34 PLANT PRODUCTS 



containing from i to 3 per cent, of nitrogen, obtained by some 

 boiling or steaming process. When finely divided, these 

 bone fertilizers are readily available in the soil, and may be 

 considered as more or less equivalent to basic slag, but of 

 course the nitrogen is in addition. The small amount of 

 calcium carbonate present in the bones is also useful to the 

 soil. lyike all other manures containing organic matter bones 

 will provide some food for bacteria or other forms of soil life. 



Bones are also treated with sulphuric acid in the same 

 way as mineral phosphates are treated for the production 

 of super-phosphates. The product is generally known as 

 dissolved bones or vitriolated bones. For the manufacture 

 of this article rather stronger acid is necessary, and it is 

 not practicable to get the whole of the phosphate into 

 solution. The general run of dissolved bones contain about 

 3 per cent, of nitrogen, 15 per cent, of phosphates which have 

 been rendered soluble, and 15 per cent, of phosphates which 

 have not been acted on by the acid at all. By these means 

 the nitrogenous matter is dissolved as well as the phosphatic 

 material, so that the resulting dissolved bones must be looked 

 upon as a mixture of four fertilizing ingredients, namely, 

 soluble phosphates, insoluble phosphates, soluble nitrogen, 

 and insoluble nitrogen. The advantage of having two 

 degrees of solubility is very marked : the insoluble phosphates 

 will, on application to the soil, remain on the surface, and 

 the soluble will penetrate to a depth of a few inches. In- 

 soluble nitrogen may be left on the surface, but the soluble 

 nitrogen in this case will penetrate probably to a foot in 

 the soil, since those portions which are in the form of amino- 

 acids will not be at all readily fixed by the soil, but will 

 penetrate to a greater depth than ammonia salts could 

 (see pp. 7 and 13). As such materials will be very mixed 

 the nitrogen will be distributed over a considerable range 

 and depth of soil, and will therefore suit a variety of crops 

 in very varied stages of growth. 



A very frequent type of bone manure is composed of 

 super-phosphate, bone flour, and sulphate of ammonia. 

 Here again there is the advantage of two kinds of phosphorus 



