RATIONAL FRUIT CULTURE. 51 



SOOT AS A FERTILISER. 



Another source of nitrate is soot. Being quite insoluble 

 in water, it cannot itself be a plant-food, but it is a carrier 

 of plant-food. When coal or wood is burned, aromoniacal 

 gases are driven off, and some of them — containing nitrogen- — 

 are absorbed in the pores of the soot. They are so powerful 

 that if fresh soot is applied to growing plants, it will burn 

 the foliage; it should first be exposed to the air for three or 

 four days to allow some of the gases to escape. It may be 

 used in orchards — in spring, or early summer — at the rate of 

 about twenty bushels to the acre. It has a further value in 

 reducing the number of injurious insects. 



PHOSPHATIC 1\LVNURES. 



The chief artificial sources of phosphate are basic slag and 

 superphosphate of lime. As they dissolve slowly they should 

 be applied in autimm or winter — basic slag at the rate of from 

 six to eight hundredweight per acre, and the superphosphate 

 at the rate of four or six hundredweight. The former should 

 be bought as a very fine powder. If the particles are coarse, 

 they will remain almost unaltered in the soil for many years, 

 and will do very little good. 



Bone-meal and guano are other phosphatic manures in 

 common use. 



SOURCES OF POTASH. 



The chief sources of potash are kainit and sulphate of 

 potash. As it remains in the ground, like phosphate, and 

 does not drain away as nitrate idoes, it is usually applied at the 

 same time as the former — kainit at the rate of four hundred- 

 weight per acre, and sulphate of potash at the rate of one 

 hundredweight. As is indicated by the difference in the rates 

 of application, the percentage of potash in the latter fertiliser 

 is very much greater than in the former, and, therefore, the 

 price is proportionately higher. As almost the whole of our 



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