392  The  Wohurn  Poi-Crdture  Experiments,  1908. 
of  using  magnesia  in  the  form  of  carbonate  of  magnesia  and  as 
the  mineral  dolomite  (carbonate  of  lime  and  carbonate  of 
magnesia)  the  latter  of  which  is  commercially  obtainable.  The 
soil  of  Stackyard  Field  contains  ’40  per  cent,  of  lime  and  -20 
per  cent,  of  magnesia,  and  it  had  been  found  that,  by  adding 
magnesia  (MgO)  so  as  to  bring  the  proportion  of  magnesia  in 
the  soil  above  that  of  the  lime  contained,  the  crop  was  increas- 
ingly diminished,  the  character  of  the  roots  altered,  while  the 
grain  underwent  an  entire  change  from  “ soft  ” or  “ starchy  ” 
wheat  to  “ hard  ” or  “ glutinous  ” wheat. 
The  materials  added  to  the  soil  in  this  experiment  were  : — 
(1)  lime  and  magnesia  ; (2)  carbonate  of  magnesia ; (3)  sul- 
phate of  magnesia;  (4)  dolomite,  finely  ground  ; (5)  lime  from 
dolomite.  The  experiments  were  in  duplicate.  Wheat 
(“Square  Head’s  Master”)  was  sown  on  November  28,  1907, 
and  came  up  well  in  all  the  sets.  At  first,  where  magnesia  had 
been  added,  the  crop  did  not  seem  to  thrive,  but  it  improved 
later  ; the  ground  dolomite  set  also  at  first  looked  better  than 
the  dolomite  lime  set,  but  this  position  was  reversed  later.  The 
one  set  that  did  not  look  well  was  that  where  the  soluble  salt, 
sulphate  of  magnesia,  had  been  used,  the  crop  being  of  much 
lighter  colour.  In  all  cases  magnesia  seemed  to  retard  the 
ripening,  as  the  untreated  sets  were  ready  for  harvesting  on 
August  13,  the  others  not  until  August  17.  The  harvest  results 
were — 
Corn 
Stra-vv 
Weight 
Percentage 
of 
untreated 
Weight 
Percentage 
of 
untreated 
No  treatment 
Grammes 
30-54 
Per  cent. 
100 
Grammes 
52-96 
Per  cent. 
100 
^ Lime  and  magnesia  added  . 
41-87 
137 
64-81 
122 
' Carbonate  of  magnesia  added 
42-83 
140 
72-00 
135 
'Sulphate  of  magnesia  added. 
' Dolomite  (finely  ground)  added 
26-61 
86 
63-26 
100 
34-84 
114 
69-23 
112 
'Lime  from  dolomite  added  . 
42-69 
139 
69-88 
132 
1 The  soil,  after  mixing,  containing  in  each  case,  CaO  ’80  per  cent.  MgO  "40  per  cent. 
From  this  experiment,  taken  in  conjunction  with  others,  it  is 
clear  that  magnesia  in  the  form  of  the  sulphate  (a  readily  soluble 
salt),  does  not  act  beneficially,  but  that  in  the  insoluble  forms 
magnesia  may  be  used  with  advantage  so  long  as  the  proportion 
of  magnesia  in  the  soil,  subsequent  to  the  addition,  is  not  in 
excess  of  the  lime.  The  results  from  addition  of  magnesia  itself, 
of  carbonate  of  magnesia,  and  of  burnt  dolomite  (magnesian 
lime)  were  much  alike,  but  the  ground  magnesian  limestone 
(dolomite)  would  seem  to  be  too  slow-acting. 
