CHAPTER XXVII 

 GREEN MANURES^ 



Feom time immemorial the turning-under of a green 

 crop to supply organic matter to the soil has been a com- 

 mon agricultural practice. Records show that the use of 

 beans, vetches, and lupines for such a purpose was well 

 understood by the Romans, who probably borrowed the 

 practice from nations of still greater antiquity. The art 

 was lost to a great extent during the Dark Ages, but was 

 revived again as the modern era was approached. At 

 the present time green-manuring is considered a part of 

 a well-established system of soil management, and is 

 given a place, where possible, in every rational plan for 

 permanent soil improvement. 



522. Effects of green-manuring. — The effects of turn- 

 ing under green plants are both direct and indirect — 

 direct as to the influence on the succeeding crop, and in- 

 direct as to the action on the physical condition of the 

 soil so treated. In the first place, certain ingredients are 

 actually added to the soil by such a procedure. The car- 

 bon, oxygen, and hydrogen of a plant come largely from 



1 Penny, C. L. Cover Crops as Green Manures. Delaware 

 Agr. Exp. Sta., Bui. 60. 1903. 



Storer, F. H. Agriculture, pp. 137-175. New York. 1910. 



Lipman, J. G. Bacteria in Relation to Country Life, Chapter 

 XXIV, pp. 237-263. New York. 1911. 



Piper, C. V. Leguminous Crops for Green Manuring. 

 U. S. D. A., Farmers^ Bui. No. 278. 1907. 



Spillman, W. J. Renovation of Worn-out Soils. U. S. D. A., 

 Farmers' BuL No. 245. 1906. 



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