76 
THE  TROPICAL  AGRICULTURIST. 
[Aug.  I,  1895. 
of  nitrogen,  equal  to  25  per  cent,  ammonia.  This 
IS  the  most  concentrated  of  all  nitrogenous  manures 
and  is  very  soluble  in  water. 
Pota^.siiiiH  Nitrate. — This  is  a compound  of  potash 
and  nitric  acid,  and  usually  contains  13  per  cent. 
Of  nitrogen,  equal  to  Iti  per  cent,  ammonia  It  also 
contains  about  45  per  cent,  of  potash  It  is  a very 
valuable  manure.  Any  gardener  can  incre.ase  the 
supply  by  the  following  process: — Make  a compost 
heap  cjf  vegetable  matter,  such  as  garden  refuse, 
and  mix  with  it  a fair  proportion  of  wood  ashes 
and  lime.  The  wood  ashes,  which  are  rich  in  potash, 
can  be  obtained  by  burning  all  fruit  tree  primings 
and  hedge  tr’iinmings  The  lime  added  helps  to 
decompose  the  organic  matter  and  liberate  the 
nitrogen,  which  then  chemically  combines  vviih  the 
lime  ; but  another  change  takes  place  by  which  the 
nitrogen  leaves  the  lime  and  combines  with  the 
potash,  thus  forming  potassium  nitrate.  The  com- 
post heap  must  be  frequently  turned  so  that  all 
parts  become  thoroughly  oxidised. 
Hodinni  Nitrate. — This  is  a compound  of  soda  and 
nitric  acid,  and  contains  about  15  joer  cent,  of  nitrogen, 
equal  to  13  per  cent,  ammonia.  It  is  very  soluble 
in  water,  o.ud  contains  its  nitrogen  in  a form  that 
can  be  immediately  appropriated  by  plants. 
I'criivian  Guano. — This  manure  varies  from  1 to 
12  per  cent,  of  nitrogen.  It  is  a more  general  manure 
than  the  preceiiug,  as  it  contains  nitrogen  in  three 
forms.  1,  As  organic  nitrogen  ; 2,  ammonia  ; 3, 
nitrates,  and  is,  therefore,  a more  lasting  manure. 
Itried  Blood. — Blood  contains  nitrogen  equal  to 
from  12  to  16  per  cent,  ainmu'ia,  but  it  is  s'ower 
in  action  than  any  of  the  above  manures,  as  it  has 
to  undergo  decomposition  before  it  is  available  as 
plant  f-iod. 
Full  Guano — This  is  also  a slow  acting  manure. 
It  contains  nitrogen  equal  to  from  8 to  10  per  cent, 
ammonia. 
Farini/ard  Manure. — This  is  Ihc  most  general  of 
all  manures.  One  ton  contains  from  3 to  15  lb.  of 
nitrogen,  besides  other  val  .able  manurial  ingredients, 
such  as  potash  and  phosphoric  acid. 
Animcd  Urine. — One  ton  of  this  from  horse  stables 
contains  36  lb.  of  nitrogen  ; from  cows,  30  lb.  ; and 
from  she  p,  38  lb.  Most  gardeners  can  get  a good 
supply  of  stable  manure,  and  many  persons  have 
noticed  the  black  streams  draining  away  from  i^  If 
the  \alueof  the  fertilising  ingredients  of  this  liquid 
contain  was  better  known  it  would  not  be  allowed 
to  waste  as  it  does.  This  is  the  analysis  of  it  in 
100  parts.  Water,  82  per  cent.,  and  dry  subslaucr 
18  per  cent.  The  dry  substanca  is  made  up  as 
follows  : — 
Ash 
10'7 
Magnesia 
. 0 4 
Nitrogen 
. . 1.5 
Phosphoric  acid 
. OT 
Potash  . . 
4-3 
Sulphuric  acid 
. 0-7 
Lime 
U-3 
Silica 
. 0 2 
It  will  be  sem  by  this  analysis  that  the  liquid 
contains,  in  addition  to  nitrogen,  live  of  the  mineral 
ingredients  that  are  essential  for  the  production  of 
a healthy  growing  plant  ; the  one  not  mentioned 
is  iron,  but  plants  only  require  a trace  of  this 
ingredient.  And  it  is  us'ually  present  in  soils.  It 
must  be  borne  in  mind  that  all  the  manures  men- 
tioned, except  the  sodium  nitrate,  the  potassium 
nitrate,  and  part  of  the  Peruvian  guano  had  to 
undergo  a process,  next  lo  be  dealt  with,  before 
they  can  become  available  as  plant  food. 
Nitrification. — This  is  effected  in  the  soil  by  two 
micro-organi.sms  (Bacteria).  The  first,  known  as  the 
nitrous  organism,  converts  ammonia  into  nitrous 
acid;  the  second,  the  nitric  organism,  converts  the 
nitrous  acid  into  nitric  acid. 
