Soluble vs. Insoluble Cane Manures. 347 
As regards phosphorus : since Mr. THOMAS JAM1ESON 
of Aberdeen in 1876 attempted to prove "that 
soluble phosphates are not superior to insoluble phos- 
phates to the extent that is generally supposed" and 
that even the purely mineral phosphates are capable 
of furnishing an adequate supply, of phosphorus to 
plants, provided they are used in a sufficiently finely 
divided state, experimenters in England and on the 
continent have been engaged in testing the com- 
parative merits of the various forms of phosphates.* 
It seems that superphosphate has yielded the best 
results in soils containing abundance of lime, but 
in soils deficient in that substance, and especially in 
those of a peaty and acid character, insoluble phosphates 
have proved to be as efficient as, and in many cases su- 
perior to, the soluble form.t In the one or two compara- 
tive trials that have been made in this colony, the efficacy of 
insoluble phosphate has also been established sufficiently 
well to warrant a continuance and extension of the 
experiments ; considering the nature of the soil, favoura- 
ble results may be anticipated in the majority of cases. 
In England the cost of 1 lb. of phosphorus as super- 
phosphate varies from 8|d. to io|d. according as mineral 
* Mr. Jamieson, in a recent paper replying to criticisms by Dr 
Voelcker estimates superphosphates as giving only ten per cent better 
results than finely-ground mineral phosphates. 
f "It is more advantageous to apply insoluble phosphates rather 
than superphosphate to humous soils, as they are capable of bringing 
insoluble into a soluble condition ; this applies, however, only to peaty 
soils as the presence of lime hinders this aftion." Researches &c. by A. 
Konig, R. Kissling and M. Fleischer, (y. Ckem.Soc. Abs. 1883, 681.) 
On the influence of lime in soils on phosphates, see also B. Dyer (y. R, 
Agric.Soc. 1884, 113.) 
XX 
