  
The length  of  rh izome produced between mature  tubers  was  a lso  measured 
in  some s t r ings .  Where  such measurements  were  made ( see  Appendix  I I I )  i t  
was  not iceable  that  the  length  of  rh izome between the  mother  and f i rs t  
tuber  was  usual ly  shor ter  than the  length  between subsequent  tubers .  Rhizome 
sec t ions  be tween tubers  var ied  from 2"  to  7" ,  wi th  an  average  a t  about  4-§" .  
This  gives  a  rough measure ,  when used in  conjunct ion wi th  ra te  of  tuber  
product ion,  to  the  degree  of  spread tha t  can occur  f rom a  s ingle  mother  tuber  
,  ( i i )  Dist r ibut ion of  tubers  
The fo l lowing are  percentage  dis t r ibut ions  of  tubers  in  the  soi l  taken 
over  three  s i tes  a t  I .C.T.A.  ( for  actua l  f igures  of  tubers  found see  
Appendix  I I )  .  
Table  3:  Tuber  d is t r ibut ion in  the  so i l  (S t  August ine  loam) 
S i te  A S i te  B S i te  C 
Depth  4  bor ings  4  bor ings  15 bor ings  
0-3"  84% 57 48% 
3-6"  10% 36% 28% 
6-9"  6% 6% 21% 
9-12"  0% 1% 0 .5% 
More bor ings  a t  s i tes  A and B could  have been taken to  get  a  more  
cer ta in  idea  of  the  d is t r ibut ion .  Both  these  s i tes  occurred on a  p iece  of  
land rare ly  cul t ivated ,  though burning of  Gl i r ic id ia  t r immings  of ten  took 
-14-
place  on s i te  B and th is  may account  for  the  lower  dis t r ibut ion in  the  
top 3  inches  as  compared wi th  s i te  A.  S i te  C was  regular ly  cul t iva ted,  the  
percentage  d is t r ibut ion being an indicat ion of  th is .  
The bor ings  were  made,  a f te r  considerable  ef for ts  to  f ind  a  sui tab le  
ins t rument ,  wi th  a  6"  d iameter  s teel  (3 /16"  th ick)  cyl inder .  This  borer  
was  made 2 '6"  in  length  and one end was  coarse ly  toothed and sharpened to  
fac i l i ta te  penet ra t ion when the  whole  cy l inder  was  screwed in to  the  so i l  by 
means  of  handles  a t tached a t  the  opposi te  end.  I t  was  found eas ier  to  
ex t rac t  each 3"  sample  in  turn  ra ther  than t ry ing to  take  a  complete  12"  
bore  a t  one t ime which then had to  be  div ided in to  the  respec t ive  sect ions .  
For  fu l ler  deta i ls  of  these  bor ings  and method of  taking them,  Scai fe  (1960)  
should  be  consul ted.  
The above percentages  compare  favourab ly  wi th  those  found by o ther  
workers  e lsewhere.  Smith  and Fick  (1937)  on a  sandy loam found tha t  92.5% 
of  the  tubers  occurred in  the  top 8"  of  so i l ;  Cruzado and Muzik  (1950)  g ive  
the  f igure  of  95% f o r  the  top 6" ,  very  few tubers  occurr ing below 9" ;  and 
Andrews (1940)  in  the  Gezira  s imi lar ly  showed that  the  bulk  occurred in  
the  top  6"  on most  so i ls .  Soi l  type  obviously  inf luences  penetra t ion and 
both  Andrews (1940)  and du Preeze  (1944)  found tubers  down to  depths  of  24"  
on r iver  s i l t s .  
( i i i )  Shoot  format ion and the  factor  of  Apica l  Dominance 
I t  has  been shown that  there  i s  no cor re la t ion  between the  number  of  
overground shoots  and the  tuber  popula t ion in  the  so i l ,  other  than the  obvious  
one of  a  large  number  of  shoots  suggest ing many tubers  in  the  so i l .  The 
resul ts  of  the  pot  exper iments  (Appendix  I I I )  fu l ly  suppor t  such fact s .  I t  
has  previously  been expla ined how f rom a  s ingle  tuber  a  tuber  s t r ing  i s  
produced,  by the  in i t ia l  product ion of  a  surface  seeking rhizome which 
resul t s  in  leaf  product ion,  and then subsequent  growth of  subterranean 
rh izomes wi th  format ion of  tubers  a t  in tervals .  The tuber  sys tem so  bu i l t  
up exhibi ts  apical  dominance,  as  has  been proved by most  workers .  This  
resul ts  in  the  new tubers  genera l ly  being unable  to  throw rhizomes which can 
te rminate  in  shoot  growth.  
Devia t ion f rom th is  genera l  ru le  i s  fu l ly  repor ted  in  the  extens ive  work 
of  Cruzado and Muzik  (1950) .  They showed tha t  polar i ty  in  a  tuber  sys tem 
-15-
was a  funct ion of  auxin  d is t r ibut ion and tha t  the  polar i ty  of  such a  tuber  
sys tem could  be  upse t  by plac ing the  tuber  s t r ing  hor izonta l ly  or  inver t ing  
i t .  This  t rea tment  resul ted  in  most  of  the  tubers  producing rh izomes which 
terminated in  shoot  format ion .  Under  f ie ld  condi t ions  the  format ion of  
hor izonta l  rh izomes ,  producing tubers  and shoots  wi l l  account  for  the  
increase  in  shoot  number  over  a  per iod (Table  I ) .  
I f  the  apical  dominance i s  broken by the  sever ing of  the  rhizome,  then 
the  tuber  immediate ly  below the  break wil l  throw a  shoot  forming rhizome.  
This  fac t  accounts  fo r  the  heavy infes ta t ion  of  nu t -grass  tha t  of ten  occurs  
a f ter  cul t ivat ing land which previous ly  showed no or  l i t t le  s igns  of  
nut -grass  popula t ion and a lso  s t resses  the  impor tance  of  obtain ing a  complete  
k i l l  of  the  weed when a t tempt ing to  e radica te  i t .  
Cruzado and Muzik  a l so  demonstra ted  that  polar i ty  exis ts  wi thin  each 
tuber ,  those  buds  a t  the  tuber  apex a lways  sprout ing f i rs t .  In  handl ing 
tubers  in  the  var ious  s tudies  made in  th is  repor t  there  has  been no evidence  
to  show tha t  th is  i s  not  the  case .  Such polar i ty  as  ex is ts  in  a  tuber  even 
on detachment  i s  less  easy to  upset  than that  in  a  tuber  s t r ing ,  the  
terminal  bud sprout ing no mat ter  a t  what  angle  the  tuber  i s  p lanted.  The 
profus ion of  shoots  tha t  a r ise  from shal low tubers  or  tubers  ly ing on the  
surface ,  as  a  resul t  of  cul t iva t ion e tc . ,  suppor ts  the  f indings  of  the  above 
workers  that  the  auxins  producing polar i ty  wi thin  a  tuber  or  tuber  s t r ing  
are  des t royed by l igh t ,  so  tha t  many ax i l la ry  buds  produce shoots  and not  
jus t  the  terminal  bud (or  sub- terminal  bud in  the  event  of  the  te rminal  one 
having previously  developed) .  
(  iv )  Tuber  dormancy 
This  i s  very  c losely  assoc iated  wi th  the  apical  dominance found in  a  
tuber  sys tem.  Tubers  ly ing in  a  chain  wi l l  not  produce a  shoot  forming 
rhizome unless  the  dominance of  the  apical  tuber  i s  removed.  So long as  so i l  
condi t ions  remain  favourable  such tubers  can be  expected to  l ie  seemingly  
inact ive  for  considerable  per iods .  Af ter  dominance has  been removed a  
tuber  ly ing a t  depth  in  the  soi l  may remain  dormant  i f  condi t ions  are  not  
complete ly  su i table  unt i l  a  t ime when they become more  favourable  to  
sprout ing .  Soi l  aerat ion may be  an  impor tan t  fac to r  in  th is  case ,  and 
Palmer  and Por ter  (1959)  have found tha t  wi th  high carbon dioxide  and low 
-16-
oxygen leve ls  germinat ion of  tubers  i s  poor  whi ls t  a t  h igh oxygen and low 
} 
carbon d ioxide  levels  tuber  sprout ing can reach a  very  h igh percentage.  
Under  the  la t ter  condi t ions  they even found tha t  apica l  dominance could  be  
suppressed and that  lower  tubers  on a  s t r ing  could  be  made to  shoot .  The 
aera t ion of  so i l s  by subsoi l ing  a f ter  r igorous  surface  clear ing of  nut -grass  
infes ted  land could  conceivably  has ten  the  recolonizat ion of  the  land by 
encouraging deep seated  tubers  to  grow.  
Much work has  been done on the  degree  of  advers i ty  that  a  tuber  can 
wi ths tand.  The amount  of  des iccat ion (Smith  and Fick ,  19 37;  Du Preez ,  1944) ,  
and the  dura t ion and in tens i ty  of  temperatures  (Smith  and Fick,  1937)  that  
can be  wi ths tood before  shoot ing abi l i ty  of  dormant  tubers  i s  los t ,  a re  two 
such condi t ions  which have been s tud ied considerably  in  ef for ts  to  f ind a  
method of  nut -grass  cont ro l .  
(b)  Seeding 
( i )  Flower  product ion 
I t  was  not iced in  the  pot  exper iments  (Sec t ion IV)  tha t  the  nut-grass  
had remained whol ly  vege ta t ive ,  whereas  in  the  area  f rom which the  tubers  
for  plant ing had been obtained there  had been profuse  f lower ing .  Andrews (1946)  
s ta tes  tha t  maximum f lower ing was  re la ted  to  per iods  of  maximum h umidi ty .  
In  the  above ins tance  a l l  tubers  would  have exper ienced the  same level  of  
a tmospher ic  humidi ty ,  and thus  i t  seemed tha t  other  factors  must  a lso  play  
a  par t  in  f lower  ini t ia t ion .  The pot  exper iments  were  car r ied  out  in  a  
p lant  house  wi th  open s ides  but  with  a  roof  cover  whichwas 50% g lass  and 
50% sh eet  i ron .  This  resul ted  in  considerable  shading and a l so  lower  
temperatures  (bo th  a i r  and so i l ) ,  and i t  was  cons idered that  these  two fac tors  
plus  tha t  of  the  nut -grass  being grown under  a r t i f ic ia l  condi t ions  in  pots  
might  be  responsib le  for  the  lack of  f lowering.  
I t  was  fur ther  observed tha t  the  number  of  leaves  produced by the  
nut -grass  shoots  in  the  exper iments  were  genera l ly  less  than those  plants  
which f lowered ou ts ide .  I t  was  decided to  examine whether  there  might  be  
some cor re la t ion  between the  number  of  leaves  produced and the  t ime of  
f lower ing.  Table  4  presents  the  numbers  of  p lants  found wi th  respect ive  
numbers  of  leaves  a t  f lower ing .  
-17-
Table  4 ;  Number  of  leaves  produced a t  f lowering 
— 
Leaf  number  Number  of  p lants  
below 7  1  
7 9  
8  17 
9  25 
10 15 
11 16 
12 14 
13 17 
14 6  
15 7  
16 10 
above 16 10 
From the  f igures  above i t  appears  tha t  f lower  in i t ia t ion  only  takes  
place  a f ter  the  appearance  of  the  seventh  leaf  ( rare ly  before) .  Also  there  
i s  indicated  a  peak of  f lower ing a t  about  the  n inth  leaf  s tage  and th is  i s  
suppor ted  by counts  made when s tudying the  overground development  of  nut -
-grass  (Sec t ion I I )  when af ter  33 days  growth ,  of  314 p lants  in  f lower  
a lmost  80% o f  these  car r ied  8 ,  9  and 10 leaves.  Such counts  were  taken in  
the  wet  season whereas  those  represen ted in  Table  4  were  made about  two weeks  
af ter  a  per iod of  heavy ra in .  This  may account  for  a  la rge  number  of  p lan ts  
f lower ing wi th  more  leaves  than 10 ,  i f  humidi ty  has  an  ef fec t  on in i t ia t ion ,  
for  dur ing the  dry  season nut-grass  p lants  tend to  remain  vegeta t ive  ,  not  
f lowering but  increas ing thei r  leaf  number .  I t  might  be  suggested  tha t  under  
ideal  condi t ions  most  p lants  would  f lower  be tween the  7th  and 14th  leaf ,  bu t  
a  considerably  larger  number  of  p lan ts  o ther  than tha t  represented in  Table  4  
would  have to  be taken when examining th is  hypothes is .  
