and  Subsoils  of  some  of  the  Fields  at  Rotliamsted.  341 
respectively  36-3  lbs.  and  33  7 lbs.  per  acre,  to  the  depth  of  18 
inches  only.  Both  amounts  are  smaller  than  those  found  to 
the  same  depth  in  soils  in  good  agricultural  condition.  The 
richness  of  the  soil  in  nitrifiable  matter  has  thus  a great  in- 
fluence on  the  quantity  of  nitrate  produced. 
The  fallow  soils  we  have  just  mentioned  were  many  of  them 
very  free  from  weeds,  and  none  were  very  foul.  In  ordinary 
practice  the  land  to  be  fallowed  is  often  so  foul  that  the  nitric 
acid  formed  during  the  first  summer  and  autumn  will  be  taken 
up  by  the  weeds  as  fast  as  it  is  produced.  When,  as  is  often  the 
case,  such  land  is  not  ploughed  till  the  following  spring,  the  loss 
of  nitrates  by  drainage  will  be  far  smaller  than  on  clean  land. 
Some  further  determinations  of  nitrates  in  uncropped  soil  will 
be  found  in  Table  IV.  The  previous  history  of  Geescroft  Field 
Table  IV. — The  Quantity  of  Nitrogen  as  Nitrates,  in  Lbs.  per 
Acre,  in  Cropped  and  Uncropped  Land,  variously  Manured. 
Little 
Hoos. 
Sept.  1877. 
Hoos  Field,  July 
1882. 
Geescroft  Field,  April  1883,  nncropped  land, 
previously  Beans. 
Barley. 
Nitrate 
and 
Superpkos. 
Bokhara 
Clover. 
Mineral 
Manure. 
White 
Clover. 
Mineral 
Manure. 
No 
Manure. 
Formerly 
Mineral 
Manure. 
Formerly 
Nitrate 
and 
Minerals. 
Formerly 
Farmyard- 
Manure. 
lbs. 
lb-. 
lbs. 
lbs. 
lbs. 
lbs. 
lbs. 
1st,  9 inches 
15*7 
3-4 
8-G 
4’2 
3-5 
33 
13-6 
2nd,  9 inches 
i-i 
1-0 
3-0 
5-4 
6 7 
60 
8-7 
3rd,  9 inches 
i-i 
0-6 
1-9 
4-7 
5-1 
4-2 
7-3 
4th,  9 inches 
1-4 
10 
31 
2-7 
26 
3-9 
8-4 
5th,  9 inches 
1-2 
0-8 
4-4 
32 
1-7 
1-9 
4-4 
6th,  9 inches 
1-4 
1-7 
5-3 
2*2 
1-4 
2-2 
2-0 
7th,  9 inches 
not 
not 
not 
3-0 
11 
1-5 
1-7 
8th,  9 inches 
sampled 
sampled 
sampled 
3 * G 
1-3 
1-7 
4-0 
Above  27  ins. 
17-9 
5*0 
13-5 
14.3 
15-3 
13-5 
29-6 
Below  27  ins. 
4-0 
3-5 
12-8 
14-7 
8-1 
11-2 
20-5 
Total  .. 
21-9 
8*5 
26-3 
29  0 
23-4 
24-7 
50-1 
has  been  already  given  (p.  337).  The  surface  soil  of  the  plot 
formerly  manured  with  farmyard-manure  is  rich  in  nitrogen, 
and  compares  perfectly  in  this  respect  with  the  farmyard- 
manure  plots  in  Broadbalk  Wheat-field  and  Hoos  Barley-field. 
The  soils  of  the  other  plots  are  very  low  in  nitrogen,  and  in  a 
decidedly  impoverished  condition.  During  the  summer  of  1882, 
the  land  was  without  a crop.  It  was  ploughed  and  harrowed  in 
February,  and  then  left  untouched  till  September,  when  it  was 
again  harrowed  and  rolled,  and  grass-seeds  sown,  which  failed. 
The  samples  of  soil  were  taken  on  April  9-13,  1883. 
