380 



Nitrate of Soda as a Manure. 



Ammonia and Nitric acid equal to a full dressing of Saltpetre or 

 Guano. Much of each, especially the Ammonia, is lost, perhaps, 

 by exhalation from the surface of plants or of the land after slight 

 showers. Enough, however, of both must remain to account for the 

 luxuriant growth which sometimes seems to follow a thunder- 

 storm, and also to illustrate the Psalmist's expression that the 

 clouds drop fatness. This atmospheric distillation may also ac- 

 count for the permanent fertility of downs from which the sheep 

 have for centuries been removed every night — in some degree 

 for the benefit conferred by rest upon fallows — partially even for 

 the remarkable repetition of wheat-crops at Lois Weedon, if we 

 suppose that the constant stirrings practised by Mr. Smith enable 

 the soil to absorb the pluvial Nitrogen that might otherwise 

 escape by evaporation. In any case, this large discharge of 

 Nitric acid as well as Ammonia is rendered important by the 

 direct evidence now attained for the action of that acid upon 

 vegetation. 



Nor will our better acquaintance with Nitric acid be limited, 

 I trust, to the theory of agriculture, or remain a dead letter, 

 without effect on our practice, for we now know with certainty 

 the efficacy' of the Nitrates. But one great chemical problem of 

 agriculture is the prevention of waste in dung-making ; yet the 

 attempts to fix the ammonia of dung have not been very happy. 

 While some methods have not fixed it at all, others have cost 

 in fixing it more than the result, if attained, would be worth. 

 The favourite proposal has been the formation of sulphate of 

 ammonia, which, under ordinary circumstances, is a fixed salt. 

 But an experiment made last spring on this farm will show how 

 little we can depend on the fixity so dearly obtained. 



A ten-acre piece of oats, looking last spring very badly, was 

 dressed on one side with nitrate of soda, and with sulphate of am- 

 monia upon the other side, a blank space being left in the middle. 

 Since the nitrogen in the ammonia and in the nitrate were in the 

 proportion of 20 and 15 respectively, I made no doubt that, as equal 

 quantities, 6 stone of each per acre, were used, the ammonia Vv^ould 

 yield the bulkier crop. On the contrary, while the nitrate, though a 

 moderate dose, gave an increase of 18 bushels per acre, forcing the 

 straw, too, a foot higher, no difference at all could be seen be- 

 tween the yield of the unmanured and of the ammoniated land. 

 This unaccountable result has been cleared up, however, by Dr. 

 Voelcker, who informs me that sulphate of ammonia had equally 

 failed on the Cirencester farm : that he had often remarked a 

 pungent odour on the land where it was used, and has little doubt 

 that this salt, however carefully fixed, had been decomposed again 

 and dissipated by the natural lime of the soil.* 



* On other soils sulphate of ammonia has been found operative, but it is 



