and  Subsoils  of  some  of  the  Fields  at  Rothamsted.  351 
in  the  soil,  or  on  the  migration  of  soluble  matters,  we  have  at 
present  no  certain  information. 
When  we  turn  to  Plots  6a,  7a,  and  8,V,  receiving  respectively 
200  lbs.,  400  lbs.,  and  600  lbs.  of  ammonium-salts,  with  all  the 
necessary  ash-constituents,  we  find  28’7  lbs.,  39-8  lbs.,  and  42-8 
lbs.  of  nitrogen  as  nitrates  per  acre,  the  quantities  increasing 
with  each  addition  to  the  manure.  The  quantity  of  nitrate  in 
the  soil  of  Plot  8 A bears  a low  relation  to  that  found  in 
Plots  6a  and  7 a.  In  the  case  of  Plot  8 A we  are  unable  to  form 
an  estimate  of  the  quantity  of  nitrate  lost  by  drainage  before 
the  sampling  of  the  soil,  as  the  drain-pipe  did  not  run  till 
afterwards ; the  quantity  lost  by  drainage  and  diffusion  may 
well,  however,  have  been  greater  than  on  Plot  7.  The  nitrate 
in  the  soil  of  Plot  8a  is  also  very  low  in  relation  to  that  found 
in  the  subsequent  drainage  from  the  plot.  If  the  proportion 
between  the  nitrate  in  the  soil  and  that  removed  in  the 
subsequent  drainage  were  the  same  as  on  Plots  6a,  7a,  and  9ab, 
the  soil  of  Plot  8a  would  contain  about  56  lbs.  of  nitrogen  as 
nitrates.  It  seems  possible  that  in  this  case  an  unusually  large 
amount  of  nitrogen  may  have  nitrified  on  the  plot  after  the 
samples  of  soil  were  taken  ; nitrates  might  thus  appear  in  the 
drainage  which  did  not  exist  in  the  soil  at  the  date  of  sampling. 
In  the  soil  of  Plot  9a,  where  nitrate  of  sodium  equivalent  to 
400  lbs.  of  ammonium-salts  is  applied  with  ash-constituents,  the 
nitrogen  as  nitric  acid  is  37’9  lbs.,  a quantity  quite  similar  to 
that  found  in  Plot  7a,  receiving  the  corresponding  amount  of 
ammonium-salts,  and  the  same  ash-constituents.  On  Plot  9b, 
where  the  same  quantity  of  nitrate  of  sodium  is  applied,  but 
without  ash-constituents,  the  nitrogen  existing  as  nitrates  rises 
to  54T  lbs.,  a large  residue  of  nitrate  unused  by  the  crop 
clearly  remaining  in  the  first  27  inches  of  soil. 
On  Plots  10a  and  10b,  receiving  400  lbs.  of  ammonium-salts, 
without  ash-constituents,  there  is  deficient  produce,  and  there  will 
be  a proportionally  large  amount  of  nitrate  annually  derived 
Irom  the  manure  unused  by  the  crop.  The  quantities  found  in 
the  soil  to  the  depth  of  27  inches  are  nevertheless  not  relatively 
large — namely  33-4  lbs.  and  28-3  lbs.  of  nitrogen  as  nitrates. 
The  smaller  amount  is  found  in  the  soil  of  Plot  10b,  where, 
owing  to  a residue  of  long  previously  applied  ash-constituents, 
the  crop  is  always  rather  better,  and  would  therefore  leave  rather 
more  crop-residue.  In  these  facts  there  would  seem  to  be 
evidence  that  the  whole  of  the  soil-nitrates  found  was  not  due 
to  crop-residue,  but  partly  to  manure-residue  also.  That  the 
amount  remaining  within  the  range  of  the  soil-sampling  was  not 
larger  on  either  plot,  is  consistent  with  the  fact  that  there  is  a 
greater  loss  by  drainage  from  these  than  from  any  of  the  other 
