and  Subsoils  of  some  of  the  Fields  at  Rothamsted.  363 
the  different  condition  of  land  in  March  after  a wheat  and 
after  a clover  crop,  will  be  found  in  Table  III.  (Nos.  11,  12)  ; 
the  comparison  is,  however,  not  perfect,  as  the  clover  land 
had  been  ploughed  the  preceding  October,  while  the  wheat- 
stubble  was  untouched.  The  clover  land  yielded  38'9  lbs.  of 
nitrogen  as  nitrates  in  the  first  27  inches,  and  the  wheat  land 
only  14  5 lbs. 
The  evidence  relating  to  the  amount  of  nitrates  in  the 
different  soils  seems  to  point  to  the  conclusion  that,  in  the  case 
of  cereal  crops,  the  nitrates  of  the  soil  are  a sufficient  source  of 
the  nitrogen  of  the  crops.  Can  the  same  be  said  with  regard 
to  beans  or  clover?  That  these  crops  do  assimilate  nitrates  in 
considerable  quantity  is  sufficiently  established.  A good  crop 
of  red  clover  may,  however,  in  land  in  favourable  condition,  but 
without  the  direct  application  of  manure,  yield  from  seed  sown 
in  the  spring  of  the  previous  year,  hay  containing  200  lbs.  of 
nitrogen  per  acre,  and  also  leave  much  nitrogenous  crop-residue 
in  the  surface-soil.  Again,  the  Bokhara  clover,  grown  in  Hoos 
Field,  in  a soil  on  which  red  clover  had  frequently  failed, 
yielded,  during  five  successive  years,  1878-82,  without  any 
application  of  nitrogenous  manure,  an  average  of  about  93  lbs. 
of  nitrogen  per  acre  per  annum.  These  quantities  much  exceed 
the  amounts  which,  according  to  our  present  knowledge,  can  be 
furnished  by  nitrates  in  the  soil.  Our  information  as  to  the 
amount  of  nitrates  available  in  the  lower  layers  of  the  subsoil 
is,  however,  as  yet  very  limited.  On  this  point  it  may  be 
stated  that  determinations  made  in  samples  collected  this  year 
(1883)  to  the  depth  of  108  inches  in  the  white-clover  soil,  have 
shown  more  than  50  lbs.  of  nitrogen  as  nitrates  per  acre  below 
45  inches  of  depth.  On  the  other  hand,  adjoining  land  in 
fallow,  which  had  been  alternately  wheat  and  fallow  without 
manure  for  about  30  years,  showed  less  than  20  lbs.  in  the 
corresponding  layers.  The  question  obviously  arises  whether 
leguminous  crops  do  not  find  in  the  soil  suited  to  their  growth 
some  other  source  of  nitrogen  than  nitrates.  The  very  large 
amount  of  nitrogen  taken  up  by  these  crops  would,  on  this 
supposition,  be  due  to  their  possession  of  a power  of  utilising 
nitrogen  existing  in  the  soil  in  a condition  of  combination,  as 
well  as  of  distribution,  not  available  to  cereal  crops. 
We  have  now  completed  our  account  of  the  quantity  of 
nitrates  found  at  various  depths,  and  at  various  seasons,  in 
cropped  land  subjected  to  a great  variety  of  manuring.  Before 
concluding,  we  must  say  a few  words  as  to  the  bearing  of  some 
of  these  results  upon  the  important  questions  raised  in  the  last 
section  of  the  previous  Report  on  Rain  and  Drainage. 
