550 NATURE AND PROPERTIES OF SOILS 



less complete delay has occurred, and the succeeding crop 

 may suffer from lack of moisture. The furrow ordinarily 

 should be turned only partly over, and thrown against and 

 on its neighbor. The green-manure is then distributed evenly 

 from the surface downward to the bottom of the furrow. 

 When decomposition occurs, the resulting materials are evenly 

 mixed with the whole furrow slice. Moreover, this method of 

 plowing does not interfere with the capillary movements of 

 water, and in actual practice is a great aid in drainage and 

 aeration. 



316. Green-manure and lime. — The decay of organic 

 matter in the soil is always accompanied by the production of 

 organic acids of various kinds. The greater the succulence 

 of the material, the more rapid is the accumulation of such 

 products. In spite of this, however, the effect of a green- 

 manure is to decrease the acidity rather than increase * it and 

 later greatly to stimulate nitrification even if the soil origi- 

 nally was quite acid. The decrease in lime requirement may 

 be due to the liberation of mineral constituents from the de- 

 caying organic matter and to the effect of the decomposition 

 on the inorganic constituents of the soil. 



The ultimate influence of green-manure on acidity is some- 

 what in doubt. The bulk of the evidence available seems to 

 indicate that decaying organic matter, if it has any effect, ulti- 

 mately tends to decrease rather than increase the lime re- 

 quirement of the soil. 2 Nevertheless, plenty of active calcium 

 should be in the soil, since it promotes the decay of the plant 

 tissue added and seems to control to a certain extent the pres- 

 ence of toxic materials. Lime may be added to the green- 

 manure seeding and be turned under with that crop. The 



1 White, J. W., Soil Acidity as Influenced by Green Manures; Jour. 

 Agr. Res., Vol. XIII, No. 3, pp. 171-197, April, 1918. 



2 Hill, H. H., A Comparison of Methods for Determining Soil Acidity 

 and a Study of the Effects of Green Manures on Soil Acidity; Va. 

 Poly. Inst., Tech. Bui. 19, April 1919. 



Ames, J. W., and Schollenberger, C. J., Liming and Lime Require- 

 ment of Soils; Ohio Agr. Exp. Sta., Bui. 306, pp. 381-383, Dec. 1916." 



