GREEN-MANURES 541 



influences, lessening the advantage that legumes as green- 

 manures are supposed to have over non-legumes, due to their 

 ability to use atmospheric nitrogen. 



311. Green-manures as cover-crops.— When green-ma- 

 nures are seeded in the late summer or early fall, they func- 

 tion as cover-crops and may have rather important influences 

 aside from their effects when turned under. Their greatest 

 influence seems to be on the nitrate content of the soil. Nitri- 

 fication is usually cheeked,^ a disappearance of nitrates gen- 

 erally following. This reduction in the amount of nitrates 

 probably occurs because of a retardation of nitrification ac- 

 companied by a stimulation of biological utilization of the 

 nitrates. Such an effect is important in conserving the soil 

 nitrogen and is of particular value in orchards,^ as it hastens 

 the maturity of the new growth. At Cornell University, 

 green-manures were seeded in July and plowed under in the 

 following spring. Nitrate determinations were made on the 

 soil in July and in October, The figures are five-year aver- 

 ages. (See Table CXXIII, page 542.) 



312. The decay of green-manure. — When a green-crop 

 is turned under, the process of its decay is the same as that 

 of any plant tissue that becomes a part of the soil body. The 

 organisms that are active are those common to the soil, to- 

 gether with such bacteria as are carried into the soil on the 

 turned-under crop. The decomposition that results is prob- 

 ably both aerobic and anaerobic in nature, carbon dioxide be- 

 ing given off continuously. When proper decay has occurred, 

 end products should result which can be utilized as nutrients. 



^Wright, B. C, TTie Influence of Certain Organic Materials upon the 

 Transformation of Soil Nitrogen; Amer. Soc. Agron., Vol. 7, pp. 193- 

 208, 1915. 



Martin, T. L., The Decomposition of Green Manures at Different Stages 

 of Growth; Thesis for degree of Doctor of Philosophy, Cornell University, 

 1919. 



^Lyon, T. L., The Formation of Nitrates m So%l Under Grass; 

 Proe. West. N. Y. Hort Soc, pp. 82-87, Jan., 1915. 



Lyon, T. L., delation of Certain Cover Crops to the Formation of 

 Nitrates %n Soil; Proe West. N. Y. Hort. Soe., pp. 32-34, Jan., 1917. 



