14 



Yield of Nitrogen in the Mixed Herbage of Grass Land. 



Another illustration of the amounts of nitrogen removed from a 

 given area of land by different descriptions of crop will be found in 

 Table III, which shows the results obtained when plants of the 

 gramineous, the leguminous, and other families, are grown together, 

 in the mixed herbage of grass land. 



Table III. 



Yield of Nitrogen on the Mixed Herbage of Permanent Grass Land 



at Rothamsted. 



Before referring to the figures, attention should be called to the 

 fact that gramineous crops grown separately on arable land, such as 

 wheat, barley, or oats, contain a comparatively low percentage of 

 nitrogen, and assimilate a comparatively small amount of it over a 

 given area. Yet nitrogenous manures have generally a very striking 

 effect in increasing the growth of such crops. The highly nitro- 

 genous leguminous crops, on the other hand, such as beans and 

 clover, yield, as has been seen, very much more nitrogen over a 

 given area : yet they are by no means characteristically benefited by 

 nitrogenous manuring, but their growth is considerably increased, 

 and they yield considerably more nitrogen over a given area, under 

 the influence of purely mineral manures, and especially of potash 



* Mean of four separations only, namely, 1862, 1867, 1872, and 1875. 



t Including potash, six years, 1856-1861 ; without potash, 14 years, 1802- 



1875. 



X Including potash, 20 years, 1856-1875. 



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