876 



Manures in December. 



[Dec. 



MANURES IN DECEMBER. 



E. J. Eussell, D.Sc, F.E.S.. 



Rothavistecl Experimental Station, Harpendcn. 



The Purity of Suiphate of Ammonia. — Correspondence has 

 recently appeared in some of the technical papers as to the 

 value of neutral sulphate of ammonia in comparison with the 

 older and somewhat acid material common some years ago, and 

 one correspondent has raised the question as to whether there 

 is any advantage to farmers in the neutral material. In favour 

 of neutrality it is urged that the bags do not rot, as they are 

 liable to do when acid is present; and further, that the neutral 

 material is almost invariably in better condition than is the 

 case with the old samples. Against this, however, it is stated 

 that the trace of sulphate of iron present in the slightly acid 

 sulphate of ammonia becomes converted, on neutralisation, 

 into oxide, which is less soluble than the sulphate, and there- 

 fore less valuable as fertiliser. 



From the agricultural point of view the neutral sulphate is 

 undoubtedly an advantage. Acidity does not help the farmer 

 in any way; it corrodes the implements, causes the bags to rot, 

 and makes the material unpleasant to handle. We should 

 not be prepared to say whether the condition is improved ])y 

 neutralisation, or whether some other part of the purifying 

 process may not tend to produce better condition of the samples : 

 it is, however, important that the fertiliser should be in as good 

 condition as possible and free from liability to cake. 



So far as is known there is no advantage in the trace of iion 

 present in the commercial sulphate, and it is quite immaterial 

 from the farmers' point of view whether this is present as 

 sulphate or as oxide. Ordinary agricultural soils contain from 

 2 J or 3 per cent, up to 6 per cent, or more, or, stated in weight, 

 from 25 to 60 tons or more per acre. It is highly improbal)le 

 that the small additional amount added in sulphate of ammonia 

 would exert any effect. 



Periodically we are asked whether the unusual ingredients- 

 iron, manganese, &c. — are of value as fertiliser. It is known 

 that some of them may act beneficially in physiological experi- 



