234 



Phosphatic Fertilisers. 



[June, 



PHOSPHATIC FERTILISERS. 



E. J. Russell, O.B.E., D.Sc, F.K.S., 



Rothamsted Experimental Station. 



Phosphates serve at least five purposes in the soil :— 



1. They cause an earlier development of the young plant 

 than would otherwise occur; 



2. They bring about a considerable development of fibrous 

 roots ; 



3. They counteract the rankness of growth which is liable to 

 occur on land richly supplied with nitrogen compounds ; 



4. They hasten ripening and improve the quality of grain. 



5. They increase the feeding value of the ordinary fodder 

 crops. 



They are more widely used than any other fertilisers, and the 

 farmers of the United Kingdom alone purchase something like 

 one and a quarter million tons each year. 



Bones. — The oldest form of phosphate used on the farm is 

 obtained from bones. In old days raw bones themselves were 

 much used. Under modern conditions the fat and often the 

 gelatine are first removed, these having considerable commercial 

 value, and the residues are then ground for manure. Some- 

 times also the bones are treated with sulphuric acid to make the 

 phosphates more soluble. There are thus four bone products 

 obtainable by the farmer : — 



(a) Raw bones, containing the whole of the material, includ- 

 ing fat and gelatine ; 



(b) Bone-meal, containing the gelatine, but not the fat: 



(c) Steamed bone flour, containing neither gelatine nor fat ; 



(d) Dissolved bones, being raw bones or bone-meal treated 

 with sulphuric acid. 



T t ypical analyses are as follows (the figures being percentage 

 constituents) : — 







Equivalent 



Phosphoric 



Equivalent 







to 



Acid. 



to tricalcic 





Nitrogen. 



Ammonia. 



(P. Q 6 ). 



phosphate. 



Raw English bones ... 



5 



6 



22 



48 



Bone-meal 



3-5-4 -5 



4-2-5-4 



20-25 



43-55 



,, usual analysis ... 



3-75 



4-5 



20-6 



45 



Steamed bone flour ... 



1-2 



1-2-5 



25-32 



55-69 



Dissolved bones 



2-3 



2-3-3-8 



15-16 



33-35 



Bone fertilisers are very safe, but they are generally less 

 effective than the substances described below. They have not 



