394  The  Woburn  Pot-Culture  Experiments,  1908. 
Magnesia  was  mixed,  with  the  entire  mass  of  soil  used  in  the 
pot.  Barley  (“  Malster  ”)  was  sown  April  3,  1908.  Before  the 
application  of  the  top-dressing  the  influence  ot  superphosphate 
and  kainit  told  markedly.  The  crop  was  harvested  August  1.5. 
In  every  case  there  was  a gain  over  the  untreated  lots,  as 
represented  in  the  following  table  : — 
No  treatment  ....... 
Grain 
per  cent. 
100 
Straw 
per  cent. 
100 
Superphosphate  and  sulphate  of  potash  . 
123 
133 
Sulphate  of  ammonia  ..... 
129 
113 
Nitrate  of  soda  ...... 
127 
129 
Superphosphate,  sulphate  of  potash,  sulphate 
of  ammonia  ...... 
159 
152 
Superphosphate,  sulphate  of  potash,  nitrate  of 
soda  ........ 
154 
154 
Superphosphate,  kainit,  nitrate  of  soda  . 
177 
153 
Magnesium  oxide  ...... 
118 
117 
Thus,  from  the  use  of  either  minerals  alone,  or  of  sulphate  of 
ammonia  or  nitrate  of  soda  alone,  there  was  a gain  of  from 
23  per  cent  to  29  per  cent,  in  corn,  while,  by  using  in  conjunc- 
tion superphosphate,  sulphate  of  potash,  and  either  sulphate  of 
ammonia  or  nitrate  of  soda,  the  gain  was  increased  to  54 — 59 
per  cent,  of  corn  and  52-54  per  cent,  of  straw.  The  substitu- 
tion of  kainit  for  sulphate  of  potash  raised  the  gain  to  77  per 
per  cent,  in  corn,  but  the  grain  was  not  of  such  good  quality. 
The  best  quality  grain  was  obtained  by  using  superphosphate, 
sulphate  of  potash,  and  sulphate  qf  ammonia.  With  magnesia 
the  gain  was  only  small,  but  the  quality  of  corn  was  improved. 
It  would  seem,  accordingly,  that  on  such  land  as  this  a 
general  manuring  of  mineral  and  nitrogenous  materials  would 
answer  well,  despite  the  richness  of  the  soil  in  nitrogen. 
5.  Experiments  on  the  Acid  Soil  of  Plot  2. — Continuous 
Barley  {Stackyard  Field). 
The  object  in  this  exjDeriment  was  to  see  whether  the  acidity 
produced  in  the  soil  of  land  continuously  manured  with 
sulphate  of  ammonia  could  be  removed  by  the  application  of  any 
material,  and  the  soil  then  be  available  for  crop-growing.  In 
1908  the  following  materials  were  tried  : — Sulphate  of  iron, 
sulphate  of  copper,  pyrogallic  acid,  animal  charcoal.  It  is  not 
necessary  to  go  into  details  of  the  applications,  save  to  say  that 
when  barley  was  subsequently  grown  in  the  pots  none  of  the 
materials  used  were  successful  in  destroying  the  injurious 
effects  of  the  acidity  and  producing  anything  like  a crop,  with 
the  single  exception  of  animal  charcoal,  which  was  given  to 
the  extent  of  TO  per  cent,  of  the  soil  weight.  Even  here  it  is 
open  to  question  to  what  the  action  of  the  animal  charcoal  was 
due,  and  whether  the  lime  in  it  may  not  have  exerted  an 
