Gypsum as a Cane Fertiliser. 141 
dissolved guano and the various cane manures made up of 
superphosphate of lime and ammonium salts, a trial 
might be made of a mixture of equal weights of dried 
blood, gypsum and finely ground South Sea Island phos- 
phate. * Such a mixture would contain nitrogen equal to 
about 5 per cent, of ammonia, 27 per cent, phosphate 
of lime and 33 per cent, of gypsum. It should not cost 
more than two-thirds the price of a dissolved manure of 
equal strength, and I see no reason why it should not 
prove equally efficacious whilst it would unquestionably 
be much more lasting. 
Respecting the action of gypsum in fixing aerial 
ammonia, I think the amount of ammonia present in air 
and rain too small for its effects in this direction to be 
appreciable. Owing to this property, however, gypsum 
is an excellent substance for mixing with decomposing 
pen or stable manure to prevent loss of nitrogen by 
ammoniacal emanations. It may also be recommended 
in place of dry soil, megass ash, etc., for mixing with 
sulphate of ammonia or guano to increase the bulk and 
insure a more equal distribution of the manures when 
they are being applied. 
The property of gypsum in facilitating the decompo- 
sition of clay is probably an important one. Sugar cane 
requires plenty of potash, and also of silica in a soluble 
form. Silica, of course, is the principal constituent of 
clay, and potash also is present in sufficient quantity ; 
but, the larger proportion of both is locked up in the 
form of insoluble compounds which are decomposed but 
slowly, and in some cases, it may be, not fast enough to 
* Or West Indian phosphate, provided it contained 80 per cent. 