( i i )  Seed product ion 
Varying degrees  of  seeding and subsequent  germinat ion have been repor ted  
in  the  l i tera ture .  Ranade and Burns  (1925)  found the  average  number  of  
seeds  per  inf lorescence  was  220,  and sowing seed immediate ly  a f ter  co l lec t ion 
a  germinat ion percentage  of  only  1 .5% was obta ined.  Andrews (1946)  repor ts  
on considerable  seed se t t ing  by nut -grass  bu t  g ives  no f igures .  He a l so  
observed tha t  sowing when f resh  gave hard ly  any germinat ion,  and he  obta ined 
a l l  h is  seedl ings  f rom s i f ted  so i l  obta ined f rom nut-grass  infested  land.  
Smith  and Fick (1937)  and Du Preez  (1944)  could  f ind  no seed se t t ing.  
Under  Tr in idad condi t ions  seeding does  occur  but  not  in  very  g rea t  amounts .  
-18-
The only  method employed to  ext ract  the  smal l  numbers  of  seed f rom the  mature  
f lower  heads  was  to  rub the  heads  between the  hands  (about  25 a t  a  t ime) ,  
col lec t ing seed and chaff  on a  piece  of  paper  and then separa t ing the  seed 
mainly  by p lac ing the  seed and chaff  on a  No. l ,  24 cm. ,  f i l te r  paper  and 
ro ta t ing th is  a t  an  angle .  I t  was  found tha t  the  seed ,  being heavier ,  
tended to  rol l  off  of  the  f i l t er  paper  before  the  major i ty  of  the  chaff .  By 
repeat ing th is  severa l  t imes  a  fa ir ly  pure  sample  of  seed was  obta ined.  I t  
was  real ised  that  th is  was  a  s low and tedious  method and an  ef for t  was  made 
to  see  i f  the  chaff  could  be  separa ted  f rom the  seed by a lcohol  f loata t ion 
(Baldwin ,  1923) .  This  was  unsuccessfu l  as  much chaff  a lso  sank a long wi th  
the  seed.  Evans  (1954)  succeeded in  separat ing good and bad grass  seed by 
f loa ta t ion wi th  a lcohol  and i t  was  found that  f rom the  samples  of  nut -grass  
seed obtained a  propor t ion sank in  95% a lcohol ,  the  remainder  f loat ing .  On 
separa t ing the  two se ts  of  seeds  i t  was  found on examinat ion tha t ,  a l though 
the  f loa t ing seeds  appeared superf ic ia l ly  heal thy,  they were  in  fac t  a l l  empty .  
In  cu t t ing  open sunken seeds  immediate ly  a f ter  separat ion and la ter  in  the  
v iabi l i ty  tes t s ,  about  1  seed in  every  20 was  found to  be  empty (5%).  
I t  was  decided to  use  only  sunken seeds  in  the  tes t s  to  be  carr ied  out .  
Table  5  presents  a  l i s t  of  the  major i ty  of  seed tha t  was  co l lec ted .  
Table  5:  Seed se t t ing  of  Cyperus  ro tundus  (nut -grass)  
No.  of  in f ls  No.  of  seeds  by No.  of  sunken seed Seeds  produced 
heads  taken hand separat ion in  95% a lcohol  per  100 heads  
100 186 used wi thout  f  ur th  er  t rea tment  
100 122 65 65 
100 198 94 94 
200 376 166 83 
200 118 63 32 
200 195 68 34 
200 358 282 141 
300 375 192 64 
300 420 used wi thout  f  u r ther  t  reatment  
500 1555 657 131 
500 151 37 7  
The f igures  show the  reasonably  smal l  amount  of  seed set t ing  that  i s  pro­
duced in  Tr inidad .  However ,  us ing the  resul ts  of  Table  1 ,  where  in  33 days  
314 f lowers  were  produced over  a  to ta l  area  of  10 ,000 sq .  cm.  (10 .8  sq .f t )  
seeds  per  100 heads ,  
and us ing the  low average  seed se t  of  50  /  then over  630,000 seeds  would  be  
produced per  acre  on nut -grass  infes ted  land over  a  per iod of  about  6-8  
-19-
weeks .  In  re la t ion  to  the  Ranade and Burns  (1925)  f igure  of  near  60 mi l l ion ,  
th is  is  smal l ,  but  i t  must  be  remembered that  such a  seed product ion could  
occur  more  than once  a  year .  
( i i i )  Seed germinat ion 
Having obta ined seed i t  was  desi rable  to  ob ta in  seedl ings .  Only  two 
methods  were  t r ied:  -
(1)  P lac ing seed on damp f i l t er  papers  in  pet r i  d ishes  
Twenty  seeds  were  used per  d ish,  the  f i l te r  paper  being kept  damp by 
means  of  a  wick running over  f rom an adjacent  water  reservoir .  Twelve  pe t r i  
d ishes  were  used,  s ix  conta ined seeds  tha t  sunk on a lcohol  separa t ion,  three  
wi th  seed tha t  f loated  and three  wi th  unseparated  seed.  The water  reservoirs  
were  f i l led  up every  day and one drop (0 .1  cc)  of  Are tan  fungic ide  (1/8  oz  in  
1  pin t  water)  was  added every  5 th  day to  keep the  seed and f i l t er  papers  
c lean of  fungi .  Af ter  10  weeks  no germinat ion had occurred but  on making 
v iabi l i ty  tes t s  wi th  Tet razol ium sal t  so lut ion on the  seeds  the  fo l lowing 
percentages  were  obta ined:  
Sunken seed = 62.5% viable  
F loat  seed = 1 .6% viable  
Unseparated  seed = 47% v iab le  
(The smal l  percentage  viable  f loat  seed was  due  to  one fu l l  seed which proved 
v iable . )  
(2)  Sowing seed in to  a  s tandard  so i l  compost  
A s tandard  compost  was  used in  case  the  work was  to  be  repeated  in  the  
fu ture .  The John Innes  seed compost  (Lawrence and Newel l ,  1939)  was  chosen.  
Andrews (1946)  suggests  tha t  higher  germinat ion resul t s  under  so i l  condi t ions  
due to  fungal  and bac ter ia l  act ion on the  seed coat .  With  th is  in  mind both  
s ter i l i sed  and uns ter i l i sed  so i l  were  used in  two separa te  mixings  ( for  
compost  de ta i l s  see  Appendix  I I ) ,  350 seeds  tha t  sunk in  a lcohol ,  250 seeds  
tha t  f loa ted  and 250 unsepara ted  seeds  were  sown separa te ly  in  boxes ,  both  
in  the  s ter i l i sed  compost  and in  the  unster i l i sed .  After  two months  no 
germinat ion had resul ted.  The seed was  too  smal l  to  be  found in  the  boxes  
to  make v iabi l i ty  tes t s .  
I t  has  been genera l ly  found wi th  t ropical  grass  seed that  under  
ar t i f ic ia l  sowing very  poor  germinat ion of ten  resul ts ,  whereas  in  nature  a  
fa i r ly  high seedl ing popula t ion can be  found.  I t  appears  that  nut -grass  
-20-
seed may show s imi lar  proper t ies ,  especia l ly  under  condi t ions  of  a r t i f ic ia l  
sowing.  
Poss ib le  reasons  fo r  low seed germinat ion 
(a)  Cl imate  
Both  Ranade and Burns  (1925)  and Andrews (1945)  found that  highes t  seed 
germinat ion percentage  were  ob ta ined at  the  beginning of  the  ra ins ,  and con­
c luded tha t  both  so i l  mois ture  and h igh a tmospheric  humidi ty  were  required.  
Al l  the  nut-grass  seed sowings  in  the  germinat ion tes t s  descr ibed above were  
done dur ing the  dry  season.  The seed boxes  wi l l  be  watered wel l  in to  the  
approaching wet  season in  order  to  see  i f  any germinat ion wi l l  resul t  .  
(b)  Hard impermeable  f ru i t  coat  and tes ta  
Cut t ing  the  seed,  or  more  correct ly  the  one seeded f rui t ,  shows the  very  
substant ia l  per icarp  ( f ru i t  coat )  which encloses  the  smal l  nut -grass  seed 
(Fig .  IV) .  I t  can be  expected that  on ly  af ter  prolonged soaking and possible  
bacter ia l  and fungal  ac t ivi ty  a t tack ing the  t i ssues ,  wi l l  they be  broken down 
suf f ic ient ly  to  a l low pene t ra t ion of  water  and subsequent  seed germinat ion.  
That  v iab i l i ty  s t i l l  exis ts  in  the  seeds  kept  on mois t  f i l te r  paper  for  10 
weeks  suppor ts  th is  supposi t ion.  
(c )  Seed dormancy 
This  i s  the  most  probable  reason why f resh  seed does  not  germinate  on 
sowing.  Andrews (1946)  found that  the  la rgest  percentage  of  seed in  a  sample  
germinated 5-7  years  af ter  co l lec t ion and s torage  in  bot t les .  I t  i s  hoped 
tha t  enough seed can be  co l lected  so  tha t  s imi la r  tes t s  can be  made under  
Tr in idad condi t ions .  The type  of  seed dormancy i s  di f f icul t  to  assess  except  
on c lose  s tudy,  but  i f  the  length  of  dormancy i s  as  long as  Andrews suggests  
then the  seed most  probably  has  to  undergo a  physiological  change e i ther  in  
the  embryo or  endosperm,  or  in  the  f rui t  coat ,  or  in  both .  
(d)  Seed viab i l i ty  
Being unable  to  ob tain  germinat ion of  the  seed i t  was  essent ia l  to  assess  
whether  the  seed was  v iab le  or  not .  On c ut t ing  seed which sank on a lcohol  
separa t ion longi tudina l ly ,  a  plump heal thy looking embryo was  not iced 
embedded in  mealy  endosperm.  I t  was  decided to  use  the  Tet razol ium sal t  
solu t ion tes t  (D a vies  and Winstanley,  1957)  to  tes t  v iabi l i ty .  Accepted 
-21-
methods  of  making the  tes t  were  reported  as  us ing a  1% so lut ion of  the  sa l t  
(2 ,3 ,5-Tr iphenyl  te t razol ium chlor ide  or  T.T.C.)  and p lac ing into  i t  the  
longi tudina l ly  cut  seed which had previous ly  been soaked whole  in  water  fo r  
several  hours .  Af ter  a  per iod of  a  few hours  in  the  sal t  so lu t ion the  seed 
was  removed and checked for  resul t s .  In  the  presence  of  v iab le  t is sue  the  
T.T.C.  so lut ion is  reduced forming an  insolub le  red  compound (diphenyl  
formazan)  .  Seeds  are  cons idered v iable  i f  the  embryo and surrounding endo­
sperm are  co loured p ink.  
Tes ts  were  made over  a  considerable  per iod because  those  t r ied  f i rs t  
were  unsuccessfu l .  At  f i r s t  unsoaked seeds  were  cu t  and tes ted  wi th  no 
resu l t s .  Then seeds  tha t  had been in  germinat ion tes t s  in  pe t r i  d ishes  under  
damp c ondi t ions  for  seven weeks  were  t r ied,  again  wi th  no resul ts ,  a l though 
the  embryo and endosperm s t i l l  appeared heal thy .  On res tudying the  repor t  
of  Davies  and Winstan ley (1957)  i t  was  noted that  workers  us ing small  grass  
seeds  s l ight ly  punctured the  f rui t  coat  before  put t ing  the  seed to  soak in  
water ,  pr ior  to  the  T.T.C.  so lut ion tes t ,  to  a l low penet rat ion of  water .  
Sa t is fac tory  resul t s  were  obta ined this  way.  Fol lowing th is  method a  few 
nut-grass  seeds  were  n icked a t  the  s tylar  end to  remove jus t  the  f ru i t  coa t .  
These  seeds  were  le f t  soaking in  water  for  10 days  and then put  in to  T.T.C.  
so lut ion .  On removal  and cut t ing  the  seed open af ter  24 hours  the  major i ty  
had become so  sof t ,  due to  the  prolonged soaking in  water ,  tha t  i t  was  d i f f i ­
cul t  to  keep the  seed contents  in tac t .  Out  of  12  seeds  th ree  showed embryos  
which had turned br ight  p ink and there  were  s igns  of  fur ther  colora t ion in  
some of  the  o ther  seeds.  
With  th is  encouraging resu l t  fur ther  tes ts  were  made reducing the  t ime 
of  soaking in  water .  I t  appeared tha t  the  bes t  resul ts  could  be  ob ta ined by 
soaking the  nicked seed for  24-36 hours  in  water  before  making the  tes t  in  
T.T.C.  sa l t .  Usual ly  the  seeds  were  lef t  in  the  sa l t  so lu t ion for  24 hours  
before  being checked ,  for  shor ter  per iods  d id  no t  g ive  bet ter  resul t s .  
With  two samples  of  50 seeds ,  29 and 28 seeds,  respect ive ly ,  gave p ink 
embryos  indicat ing viabi l i ty ,  whi ls t  21 and 22 remained uncoloured.  This  
indicates  a  v iabi l i ty  of  58% and 56% in  the  sunken seeds .  
