276 Bureau of Farmees' Institutes. 



spread it, instead of letting it pile up about the barns or in the 

 barnyard. 



(c) Applying in Bow. 



This method has the advantage of placing the manure where it 

 will reach the plant most quickly and of enabling one to use 

 smaller amounts than in broadcasting. It is especially applicable 

 for forcing some garden crops. Rotted manure gives good re- 

 sults when used this way. 



10. The Use of Green Manures. 



Definition. — The term " green manures," properly used, 

 means any crop grown chiefly with the object of improving the 

 soil, and not for securing the harvested product. 



Leguminous Crops or " Nitrogen Gatherers " as Green 

 Manures. — Those plants belonging to the legume or clover family 

 have the power to secure a large part of their nitrogen from the 

 air. When these are turned under the soil as green manures, 

 they add nitrogen to the soil. The nitrogen brought into the 

 soil in this manner is in a form that tends to decompose rapidly 

 and thus furnish plant food for other crops. It must be kept 

 clearly in mind that these nitrogen-gathering crops cannot be suc- 

 cessfully grown unless the soil contains an abundance of phos- 

 phoric acid, potash and lime. The crop absorbs only such min- 

 eral plant food as it finds in the soil and it is a serious mistake 

 to suppose that any green crop adds anything to the mineral plant 

 food of the soil. It may make more available for other crops 

 the phosphoric acid and potash compounds already existing in the 

 soil. Therefore, in growing green crops there should generally 

 be liberal applications of phosphoric acid and potash and often 

 also of lime. 



The crops that have been found most efficient as nitrogen- 

 gathering green manures are red clover, crimson clover, cow peas, 

 and soja beans. The clovers tend to improve the physical con- 

 dition of the soil also, sending down their roots to considerable 

 depths. They are able also to get considerable food from the 

 subsoil. These are marked advantages in their favor in addition 

 to their power to get nitrogen from the air. 



The amount of nitrogen these crops draw from the air depends 

 upon the amount of nitrogenous and other plant food in the soil. 



