The  Wohurn  Field  Experiments,  1909.  381 
Table  IX. — Potato-spraying  Experiments  {Great  Hill),  1909. 
Produce  of  Tubers  per  acre. 
Plot 
Treatment 
Ware 
Seed 
Small 
Diseased 
Total 
produce 
1 
Not  sprayed— tops  left  on . 
T.  c.  q.  lb. 
3 5 0 17 
C.  q.  lb. 
35  1 21 
C.  q. lb. 
22  0 23 
0.  q.lb. 
5 1 21 
T.  c.  q.  lb 
6 8 0 26 
2 
„ „ tops  cut  off . 
5 6 0 20 
34  0 8 
22  2 20 
18  0 0 
9 0 3 20 
3 
Sprayed  with  “Bordeaux 
Mixture  . 
6 7 0 23 
34  3 12 
7 1 13 
29  2 10 
9 19  0 2 
4 
Sprayed  with  “ Woburn 
Paste”  .... 
6 1 1 18 
37  0 17 
8 3 6 
18  0 21 
9 5 2 6 
5 
Sprayed  with  “ Straw- 
sonite  ” . . . . 
6 11  1 5 
30  0 14 
20  1 15 
21  2 6 
10  3 1 12 
It  will  be  seen,  in  the  first  place,  that  all  the  different 
methods  of  spraying  produced  a beneficial  effect,  increasing 
the  crop  largely,  though  the  actual  quantity  of  diseased  tubers 
was  larger  than  on  the  unsprayed  plots.  As  between  the 
different  materials  tried,  the  results  must  be  left  to  Mr. 
Pickering  to  discuss,  in  view  of  the  relative  cost  and  trouble 
of  application  involved.  It  is  noticeable,  however,  that  the 
simple  device  of  cutting  off  the  tops  of  the  plants,  as  soon  as 
the  leaves  began  to  be  infected  with  disease,  had  the  result  of 
considerably  increasing  the  yield  of  sound  tubers  and  of  total 
produce.  How  such  an  increase  could  have  taken  place  in  view 
of  the  larger  quantity  of  diseased  tubers,  is,  however,  hard  to 
explain.  In  the  case  of  the  “ sprayed  ” plots  it  may  be  assumed 
that  the  stopping  of  the  ravages  of  the  disease  prolonged  the 
growing  period  of  the  tops  and  hence  the  time  of  assimilation 
of  starch  in  the  tubers  (though  here  again  the  quantity  of 
diseased  tubers  was  above  that  of  the  unsprayed  plots),  but  this 
explanation  would  not  hold  good  where  the  tops  had  been  cut 
off.  These  points  seem  to  open  up  interesting  considerations 
as  to  what  are  the  changes  that  really  take  place  under  the 
influence  of  spraying. 
Expbkimbnts  with  Nitrogenous  Top-dressings,  1909. 
In  1908  experiments  with  calcium  cyanamide  (“  nitrolim  ”) 
were  conducted  at  the  Woburn  Farm  with  barley,  mangolds, 
and  potatoes.  These  were  continued  on  a more  extensive 
scale  in  1909,  the  experiments  being  extended  to  the  wheat 
crop  ; and,  further,  calcium  nitrate  was  now  included  in  the 
inquiry,  this  material  having,  since  the  earlier  trial,  become 
more  generally  available.  The  comparison  was  in  each  case 
made  with  sulphate  of  ammonia  and  nitrate  of  soda,  a dressing 
of  1 cwt.  per  acre  of  sulphate  of  ammonia  being  taken  as  the 
basis,  and  the  relative  amounts  of  nitrate  of  soda,  calcium 
cyanamide,  and  calcium  nitrate  used  being  arranged  so  that  in 
