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THE  TROPICAL  AGRICULTURIST. 
[Nov.  2,  1896, 
we  are  not  just  now  in  a position  to  disclose, 
became  possessed  of  a number  of  n'cpresentative 
analyses  of  the  soils  of  the  diilercnt  cotTee  districts 
of  South  India.  Having  liad  some  experience  with 
scientilie  English  agriculture,  the  marked  dillerence 
between  the  nature  of  the  Indian  and  English  soils 
at  once  struck  his  attention.  Apart  from  the 
fact,  now  generally  known,  of  their  great  poverty 
in  i)laut  food,  he  noted  that  almost  one  and  all  were 
also  markedly  deficient  in  the  jjroperty  of  allowing 
the  free  ])assage  of  atmospheric  air  within  their  pores. 
Nor  was  this  difficult  to  understand,  as  the  propor- 
tion of  their  harmful  iron  and  ahmiina  constituents 
was  unusally  great.  The  importanee  of  this  may 
not  be  at  first  sight  apparent  to  the  ordinary 
reader,  hut  it  is  simple  enough  in  reality.  The 
roots  of  plants  cannot  thrive  without  a free  supply 
of  oxygen  ; and  in  fact,  experiments  have]  demons- 
trated beyond  fpiestion  that  oxygen  is  an  essential 
of  the  life  of  plant-roots  ; depriveil  of  this  element, 
they  inv.ariably  die,  though  furnished  with  abun- 
dance of  all  other  neeessaries  to  their  well-being. 
Now  there  are  certain  forms  of  iron  that  have  a 
great  .affinity  for  o.xygen,  .and  it  is  in  this  h.armful 
form  that  by  far  the  greater  proportion  of  the  iron  in 
our  coffee  soils  is  found.  To  p>it  it  plainly,  the  iron 
in  our  soils  is  unrusted,  and  until  it  has  rusted  is  na- 
turally a great  absorber  of  oxygen.  For,  as  every- 
one knows,  rust  is  merely  a combination  of  iron  .and 
oxygen.  Here  it  will  be  seen  that  we  have  two 
rivals  for  oxygen  in  the  soil : the  plant  roots 
and  the  unrusted  iron,  and  the  metal  being  the 
stronger  of  the  two,  the  roots  are  starved  of 
their  great  essential  and  consequently  the  plant 
cannot  thrive.  Thus  far  it  is  very  clear  and 
simple,  but  the  matter  does  not  end  here. 
Another  essential  to  plant  life  is  nitrogen,  and  it 
is  well  known  that  this  element  cannot  be  taken 
up,  except  by  legumes,  in  its  free  state.  The 
manner  in  which  such  plants  as  coffee  take  it  up 
is  in  the  1‘eady  digested  form  of  nitrates.  Nitrates 
are  formed  by  the  action  of  certain  bacteria  wliich 
live  in  the  soil,  nitrates  being  the  vegetable 
matter  in  the  .soil  that  h.as  (after  jjassing 
through  certain  processes)  been  absorbed  by 
them  and  passed  out  in  the  ordinary  course  of 
nature.  These  bacteria  are  living  organisms 
and  they  cannot  do  without  oxygen.  It  is  easy 
to  see,  therefore,  that  in  soils  where  large 
(piantities  of  unrusted  iron  take  up  the  bulk  of 
the  oxygen  these  unhappy  bacteria  cannot  thrive, 
and  n.aturally  can  do  but  very  little  to  con- 
vert the  dead  nitrogenous  matter  into  food  avail- 
able to  plants.  In  agriculture  at  home  this  has 
been  recognised  for  ages  past,  and  through 
tillage  has  got  to  be  looked  upon  as  one  of  the 
first  essentials  to  achieve  success.  The  condi- 
tions that  obtain  in  plantation  culture  un- 
happily do  not  allow  thi.s-  to  be  carried  out 
with  any  attempt  at  completeness,  so  that  the 
malign  inlluences  of  the  .airless  soils  are  left 
almost  unchecked.  This  is  not  all.  The  v.alu- 
able  nitrates  are,  as  we  .all  know,  extremely 
soluble,  and  therefore  are  washed  out  of  the  soil 
in  huge  qu.antities  by  every  heavy  rain.  Now 
iron  in  its  unrusted  form  effects  a combination 
with  nitrates  th.at  is  es|)ecially  soluble  and 
liable  to  be  e.asily  carried  aw, ay  by  r.ain.  But 
when  duly  exposed  to  the  .air  .and  sufficiently  rusted 
it  forms  a combination  chat  can  resist  in 
great  measure  the  washing  effects  of  even  tropi- 
cal rain  ball. 
Knowing  all  this — which  has  been  set  forth 
here  for  those  unfamiliar  with  the  subject — our 
inve.stigator  fell  to  considering  the  matter  further. 
