CHAPTER XXV 

 GREEN-MANURES * 



From time immemorial the turning-under of a green-crop 

 to supply organic matter to the soil has been a common agri- 

 cultural 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 greater originality. The art was lost to a great extent dur- 

 ing the Middle 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 man- 

 agement, and is given a place, when possible, in every ra- 

 tional plan for permanent soil improvement. 



309. Importance of green-manures. — The plowing under 

 of some succulent rapid-growing crop, such as oats, rye, or 

 clover, tends to bring about three desirable soil conditions; 

 additional organic matter, a betterment of the physical con- 

 dition of the soil, and a rise in the nitrogen content of the 

 land, if the crop is an inoculated legume. If conditions are 



1 Penny, C. L., Clover Crops as Green Manures; Del. Agr. Exp. Sta., 

 Bui. 60, 1903. 



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



Lipman, J. G., Bacteria in Eelation to Country Life, Chapter XXIV, 

 pp. 237-263; New York, 1911. 



Piper, C. V., Leguminous Crops for Green Manuring; U. S. Dept. Agr., 

 Farmers' Bui. 278, 1907. 



Spillman, W. J., Renovation of Worn-out Soils; U. S. Dept. Agr., 

 Farmers ' Bui. 245, 1906. 



Pieters, A. J., Green Manuring: A Review of tine American Experi- 

 ment Station Literature; Jour. Amer. Soe. Agron., Vol. 9, No. 2, pp. 

 62-82, Feb. 1917; Vol. 9, No. 3, pp. 109-126, Mar. 1917; Vol. 9, No. 4, 

 pp. 162-190, Apr. 1917. 



537 



