The  Woburn  Pot-Culture  Experiments,  1909.  349 
Weight  of  clover  (green) 
Weight  of  beans 
1st  cutting 
2nd  cutting 
Corn 
Straw 
No  treatment  .... 
Grammes 
1818 
Grammes 
1 32-4 
Grammes 
35-9 
Grammes 
367 
With  magnesia  a<lded  to  soil, 
to  ‘05  per  cent. . 
1691 
111-4 
308 
29  4 
With  magnesia  added  to  soil, 
to  "10  per  cent. . 
1392 
110-8 
21-2 
35  1 
With  magnesia  added  to  soil, 
to  "20  per  cent. . 
64-9 
74  1 
6-3 
19  6 
From  both  these  sets  the  general  result  is  obtained  that  as 
the  quantity  of  magnesia  in  the  soil  is  increased  so  is  the 
produce  lowered.  This  is  more  marked  in  the  first  cutting  of 
clover  than  in  the  second,  and  not  so  clear  in  the  strawi  of  the 
beans  as  in  the  corn. 
5.  Green-manuring  Experiment. 
The  experiments  of  1908  had  shown  that  an  alteration  in 
the  consolidation  of  the  soil,  produced  by  the  addition  of 
materials  such  as  silicate  of  alumina  and  silicate  of  soda, 
exercised  a marked  influence  in  bringing  out  the  benefit  of  the 
previous  green-manuring.  The  work  was  continued  in  1909, 
silicate  of  alumina  again  being  used,  and  also  clay  itself,  mixed 
with  the  soil.  Again  the  beneficial  influence  was  experienced, 
and  the  results  generally  tended  to  show  that  the  action  on  the 
organic  matter  in  the  soil  had  been  the  main  cause  of  increase. 
Analyses  of  the  grain  produced  and  of  the  soils,  after  the  several 
years  of  green  manuring,  were  made,  but  the  results,  while 
highly  interesting,  do  not  lend  themselves  to  brief  treatment 
such  as  is  called  for  in  the  present  summary. 
fi.  Experiments  with  Nitrogenous  Top-dressings. 
Pot  experiments  were  conducted  in  1909  on  the  comparative 
values  of  sulphate  of  ammonia,  nitrate  of  soda,  calcium 
cyanamide,  and  nitrate  of  lime  as  top-dressings  for  wheat  and 
barley.  These  experiments  were  carried  on  simultaneously 
with  others  on  a field  scale,  and  led  to  much  the  same  con- 
clusion, viz.,  that,  provided  the  same  amount  of  nitrogen  was 
supplied,  it  was  not  very  material  in  what  form  it  was  given. 
With  wheat  the  percentages  of  corn  yield,  taking  the  “ untreated  ” 
as  100,  were  : sulphate  of  ammonia,  124  ; nitrate  of  soda,  143  ; 
calcium  cyanamide,  120,  and  nitrate  of  lime,  143  ; with  barley  : 
sulphate  of  ammonia,  139  : nitrate  of  soda,  133  ; calcium  cyana- 
mide, 122,  and  nitrate  of  lime,  140. 