This  viabi l i ty  tes t  was  used on the  seed in  the  germinat ion tes t  carr ied  
out  in  f i l te r  papers  ( see  above) .  
-22-
( iv)  Fac tors  af fect ing seed product ion 
Having only  been able  to  col lect  a  relat ive ly  smal l  amount  of  seed,  i t  
was  considered worthwhi le  to  examine some of  the  poss ible  reasons  why th is  
was  so .  The immediate  a im was  to  unders tand the  mechanism of  f lower ing and 
th is  was  la ter  fo l lowed by pol len  v iabi l i ty  tes ts .  
1 .  Mechanism of  f lower ing 
In  making th i s  s tudy,  p lants  wi th  an  inf lorescence  appearing in  the  
basa l  c luster  of  leaves  were  dug up and po t ted.  The fol lowing i s  a  summary 
of  the  s tages  of  f lowering tha t  were  noted dur ing subsequent  observat ions .  
The inf lo rescence  spikes  a re  a t  f i r s t  shor t  and held  t ight ly  toge ther .  
As the  f lowering s ta lk  lengthens  these  spikes  a lso  lengthen and open out .  
When fu l ly  spread the  s t igmas commence t o  lengthen and prot rude f rom the  
lower  b racts  of  each spike let .  At  th is  t ime the  inf lorescence  head i s  held  
wel l  above the  leaves  and the  f lower  s ta lk  cont inues  to  lengthen wel l  on in to  
anthes is .  The s t igmas appear  to  cur l  and commence to  shr ivel  af ter  3-4  days  
( indicat ing tha t  they are  no longer  recept ive) ;  4-5  days  a f ter  prot rus ion of  
the  s t igmas anthes is  commences .  F lowers  open f rom the  bot tom of  the  spike le t  
upwards ,  2-4  f lowers  opening da i ly ,  thus  on an  average  s ized spikele t  s t igmas 
can be  found in  a  recept ive  s ta te  towards  the  top  of  the  sp ikele t  when there  
are  an thers  a t  the  base .  Pol len  i s  produced copiously  on prot rus ion of  the  
an thers ,  be ing l ight ,  smooth  surfaced and about  0 .03 mm (3 0 y)  in  
diameter .  I t  i s  concluded that  nut -grass  i s  dependent  on wind for  pol l ina t ion 
and i s  cross  fer t i l i sed.  
2 .  Pol len  v iabi l i ty  
The method used to  tes t  pol len  viab i l i ty  was  tha t  of  the  hanging drop 
(White ,  1954) .  A s mal l  g lass  r ing (about  1  cm.  in  diameter  and J  cm.  in  
depth)  was  a t tached by pe t ro leum je l ly  to  a  microscope s l ide  and a  smal l  
volume of  d is t i l led  water  p laced ins ide .  A cover  s l ip ,  carrying a  drop of  
sucrose  solut ion wi th  pol len  gra ins ,  was  then inver ted  and p laced on top  of  
the  g lass  r ing  which had previously  been greased.  By a pplying s l ight  
pressure  to  the  cover  s l ip  an a i r - t igh t  seal  was  ob ta ined between the  cover  
s l ip  and g lass  r ing.  The water  previously  p laced ins ide  the  r ing produced 
a  sa tura ted  a tmosphere  which i s  des i rable  for  pol len  tube  growth.  
Repor ts  tha t  the  concent  ra t ion  of  sucrose  so lut ion was  c r i t ica l  for  
opt imum values  of  po l len  germinat ion and var ied  for  d i f fe rent  p lan t  
-23-
species  meant  tha t  d i f ferent  concentra t ions  of  the  sucrose  would  have to  be  
t r ied  in  order  to  f ind the  cor rect  so lut ion.  Three  ser ies  of  t es ts  were  made 
us ing var ied  sucrose  concentra t ions  as  fol lows:  
Tes t  1 .  % c oncentra t ions :  40,  20 ,  13 .3 ,  10 
Tes t  2 .  % c oncentra t ions :  20,  13 .3 ,  10 ,  8 ,  6 .6  
Tes t  3 .  % c oncentrat ions :  20,  13 .3 ,  10,  6 .6 ,  2  and d is t i l led  water  
In  a l l  tes ts ,  under  microscopic  examinat ion no po l len  germinat ion could  be  
found .  In  these  tes t s  s ingle  anthers  had been used in  each drop,  and i t  was  
considered des i rable  to  use  a  mixed sample  of  po l len  in  a  fur ther  t es t .  
Inf lorescences  ga thered in  the  evening had a l l  anthers  removed.  By morning 
a l l  f resh  pro t ruding anthers  were  col lec ted  and pol len  teased ou t .  This  
ext racted  pol len  was  submit ted  to  Test  4  which was  ident ica l  to  Test  3  wi th  
an  addi t ional  1% s o lut ion.  On e xaminat ion af ter  24 hours  one  gra in  was  found 
to  have germinated and two more  showed s igns  of  germinat ion in  the  6 .6% 
solut ion.  
Bel ieving th is  to  be  in  proximity  to  the  concentra t ion required  for  
pol len  germinat ion a  fur ther  tes t  was  devised:  
Tes t  5 .  % c oncentra t ion :  8 ,  7 ,  6 ,  5 ,  6 ,  5 .5 ,  5 ,  4 ,  3 .  
Pol len  was  ob tained in  a  s imi lar  way.  Af ter  prolonged scru t iny no germinated 
pol len  could  be  found in  any of  the  drops .  I t  was  decided to  discont inue  the  
t es t s .  
I t  had been noted whi ls t  making the  t es ts  tha t  a  la rge  propor t ion of  the  
pol len  was  shr ivel led  and empty.  With  fu l l  grains  i t  had been expected tha t  
plac ing them in  s t rong and weak sucrose  solu t ions  would  have resul ted  in  the  
gra ins  plasmolysing and burs t ing  respect ively ,  but  there  had been no evidence  
of  e i ther  taking p lace .  
The resul t s  descr ibed above would  indica te  tha t  the  major i ty  of  po l len  
i s  non-viable .  That  70% o f  the  pol len  is  not  v iab le  was  proved when making 
s l ides  of  ext racted  pol len  gra in  and s ta in ing wi th  cot ton b lue  in  lac tophenol .  
On m aking a  large  number  of  counts  a t  random only  30% of  the  grains  had taken 
up the  dye.  Whether  a l l  of  th is  30% o f  po l len  produced i s  v iable  would  appear  
doubtful  f rom the  tes ts  above.  That  some seed i s  produced means  that  some 
pol len  must  be  a l ive .  I t  is  in te rest ing to  note  that  wi th  the  numbers  of  
seed obta ined (Table  5) ,  the  highes t  col lect ions  were  obta ined f rom heads  
where  nut -grass  was  found in  profus ion.  Al l  the  smal l  co l lec t ions  came f rom 
-24 
snai l  i so la ted  communi t ies .  This  would  be  expected in  the  case  of  a  wind 
pol l ina ted  plant  and more  so  where  po l len  v iabi l i ty  i s  very  low.  
(v)  Sha t ter ing of  seed 
Other  seed se t t ing  Cyperus  spp.  drop the i r  glumes when the  seed i s  r ipe  
and the  seed fa l l s  to  the  ground.  No s igns  of  th is  proper ty  was  found wi th  
nut -grass .  The inf lorescence  usual ly  s tays  in tact  af ter  f lower ing for  a  
considerable  period and i f  i t  i s  al lowed to  remain  s tanding,  f ina l  breaking 
up i s  by separa t ion of  the  inf lorescence  spikes  f rom the  main  f lower  s ta lk .  
That  l i t t le  seed i s  lost  whi ls t  such inf lorescences  remain  s tanding was  
proved by co l lect ions  made immediate ly  and a t  two months  a f ter  seed r ipening.  
There  was  no reduct ion in  the  seed number  ob ta ined per  100 inf lorescences  
(131 and 141 respect ive ly;  see  Table  3) .  
(vi )  Seed d ispersa l  
Andrews (1945)  regards  i r r igat ion water  and s t rong gusty  winds  as  the  
main  methods  of  seed disseminat ion in  the  Sudan.  In  Tr inidad methods  of  
d ispersal  ( i f  any)  can only  be  conjec tured .  Soi l ,  carry ing the  seed ,  t rans­
fer red  f rom one p lace  to  another  e i ther  purposefu l ly  or  on implements ,  
shoes ,  e tc . ,  would  a lmost  surely  be  the  only  method of  spread over  la rge  
d is tances .  I r r iga t ion water  i s  only  used in  l imi ted  areas ,  bu t  in  such 
areas  may be  an  impor tan t  method of  d ispersal .  Elsewhere  dra inage water  
af ter  heavy ra ins  would  serve  much the  same purpose .  High winds  are  infrequent  
but  occas ional ly  occur  in  s t rong enough gus ts  to  carry  seed shor t  d is tances .  
Birds  have been suggested  as  carrying the  seed bu t  th is  i s  very  unl ikely ,  
mainly  because  of  the  smal l  quant i ty  of  seed produced,  and there  have been 
no ins tances  of  b i rds  seen feeding on mature  nut -grass  heads.  
-25-
Sect ion IV 
COMPETITIVE EFF ECT OF NU T-GRASS 
(a)  Compet i t ion  exper iment  
The impor tance  of  nut -grass  as  a  weed has  been fu l ly  real i sed  throughout  
the  t ropics ,  but  there  a re  few references  to  the  ac tual  depress ion i t  causes  
in  c rop y ie ld  and the  assoc iated  economic  loss .  In  India  the  est imated 
reduct ion in  y ie ld  was  g iven as  25-30% (Ranade and Burns ,  1925)  bu t  l i t t le  
has  been repor ted  e lsewhere.  In  ta lk ing to  loca l  peasant  farmers  the  
impress ion gained was  that  they regarded nut -grass  purely  as  a  nuisance  weed 
in  the  ear ly  s tages  of  a  c rop.  Once the  crop was  es tabl ished they made l i t t le  
or  no e ffor t  to  control  i t .  
I t  was  decided to  run a  smal l  exper iment  to  discover  i f  nut -grass  offered 
any ser ious  compet i t ion  to  crops ,  and i f  so  to  what  degree .  As such an 
exper iment  would  be  in  progress  a t  the  same t ime as  genera l  observat ions  were  
being made,  i t  was  essent ia l  tha t  i t  should  be  s imple  and yet  g ive  worthwhi le  
resul ts .  
(  i )  Exper imenta l  design 
I t  was  decided to  have a  pot  exper iment  us ing 8"  pots  where  the  t rea t ­
ments  would  be  a  vary ing number  of  nu t -grass  plants  growing wi th  two crops  of  
s imi lar  height ,  one  being broad lea fed and the  o ther  narrow leafed.  Crops  
which were  quick matur ing had to  be  chosen because  of  the  res t r ic ted  t ime 
avai lable  .  After  considerab le  discuss ion the  two crops  chosen were  Morei  
rad ish  (Raphanus  sa t iva  var .  radicula)  and Finger  mi l le t  (Eleus ine  coracana) .  
I t  soon became apparent  tha t  an  exper iment  se t  up us ing a  s tandardised soi l  
(John Innes  po t t ing  compost  was  contemplated)  purely  to  discover  i f  compet i t ion  
was  present ,  would  supply  a  l imi ted  number  of  resul ts ,  which being obta ined 
in  an  ar t i f ic ia l  compost  of  good texture  and high nut r ient  s ta tus  would  hardly  
bear  any re la t ion  to  f ie ld  condi t ions .  By adjus t ing the  des ign of  the  
exper iment ,  ar r i  us ing a  f i e ld  so i l  wi th  a  low nutr ient  s ta tus ,  which was  not  
incl ined to  pan too  badly ,  much more  informat ive  resul ts  could  be  obta ined.  
Such resul t s  could  g ive  a  def ini te  indica t ion as  to  the  type  of  compet i t ion  
tha t  occurred.  The so i l  chosen was  a  River  Es tate  sandy loam which i s  
recognised (Chenery ,  1949)  as  being low in  nut r ients .  
On the  above basis  a  fac tor ia l  exper iment  was  des igned which consis ted  of :  
two levels  of  nu t r ient  s ta tus  -  unfer t i l i sed  and fe r t i l i sed  pots ,  
two levels  of  water ing -  adequate  and res t r ic ted  water ing ,  
four  levels  of  nut -grass  -  28,  14,  7  and 0  tubers  per  po t ,  
two repl ica t ions .  
Such an  exper iment  was  to  be  repeated  for  each crop,  resul t ing  in  a  to ta l  
of  64  pots .  The cons t  ant  number  of  c rop p lants  per  pot  was  to  be  decided 
af te r  seed germinat ion.  