Carbon  as  organic  matter  must  be  present  for  the 
existence  of  these  micro-organisms.  Air,  heat,  and 
moisture  are  the  three  tilings  that  promote  nitrifi- 
cation. It  is  very  feeble  at  a temp,  of  10°  P.,  and 
ceases  ot  32°  F.  It  is,  therefore,  necessary  that  the 
soil  fhould  be  well  drained.  If  the  soil  is  water- 
logged the  air  is  shut  out,  and  nitrification  ceases, 
the  nitrates  present  becoming  denitrified,  with  the 
result  that  the  nitrogen  is  set  free.  We  must  under- 
stand that  nitrification  takes  pl.acc  exactly  the  same 
ju  the  soil  of  the  smallest  pot,  under  the  gardener's 
care,  as  it  does  in  any  prepared  border,  or  in  the 
open  field.  If  the  soil  in  pots  become  waterlogged 
nitrification  ceases,  and  if  allowed  to  remain  long 
in  this  condition  the  roots  will  perish. 
yirtstc  Condition  0/' soils. — Sufficient  lime  and  potash 
must  be  present  as  carbonates  or  sulphates  for  the 
nitrates  when  formed  to  combine  with,  nitrate  of 
lime  and  nitrate  of  pota-h  then  being  formed,  and 
these  are  the  tw'o  sources  from  which  all  plants 
obtain  their  nitrogen  from  the  soil.  If  any  soil  is 
not  in  a good  basic  condition  it  cannot  be  fertile. 
I/oir  Plants  Obtain  Their  Nitroffen. — The  dry  sub- 
stance of  plants  usually  contain  from  2 to  3 per 
cent,  of  nitrogen,  and  they  all  (except  the  leguminous 
plants)  obtain  it  from  the  soil  principally  as  nitrates. 
Borne  gardeners  still  favour  the  idea  that  the  foliage 
of  pla'  ts  has  the  power  of  absorbing  nitrogen  as 
ammonia  from  the  a r,  but  the  most  eminent 
botanists  in  England  and  on  tlm  Contine  t have 
concluded  that  the  quantity  obtained  by  plants  in 
this  way  is  so  small  as  not  to  be  worth  consider- 
ing. We  may  deduce  from  this  that  damping  down 
houses,  when  closing  in  the  afternoon,  with  liquid 
manure,  as  practised  by  some  gardeners,  does  not 
benefit  t e plants  so  much  as  they  think.  Some, 
however,  consider  that  the  fumes  of  ammonia  are 
injurious  to  red  spider  and  oth“r  insect  pests. 
Le</uininous  Plants. — Peas,  Beans,  and  Clover 
belong  to  th’s  family’.  These  p'ants  have  some 
power,  not  yet  properly  understood,  of  absorbing 
the  free  nitrogen  from  the  atmosphere,  I r.  Paul 
Sorauer,  in  his  popular  treatise  on  the  “ Physiology 
ot  riauts  ” (1895),  says  “ As  far  as  our  scientific 
knowledge  goes,  the  leguminous  plants  can  subsist 
on  the  1 itrogen  they  take  from  the  atmosphere, 
while  cereal  crops,  fruit  trees,  and  indeed  all  other 
phanerogams,  must  obtain  this  substance  in  some 
soluble  form  from  the  soil.  Nitrates  seem  to 
he  the  most  suitable  form  of  salt  from  which  plants 
obtain  their  nitrogen.  Ammonia,  which  can  pro- 
bably be  absorbed  in  minute  quantities  even  in  a 
gaseous  state,  is  less  suitable.  ” It  is  a fact  that 
leguminous  plants  can  be  grow'n  in  a soil  devoid 
of  nitrogen.  These  plants  do  not  rob  the  soil  of 
this  clement,  but  act  as  purveyors  of  it  to  the  soil. 
117///  is  Good  J.oani  so  Ualnahle  f — The  first 
3 inches  of  an  old  well-drained  pasture  is  full  of 
nitrogen,  in  three  forms — nitrates,  ammonia,  a’jd 
organic  matter.  The  first  Pinches  of  soil  in  1 acre, 
if  weighed  when  dry  and  all  roots  removed,  wouid 
contain  about  2,250,000  lb.  of  soil.  At  0 10  per  cent, 
of  nitrogen  this  quantity  of  soil  would  therefore 
contain  2250  lb.  ; but  the  turf  we  use  for  potting 
has  all  the  roots  in  it,  and  these  by  their  decom- 
position yield  a targe  supply  of  nitrogen.  Clove 
being  a leguminous  plant,  greatly  increases  the 
nitrogen  in  a pasture. 
J/oic  is  the  Nutrition  of  Tut  Plants  Fjlected  f — The 
various  comp.osts  we  use  for  potting  purposes  should 
contain  sufficient  food  for  the  growth  of  the  plants; 
but  the  food  in  the  richest  soil  can  only  last  for 
a short  time  in  the  limited  space  of  a pot,  and 
therefore  we  should  try  to  make  the  best  of  the 
soil,  it  is  a common  practice  wheu  sifting  soil  to 
throw  but  the  lumps  of  turf  that  will  not  pass 
through  the  sieve.  This  is  a great  mistake.  These 
lumps  should  be  rubbed  through,  as  their  decay 
greatly  increases  the  supply  of  nitrogen  to  serve  as 
plant  food. 
When  the- soil  in  pots  is  getting  exhausted  the 
plants  cease  to  grow  vigorously,  the  foliage  becomes 
pale,  and  the  plants  is  weak  in  the  growing  point. 
We  must  now  supply  it  with  food.  Soluble  ariificiai 
manures  are  generally  used  where  good  liquid 
manure  cannot  be  obtained.  Great  care  should  bo 
taken  not  to  overfee  ’.  as  this  encourages  rank 
growth;  young  tissues  are  built  up  too  fast;  the 
plants  are  not  well  matured,  aud  when  in  this 
CO  dition  arc  more  liable  to  prevalent  diseases. 
Dr.  Sorauer  says  that  “ the  majority  of  diseased 
plants  ho  received  from  gardeners  was  the  result 
of  overfeeding.  ” 
I iiave  us/’d  tons  of  chemical  manure,  and  from 
practical  experience  I find  it  better  to  under  than 
over-feed,  If  wo  wish  to  keep  our  plants  healthy 
