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ANNUAL REPORT OF THE 



Off. Doc. 



considerably increase our supplies of available nitrogen, and in turn 

 reap the rewards of such an increase in larger crops. 



Such a system of intensive cultivation carried on year after year 

 would, however, result in the burning out of the land, and in greatly 

 reducing the fertility. It is, therefore, necessary to make good these 

 losses of organic nitrogen by the growth of such crops, or by the use 

 of animal manures, as shall add to the stock of humus already in the 

 soil. The eflect of stable manure and clover in increasing the quan- 

 tity of nitrates in the soil is brought out in the following table :=» 



Table X. 



Nitrogen as Mtric Acid in Pounds per Acre in Soils of Geescroft and 

 Hoosfield Experimental Plots, Eothamsted. 



1-9 



10-19 



19-27 



28-36 



37-45 



45-54 



55-63 



64-72 



Total, 



The results given in column I are from a field left for 30 years un- 

 manured and exhausted by continuous cropping to beans, followed by 

 fallowing. In column II it is seen how, even under condition of the 

 most heavy drain upon a soil, the supply of available nitrogen can be 

 maintained by the use of stable manure. 



In columns I and II above, the comparatively large quantities of 

 nitrates in the lower zones of the soil will be noted as indicative of 

 the effect of excessive downward percolation during 4-5 years of 

 fallowing; for this reason the soils of the Geescroft field are really 

 poorer in available nitrogen, within that zone occupied by the bulk 



