The  Woburn  Field,  Experiments , 1910. 
337 
Table  XI. — Experiment  with  Nitrogenous  Top-dressings  on 
Mangolds , 1910. 
Warren  Field. 
Plot 
Manures  per  acre 
Produce  of  roots 
per  acre 
T. 
c. 
q. 
lb. 
1 
Standard  dressing1  only 
31 
11 
3 
14 
2 
,,  „ with  sulphate  of  ammonia  1 cwt. 
29 
3 
3 
0 
3 
„ „ „ nitrate  of  soda3 
34 
15 
0 
0 
4 
„ „ „ calcium  nitrate2 
36 
16 
3 
14 
5 
„ „ „ calcium  cyanamide3  . 
35 
15 
2 
14 
6 
„ „ „ soot2  
33 
0 
0 
0 
i Dung  12  tons,  superphosphate  3 cwt,  sulphate  of  potash  1 cwt.,  salt  2 c wt.  per  acre. 
3 In  quantity  to  supply  as  much  nitrogen  as  that  contained  in  1 cwt.  sulphate  of 
ammonia. 
than  calcium  nitrate.  These  were  the  relative  positions  occupied 
in  the  experiments  of  1909. 
Accordingly,  both  the  new  materials — calcium  cyanamide 
and  calcium  nitrate — would  seem  to  answer  perfectly  well  for 
the  mangold  crop,  and  to  be  quite  as  good,  or,  possibly,  slightly 
better  for  them  than  nitrate  of  soda  supplying  the  same  amount 
of  nitrogen.  Sulphate  of  ammonia,  on  the  other  hand,  would 
appear  to  be  less  beneficial  than  the  other  nitrogenous  top- 
dressings  for  a mangold  crop. 
( c ) Residual  value  of  Nitrogenous  Top-dressings. 
In  comparing  the  different  nitrogenous  top-dressings  used 
in  the  foregoing  experiments,  it  was  of  importance  to  consider, 
not  only  the  effect  produced  upon  the  particular  crop  to  which 
they  were  applied,  but  also  whether  they,  or  any  of  them,  left 
any  residue  over  for  the  use  of  subsequent  crops.  It  is  well 
known  that  nitrate  of  soda  and  sulphate  of  ammonia — more 
particularly  the  former — leave  practically  nothing  for  a second 
crop,  but  it,  was  thought  possible  that,  on  a light  soil  such  as 
that  of  Woburn,  and  deficient  in  lime,  calcium  nitrate  and 
calcium  cyanamide  might  do  some  good  by  reason  of  the  lime 
they  respectively  contained.  Accordingly  it  was  decided,  after 
the  mangold  experiment  of  1909  in  Road  Piece  Field,  to  grow 
a wheat  crop  in  1910,  and  to  give  no  further  manuring,  but  to 
see  what  was  left  over,  possibly,  from  the  applications  of  1909. 
All  the  plots  had  been  manured  for  mangolds,  in  1909,  with  12 
tons  per  acre  of  dung,  3 cwt.  per  acre  of  mineral  superphos- 
phate, 1 cwt.  per  acre  of  sulphate  of  potash,  and  2 cwt.  per  acre 
of  common  salt,  the  nitrogenous  top-dressings  (each  supplying 
the  same  amount  of  nitrogen  as  in  1 cwt.  of  sulphate  of 
ammonia)  being  given  additionally.  Nine  pecks  per  acre  of 
“ Square  Head’s  Master  ” wheat  were  drilled  on  the  plots  on 
VOL.  71.  Z 