Problems were  soon envisaged in  t ry ing to  apply  water  res t r ic t ively  and 
yet  uni formly and in  order  to  keep the  exper iments  as  s imple  as  poss ible  i t  
was  decided to  replace  the  levels  of  water ing wi th  two harvest ing per iods .  
I t  was  hoped that  th is  would  indica te  whether  the  degree  of  compet i t ion  o ffered 
by the  nut -grass  af fec ted  crop equal ly  throughout  the  l i fe  of  the  crop.  
Thus  the  f inal  des ign of  the  exper iments  was  to  have two levels  of  so i l  
nut r ien ts ,  two harves t ing per iods ,  four  nut -grass  l evels ,  a l l  of  which were  
repl icated  twice  in  each exper iment .  The analys is  of  var iance  for  such an  
exper iment  was  adequate  ( see  Appendix  I I I ) .  
( i i )  Si te  
A p lant  house  wi th  open s ides  and a  roof  hal f  g lass  and hal f  sheet  i ron 
was  avai lable  for  the  exper iment .  I t  was  hoped tha t  the  degree  of  shade 
thrown by the  roof  would  no t  a f fec t  the  outcome of  the  exper iments ,  but  
ra ther  offer  the  pots  some pro tec t ion as  the  exper iments  were  to  be  conducted 
in  the  dry  season.  An a rea  in  the  cent re  of  the  house  was  se lected ,  where  
i t  was  expected that  condi t ions  would  be  fa i r ly  uniform,  and i t  was  ar ranged 
to  s tand the  po ts  on open gr ids  placed about  6"  off  the  p lant  house  f loor  
(see  photo  Appendix  I I I ) .  
( i i i )  Set t ing  up exper iments  
To obta in  the  requis i te  number  of  nut -grass  tubers  for  p lant ing,  a  large  
number  were  co l lected  f rom infes ted  sawdust  heaps ,  sor ted  to  re ta in  only  
those  of  medium s ize .  They were  then plan ted in  seed boxes  a t  the  ra te  of  
about  300 per  box.  On p lant ing up the  exper imenta l  po ts  f ive  days  l a ter  wi th  
28 ,  14,  7  and no tubers  respect ive ly ,  only  tubers  wi th  one or  two vegetat ive  
shoots  were  selec ted  f rom the  seed boxes .  In  th is  way i t  was  hoped to  use  
the  most  un i form mater ia l  as  possib le .  
In  applying fer t i l i ser  to  the  so i l  fo r  the  h igh nut r ient  po ts ,  i t  was  
-27-
suggested  tha t  the  ra tes  used should  be  equivalent  to  5  cwts  per  acre  of  
su lphate  of  ammonia ,  4  cwts  of  potass ium sulpha te  and 6  cwts  of  super  phosphate .  
Enough so i l  was  mixed to  f i l l  36 pots  g iving a  safe ty  margin  fo r  the  32 po ts  
required ,  the  amounts  of  fe r t i l iser  added being 32.5  gm su lphate  of  ammonia ,  
26.0  gm p otass ium sulpha te ,  and 39.0  gm su per  phosphate  ( for  ca lcu lat ions  
see  Appendix  I I I ) .  
Before  addi t ion  of  the  fe r t i l i ser  and f i l l ing  the  64 po ts  wi th  so i l  
(32 wi th  pla in  so i l  and 32 wi th  soi l  plus  added fe r t i l i ser )  the  so i l  was  a l l  
passed through a  ;§"  s ieve.  Since  the  8"  pots  were  hand made and varied  in  
s ize  a  measure  was  used in  f i l l ing  the  po ts  so  that  a l l  po ts  should  contain  
the  same amount  of  so i l .  
Over  the  dra inage hole  of  each pot  was  p laced a  3"  square  of  pa inted  
wire  gauze,  on top of  which was  added a  thin  layer  of  f ine  gravel  ( re tained 
on a  4"  s ieve  having passed a  2"  s ieve) .  A la rge  measure  of  so i l  was  then 
added and f i rmed,  the  tubers  p laced on top  of  th is  and then covered by a  
fu r ther  depth  of  so i l  (about  £") .  This  surface  was  level led  and f i rmed 
before  the  crop seeds  were  sown on i t .  The radish  seed had g iven a  germinat ion 
percentage  of  88 ,  and the  f inger  mi l le t  96%.  Sowings  were  th in  and the  seed 
was  covered by a  very  th in  layer  of  - 4 "  s i f ted  so i l .  Al l  po ts  were  careful ly  
label led  and p laced in  thei r  respect ive  exper iment  s i tes  a t  random on the  
i ron gr ids .  For  layout  and label l ing  used see  Appendix  I I I .  
( iv)  Progress  of  exper iments  
Al l  po ts  were  watered twice  dai ly  wi th  a  hose  pipe .  Dur ing the  seedl ing 
growth of  the  crops  a  f ine  rose  was  a t tached to  prevent  damage.  Af ter  3  
days  many nut -grass  shoots  were  showing and the  major i ty  of  the  crop seeds  
had germinated.  A gradual  th inning of  the  crop seedl ings  was  made over  the  
f i rs t  few days ,  a  f inal  thinning on the  10th  day leaving 9  radish  seedl ings  
and 14 f inger  mi l le t  seedl ings  per  pot .  Considerable  d i f f icul ty  was  
encountered wi th  the  radish  seedl ings  vi i ich  became e t io la ted  probably  as  a  
resul t  of  the  shady house  and too shal low sowing.  By c areful  water ing the  
seed l ings  managed to  get  wel l  rooted and s t i f fen  up,  though thei r  s tems did  
not  th icken as  expected and the  leaves  were  he ld  very  high.  
S igns  of  insect  damage a f ter  about  two weeks  on bo th  the  radish  and 
f inger  mi l le t  made i t  necessary  to  dust  wi th  B.H.C.  This  pract ice  was  
was cont inued a t  about  ten  day in tervals  throughout  the  course  of  the  exper i ­
ments .  Pots  were  kept  weeded dur ing the  f i rs t  th ree  weeks ,  a f ter  this  per iod 
no weeding was  found necessary .  Harves ts  of  the  rad ish  exper iment  took 
p lace  f ive  weeks  a f ter  sowing and when plants  s tar ted  to  f lower  (e ight  weeks) .  
The mil le t  exper iment  was  harves ted  a t  seven weeks  and a t  twelve  weeks  when 
the  gra in  s tar ted  to  r ipen.  When harves t ing ,  the  po ts  were  knocked out  and 
so i l  broken up careful ly .  The crop p lants  were  ex t racted  wi th  as  much root  
as  poss ible ,  washed to  remove so i l ,  and then dr ied  in  an  oven for  twenty  four  
hours  a t  about  95°C.  Dry weight  was  then taken.  With  the  nut -grass ,  the  
shoots  wi th  s t r ings  of  tubers  a t tached,  were  knocked f ree  of  the  major i ty  of  
the  so i l .  The shoots  were  counted and cu t  of f  about  above the  cormlike  
swel l ing,  washed and oven d r ied  for  th i r ty  s ix  hours  before  being weighed.  
The number  of  leaves  produced by the  crop plants  were  counted,  and in  
the  second harves t  of  the  radish  exper iment  these  were  weighed separate ly  to  
the  remainder  of  the  p lants .  The gra in  heads  of  the  mi l le t  were  a lso  removed 
when making the  second mil le t  harves t  and these  were  l ikewise  dr ied  and 
weighed separa te ly.  
That  p lan ts  were  pot  bound was  very  not iceable  when making the  f ina l  
harves t ings  and i t  was  fe l t  tha t  the  pot  s ize  had hardly  been adequate .  
Insec t  damage in  some of  the  mi l le t  po ts  had reduced the  number  of  crop p lants  
but  such pots  conta ined the  h igher  populat ions  of  nut -grass  tubers  and i t  
was  considered a  t rea tment  e f fec t .  
(v)  Resul ts  ( see  Appendix  I I I  for  de tai l s  and analys is  tables)  
That  nut -grass  does  offer  severe  compet i t ion  under  the  condi t ions  of  the  
exper iments  i s  indicated  by the  dry  weights  of  c rop y ie lds .  Below are  se t  
out  the  percentage  y ie lds  occurr ing under  the  four  nut -grass  levels .  
Table  6 :  % Y ield  (dry  weight  bas is )  of  c rop p lants  
% Y ield  Radish  % Yi e ld  Mil le t  
Number  of  Unfer t i l ised  Fer t i l i sed  Unfer t i l i sed  Fer t i l i sed  
tubers  per  pot  so i l  Soi l  so i l  so i l  
0  100% = 8g 100% = 15g 100% = 25g 100% = 45g 
7  68% 57% 47% 43% 
14 42 52 26 25 
28 38 27 16 4  
-29-
The reduct ion of  y ie ld  in  the  broad leafed radish  exper iment  appears  
propor t ionate ly  less  than tha t  for  the  narrow leafed mi l le t  and i t  might  be  
suggested  tha t  the  radish  could  s tand up to  the  compet i t ion  offered by the  
nut -grass  be t ter  than the  mi l let .  
Besides  reduct ion in  to ta l  plant  weight  increas ing densi ty  of  nut -grass  
s ignif icant ly  reduced radish  and mi l le t  leaf  number  and a lso  the  y ie ld  of  
mi l le t  heads.  By adding fe r t i l i sers  to  the  soi l  increase  in  crop growth was  
ob ta ined ,  but  i t  did  not  counterac t  the  compet i t ive  ef fect  of  the  nu t-grass  
also 
to  any degree.  Leaf  number  was  only  increased for  the  radish  p lants .  The 
fer t i l i sed  so i l  pots  mainta ined an equal  amount  of  leaf  product ion on a l l  
plants  no mat ter  what  the  nu t -grass  popula t ion was ,  as  shown by the  non 
s igni f icance  of  the  nut -grass / fer t i l i ser  in terac t ion .  This ,  as  expected ,  
was  not  the  case  for  to ta l  p lan t  y ie ld .  
Harves t ing per iods  d id  no t  show s ign i f icant ly  d i fferen t  numbers  of  
leaves  for  the  radish ,  showing tha t  fu l l  leaf  product ion had taken place  by 
the  t ime of  the  f i r s t  harves t  af ter  f ive  weeks  of  growth .  The subsequent  
three  weeks  of  the  e ight  weeks  growth be ing a  per iod of  matura t ion and f lower  
product ion.  The non s igni f icant  in teract ion between harves t ing per iods  and 
nut -grass  leve ls ,  for  radish  plan t  y ie lds  indicates  that  propor t iona te  growth 
occurred wi th  the  c rop p lan ts  under  a l l  condi t ions .  Wi th  mi l le t  th is  was  not  
the  case ,  the  increase  in  dry  weight  between f i r s t  and second harves ts  be ing 
far  less  in  rela t ion  to  the  dry  weight  a t  the  f i rs t  harvest  wi th  p lants  
growing in  a  high popula t ion of  nu t -grass ,  than wi th  those  in  c lean soi l  or  
so i l  wi th  a  low nut-grass  populat ion .  This  fur ther  re f lects  the  powers  of  
radish  to  wi ths tand the  compet i t ion  of  nut -grass  bet ter  than the  mi l le t .  
That  no in terac t ions  appear  s igni f icant  for  leaf  number  in  the  crop 
p lants ,  indica tes ,  tha t ,  a l though plant  growth i s  great ly  af fec ted  by the  
di f ferent  t rea tments ,  leaf  product ion wi th in  each t rea tment  ca rr ies  on a t  a  
uniform rate .  
Tuber  number  was  found to  be  s ignif icant ly  grea ter  in  the  fe r t i l i sed  
pots .  There  was,  however ,  no  d i f ference  in  mean tuber  weight  and bare ly  any 
be tween mean shoot  weight .  I t  would  seem tha t  no compet i t ion  between 
nut -grass  p lants  had occurred ,  though f rom prev ious  s tudies  i t  would  appear  
tha t  the  nut -grass  p lan t  wi l l  s tabi l i se  i t s  overground growth as  a  resul t  of  
of  se l f  compet i t ion  and th is  could  a lso  account  for  a  fa i r ly  constan t  shoot  
weight .  
In  analys ing the  var ious  resul t s  obta ined f rom the  above exper iments ,  
i t  was  advised tha t  unless  the  er rors  present  for  each harves t  per iod were  of  
the  same order ,  showing tha t  f igures  obta ined were  done so  under  equivalent  
condi t ions ,  then the  harves t  per iods  should  be  analysed separa tely .  When 
ca lcula t ing resul t s  i t  was  fe l t  tha t  such er rors  were  of  the  same order  and 
that  to  analyse  the  harves ts  toge ther  as  one exper iment ,  as  was  or igina l ly  
p lanned,  would  be  jus t i f ied .  
