198 COMPARATIVE EXPERIMENTS WITH THE 



plants are accustomed to take up and appropriate it, has 

 rendered it probable that, weight for weight, the nitrate of 

 ammonia would more largely promote the growth of plants 

 than any other salt of ammonia. It is expensive, however, and 

 is not a usual article of commerce, and therefore few experi- 

 ments have hitherto been made with it. But it is very desirable 

 that such experiments should be made, as they would not only 

 throw light on some interesting points of theory, but might 

 lead to useful suggestions in matters of practice. 



7. Results of comparative, experiments with the different salts 

 of ammonia, and with the nitrates of potash and soda. 



It will be interesting to compare together, so far as our pre- 

 sent defective materials will allow, the actions of the several 

 salts of ammonia upon the same crop, and the effects produced 

 at the same time by the nitrates of potash and soda. The only 

 comparative experiments of this kind I have been able to meet 

 with are the following upon oats and hay : 



1. On oats, after turnips, in 1846, Mr Main applied the 

 sulphate and muriate of ammonia in comparison with nitrate of 

 soda and the sulphates of soda and magnesia. The soil was 

 light and sandy, and had been long cultivated without rest. 



Grain. Straw. Increase of grain. 



No application . . gave 45 bush. 24 cwt. 



Sal-ammoniac, 2 cwt 71^ ... 32 "... 26 bush. 



Sulphate of ammonia, 2 cwt. ... 62 ... 27J ... 17 



Sulphate of soda, 2 cwt. ... 64 ... 26^ ... 19^ ... 



Sulphate of magnesia, 2 cwt. ... 58f ... 26^ ... 13| ... 



Nitrate of soda, 2 cwt 45 ... 21* ... ... 



In this experiment all the applications, except the nitrate of 

 soda, did good. The action of the sal-ammoniac was most 

 striking, but that of the sulphate of soda exceeded that of the 

 sulphate of ammonia. If these results could be confidently 

 relied on, we might suspect from them 



a That sal-ammoniac exercised a special action, under the 

 circumstances, which neither the sulphate of ammonia nor the 

 nitrate of soda was capable of doing. 



'b That the sulphuric acid in the three sulphates had more 

 * Transactions of the Highland Society, January 1848, p. 177. 



