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Gramineae. Lastly, what is the significance of the great decline in the 

 yield of nitrogen in all the crops grown on arable land when none is 

 supplied in the manure ? 



Combined Nitrogen in Bain, 8fc. 



It has been assumed by some that the amount of combined nitrogen 

 annually coming down in the measured aqueous deposits from the 

 atmosphere is sufficient for all the requirements of annual growth. In 

 Liebig's earlier writings he assumed the probability of a very much 

 larger quantity of ammonia coming down in rain than he did subse- 

 quently ; but even in his more recent work, " The Natural Laws of 

 Husbandry," published in 1863, he supposes that as much as 24 

 pounds of nitrogen per acre may be annually available to vegetation 

 from that source. Such an amount would, it is obvious, do much 

 towards meeting the requirements of many of the crops the nitrogen 

 statistics of which have been given. 



The earliest considerable series of determinations of the amount of 

 ammonia coming down in rain in the open countiy were by Boussin- 

 gault, in Alsace. He gives the amount of ammonia per million of 

 rain-water in each fall for a period of between five and six months, 

 May-October, 1852 ; but he does not calculate the amount so coming- 

 down over a given area of land. His average amount per million 

 was, however, somewhat less than that found at Rothamsted in 1853 

 and 1854, and found by Mr. Way in Rothamsted rain-water collected 

 in 1855 and 1856 ; which, calculated according to the rain-fall of the 

 periods, give the following amounts of nitrogen so coming down per 

 acre. The amounts of nitrogen as nitric acid, as determined by 

 Mr. Way, and the amount of total combined nitrogen as ammonia 

 and nitric acid together, are also given. 



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