(b)  Cover  crops  
I t  has  ear l ie r  been repor ted  tha t  nut -grass  wi l l  not  f lour ish  under  
shade or  in  assoc iat ion wi th  ta l ler  vigorous  vegeta t ion .  Work o n a  weed 
succession (Haggar ty ,  Grime,  1960)  showed tha t  the  very  heavy infes ta t ion  of  
nu t -grass  which appeared shor t ly  af ter  rotovat ing decl ined in  impor tance  as  
o ther  weeds  developed.  Af ter  three  months  i t  had become complete ly  swamped 
and i t  was  di f f icul t  to  f ind  aer ia l  shoots .  The suppress ion of  nut -grass  
growth e i ther  by a l lowing natural  regenera t ion of  the  vegeta t ion or  by 
purposefu l  sowing of  s t rong vigorous  cover  crops  has  been rea l ised  for  many 
years .  Loustalo t  and Delgado (1948)  acc identa l ly  found that  the  ra ther  open 
sward tha t  nut -grass  develops  a l lowed germinat ion and subsequent  growth of  
velve t  beans  (St izolobium ater r imum),  a  s t rong growing annua l ,  such that  
a f ter  the  f i rs t  two months  of  the  ra iny season the  nu t-grass  had a l l  been 
shaded out  .  This  i l lus t ra tes  tha t  heavi ly  in fes ted  areas  of  nut -grass  can be  
used successful ly  but  wi thout  e rad ica t ing the  weed.  To obta in  eradicat ion 
cover  cropping should  be  used in  associa t ion wi th  dry  season t i l l age  of  the  
soi l  over  a  per iod of  a  few years .  The t i l lage  resul ts  in  tuber  des iccat ion 
and dea th ,  whi ls t  the  cover  crop suppresses  any growth f rom tubers  le f t  a l ive  
in  the  so i l .  
-31-
Sect ion V 
THE COOTROL OF N UT-GRASS 
Spar row (1958)  g ives  a  de tai led  review of  the  methods  employed to  control  
the  weed,  and i t  only  remains  to  give  a  shor t  summary of  the  present  pos i t ion  
(a )  Peasant  methods  
During the  prepara t ion of  the  land an  ef for t  may be  made to  col lec t  
v is ib le  tubers ,  but  th is  i s  obviously  a  f ru i t less  t ask .  The main  con trol  
re l ies  ent i re ly  on hand hoeing especia l ly  dur ing the  es tabl ishment  of  a  crop .  
With  ground leve l  crops  ( le t tuce ,  e tc . )  hand forking is  somet imes  used around 
the  plants  to  remove adjacent  tubers .  Af te r  es tabl ishment  l i t t l e  concern  i s  
shown and the  nut -grass  i s  of ten  a l lowed to  grow unchecked,  surface  c lear ing 
taking p lace  inf requent ly .  These  methods  probably  do more  harm than good by 
inducing under ly ing tubers  to  shoot  and bui ld  up a  la rger  nut -grass  popula t ion 
(b)  Genera l  agr icu l tura l  methods  
( i )  Cul tura l  
This  appears  to  be  the  cheapes t  way of  contro l l ing  the  weed,  i f  i t  i s  
done proper ly  and successful ly .  A f a i lure  wi th  such methods  can only  lead to  
worse  t rouble  than before .  The genera l  pr inc iple  of  cul tura l  contro l  re l ies  
on the  k i l l ing  of  tubers  by desiccat ion af ter  deep ploughing and subsequent  
harrowing to  dry  out  the  so i l  in  the  dry .  season.  I t  impl ies  tha t  land must  
be  fa l lowed for  a  per iod and th is  may mean the  sacr i f ice  of  a  cropping 
season.  The use  of  cover  crops  in  the  wet  season to  suppress  any nut -grass  
growth tha t  may resul t  f rom pers is tent  tubers  af ter  deep ploughing,  and then 
repea t ing the  process  in  the  fol lowing dry  season can usua l ly  lead to  a  
higher  level  of  e radicat ion.  
Cont inued sur face  cut t ing  of  shoots  a t  shor t  in tervals  (1-2  weeks)  has  
been found to  weaken the  p lant ,  bu t  needs  to  be  prolonged in  order  to  gain  a  
control .  
( i i )  Herbic idal  
A vas t  number  of  herbic ides  have been t r ied  in  a t tempts  to  eradica te  the  
weed.  None have been found complete ly  successful  i f  appl ied  a t  economic  
ra tes .  The hormonal  herb ic ides ,  especia l ly  the  amines  and es ters  of  2 ,4-D,  
-32-
have been found most  promis ing,  bu t  tend only  to  reduce  tuber  number  and 
have to  be  used repeatedly  to  obta in  a  contro l .  Soi l  fumigants  (methyl  
bromide)  have been found h ighly  successful  on smal l  a reas ,  but  are  l imi ted  to  
such by nature  of  thei r  appl ica t ion .  
( i i i )  Combinat ion of  cul tura l  and herbic ida l  methods  
A h igh degree  of  contro l  has  been a t ta ined by the  repeated  cul t ivat ion 
of  in fes ted  nut-grass  land dur ing the  growing season,  to  induce shoot ing of  
tubers .  Each cu l t iva t ion fol lowed when growth has  s tar ted,  by a  herbic ida l  
appl ica t ion .  The contro l  ga ined th is  way can be  achieved over  a  fa i r ly  
shor t  per iod .  
(c)  Dif f icul t ies  of  eradicat ing nut-grass  
The main  obs tacle  in  r idding land of  nut -grass  i s  the  depth  of  the  soi l  
to  which tubers  penet ra te ,  and the  reserves  of  food mater ia l  which they conta in  
enabl ing them to  wi ths tand unfavourab le  condi t ions  and yet  take  immediate  bene­
f i t  when such condi t ions  change and growth i s  poss ib le .  
With  cu l tura l  contro l  the  a im must  be  to  sever  a l l  root  connect ions  of  
even the  lowest  tubers  to  prevent  the  tapping of  deep water  suppl ies ,  so  
that  des icca t ion can be  successful .  However  i f  the  thorough drying out  of  
the  topsoi l  i s  not  a t ta ined dur ing the  cul t iva t ions  appl ied,  the  severed 
tuber  sys tems wi l l  resul t  in  a  higher  nu t -grass  popula t ion than was  previous ly  
present .  Cul tura l  con trol  i s  consequent ly  largely  a t  the  mercy of  the  weather .  
For  herb ic idal  appl icat ions  to  be  successful ,  the  herbic ide  must  l ikewise  
k i l l  a l l  the  tubers  in  the  so i l .  The hormonal  herb ic ides  seemed most  promis ing 
f rom th is  aspec t  as  they would  be  t rans located  throughout  the  p lant .  Muzik  
and Cruzado (1950)  found that  the  faul t  wi th  2 ,4-D was  that  the  t rans locat ion 
was  too  s low and tha t  only  the  top two tubers  of  any sys tem were  k i l led .  
They rea l i sed  tha t  the  problem was  to  f ind a  herb ic ide  which would  be  t rans­
loca ted  quickly  to  reach and k i l l  even the  lowest  tuber .  No h erb icide  wi th  
such proper t ies  has  yet  been found.  The use  o f  so i l  fumigants  has  par t ly  
solved the  problem for  wi th  adequate ly  sea led  so i l  covers  af ter  appl ica t ion ,  
they can penet ra te  f reshly  moved so i l  to  a  depth  of  up  to  one foot ,  but  as  
s ta ted  above thei r  use  i s  l imi ted  to  smal l  areas .  
-33-
Sec t ion VI 
CONCLUSIONS 
From the  account  in  th is  repor t  of  the  l imi ted  s tudies  made on Cyperus  
ro tundus  ,  nut -grass ,  i t  would  appear  that  the  problem which i t  presents  in  
Tr in idad i s  not  widely  d i f ferent  f rom tha t  found e lsewhere  in  the  world .  
The d is t r ibut ion of  tubers  in  the  soi l  in  the  vic ini ty  of  the  Col lege  
(St  August ine  loam) was  found to  be  a lmost  en t i re ly  in  the  top n ine  inches .  
The product ion of  new tubers  in  the  so i l  i s  about  three  weeks  f rom an 
i so la ted  tuber  and about  every  two weeks  once  a  tuber  s t r ing  has  been formed.  
These  ra tes  of  new tuber  format ion when recognised with  the  fac t  tha t  
in ter- tuber  rhizome lengths  averaged about  4-2" ,  g ive  an  ind ica t ion as  to  the  
speed o f  the  underground spread of  the  plan t  and the  potent ia l  the  plan t  
possesses  for  infect ing c lean land af ter  i t  has  f i rs t  gained en t ry.  The 
development  of  an  extens ive  underground tuber  sys tem occurs  wi thout  any 
v is ible  evidence  because  of  the  apical  dominance phenomenon which exis t s ,  
prevent ing low ly ing tubers  producing the  type  of  rh izomes which resu l t  in  
shoot  product ion.  Counts  of  ground level  shoots  wi l l  however  g ive  an  idea  
of  the  number  of  tuber  s t r ings  in  the  ground,  but  these  wi l l  carry  a  var iable  
number  of  tubers .  Longer  s t r ings  being obta ined in  underpopula ted  so i l s ,  
becoming shor ter  as  the  degree  of  infes ta t ion  increases .  Cul t iva t ion breaks  
up these  tuber  s t r ings ,  upsets  the  apica l  dominance and a l lows deep seated  
tubers  to  throw leaf  producing rh izomes .  Aerat ion of  the  soi l  wi l l  a lso  
occur  and th is  may a lso  encourage dormant  tubers  to  sprout .  
I t  was  found that  under  good growing condit ions  on ly  one month  would  
e lapse  between shoot  emergence and f lowering.  Flower ing genera l ly  occurred 
a f ter  product ion of  the  seventh  leaf  and,  under  ideal  condi t ions ,  before  the  
four teen th  leaf .  With  poor  growing condi t ions ,  only  leaf  product ion occurred 
and th i s  at  a  very  s low ra te .  When fu l l  growth could  be  resumed,  as  a t  the  
beginning of  the  ra ins ,  f lowering would  take  place .  These  fac ts  indica te  
tha t  the  p lant  has  a  def in i te  vegeta t ive  phase ,  as  a  pre lude to  f lowering.  
In  adverse  condi t ions  only  leaves  are  produced and a  few p lants  wi th  over  
twenty  leaves  have been found in  the  dry  season.  On return  of  favourab le  
condi t ions  f lower ing resul ts .  Humidi ty  would  be  one  of  the  most  impor tan t  
factors  inf luencing f lora l  in i t ia t ion ,  bu t  i s  not  the  so le  fac tor .  Light  
-34-
and,or  tempera ture  may exer t  a  contro l l ing  inf luence.  
Flower ing commences  before  the  scape has  fu l ly  lengthened.  The individ­
ua l  f lowers  on the  spikele t  open f rom the  bot tom upwards ,  two or  four  
f lowers  per  spike le t  opening da i ly .  The s t igmas prot rude f i r s t ,  remaining 
recept ive  for  about  three  days ,  fo l lowed four  to  f ive  days  l a ter  by the  an­
thers ,  which on emergence produce copious  pol len .  From c ounts  made 70% o f  
th i s  pol len  i s  empty and of  the  remaining 30% l i t t le  v iabi l i ty  could  be  
shown.  A sucrose  solu t ion of  a round 6% seemed to  be  the  most  l ike ly  
concentrat ion for  ge t t ing  pol len  to  germinate  by the  hanging drop method.  
The fac t  tha t  seeds  are  formed indicates  that  there  must  be  some d egree  of  
v iabi l i ty .  
The amount  of  seeding shown by the  plan t  i s  smal l .  In  a reas  of  heavy 
in fes ta t ion  an average  of  jus t  over  one  seed per  inf lorescence  was  produced,  
bu t  in  i sola ted  and smal l  communi t ies  th is  dropped to  under  hal f  th is  ra te .  
The major i ty  of  empty and incomplete ly  formed seed was  separa ted  f rom that  
col lec ted  by f loa ta t ion in  95% a lcohol .  Of  the  sunken seeds ,  a  v iabi l i ty  of  
about  55-60% was shown by use  of  the  Tet razol ium sa l t  t es t .  Using th is  tes t  
the  h ighes t  viabi l i ty  was  obta ined by soaking seed in  water  for  24-36 hours  
before  emers ing in  a  1% s a l t  so lu t ion for  24 hours .  Before  soaking in  the  
water  the  per icarp  was  punc tured a t  the  s ty la r  end.  Af ter  the  per iod in  
the  sal t  so lut ion the  seed was  removed,  cu t  open and a  note  made of  any 
colora t ion of  the  embryo and surrounding endosperm indicat ing viabi l i ty  of  
the  seed.  
