OFTHE 



UNIVERSITY 



CHAPTEE IX 



PHOSPHO-NITKOGENOUS MANURES 



UNDER this head are included a number of products 

 which contain appreciable quantities of both phosphates 

 and nitrogen. They are all waste or bye-products of 

 animal origin, but most of them are subjected to special 

 treatment to render them suitable for manurial pur- 

 poses before they are put on the market. 



They are not generally relegated to a separate class, 

 but are treated as phosphatic manures or nitrogenous 

 manures according to the nature of the predominant 

 constituent. For example, bones containing over 45 per 

 cent, of phosphates and less than 4 per cent, of nitrogen, 

 are generally treated as phosphatic manures, and meat 

 meals containing more than 10 per cent, of nitrogen and 

 less than 5 per cent, of phosphates are dealt with under 

 nitrogenous manures. It must, however, be remembered 

 that, notwithstanding the great difference in the pro- 

 portions of the two ingredients, nearly half the value 

 of the bones is attributable to the nitrogen. Also, although 

 in some samples of meat meal, etc., the proportion of 

 phosphates may be negligible, in others it actually exceeds 

 that of the nitrogen, and must be taken into account. It 

 is therefore convenient, as well as theoretically sound, 

 to treat the phospho-nitrogenous products as a separate 

 group, intermediate between the phosphatic manures on 

 the one hand, and the nitrogenous manures on the other. 



General Properties. It is characteristic of these pro- 

 ducts that the fertilising ingredients are insoluble in 

 water, and only become available to plants when the 



