30 



On Agricultural Chemistry. 



limits, identical ; that of the nitrogenous proximates fixed is, on 

 the other hand, about tioice as great in the Leguminosas as in the 

 Graminaceae. This fact, too, perfectly coincides with the results 

 of our experiments in the field, with wheat and beans respectively, 

 which show that under the same circumstances of growth, as to 

 manure, &c., and in the same season, the acreage yield of nitrogen 

 is twice or thrice as great in beans as in wheat. It cannot be 

 supposed, however, that with the larger amount of nitrogen 

 harvested in the leguminous crop the soil would be proportion- 

 ally exhausted of it, for common practice teaches that, other 

 things being equal, wheat, which is especially dependent on the 

 supply of nitrogen in the soil, would give a larger produce after 

 a bean than after a wheat crop. 



Here then it would appear that there is evidence of a superior 

 power in the leguminous, as compared with the graminaceous 

 plants, of obtaining their nitrogen from the atmosphere rather than 

 from the soil ; or it may be supposed that the expenditure of it 

 during the growth of the plant is greater in the one case than in 

 the other. 



In support of the view that leguminous plants do possess a 

 superior power of reliance upon the atmosphere for their nitrogen, 

 and, indeed, that it is to this property that they materially owe 

 their efficacy in rotation with grain, we may refer to the admirable 

 investigations into the Chemistry of Agriculture of M. Boussin- 

 gault. His experiments, however, have not received the attention 

 which they merit from the agriculturists of this country ; probably 

 on account of the small amounts of produce which he obtained. 

 But it must be remembered that his investigation had for its object 

 to explain the practices of agriculture as he found them in his own 

 locality, before attempting to deviate from its established rules. 

 M. Boussingault states the rotation usually adopted at Bechel- 

 bronn, and throughout the greater part of Alsace, to be as 

 follows : — 



" Potatoes or beet-root," 

 -Wheat," 

 " Clover," 

 " Wheat 



and that the average of wheat so obtained is, after potatoes 

 19 J bushels, after beet-root 17 bushels, and after clover 24 bushels. 

 Now we find by reference to his table that the first crop of wheat, 

 grain, and straw removed 17 lbs. of phosphoric acid and 24 lbs. 

 of potash and soda ; the following clover crop, i 8 lbs. of phos- 

 phoric acid and 77 lbs. of potash and soda ; and after this 

 removal of alkalies and phosphates by the clover, a larger crop of 

 wheat is obtained. Surely it would seem impossible to reconcile 



