MANURES 39 



Sulphate of ammonia is a by-product from gas works 

 and contains about 20 per cent of nitrogen. It does not 

 act as quickly as nitrate of soda; but for late crops, to be 

 applied during warm weather, it is one of the best sources 

 of nitrogen. 



Acid phosphate is an acidulated bone meal made by 

 treating ground bone or raw rock phosphate with sulphuric 

 acid, to render the phosphates soluble. These are rich 

 in available phosphoric acid, and some acidulated bone 

 contains a considerable quantity of nitrogen. They 

 vary much in quality. The better kinds are generally 

 used at the rate of about 400 pounds per acre. 



Raw rock phosphate, or "floats," is perhaps the most 

 suitable source of phosphorus for market gardeners. The 

 phophorus in this is slowly available, but in a soil rich 

 in organic matter it becomes soluble rapidly enough for 

 the use of the crop. 



Wood ashes are rich in potash and are a valuable fer- 

 tilizer in many cases, provided they have not been leached ; 

 if leached greatly they are practically worthless as a fer- 

 tilizer. Ashes from hard wood are more valuable than 

 those from soft wood, on account of containing much more 

 potash. Ashes are one of the best fertilizers for fruit trees 

 and plants. About twenty bushels of unleached hardwood 

 ashes are generally sufficient for one acre, but much more 

 may be safely used. Coal ashes are worthless for fertiliz- 

 ing purposes. 



Kainit. Potash is also applied to the land in the form of 

 German potash salts, a grade of which, known as kainit, 

 is very commonly used as a fertilizer. These salts are 

 more or less mixed with common table salt and other 

 impurities and form a cheap and very useful supply of 

 potash. They are generally sold on a valuation based 