If  the.se  soils  can  neither  manufacture  nor  retain 
nitrates  in  sufficient  quantities,  the  coffee  grow- 
ing therein  must  suffer  from  want  of  nitrogen. 
If  so,  the  an.aly.sis  of  the  sap  would  undoubtedly 
show  this.  Analyses  were  therefore  made  of  sap 
from  trees  grown  respectively  in  soils  poor  in 
.air  and  consequently  in  nitrates,  and  also  from 
trees  grown  in  rich  well-aer.ated  soils.  The  re- 
sults were  striking.  In  the  first  c.ase,  the  .analysis 
revealed  a woeful  deficiency  in  the  necessary  com- 
])ounds  of  nitrogen  ; in  the  latter  an  abundance 
of  these  indispensable  constituents  was  [found. 
To  be  successful  in  its  attacks,  disease  must,  as 
a very  general  rule,  find  a.ssistance  in  the 
weakened  constitution  of  its  victim.  Coffee  trees 
whose  saji  is  poor  in  nitrogen  are,  and  must  be, 
delicient  in  vital  power,  consequently  easy  vic- 
tims to  the  fell  apijro.aches  of  the  germs  of  leaf- 
disease.  To  support  this  further,  the  sap  of 
leaf-dise,ased  trees  w.as  foiind  to  be  extremely 
poor  in  nitrogen,  and  the  same  state  was  re- 
vealed in  the  soils  from  which  it  was  drawn. 
Clearly  then,  there  is  shown  to  be  a most  striking 
and  close  connection  between  the  physic.al  and 
chemical  conditions  of  the  soil  and  the  constitu- 
tion of  the  plants  growing  therein,  and  therefore 
between  the  soil  and  leaf-disease. 
To  sum  up  briefly,  leaf-di.sease  attacks 
weakened  and  unhealthy  trees  (as  shown  by  after- 
effects of  heavy  cropping)  far  more  severely  than 
those  of  a robust  and  vigorous  constitution. 
Coffee  cannot  remain  in  full  vigour  without  an 
abundance  of  nitro-carbons  in  its  sap.  These 
compounds  of  nitrogen  must  be  derived  from 
nitrates  in  the  soil.  Nitrates  cannot  be  formed 
without  the  action  of  bacteria  on  vegetable  matter 
in  the  soil.  These  bacteria  cannot  thrive  without 
an  abundance  of  oxygen.  The  majority  of  our 
Indian  coffee  soils  contain  a very  large 
proportion  of  unrusted  iron,  which  is  a most 
greedy  absorber  of  oxygen.  To  reverse  the  ai'gu- 
ment.  Naturally  the  want  of  oxygen  results  in 
a lack  of  bacteria  ; without  bacteria  nitrates 
cannot  be  formed  ; owing  to  hack  of  nitrates 
the  sap  of  the  coffee  tree  is  deficient  in 
nitro-carbons  ; as  a result  of  this  again 
the  vigour  of  the  tree  is  impaired,  and  thus 
can  i)resent  no  effectual  resistance  to  the 
attacks  of  the  everpresent  germs  of  le.af-disease. 
-Q.  E.  D. 
Such  is,  in  brief,  the  theory  of  the  relation 
between  assimilable  nitrogen  and  leaf-disease, 
which  we  hope  very  shortly  to  publish  in  all 
detail.  Some  of  our  j)ractical  re.aders  may  demur 
at  the  import.ance  we  have  attached  to  the  above: 
what  benefit  can  be  derived  from  knowing  the 
cause  of  the  dise.ase  without  being  told  the 
cure  ? Let  these  doubters  be  patient : on  the 
correct  diagnosis  of  a disease  depends  altogether 
the  success  of  the  tre.atment  applied.  Once  the 
true  cfuise  of  le,af-disease  is  fully  demonstrated, 
the  cure  will  follow  as  a matter  of  course  and 
certainty. — Plantiiuj  Opinion,  Sept.  12. 
ITiOSFECTS  OF  INDIAN  TEA. 
The  rapid  strides  that  have  recently  been  made 
in  the  consumption  of  Indian  tea  in  America  and 
Australia  would  seem  to  justify  the  assumption  that 
the  conversion  of  our  cousins  to  a taste  for  our  teas 
will  not  take  a tithe  of  the  time  which  elapsed  ere 
the  average  of  .'ilb.  per  head  of  the  population  of 
Groat  Britain  was  reached.  It  must  be  remembered 
that,  with  the  exception  of  the  outturn  of  the  Assam 
Company,  no  Indian  teas  worth  mentioning  were  put 
upon  the  London  market  until  1802,  and  certainly 
they  were  not  calculated  to  recommend  themselves  to 
