in succession on the same land ; barley for thirty-one years ; wheat in 

 alternation with fallow thirty-one years ; beans for nearly thirty 

 years ; clover for many years ; turnips, sugar-beet, or mangels, nearly 

 forty years ; whilst experiments on the mixed herbage of grass land 

 have been continued for twenty-seven years, and on an actual course 

 of rotation for thirty-five years. "We have, from time to time, pub- 

 lished what we may call the nitrogen statistics of the crops so grown ; 

 and we have compared these facts of production with what is known 

 of the sources of nitrogen available to the crops. 



Yield op Nitrogen in Different Crops. 



The following table (I) shows the yield of nitrogen per acre per 

 annum, in wheat, barley, root-crops, beans, clover, and in ordinary 

 rotation, in each case without any nitrogenous manure. It will be 

 observed that only in the case of the root-crops is the record brought 

 down to a later date than 1875. Independently of the fact that the 

 requisite nitrogen determinations are not yet completed for the subse- 

 quent period, it has been decided that, owing to the number of very 

 exceptionally unfavourable seasons for corn crops which have occurred 

 since 1875, it would be fallacious to bring the result'' for those crops 

 in the later seasons as illustrating the falling off of yield due to soil 

 exhaustion. 



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