EXPERIMENT STATION BULLETINS. 



353 



The losses of plant-rood elements from the 100-acre general farm 

 are somewhat less than from the grain farm of similar size but they 

 are still menacingly large. The keeping of enough livestock to consume 

 a considerable portion of the farm produce has reduced the annual loss 

 of fertility but not so much as is generally believed. 



The clover hay has taken its nitrogen from the air rather than from 

 the soil. The amount of nitrogen so removed, however, is equal to the 

 nitrogen contained in the tops or hay, that in the roots being drawn 

 from the soil. It is evident, therefore, that the mere growing of clover 

 does not increase the supply of nitrogen in the soil unless the clover is 

 returned directly or as manure. If the clover is fed to dairy stock a 

 considerable percentage of the nitrogen it contains is retained by the 

 animal. The clover also draws its supply of mineral elements from the 

 soil and hence there is a direct loss of these materials. 



In general a larger crop follows the plowing under of a clover sod 

 even when all the hay has been removed. This is due to the fact that 

 the roots, stubble and fallen leaves of clover decomposes rapidly releas- 

 ing their supply of plant-food elements. This decomposition may force 

 the soil particles to release a portion of their elements in an available 

 form. The result is then available plant-food rather than an increased 

 supply in the soil. 



Conditions on a dairy farm. Dairy farming is widely practiced in 

 Michigan. The plant-food condition on a farm carrying sufficient stock 

 to consume practically all the feed crops which can be grown and still 

 maintain a fairly well balanced farming system in addition to purchased 

 concentrates will be studied here. 



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FiQOBB 8. — Much organic matter is destroyed and considerable quantities of nitrogen, phosplioric 



acid and potash are retained by dairy cows, 

 45 



