and  Subsoils  of  some  of  the  Fields  at  Rothamsted.  367 
constituents,  a mean  of  23'3  lbs.  Plots  receiving  1000  lbs.  of 
rape-cake,  with  or  without  ash-constituents,  a mean  of  30T  lbs. 
The  plot  receiving  14  tons  farmyard-manure,  44T  lbs.  The 
residues  of  the  rape-cake  and  of  the  farmyard-manure  added 
considerably  to  the  quantity  of  nitrate  produced.  The  influence 
of  crop-residues  in  increasing  the  production  of  nitrate  is  not  so 
marked  as  in  the  wheat-field,  barley  leaving  a smaller  residue 
in  the  soil  than  wheat. 
11.  A comparison  of  the  quantity  of  nitrate  found  in  soils 
cropped  with  beans  or  clover,  with  that  found  in  corresponding 
land  in  bare  fallow,  showed  that  nitrates  are  assimilated  by 
leguminous  crops.  A similar  result  appeared  when  the  com- 
parison was  made  between  a vigorous  deeply-rooted  leguminous 
plant  (Bokhara  clover)  and  a delicate  short-rooted  one  (white 
clover),  the  former  taking  more  nitrate  from  the  subsoil  than 
the  latter. 
12.  The  quantity  of  nitrogen  in  luxuriant  leguminous  crops 
appears  too  great  to  be  accounted  for  by  the  quantities  of  nitric 
acid  at  present  recognised  in  soils.  We  have  however  as  yet 
very  limited  information  as  to  the  quantity  of  nitric  acid  in  the 
lower  layers  of  the  subsoil.  The  question  remains  whether 
leguminous  crops  have  the  power  of  utilising  nitrogen  existing 
in  the  soil  in  a condition  of  combination  (as  well  as  of 
distribution),  not  available  to  cereal  crops  ? 
13.  The  results  relating  to  the  soils  in  the  Broadbalk  Wheat- 
field,  together  with  those  relating  to  the  pipe-drainage-waters, 
confirm  the  conclusion  put  forward  in  the  former  Report — 
that  the  estimates  of  loss  by  drainage  founded  on  the  amount  of 
water  passing  through  the  60-inch  soil  drain-gauge,  and  on  the 
composition  of  the  pipe-drainage  in  the  wheat-field,  are  too 
low  ; it  appearing  that  considerably  more  nitrates  pass  into  the 
subsoil  than  such  a calculation  shows. 
14.  It  is  a question  whether,  under  some  circumstances,  and 
especially  if  the  subsoil  is  saturated  with  water,  nitrates  which 
have  passed  into  the  lower  layers  of  the  subsoil  are  not  there 
destroyed  by  reduction  ; or  whether,  and  to  what  extent,  the 
nitrates  which  are  not  reduced,  or  not  finally  lost  by  drainage, 
return  upwards  in  dry  weather,  or  are  available  to  plants  of 
deep-rooting  habit  and  vigorous  growth. 
