ON MANURES. 



II37 



potash salts or kainit, and will be found beneficial in old kitchen- 

 gardens rich in organic matter. Experiments have proved that 

 mixtures of bone-meal and wood-ashes serve an excellent purpose 

 when used as a substitute for farmyard manure. 



Basic Slag. — Basic slag, or "Thomas's phosphate," of which 

 the following data show the chief constituents, is a manure 

 which has come largely into use in the last few years. The 

 figures show that it contains a large proportion of lime (which is 

 in a caustic condition), phosphoric acid, and iron oxides. It is 

 of various manurial qualities, ranging from about 12 per cent, of 

 phosphoric acid (equal to 26 per cent, of tribasic phosphate 

 of lime) to over 20 per cent, of phosphoric acid (equal to 

 nearly 44 per cent, of phosphate), so that guarantees of quality 

 should be carefully considered by the purchaser. 



Selected Constituents in Basic Slag. 



Lime.. .. ., .. .. .. .. ^5-04 per cent. 



Magnesia . . . . . . . . . . . . 6*20 ,, 



Phosphoric acid .. . .. .. .. i8-ii ,, 



Iron oxides .. .. .. .. .. .. I7'56 ,, 



Silica . . . . . . . . . . . . 6-90 



Manganese . . . . . . . . . . . . 3-51 



Experiments with basic slag have indicated that to produce 

 the same effects as superphosphate, at least twice the quantity 

 should be applied in the form of slag as would suffice in that 

 of superphosphate,,,..— Soils poor in lime, or those inclined to be 

 wet and sticky^/'^e most benefited by basic slag, provided that 

 they contain plenty of organic matter. Basic slag is a manure 

 wxll adaptej^ for fruit-trees, flowering shrubs, Roses, lawns, pad- 

 docks, and pastures. It must not be used in combination with 

 ammonia salt, because it sets the ammonia free, and causes, 

 a loss of plant-food. It may, however, be mixed with nitrate 

 of soda. 



Superphosphates. — Mineral superphosphate is the cheapest source 

 of soluble phosphate manure, and is made by treating with 

 sulphuric acid very finely-ground mineral rock phosphates. The 

 value of the superphosphate for manurial purposes ' is indicated 

 by the percentage of phosphate made soluble, which may range 

 from 25 per cent, to 28 per cent. Superphosphates are frequently 

 made containing as much as from 35 per cent, to 40 per cent, 

 of soluble phosphate, or even more. They are then called 

 " double superphosphates," and are practically free from sul- 

 phuric acid, which is a decided advantage on soils that are 

 subject to the disease known as " Club-Root " in the Brassica 

 family. 



When superphosphate is applied, the first rainfall or artificial 

 watering, or even the moisture of the soil, dissolves the- 



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