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difficulty in obtnining a sufficient supply. The acid sap of the roots 

 is necessiiry to dissolve these phosphates, though the carbonic acid gas 

 produced by the decay of vegetable matter, assists in their solution. 

 In some foims, then, of phosphatic manures, the phosphate is in a 

 much more soluble state than in others. Hence the purchaser should 

 always insist upon an analysis stating^ the proportion of phosphate 

 which is soluble. Bodies are the oldest special manure of any kind in use. 

 Ihey were first applied in inch or half-inch piece- ; later tliey were 

 ground to a powder. In either case they were a long time in coming 

 into use on account of the insoluble nature of the phosphate they con- 

 tained. It Avas found that fermenting — by makinj^ a heap and watering 

 with urine — rendered them more readily available. The phosphate of 

 steamed bones, i.e. bones which have been steamed in order to remove 

 their gelatin for glue-making, is also more soluble than that of raw 

 bores. The conversion of insoluble into soluble phosphate is brought 

 about most completely by dissolving the bones in sulphuric acid. This 

 process is the basis of the manufacture of superphosphates. 



As the supply of bones for such purposes is necessari y limited, su- 

 perphosphates are now more frequently made from what are known as 

 mineral phosphates. These are of t a o kinds, viz., the rock phosphate 

 found in Canada, and coprolites, which are little lumps of fossilised 

 dung. The latter are mined in many parts of the world, e.g. in seve- 

 ral of the West Indian Islands. These hard insoluble masses are 

 ground and treated with siilpluric acid, when they yield a manure 

 composed chiefly of soluble phosphate. 



(iii ) Potassic manures. — Since the production of sugar and starch, 

 by plants causes the removal of potash from the soil, sugar, and starch- 

 producing crops should receive potassic manures. This accounts for 

 the increase in yield of Irish potatoes in land that had received an ap- 

 plication of sea-weed. Similarly, it has been found in Jamaic t that wood 

 ashes improve the quality of oranges, that is to say, make them sweeter. 

 In a country where so much wood is used for fuel, there is 

 scarcely any necessity for buying potash fertilisers. Wood ashes 

 contain a fairly high percentage of pot;ish in u read ly available form. 

 In the United States wood ashes are an article of commerce, the price 

 per ton varying from 10 to 12 dollar--. This fact should suggest to the 

 cultivator in Jamaica the \alue of the ashes from his kitchen and the 

 desirability of making use of them. He must, however, be warned 

 against allowing them to be washed by rain By leaching, wool ash.es, 

 like stable mauure, lose all their soluble matter. Ashes may with ad- 

 vantage be applied to tobacco and leguminous crops. 



Growers of tobacco have at their disposal another potash manure. 

 Tobacco stalks are rich in this constituent and should always be re- 

 turned to the soil. If potash in an available form be requiie l, the 

 stalks should be burnt ; otherwise they should be allowed to xoi in the 

 soil, thereby adding also a small amount of nitrogen. 



Kainit is the chief chemical fertilizer supplying potash. It is 

 obtained from the huge salt mines of Greimany, and can be placed on 

 the market at a low price. 



Indirect manures. — It has been shown that substances like stable 

 manure, besides adding plant food to the soil, have an indirect actio i 



