REVERSION OF SUPERPHOSPHATE. 227 



Of these brands, it is seen some cost for the available 

 phosphoric acid nearly twice as much as others, and it is of 

 course requisite that great circumspection be used in the 

 purchase of these costly forms of plant food. 



If the farmer wish to do so, he can make his own super- 

 phosphate from bones in the following manner. A wooden 

 vat is provided in which the bones, coarsely broken or 

 ground fine as the case may be, are heaped and thoroughly 

 wetted with w r ater. Sulphuric acid is carefully poured up- 

 on the heap of bones, and a strong effervescence at once 

 takes place accompanied by considerable heat. The bone 

 is shoveled over to keep it in condition to be acted upon by 

 the acid. About 50 Ibs. of acid is required for 100 Ibs. of 

 bones to make a complete decomposition. In course of time 

 the bone is reduced to a pasty condition when it may be 

 dried by the addition of wood ashes, or potash salts, and 

 fish scrap, which will add the potash and nitrogen to the 

 fertilizer to make it a complete manure for crops; that is 

 one that contains nitrogen in an available form, soluble 

 phosphoric acid, and potash. When the potash salts are 

 used, there will be magnesia, soda and chlorine also added. 



Superphosphate of lime reverts to the condition of bi- 

 phosphate or ordinary phosphate, when there is lime in the 

 soil. This change however occurs slowly unless the lime is 

 in excess, when the present use of the phosphate is neutral- 

 ized because it is made insoluble. Hence superphosphate 

 should never be used when the land is limed. 



It is usually applied to the fall grain crops in quantities 

 varying from 200 to 400 Ibs. per acre, and is sown by means 

 of an attachment to the drill which drops it in the row near 

 the seed, and thus makes it immediately available for the 

 crop in its early stages and when the young plants need an 

 abundant supply of food. Or it is sown broadcast as soon 

 as the seed is sow y n and both are harrowed in together, when 

 the drill is not used. It is also used for the corn crop either 

 dropped in the hill at planting, or harrowed in before plant- 

 ing. From its soluble character it should be brought as 

 near the seed as possible, that it may be absorbed by the 



