FUNCTION AS MANURE 29 



the sulphate of ammonia was inferior in its action to the 

 nitrate of soda, and in most cases probably poisonous. On the 

 other hand, where lime was applied in connection with the two 

 forms of nitrogen, the ill effect of the sulphate of ammonia was 

 not only overcome, but in (the) case of several crops the yield 

 from the limed sulphate of ammonia plots even exceeded that 

 where lime was used in connection with the nitrate of soda. 

 \Yith but few exceptions the results show conclusively that 

 the value of the lime was more due to its overcoming 

 the natural acidity of the soil, and the acid tendency of the 

 sulphate of ammonia, whereby the nitrogen was changed into 

 a form available to the plant, than to its direct fertilising 

 value. . . . Among the cereals we find that barley was less 

 able to withstand the acid soil conditions than the oats and 

 rye." 



4. Special Function as a Manure. Sulphate of 

 ammonia is to be regarded as a purely nitrogenous manure. 

 Its sulphuric acid is doubtless sometimes of advantage, 

 and tends in some cases to increase the fertility of the 

 soil, or supplies directly the demand for sulphur by the 

 crop. Sulphate of ammonia would, however, never be em- 

 ployed for the sake of the sulphuric acid which it contains, as 

 other manures, gypsum for instance, would supply this con- 

 stituent at far less cost. Sulphate of ammonia is profitable 

 when an additional supply of an active nitrogenous plant food 

 is required in the soil. Its use is thus limited to those crops 

 which depend for their luxuriance on the presence of a con- 

 siderable supply of available combined nitrogen in the soil, 

 and it is of no practical use to crops which obtain their principal 

 supply of nitrogen from the atmosphere. That sulphate of 

 ammonia could not be used with profit for leguminous crops 

 was discovered in some of the earliest experiments with this 

 manure, its inefficiency for such crops was indeed well known 

 long before the cause of that inefficiency was understood. To 

 employ sulphate of ammonia for beans, peas, vetches, clover, 

 lucerne, sainfoin, etc., is generally to throw the manure away. 

 Sulphate of ammonia may often be applied with advantage to 

 mixed seeds, as clover and rye-grass, vetches and oats, but in 



