Report  on  the  Field  and  Feeding  Experiments  at  Woburn.  217 
the  course  of  some  years  to  what  extent  good  farmyard-manure 
parts  with  its  fertilising  properties  in  a single  season  ; and  how 
many  years  it  will  take  practically  to  exhaust  the  fertilising 
properties  of  a definite  quantity  of  good  dung  of  known  com- 
position. 
The  results  obtained  last  season  on  plots  8,  9,  10,  and  11  are 
most  instructive,  and  Table  I.,  showing  the  produce  of  con- 
tinuous wheat  in  the  sixth  season,  1882,  is  well  worthy  of  an 
attentive  study. 
Referring,  in  the  first  place,  to  the  plots  8 and  9,  manured 
heavily  with  mineral  and  soluble  nitrogenous  manures,  it  will 
be  seen  that  on  the  half-plots  which  were  merely  manured  wTith 
mineral  manures,  the  produce  in  corn  and  straw  was  not  larger 
than  on  the  plots  upon  which,  for  the  last  seven  years,  wheat 
was  grown  without  any  manure  whatever.  Singularly  enough, 
plot  8a  yielded  almost  exactly  the  same  produce  as  the  adjoin- 
ing continuously  unmanured  plot  7,  and  plot  9b  almost  exactly 
the  same  produce  as  the  unmanured  plot  1. 
Although  these  plots  had  been  heavily  dressed  in  each  of  the 
preceding  five  seasons  with  nitrate  of  soda  or  with  ammonia- 
salts,  the  produce  was  reduced  to  the  level  of  the  continuously 
un manured  plots  as  soon  as  the  nitrogenous  manures  were  with- 
held the  next  season.  The  yearly  and  liberal  supply  of  mineral 
manures  did  not  raise  the  produce  in  wheat,  and  the  results  on 
plots  Sa  and  9a  clearly  show  that  there  was  no  available 
residue  of  nitrate  of  soda  or  salts  of  ammonia  left  in  the  land 
from  the  previous  applications  of  these  readily  soluble  nitro- 
genous manures. 
On  the  second  half  of  plot  Sb,  manured  with  minerals  or 
ammonia-salts,  the  produce  of  dressed  corn,  it  will  be  seen,  was 
43^  bushels,  weighing  59  lbs.  per  bushel,  and  that  of  straw 
2 tons  15  cwts.  and  6 lbs.  The  addition  of  ammonia-salts  to 
the  minerals,  which  alone  produced  only  13’3  bushels  of  dressed 
corn  and  17  cwts.  2 qrs.  and  6 lbs.  of  straw,  thus  more  than 
tripled  the  wheat- crop. 
On  plot  9b  a similarly  large  increase  was  obtained  by  the 
application  of  nitrate  of  soda.  Minerals  without  nitrate  on 
plot  9a  produced  only  12*2  bushels  of  dressed  wheat,  weighing 
only  56  lbs.  per  bushel,  and  18  cwts.  1 qr.  and  8 lbs.  of  straw  per 
acre.  The  same  amount  of  mineral  manures,  with  the  addition 
ol  550  lbs.  of  nitrate  of  soda  per  acre,  raised  the  crop  to  35'S 
bushels  of  dressed  wheat,  weighing  58'8  lbs.  per  bushel,  and 
49  cwts.  2 qrs.  and  22  lbs.,  or  nearly  2J  tons  of  straw  per  acre. 
It  is  scarcely  needful  to  state  that  in  actual  practice  nobody 
would  think  of  applying  to  the  land  such  large  quantities  of 
ammonia-salts  or  nitrate  of  soda  as  those  which  were  applied 
