386  The  Woburn  Field  Experiments,  1909. 
whole  series,  the  average  of  the  two  plots  giving  no  less  than 
54'2  bushels  of  corn  per  acre,  with  37  cwt.  2 qr.  per  acre  of 
straw.  This,  for  light  land  of  this  kind,  is  an  enormous  crop  ; 
it  was  9 bushels  more  than  on  the  highest  plot  of  the  continuous 
barley  series,  and  11  bushels  more  than  the  highest  yield  of 
the  rotation  series.  This  being  so,  it  is  clear  that  no  deductions 
could  be  drawn  from  this  experiment,  except  to  show  that  the 
land,  owing  to  the  previous  sheep-feeding,  was  amply  supplied 
with  nitrogen  and  needed  no  more  ; hence  the  extra  nitrogen 
in  the  top-dressings  could  not  “ tell.”  Indeed,  it  is  likely  that 
the  higher  produce  of  plots  5 and  8 was  in  measure  due  to  the 
fact  that  the  crop  here  stood  up,  whereas  with  the  heavier 
dressings  of  nitrogen  it  went  down,  and  did  not  ripen  so  well. 
This  is  borne  out  by  the  valuation  of  the  corn,  which  showed 
the  highest  figure  in  the  case  of  plots  5 and  8.  The  crops,  as 
already  stated,  were  a credit  to  the  farm,  but  were  not  such  as 
could  determine  an  experiment. 
In  the  mangold  experiment  in  Road  Piece  Field  much  the 
same  happened  as  with  the  barley.  Here  the  crops  again  were 
splendid  ones,  a produce  of  40  tons  per  acre  of  mangolds  on 
light  sandy  loam  being  quite  exceptional.  Plot  5,  which  had 
no  top-dressing,  gave  within  2 cwt.  of  the  highest  produce, 
this  latter  being  obtained  with  calcium  nitrate.  Nitrate  of 
soda,  which  at  one  time  during  the  period  of  growth  seemed 
to  be  the  best  crop,  gave  the  lowest  yield  but  one,  and  it  was 
clear  that  in  a season  such  as  that  of  1909  all  that  the  extra 
nitrogen  supplied  had  done  was  to  force  on  the  leaf  growth 
without  increasing  the  bulb.  Under  such  circumstances,  as 
with  the  barley  crop,  no  conclusions  could  be  drawn  from  the 
experiment  as  regards  the  relative  efficiency  of  the  different 
nitrogenous  top-dressings. 
Taking,  lastly,  the  experiment  in  Warren  Field  on  potatoes. 
Here,  too,  the  crops  were  good,  but  the  nitrogenous  top- 
dressings  did  in  each  case  exert  an  influence,  though  not  a very 
strongly  marked  one.  The  actually  greatest  increase  was 
obtained  with  sulphate  of  ammonia,  a result  previously 
experienced  on  this  farm.  There  was  an  increase  of  1 ton 
7 cwt.  per  acre  in  the  total  crop  over  plot  1 (“  standard  ” 
dressing  only)  and  of  nearly  1 ton  in  saleable  potatoes,  but  it  is 
remarkable  that  calcitim  nitrate,  while  producing  13  cwt.  less 
total  crop  per  acre,  gave  2 cwt.  more  per  acre  of  saleable 
potatoes,  and  also  less  diseased  tubers  than  on  any  of  the  other 
plots.  Between  nitrate  of  soda  and  calcium  cyanamide  there 
was  nothing  to  choose,  they  both,  however,  falling  somewhat 
below  sulpha,te  of  ammonia  and  calcium  nitrate. 
To  sum  up,  though,  for  reasons  given,  the  experiments  with 
barley  and  with  mangolds  did  not  permit  of  definite  conclusions 