No g erminat ion of  seed could  be  ob ta ined e i ther  a f ter  ten  weeks  on 
damp f i l t e r  paper  or  a f ter  twelve  weeks  in  bo th  s ter i l i sed  and uns ter i l i sed  
soi l  composts .  The probable  reason for  th is  i s  the  presence  of  the  very  
th ick  and hard  f ru i t  coa t ,  or  the  need for  a  dormancy per iod ,  or  a  combin­
a t ion  of  bo th.  Very l i t t le  seed sha t te r ing from the  inf lorescence  head 
appears  to  occur ,  and means  of  seed d ispersa l ,  i f  any,  i s  not  known.  
From the  compet i t ion  exper iments  i t  would  appear  tha t  nut -grass  can 
offer  a  high degree  of  compet i t ion  when i t  is  found in  la rge  numbers .  The 
resul ts  were  ob tained under  ar t i f ic ia l  condi t ions  in  a  res t r ic ted  soi l  
volume,  but  i t  can be  expected tha t  s imi lar  ef fects  would  be  ob ta ined in  
f ie ld  condi t ions ,  but  a t  a  lower  l evel .  Soi l  of  h igher  fer t i l i ty  appears  
-35-
to  has ten  tuber  development  g iv ing r i se  to  a  la rger  tuber  popula t ion,  and 
speedier  underground spread of  the  plant .  Tuber  s ize  would  seem to  be  
fa i r ly  constant  under  a l l  condi t ions .  Of  the  two crop p lants  used in  the  
exper iments ,  the  broad leafed rad ish  seemed to  be  able  to  wi ths tand the  
nut-grass  compet i t ion  bet ter  than the  narrow leafed mi l le t ,  though in  both  
cases  a  considerable  reduct ion in  yie ld  occurred wi th  increas ing nut-grass  
popula t ion.  The nut -grass  natura l ly  seems to  present  a  ba lance  between 
shoot  produc t ion and the  varying res t r ic t ive  effec ts  of  the  compet i t ive  
environment  a f ter  co lonisa t ing an a rea .  
Under  compet i t ion  f rom s t rongly  growing vege ta t ion nu t-grass  is  suppressed.  
This  has  been not iced by most  workers  and forms the  bas is  for  the  use  of  cover  
crops  on nut -grass  infes ted  land.  
By way of  con trol  the  only  poin t  tha t  can be  drawn f rom the  above 
s tudies  i s  tha t  erad ica t ion of  the  weed should  be  a t tempted before  f lower ing 
and subsequent  seed se t .  The smal l  amounts  of  seed produced must  contr ibute  
to  d ispersa l  and be  a  potent ia l  method of  infec t ing c lean land.  Methods  of  
control  used wil l  vary  f rom d is t r ic t  to  d is t r ic t  but  those  most  l ikely  to  
give  the  bes t  resu l ts  under  Tr in idad condi t ions  should  be  based on e i ther  
extensive  cul t iva t ions  in  the  dry  season fol lowed by cover  cropping in  the  
wet ,  or ,  the  jo int  use  of  a  ser ies  of  cul t ivat ions  in  the  wet  season wi th  a  
para l le l  ser ies  of  hormonal  herb icide  appl icat ion on the  induced young 
shoow growth.  
Summary of  conclus ions  
1 .  The nut -grass  problem in  Tr inidad i s  not  widely  d i f feren t  to  tha t  
found e l sewhere  in  the  t ropics .  
2 .  Dist r ibu t ion of  tubers  in  the  so i l  a t  the  Col lege  was  a lmost  en t i rely  
in  the  top  n ine  inches .  The fac tor  of  ap ica l  dominance which i s  found in  the  
underground sys tem a l lows underground spread of  the  p lant  to  take  p lace  
wi thout  obvious  increase  in  shoot  product ion.  Sever ing of  tuber  s t r ings  breaks  
th is  apica l  dominance and leads  to  considerable  overground shoot  product ion 
and fur ther  spread .  New t ubers  form a t  about  for tn ight ly  in terva ls  on 
exis t ing  tuber  s t r ings .  
3 .  The swel l ing  which occurs  a t  the  junc t ion of  rh izome and leaves  i s  
bes t  refer red  to  as  cormlike .  I t  i s  not  a  'basal  bulb ' .  
-36-
4.  Under  favourab le  condi t ions ,  f lower ing occurs  in  one month  af ter  
shoot  emergence.  I t  occurs  a f ter  a  def ini te  vegeta t ive  phase .  
5 .  The sol i tary  f lowers  occurr ing on spike let s  of  the  umbel  l ike  
inf lorescence  expose  the ir  s t igmas f i r s t ,  fo l lowed a f ter  about  f ive  days  by 
the  an thers .  Flowers  a re  cross  and wind pol l ina ted.  
6 .  Viabi l i ty  of  the  pol len  i s  very  low.  
7 .  Seeding does  occur  to  a  l imi ted  degree  (about  1  seed per  in f lores­
cence)  .  Ful l  seeds  showed a  v iabi l i ty  of  50-60% and wi l l  not  germinate  when 
f resh  as  a  resul t  of  a  very  hard  f ru i t  coat ,  or  the  need for  a  dormancy 
per iod,  or  bo th.  
8 .  Nut-grass  of fers  severe  compet i t ion  to  annual  c rops .  Of  the  two 
crops  mil le t  and rad ish,  the  l a t te r  could  wi ths tand the  compet i t ion  best ,  bu t  
even then suffered grea t ly  wi th  increas ing nut-grass  popula t ion .  
9 .  More  nut -grass  tubers  are  produced under  more  fe r t i le  so i l  condi t ions .  
S ize  and weight  of  tubers ,  however ,  remains  fa i r ly  constant .  
10 .  Contro l  of  nu t -grass  weed should  be  made before  f lowering and seeding .  
The use  of  cover  crops  to  suppress  the  weed,  and cul t ivat ion in  the  dry  
season to  desiccate  tubers  probably  suggests  the  bes t  method of  contro l .  
RECOMMENDATIONS 
Throughout  the  s tudies  descr ibed in  th is  repor t  cer ta in  problems have 
ar isen.  Some of  these  were  g iven pre l iminary  examinat ion,  but  fur ther  
invest igat ions  into  these  and o ther  points  would  add to  the  understanding of  
the  nut -grass  p lant .  Below are  presented the  points  on which fu r ther  s tudy 
might  be  wor thwhi le .  
Ranade and Burns  (1925)  repor t  d i f ferent  forms of  geot rophy in  the  
rhizomes.Whether  the  d i f ference  in  rhizome habi t  i s  a  resu l t  of  geot rophy or  
purely  an  ef fec t  produced by bet te r  aerat ion,  so i l ,  temperature  or  l ight  on 
the  surface  l ayer  of  so i l  i s  not  known and would  be  of  in teres t  to  discover .  
Higher  oxygen leve ls  were  found by Palmer  and Por te r  (1959)  to  break tuber  
dormancy,  and even upset  apica l  dominance on a  tuber  s t r ing ,  so  tha t  tubers  
would  produce shoot  forming rhizomes.  The factor  of  so i l  aera t ion may p lay  
an  impor tant  par t  in  shoot  product ion ,  and may la rge ly  account  for  the  high 
propor t ion of  aer ia l  growth a f ter  cul t ivat ing infes ted  land.  The breaking 
-37-
of  ap ical  dominance in  the  tuber  sys tem by the  sever ing of  rh izomes i s  mainly  
responsib le  for  th is .  
The format ion of  the  cora l ike  swel l ing  a t  the  junct ion of  the  rhizome and 
leaves  has  been regarded as  impor tant  for  fu l l  leaf  product ion .  Whether  i t  
actua l ly  forms before  leaf  product ion o r  as  a  resul t  of  leaf  product ion has  
not  been cons idered .  The fac t  tha t  i t  i s  a  rh izomatous  swel l ing ,  presumably  
contain ing s tored food products  may be  an  ind ica t ion tha t  i t  forms as  a  
resu l t  of  leaf  product ion .  Workers  have fur ther  s ta ted  tha t  other  fac tors ,  
such as  l ight ,  have a  contro l l ing  inf luence  on i t s  format ion.  The actua l  
condi t ions  of  format ion of  th is  swel l ing  might  wel l  be  c lar i f ied  a long wi th  
an anatomical  s tudy of  the  nodes.  Because  of  i t s  importance  in  the  vegeta t ive  
l i fe  his tory  of  the  p lant  th is  knowledge may h ave an impor tant  bear ing on 
t imely  control  of  the  nut -grass  weed.  Likewise  the  fac tors  af fect ing f lower  
in i t ia t ion,  whether  humidi ty  i s  the  a l l  impor tant  fac tor  or  whether  i t  i s  
re la ted  to  o ther  c l imat ic  and so i l  fac tors ,  could  wel l  be  de termined.  
In  fur ther  consider ing the  f lowering of  nut -grass ,  i t  would  be  of  
in teres t  to  f ind  whether  th is  breaks  the  ap ica l  dominance found in  a  tuber  
sys tem.  That  i t  d is turbs  the  polar i ty  of  the  cormlike  swel l ing,  i s  shown by 
the  format ion of  several  shoots .  I f  the  same d is turbance  resul t s  both  in  the  
under ly ing tubers  and tuber  sys tem f lower ing may be  impor tant  in  rela t ion  to  
subsequent  vegeta t ive  spread.  The ind ica t ion that  f lowering occurs  af te r  a  
def ini te  vegeta t ive  phase  of  the  aer ia l  shoo t  and tha t  there  may be  a  peak 
wi thin  cer ta in  l imit s  of  leaf  product ion under  favourable  growing condi t ion  
leads  to  the  suggest ion that  fur ther  s tudies  should  be  made to  ver i fy  these  
s ta tements .  
More  es t imates  as  to  the  amount  of  v iab le  seed produced would  be  worth­
whi le .  In  par t icu lar ,  monthly  f igures  would  de termine i f  a  par t icular  per iod 
or  season of  the  year  i s  favourable  to  seed se t .  The cause  of  non-germinat ion 
of  f reshly  col lected  seed should  be  ascer ta ined.  This  wi l l  a lmost  surely  
lead the  worker  in to  considera t ions  of  seed dormancy and the  breaking down of  
the  thick ,  hard  f ru i t  coat .  Fur ther  t rea tment  of  seed by ac id,  hea t ,  s torage,  
e tc .  should  a l so  be  made in  t ry ing to  obta in  germinat ions .  
Effor ts  to  obta in  va lues  of  pol len  viabi l i ty  were  unsuccessful .  That  
some v iab le  pol len  i s  produced i s  shown by the  product ion of  seed.  I t  may 
be  that  the  correct  condi t ions  were  not  found for  pol len  growth,  and tha t  
-38-
on repeat  of  the  tes ts  i f  the  hanging drop method again  appears  unsuccessful ,  
an  agar  cul ture  might  be  worth  t ry ing.  
In  conclus ion,  in  order  to  obta in  a  ful l  unders tanding of  the  plan t  
under  Tr inidad condi t ions ,  a  fu l l  ecological  survey much a long the  same l ines  
as  tha t  repor ted  by Rochecouste  (1958)  i s  required .  This  would  a l so  give  an 
ind ica t ion as  to  which soi l s  and areas  are  poten t ia l ly  sui table  for  nut -grass  
in fes ta t ion,  so  tha t  cu l tura l  methods  could  be  used a t  in tervals  to  keep 
present  c lean land f ree  f rom the  nut -grass  weed.  
« 
-39-
ACKNOWLEDGEMENTS 
I  wish  to  acknowledge,  wi th  thanks ,  Mr P .T.  Richards  under  whose  aegis  
and supervis ion the  repor ted  s tud ies  were  made.  For  h is  he lpful  advice  and 
cr i t ic ism dur ing the  course  of  the  inves t igat ions  and in  prepara t ion of  the  
drawings  and scr ip t .  
My thanks  a re  a lso  due to :  
Dr  G.K.  Mal iphant  and Mr I .T .  Twyford  of  the  Regional  Research Centre  
(Soi ls )  for  thei r  advice  on crop p lants  to  use  in  the  compet i t ion  exper iments ,  
suggest ions  as  to  the  des ign of  the  exper iments ,  and for  obta ining the  soi l  
used f rom River  Es ta te .  
Mr G .E.  Hodnet t  for  discuss ing the  s ta t i s t ica l  analys is  of  the  
compet i t ion  exper iments .  
Miss  I .  Assing fo r  the  typing of  th is  repor t .  
The Junior  Staf f  of  the  Botany depar tment  for  the  carry ing out  of  menia l  
tasks  which ass is ted  the  smooth  running of  the  inves t igat ions  made.  
B.L .H.  
-40-
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ANDREWS, F .W.  ,  1945.  Ann.  appl .  Bio  32(1) ,  1 .  
