and  Subsoils  of  some  of  the  Fields  at  Rotliamsted.  345 
titrates  was  now  11*1  lbs.  per  acre  in  the  first  18  inches,  and 
14*5  lbs.  in  the  first  27  inches  of  soil. 
In  Table  IV.  we  have  a determination  of  nitrates  in  a barley- 
stubble  in  Little  Hoos  Field.  The  land  had  grown  9 crops 
of  barlt-j  in  succession  with  artificial  manures  alone,  chiefly 
nitrate  of  sodium  and  superphosphate.  The  crop  was  cut  on 
Aug.  14-21,  1877  ; it  amounted  to  48  bushels.  The  samples  of 
soil  were  taken  Sept.  26—29.  The  land  had  not  been  ploughed 
at  the  time  of  sampling.  The  nitrogen  in  the  form  of  nitrates 
is  here  15'7  lbs.  per  acre  in  the  first  9 inches.  It  seems  im- 
probable that  this  nitrate  was  a residue  of  the  2^  cwts.  of  nitrate 
of  sodium  (44  lbs.  of  nitrogen)  applied  as  manure ; the  greater 
part  of  it  had  more  probably  been  produced  in  the  soil  since 
Midsummer,  especially  as  the  rainfall  in  July  and  August  was 
■considerable.  On  a duplicate  plot  in  the  same  field,  in  which 
clover  had  been  sown  with  the  barley,  only  6T  lbs.  of  nitrogen 
. as  nitrates  were  found  in  the  first  9 inches  of  soil.  The  young 
■clover  had  thus  evidently  continued  to  take  up  nitrates  from 
the  soil  after  the  growth  of  the  barley  had  ceased.  The  chief 
interest  of  the  experiment  centres,  however,  in  the  analyses  of 
the  subsoil,  which  in  this  case  was  sampled  to  an  unusual  depth. 
The  insignificant  amount  of  nitrate  found — only  63  lbs.  of 
nitrogen  per  acre  in  45  inches  of  subsoil — presents  a vivid 
picture  of  the  exhaustion  of  soil-nitrates  which  may  take  place 
during  the  growth  of  a vigorous  cereal  crop. 
We  turn  now  to  Broadbalk  Wheat-field.  A plan  of  this 
field,  showing  the  position  of  the  plots,  and  the  system  of  drain- 
pipes, has  been  given  in  the  previous  Report.  Samples  of  soil 
were  taken  from  many  of  the  plots  in  October  1865,  and  in 
some  of  these  nitric  acid  was  determined  in  the  following  year 
by  Dr.  Pugh’s  method.  The  quantity  of  nitric  acid  found 
was  large  ; but  as  the  soils  had  been  stored  in  a moist  condition, 
nitrification  had  probably  taken  place  after  the  collection. 
The  plots  of  Broadbalk  Field  were  again  sampled  in  October 
1881.  The  manuring  of  the  field,  the  average  produce  of  each 
plot,  and  the  produce  of  the  particular  harvest  (1881),  after  which 
the  soil  was  sampled,  have  been  already  given  in  Table  II. 
From  the  end  of  March  to  the  end  of  July  the  weather  had 
been  decidedly  dry.  The  wheat  was  cut  on  Aug.  8—11.  Im- 
mediately after  followed  a deluge  of  rain,  amounting  in  the 
whole  month  to  5-817  inches.  The  crop  was  not  carted  till 
Aug.  29-Sept.  1,  and  was  greatly  damaged.  In  September  the 
rainfall  was  2T71  inches.  The  land  was  scarified  in  the  be- 
ginning of  the  month,  and  ploughed  towards  the  end  of  it.  The 
samples  of  soil  were  taken  between  October  10  and  18,  the 
sampling  being  interrupted  by  heavy  rain  on  the  14th.  The 
VOL.  XIX. — 8.  S.  2 A 
