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A gricultura I Chemistry. 



of the crop, is assimilated, converted into complex organic com- 

 pounds in the plant and restored to the soil. Without the crop 

 these nitrates would have been to a large extent lost by drainage. 

 The planting of "catch crops" for this purpose is best done in 

 the autumn, since nitrification is then very rapid and loss from 

 washing out of nitrates by winter rains is to a great extent pre- 

 vented. 



For green manuring, two classes of crops are in common use. 





Experiments showing that "green manuring" with legume plants can 

 supply all the nitrogen needed by a succeeding crop (after Wagner). 



To the first class belong such crops as buckwheat, mustard, rye, 

 rape, etc. These kinds of plants are efficient in restoring car- 

 bonaceous matter and what nitrogen was available for their 

 growth. They have added no essential element of plant growth. 

 They should be plowed under before seed is produced or other- 

 wise the land would be fouled for the next year. 



To the second class belong the legumes. They have all the ad- 

 vantages of the first class, but in addition, increase the amount 

 of nitrogen in the soil. Those most often recommended are red 

 clover, the lupines, cow peas, crimson clover, soy bean and the 