ANDREWS, F .W. ,  1946.  Ann.  Bot . ,  N.S.10,  15 .  
BALDWIN,  I .H.  ,  1923.  Araer .  Jour .  Bot . ,  19,  1 .  
BOYD, A.J .  ,  1921.  Q ' land Agr .  Jour . ,  26 ,  121.  
CHENERY, E .M. ,  1949.  The Soi ls  of  Centra l  Tr in idad.  Rothamstead Exp.  Stn ,  
I larpenden,  England.  (Pr inted  by Gov ' t  Pr in t ing Off ice ,  Tr inidad,  1952)  
COX, J .R. ,  1959.  World  Crops ,  11.(12) ,  435.  
DAVIS,  C.H.  ,  1942 .  PI .  Phys . ,  17 ,  311.  
DAVIES,  P .W.A.  and WINSTANLEY, J . ,  1957.  Trop .  Agr . ,  34,  144 .  
DU PREE2,  W.B. ,  1944 .  Fmg.  S .  .  I f r .  ,  19 ,  11.  
EVANS,  D.C.P.  ,  1954.  D.T.A.  Repor t .  
GRIME,  R.C.  ,  1960.  D.T.A.  Repor t .  
HAGGARTY, R .A. ,  1960.  D.T.A.  Repor t .  
LAWRENCE,  W.J .C.  and NEWELL,  J . ,  1957.  Seed and Pot t ing  Composts .  London;  
George  Al len  and Unwin Ltd .  
LOUSTALOT,  A.J .  and DELGADO, R.F. ,  1948.  Rep.  Agr .  Exp.  S ta .  ,  Puer to  Rico.  
MUZIK,  T .J . ,  1950.  Rep.  Agr .  Exp.  S ta . ,  Puer to  Rico.  
MUZIK,  T .J .  and CRUZADO, H .J . ,  1950.  Rep.  Agr .  Exp.  S ta . ,  Puer to  Rico.  
PALMER, R.D.  and PORTER,  W.K. ,  1959 .  'Weeds ' .  Jour .  Weed S oc.  Amer . ,  7 (4) ,  
481.  
RANADE, S .B.  and BURNS,  W.  ,  1925.  Mem. Dept  Agr .  India . ,  13,  99 .  
ROCIIECOUSTE,  E. ,  1958.  Maur i t ius  Sugar  Ind .  Res .  Ins t . ,  Bul l .10.  
SCAIFE,  M.A. ,  1960.  D.T.A.  Report .  
SMITH,  E.V.  and MAYTON, E .L. ,  1938 .  Jour .  Amer .  Soc .  Agron. ,  30 ,  18 .  
SPARROW, D.M.L. ,  1958.  Pes t  Abst r .  and News Summ. C . ,  4(3) ,  135 .  
U.S.DEFT OF AGRIC. ,  1958.  Agr ic .  Res . ,  7(4) ,  15 .  
WHITE,  P .R. ,  1943.  A Hand book of  Plant  Tissue  Cul ture .  Lancas ter ,  Penn­
sylvania .  Jacques  Cat te l l .  
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Appendix  I I  
( i )  Dis t r ibut ion of  tubers  in  the  soi l  a t  three  s i t es  
S i te  A (4  bor ings)  S i te  B (4  bor ings)  
1  2 3  4  Tota l  1  2 3  4  Total  
0-3"  3  10 0  114 127 0-3"  186 140 66 0  392 
3-6"  0  6  0  11 17 3-6"  80 146 16 9  251 
6-9"  0  6  1  4 11 6-9"  2  19 3  19 43 
9-12"  0  0  0  0  0  9-12"  0 0 0 5  5  
S i te  C (12 bor ings)  
1  2 3  4  5  6  7  8  9  10 11 12 Tota l  
0 -3"  29 1  4 27 16 0  2  9  0  0  0  0  84 
3-6"  1  0 6  21 15 0  1  5 0  0  0  0  49 
6-9"  1  0 0  31 5  0  0  0  0  0  0  0  37 
9-12"  0  0  0  0  1  0 0  0  0  0  0  0  1  
Si te  C bor ings  made on a  square  as  shown below:  
x 4  x 5  x 1  
x 6  x 7  x 8  
X9 xlO x" 
x3 x 12 x2 
( i i )  Calcula t ion for  degree  of  seed se t t ing  
314 f lowerheads  produced in  33 days .  
Assuming hal f  of  th is  number  produces  one  seed ,  then 152 seeds  produced.  
This  occurred on 10 ,000 sq.cms (4  x  2 ,500)  = 1549.8  sq . ins  = 1 0.8  sq . f t .  
Then seeds  per  acre  = 1 5 7  * 4 p T 5 6 °  = 633,233.3  630,000 
10 .  O ~~ 
Therefore  average  seed produced per  acre  per  seed se t  i s  630,000 
(  ii i )  Seed compost  used 
2  par t s  by loose  bulk  medium loam 
1  par t  "  "  "  good peat  
1  par t  "  "  "  coarse  sand 
To each bushel  of  th is  mixture  are  added:  
I f  oz .  superphosphate  (16% P2O5)  
4 oz .  ground l imestone or  chalk .  
N.B.  1  kerosene t in  ho lds  \  bushel  and th i s  measure  was  used in  the  mixings .  
Cfc)  
Appendix  I I I  
Compet i t ion  exper iments  -  Layout  
Lef t  ( looking Nor th) :  
Showing spacing of  pots  
on the  wire  gr ids  and 
degree  of  shade t  hrown 
by the  roof  of  the  p lant  
house .  
M.0.28 *M.F.28 
M.F.O *M .0 .7  
M.F.28 *M.F .0  
M.F.14 *M. 0 .14 
*M.F.28 M.0.14 
M.F.7  M.0.0  
*M.O.28 M.F.7  
*M.O.O M.0.7  
57 to  64 49 to  56 
R.F.O *R.O.7 
R.F.O *R.0.28 
R.F .28 R.F.7  
R.0 .0  *R.F.14 
R.0 .14 *R.0 .14 
R.0 .0  R.F.7  
R.0.28 R.F.14 
R.0 .7  *R.F.28 
25 to  32 17 to  24 
M.0.0  *M. 0 .  7  
M.0.7  *M.0.28 
*M.F .  0  M.0.14 
*M.F.14 *M.F.14 
M.F.28 *M. F .  7  
*M.0.0  M.F.14 
M.F.7  M.0.28 
M.F.O *M.F.14 
41 to  48 33 to  40 
*R.F.14 R.F.  28 
R.0.7  *R.0.28 
R.0.28 *R.F.28 
R.0 .14 *R.F.o  
*R.F .o  R.F.14 
*R.O.O *R.0.0  
; *R .0 .14 *R.  F .  7  
*R.O.7 *R.  F .  7  
9  to  16 1  to  8  
*Taken for  f i r s t  harves t  
R = Radish  
M = Mil let  
F = Fert i l i sed  
0 
= Unfer t i l i sed  
0 
= No tubers  p lanted  
7  = y M »« 
14 = 14 
28 S 28 "  "  
Pot  Numbers  
( reading upwards)  
CD 
( i i i )  Calculat ions  for  amounts  of  fer t i l ise r  to  be  used 
• lecommended ra tes :  5  cwts/acre  Sulphate  of  ammonia  
6  cwts /acre  Superphosphate  
4  cwts /acre  Potass ium sulphate  
An 8"  pot  was  found to  contain  about  8  lbs  of  so i l .  
Enough so i l  was  mixed up to  f i l l  36 po ts  = 288 lbs  of  so i l .  
288 x  453 = 131370 g .  (131400 g .  approx. )  
1  cwt  per  acre  i s  recognised as  a  ra t io  of  1 /20,000.  
.  .  in  amount  of  so i l  mixed equivalent  of  1  cwt  per  acre  = 6 .5  g . /131400.  
Then 5  cwts /acre  Sulphate  of  ammonia  i s  32.5  g .  in  288 lbs  soi l  
6  cwts /acre  Superphosphate  i s  39.0  g .  "  "  "  "  
4 cwts /acre  Potass ium sulphate  i s  26.0  g .  "  "  "  "  
( iv)  Number  of  tubers  per  s t r ing  
Counts  made a t  second harves t  of  mi l le t  exper iment .  Unbroken 
s t r ings  of  more  than th ree  tubers  recorded.  
M.0.7  5 ,8 ,6  
M.0.7  4 ,8 ,5 ,8  
M.0.14 6 ,6 ,8 ,5 ,8 ,5 ,5 ,5 ,5  
M.0.14 5 ,5 ,4 ,4  
M.0.28 5 ,4 ,4 ,6 ,5  
M.0 .28 6 ,5 ,5 ,6 ,5 ,6  
M.F.7  4 ,11,9 ,5 ,6  
M.F.  7  8 ,5 ,7  
M.F.14 14,7 ,4 ,4 ,7 ,6 ,6 ,5  
M.F .14 5 ,6 ,9 ,5 ,5  
M.F.28 5 ,5 ,4 ,4 ,5 ,4 ,5  
M.F.28 7 ,5 ,5 ,5 ,6 ,5 ,5 ,5  
(v)  Rhizome lengths  be tween mature  tubers  
Counts  made on a  select ion of  s t r ings  (measurements  in  inches)  
M.0.7  5 ,4i ,3 i*  
M.0.14 5 ,6 i ,  5-J ,  2 i*  
4 ,3*,4*,5i ,3 j  
M.0.28 4J* ,6 ,7 ,  
5 i ,3f* ,2£*,5 i  
3 j ,7-I,7 j  
M.F.7  
3 ,  3-  ,4  .  ,2> 
5,4 j ,3 i* ,2 |*  
4 ,S i ,5 ,5 |* ,2 |* ,4i ,3 i  
M.F.14 5 | ,7 ,5 |* ,3$*,6  
*Rhizone f rom mother  tuber  
w 
(Vi)  Compet i t ion  exper iment I  (Radish)  Resul t s  (a l l  weights  in  g . )  
A 
* 
* 
* 
•A-
Pot  
i No.  
Pot  
Type 
No .of  
tubers  
Wt of  
tubers  
Mean 
tuber  
wt  
1 No.  of  
nu t -grass  
shoot  s  
Wt of  
shoots  
Mean wt  
of  
shoots  
No.  of  
crop 
leaves  
Wt of  
leaves  
Wt of  
s tem 
Tota l  
P lant  
3  0 .0  - - - - - 54 2 .56 
11 
0.0  - - - - -
i  
52  2 .35 
27 0 .0  - - - - - 53 2 .56 1 .52 4 .08 
29 0 .0  - - - - - 51 2 .79 1 .09 3 .88 
9  0 .7  13 5 .5  9  1 .64 45 2 .06 
24 0 .7  15 7 .0  7  1 .70 
0  .21"  
51 1.96 
15 0 .7  37 13 .5  16 2 .50 48 2 .03 1 .13 3 .16 
25 0 .7  38 17.0  12 4 .02 
' U J  
44  1 .38 0.91 2 .29 
10 0 .14 33 14 .0  29 3 .66 39 1 .34 
20 0 .14 33 17.5  20 3 .82 
U . ID 
40 1 .42 
13 [0 .14 48 25 .5  21 4 .88 38 1 .15 0 .66 1 .89 
28 0 .14 55 28.0  23 5.03 37 1 .02 0 .44"  1 .46 
7  0 .28 49 23.0  44 6 .22 
1 
46 1 .00 
23 0 .28 57 31.5  
~"0.5 .1"  
38  6 .55 40 1 .40 
14 0 .28 88 42.0  O AP 47 7 .44 O 10 37 0 .70 0 .41 1.11 
26 0.28 99 48.5  
. 
36 8 .32 42 1 .16 0 .76 1 .92 
5  IF.O - - - - 65 4 .40 
12 F.O -
" -
- - 65 4 .96 
31 F.O - - - - - 60 4 .11 2 .46 6 .57 
32 F.O - _ - - - - 59 4 .81 3 .54 8 .35 
• 
ic  
1 
1  F.7  21 8 .5  14 2.27 o  ^  1 51  
2 .75 
2  F .7  31 14.0  16 4 .05 54 2 .30 
19 F.7  46 25.0  • .0  so ,  13  4 .90 0  ?o 54 2 .03 1.42 3 .45 
22 F.7  43 19 .5  18 4.17 63 3 .02 2 .10 5 .12 
*t  16  F .  14 27 16 .5  19 3 .85 47 1 .82 
21 F.14 40 22 .0  
• -  U •  J  / '  
22  5 .94 
• "  U.^4 
54 2 .73 
4  F .  14  58 22.5  26 5 .06 -  0  ?? 
59 2 .74 2 .10 4 .84 
18 F.14 57 27 .0  27 6 .76 42 1 .58 1 .38 2 .96 
* 6 F.  28 54 41 .0  
—-O 
50 11 .79 O °1  44 1 .22 
*- 17 F.28 55 33.5  48 8 .30 45 1 .65 
• }  
8 F.28 104 49 .0  0  50 -
39 10.18 -0.24 43 1 .28 0 .72 2 .00 f-
30  F.  28  107 57.0  49 10.53 34 1 .11 0.88 1 .99 
* l s t  Harves t  
LV 
Cvii)  Analys is  of  compet i t ion  exper iment  I  (Radish)  Resul ts  
Total  radish  plant  weight  
F i rs t  harves t  
D.F.  S .S.  M.S.  F .  
