April  29,  1897. 
JOURNAL  OF  HORTICULTURE  AND  COTTAGE  GARDENER. 
367 
calculations,  yet  much  in  [this  direction  has  been  ascertained  by  Prof. 
Bernard  Dyer  (“  On  the  Analytical  Determination  of  probably  Avail¬ 
able  Mineral  Plant  Food  in  Soils.”  Messrs.  Harrison  &  Sons,  St.  Martin’s 
'Lane,  London.)  _ 
A  soil  analysis,  therefore,  is  not,  as  at  first  sight  appears,  a  definite 
determination  of  the  needs  of  that  sample  for  chemical  fertilisers.  When 
analysed  some  soils  are  shown  to  contain  enough  plant  food  for  many 
crops,  yet  the  yield  on  such  soils  has  been  doubled  by  the  supplying  of 
a  few  pounds  per  rod  or  cwts.  per  acre  of  chemicals.  Thus,  though  the 
total  quantity  of  plant  food  present  was  large,  the  amount  of  available 
available  elements  in  the  soil,  for  the  increase  is  greater  than  could  nave 
been  caused  by  the  added  chemicals  alone.  The  impression  is  that 
chemicals  act  as  Btimulants,  but  the  term  is  inapplicable  to  plants,  for 
nitrates,  sulphates  and  phosphates  supply  food  ;  hence  it  is  a  matter  of 
feeding,  and  a  substantial  dietary  of  nitrogen,  phosphoric  acid  and 
potash,  with  proper  conditions  of  heat  and  moisture,  enable  plants  to 
make  extra  growth  and  cause  them  to  make  use  of  otherwise  unavailable 
plant  food  in  the  soil.  _ 
There  is  another  side  to  this  question — that  of  the  action  of  chemicals 
on  the  soil  constituents  and  on  the  plant.  As  regards  sodium  or  soda. 
Fig.  75— LYCASTE  SKINNERI. 
nutriment  was  shown  to  be  practically  small.  If  the  soil  be  deficient  in 
*»ny  one  element  an  analysis  wil1  show  it  ;  but  when  it  indicates 
•an  abundance  of  plant  food  there  is  still  question  as  to  its  available 
fertilitv 
Turfy  >loam, '4'with  additions  of  horse  droppings,  decayed  manure,  or 
leaf  soil,  even  heavily  manured  fields  or  gardens,  will  show,  on  analysis, 
enough  plant  food  to  grow  a  prodigious  crop,  yet  the  tardy  growth  of 
•  plants  in  such  soils  demonstrates  that  but  a  small  proportion  is  available  ; 
while,  on  the  other  hand,  if  a  Bmall  amount  of  readily  available  plant 
food  jis  supplied  it  enables  the  plants  to  make  use  of  some  of  the  partially 
to  which  weiwill  now  confine  our  remarks,  we  have  it  both  in  the  soil 
and  plant  as  nitrate,  sulphate,  chloride,  and  carbonate.  These  are  all 
commercial  substances,  and  owe  their  value,  from  a  chemist’s  point  of 
view,  for  manorial  purposes  to  the  element  with  which  the  sodium  is 
combined.  Nitrate  of  soda  is,  therefore,  the  most  important  from  this 
standpoint  as  supplying  nitrogen  to  the  plant.  What  is  the  soda  to  the 
soil  ?  Does  it  accumulate  therein  to  the  prejudice  of  crops  from 
consecutive  applications?  and,  if  so,  what  is  the  substance  to  apply  to 
afford  the  needful  relief?  Here  we  have  the  sodium  of  the  chemist, 
which  is  not  a  plant  food.  But  the  chemist  is  prepared  for  contingencies, 
and  in  cases  of  prejudicial  isoil  alkalinity  from  abuse  of  nitrate  of  soda 
