CANE SUGAR. 



Choice of Phosphatic Manures. All phosphates when applied 

 to soils are fixed, and rendered insoluble ; the rationale of the use of a soluble 

 superphosphate, as opposed to the use of an insoluble phosphate, is that the 

 solution of phosphoric acid is precipitated within the soil in a much finer state 

 of division than can be obtained by grinding an insoluble phosphate, and 

 mechanically ploughing it into the soil. Dependent on the type of the soil, the 

 phosphoric acid will be precipitated within the soil as phosphate of lime, or 

 iron or alumina. The former of these bodies is available to the plant, the 

 latter is not ; hence it is an axiom in manuring that superphosphates are suitable 

 for calcareous soils or such as contain a considerate proportion of lime carbonate. 

 On heavy clays such as constitute the cane lands of British Guiana super- 

 phosphates are contraindicated. On such, soils basic slag is the form of 

 phosphatic manure from which benefit is to be expected. It has been shown 

 by many experiments that on clayey and peaty soils, where an alkaline base is 

 required to neutralize the nitric acid formed by soil organisms, this form of 

 phosphoric acid gives the best results. 



Artificial Manures. The properties of the manures occurring in 

 commerce are briefly mentioned below : 



Sulphate of Ammonia. The pure body contains 2T21 per cent, nitrogen, 

 and as found on the market contains about 20 per cent, nitrogen. 



Nitrate of Soda. This material is extremely hygroscopic. The pure 

 body contains 16'5 per cent, nitrogen, the commercial body containing about 

 4 per cent, of impurities ; these impurities are in English commerce grouped 

 together under the peculiar term of refraction. 



Nitrate of Potash. The pure body contains 13'8 per cent, nitrogen, and 

 46*5 per cent, of potash; it is but seldom used as a manure, the supply being 

 devoted to other purposes; in an impure form it however finds its way to 

 Mauritius from India, and being of local occurrence is used to a certain extent 

 in Egypt. 



Seed Cake Manures. The refuse of seeds, &c., that have been crushed for 

 oil, comes into the market in large quantities as manure. The plants that 

 most largely contribute are cotton, flax, castor oil, cocoanut ; their composition 

 of course varies with the origin. In general these manures can be used only 

 in the country of their origin, drawbacks of freight prohibiting their more 

 extended use. Some analyses of these materials, collected from various sources, 



are given below : 



Nitrogen per cent. 



Ground nut (Aracliis hypoyaea] 4'06 - 7 '94 



Kapok meal (Eriodendnon anfraduosum) .'. ... 4'40 



Castor cake (Ricinus communis) .. .... .... 4'20 



Coconut meal (Oocos nucifera) . . ..-....:. ' 3 -62 



Cotton seed meal (Gossypium sp.} . . ..-:.' ;. 7*00 



Chinese bean meal . . ..-..-.. . . "-. . ' . . .-. 6'96 



Soja cake (Soja hispida) "; .....- ,.'" : 6-12 



72 