Repl ica tes  1  0.16 0 .16 Not  s igni f icant  
Nut-grass  levels  3  11.14 3 .71 36.57 x x x  x = 2 .25 
Fer t i l i ser  levels  1  3.74 3 .74 36.88xxx C.of  V.  =  13 .03 
Nut-grass  x  Fer t i l i ser  3  2 .33 0 .78 7.65 x  S.E.  = 0 .32 
Error  7  0 .71 0 .10 
Tota l  15 18.08 
Second harves t  
Repl ica tes  1  0.05 0 .05 Not  s igni f icant  
Nut-grass  levels  3  33.87 11 .29 14.32XX x  = 3 .44 
Fer t i l i ser  levels  1  15.00 15.00 19 ,03 x x  C.of  V.  =  25 .74 
Nut-grass  x  Fer t i l i ser  3  4.73 1 .58 Not  s igni f icant  S .E.  = 0 .89 
Error  7  5 .52 6 .79 
Tota l  15 59.16 
Both  harves t  per iods  
Repl ica tes  1  0 .19 0 .19 Not  s igni f icant  
Nut-grass  levels  3  41 .91  13.64 37.10XXX 
Fer t i l i ser  levels  1  16.86 16 .86  45.88 x x x  x 2 .89 
Harves t ing t ime 1  11.46 11.46 31.18XXX C.of  V = 20 .17 
Nut-grass  x  Fer t i l i ser  3  6 .68 2 .23 6 .06 x x  S.E.  = 0 .61 
Nut-grass  x  Harves t ing 3  3 .10 1 .03 Not  s igni f icant  
Harves t ing x  Fer t i l i se r  1  1.88 1.88 5.11 x x  
Error  18 6 .62 0 .37 
Tota l  31 
Radish  leaf  weight  
Repl ica tes  1  0.01 0 .01 Not  s igni f icant  
Nut-grass  levels  3  13.83 4 .61 18.28 x x x  x 2 .09 
Fer t i l i ser  levels  1  3.89 3 .89 15 .39 x x  C. of  V.  =  20.98 
Nut-grass  x  Fer t i l i se r  3  1 .19 0 .40 Not  s igni f icant  S .E.  = 0 .50 
Error  7  1 .77 0 .25 
Tota l  15 20 .69 
(!?) 
Radish  leaf  number  
D.F.  S .S .  M.S.  F .  
Repl ica tes  1  3 3  N.S.  
Nut-grass  levels  3  12,24 408 18 .55 x x x  
Fer t i l iser  levels  1  464 464 21 .09 x x x  
Harvest ing t ime 1  24 24 N.S 
Nut-grass  x  Fer t i l iser  3  159 53 N.S.  
Nut-grass  x  Harves t ing 3  32 11  N.S.  
Fer t i l i ser  x  Harves t ing 1  2 2  N.S.  
Error  18 397 22 
Total  31 2305 
Nut-grass  tuber  number  
Repl icates  1  70 70 N.S.  
Nut-grass  leve ls  2  9599 4800 223.2 ,6 X X X  
Fer t i l ise r  levels  1  330 330 15 .35  x x x  
Harvest ing t ime 1  4845 4845 225.  36 x x x  
Nut-grass  x  Fer t i l i ser  2  52 26 N.S.  
Nut-grass  x  Harves t ing 2  638 219 10.19 x x  
Fer t i l i ser  x  Harvest ing 1  5 5  N.S.  
Error  13 279 21.5  
Tota l  23 
x  =50.8  
C.  of  V.  =  9 .13 
S .E.  = 4 .64 
Mean t uber  weight  
Nut-grass  levels  2  122 61 N.S.  
Fer t i l iser  levels  1  29 29 N.S.  
Harvest ing t ime 1  43 43 N.S.  
Error  7  199 28.4  
Tota l  11  393 
x  = 0 .49 
C.  of  V.  =  13.58 
S.E.  = 0 .053 
Mean nut -grass  shoot  weight  
Nut-grass  levels  2  26 13  N.S.  
Fer t i l i ser  levels  1  48 48 8 .617 x  
Harvest ing t ime 1  40 40 7 .181 x  
Error  7  39 5 .57 
Tota l  11  153 
x  = 0 .22 
C.  of  V.  = 1 0 .97 
S.E.  = 0 .024 
IS) 
Cvii i )  Compet i t ion  exper iment  I I  (Mil le t )  Resul ts  (a l l  weights  in  g . )  
* 
* 
* 
Po 
No 
t  Pot  
.  Type 
No.  of  
tubers  
Wt of  
tubers  
Mean 
tuber  
wt  
No.  of  
nut -grass  
shoots  
Wt of  
shoots  
Mean wt  
of  
shoot  s  
J No.  of  
crop 
le  aves  
No.  of  
c rop 
plants  
Wt of  Plant  
ears  wt  
Tota l  
p lant  
wt  
43  0 .0  - - - - 95 14 5 .07 
•J 57  0 .0  - - - - _ 98 14 5 .04 
48 0 .0  - - - - - 75 14 4 .76 6 .27 11 .03 
51 0 .0  - - - - - - 68 14 2 .90 11.55 14 .45 
40 0 .7  26 17.0  
0 .70 13 3 .8  0  36 8  0 .37 
55 0 .7  25 18 .5  13 3.8  85 14 2 .15 
47 0 .7  46 30.0  15 3 .72 53 14 2 .11 2 .32 4 .43 
49 0 .7  38 24.0  14 2 .33 58 14 3 .43 4 .13 7 .56 
37 0 .14 44 21.5  21 4 .61 85 14 1 .13 
53 0 .14 41 21 .0  24 4 .81 85 14 1 .73 
38 0 .14 77 40 .5  O ^A 25 4 .84 57 14 2 .15 2 .09 2 .32 
52 0.14 77 42.0  25 5 .14 66 14 1 .03 1 .29 2 .32 
39 0 .28 76 42.5  40 7 .73 33 11 0 .11 
58 0 .28 71 36 .0  42 7 .38 72 13  1 .05 
34 0 .28 123 63.5  0  *i7  50  7 .66 0  17 57 14 0 .79 0 .90 1 .69 
64 0 .28 120 75 .0  44 8 .00 47 13 1.06 1 .45 2 .46 
46 F.O - - _ - - - 107 14 10.09 
* 54 F.O - - - - - - 114 14 9 .11 
41 F.O - - - - - - 87 14 8 .19 17.12 25 .31  
k 
it 
63 F.O.  - - - - - - 63 14 8 .91 12.39 21 .30 
36 F .  7  33 20.0  
0  *51 - 18 
4 .76 0  °5  76 14 2 .26 
50 F .  7  42 18 .5  17 3 .97 108 14 7 .95 
42 F .  7  51 22.5  
—O 7  J  
16 3 .30 
• 0  
57 14 4 .25 6 .49 10.74 
59 F .7  53 37.0  15 4 .01 44 14 3 .27 6 .24 9.51 
33 F.  14 47 23.5  
—0 57- .  
25  4 .71 
.. .  0  21 
84 14 1 .94 
45 F .  14 49 31.0  28 6 .61 77 13  1 .58 
35 F .  14 90 52.0  O 57- 27 6 .66 • 0  "M 66 14 2 .77 3 .69 6 .46 
61 F .14  75 42.0  25 5 .56 37 14 2 .65 2 .46 5.11 
it 56 F .28 72 40.0  50 9 .13 O 20 
55 12 0 .29 
60 F  .28  99 55 .5  50 10.96 74 14 1.07 
44 F .28 135 79.5  54 10 .50 • 0  °0  • 40  11  0 .58 0 .63 1 .21 
62 F .28 136 76.5  44 |  9.44 51 11 0 .35 0 .44 0 .79 
*  1s t  Harves t  
(IV 
( ix)  Analys is  of  compet i t ion  exper iment  I I  (Mil le t )  Resul t s  
Tota l  Mil le t  p lan t  weight  
F irs t  harves t  
D.F.  S .S.  M.S.  F .  
Repl ica tes  1  4.43 4 .43 N.S.  
Nut-grass  level s  3  104.87 34 .96 16 .52 x x  
Fer t i l i ser  levels  1  19.45 19.45 9  .19 x  
Nut-grass  x  Fer t i l i ser  3  16.11 5 .37 N.S.  
Error  7  14.81 2 .12 
Tota l  15 159.67 
x  
C.  of  V.  
S .E.  
3 .18 
45 .75 
1 .46 
Second harvest  
) Repl icates  1  0.16 0 .16 N.S.  
Nut-grass  levels  3  616.94 205.65 63 .61 x x x  
Fer t i l i ser  leve ls  1  64 .84  64 .84  20 .05 x x  
Nut-grass  x  Fer t i l i ser  3  71 .15  23.72 7 .33 x  
Error  7  22 .63 3.23 
Tota l  15 775.73 
x  
C.  of  V.  
S .E.  
= 8 .04 
= 22 .37 
= 1 .80  
Both harvest  per iods  
> 
Repl ica tes  1  1.45 1  .45 N.S .  
Nut-grass  levels  3  615.08 205 .03  67.07*** 
Fer t i l i ser  levels  1  77.78 77 78 25 ,44 x x x  
Harvest ing t ine  1  188.52 188 52 61.67 x x x  
Nut-grass  t  Fer t i l iser  3  72.67 24 .23  7 .9  2X X  
Nut-grass  k Harvest ing 3  106 .73 35 58 11 .  64 x x x  
Harvest ing x  Fer t i l i ser  1  6.67 6  67 N.S.  
Error  18 55.02 3  06 
Tota l  31 1123.92 
x  = 5 .61 
C.  of  V.  =  31 .16 
S .E.  = 1 .75 
Mil le t  head weight  
Repl ica tes  
Nut-grass  levels  
Fer t i l i ser  levels  
Nut-grass  x  Fer t i l i ser  
Error  
1  
3 
1  
3 
7  
0 .26 
65.28 
10.22 
14 .48  
3 .76 
0 .26 
21.76 
10 .22 
4 .83 
0 .54 
N.S.  
40.48 x x x  
19.02 x x x  
8.98 x x  
Total  15 94 .00 
x  = 3 .07 
C.  of  V.  = 23 .89 
S .E.  = 0 .73 
as 
Mille t  leaf  number  
D.F.  S .S .  M.S.  F .  
Repl ica tes  1  220 220 N.S .  
Nut-grass  leve ls  3  5049 1683 8 .09 x x  
Fer t i l i ser  levels  1  153 153 N.S.  
Harvest ing t ime 1  4005 4005 19.26 x x x  
Nut-grass  x  Fer t i l iser  3  473 158 N.S.  
Nut-grass  x  Harves t ing 3  476 159 N.S .  
Fer t i l i ser  x  Harvest ing 1  631 631 N.S.  
Error  18 3743 208 
Total  31 14750 
x  = 69 .06 
C.  of  V.  = 16 .46 
S.E.  = 14.42 
Nut-grass  tuber  number  
Repl ica tes  1  2 2  N.S.  
Nut-grass  l evels  2  17215 8608 193.44 x x x  
Fert i l i ser  levels  1  580 580 13.0  3 X X  
Harvest ing t ime 1  6534 6534 146.83 x x x  
Nut-grass  x  Fer t i l i ser  2  60 30 N.S .  
Nut-grass  x  Harves t ing 2  1129 565 12 .69 x x x  
Fert i l i ser  x  Harves t ing 1  0 0  N.S.  
Error  13  578 44.5  
Total  23 26098 
x  = 68 .58 
C.  of  V.  = 9 .73 
S.E.  = 6 .67 
Mean tuber  weight  
Nut-grass  l eve ls  2  80 40 N.S .  
Fer t i l iser  levels  1  7 7  N.S.  
Harves t ing t ime 1  14 14 N.S.  
Error  7  22,8 33 
Tota l  11 329 
x  = 0 .57 
C.  of  V.  =  10 .10 
S.E.  = 0 .057 
Mean nut -grass  shoot  weight  
Nut-grass  l evels  2  66 33 7 .5 X  
Fert i l i ser  levels  1  3 3  N.S.  
Harves t ing t ime 1  7 7  N.S.  
Error  7  31 4 .4  
Tota l  11  107 
x  = 0 .21 
C.  of  V.  = 9 .94 
S .E.  = 0 .021