140 PRACTICAL FARM CHEMISTRY. 



surface feeding, and do not bring up plant foods 

 from the subsoil. The black pea or southern cow 

 bean is one of the best plants for the purpose. The 

 cases are few, I think, where it would be advisable 

 to use rye or buckwheat for green manuring. The 

 roots of clover and other leguminous plants have 

 swellings or tubercles, caused and inhabited by 

 bacteria which are the real nitrogen gatherers. 



Green vegetable matter is not plant food. To 



promote its speedy decay, and fit it for the use of 



other crops, we may plow it under just deep enough 



to keep it moist, and shallow enough 



Gre^^cfops. ^^^ ^^^^ access of air. The drainage on 

 soil thus manured should be perfect, 

 and the surface kept well tilled. If lime is absent 

 in the soil, its application will be needed, in order 

 to hasten the decay of the vegetable matter and 

 prevent acid fermentation. 



The next query is, how much of the minerals 

 should be applied along with the green manure in 

 ordinary grain farming, if we desire to maintain our 

 standard of fertility? The object might be accom- 

 plished by one of the following applications, viz. : 



1. 600 pounds (18 bushels) unleached wood ashes. 



1 00 pounds of bone meal (or 150 pounds of acid phosphate). 



2. 75 pounds muriate of potash (or 300 pounds kainit). 



200 pounds acid phosphate (dissolved bone black) or 140 

 pounds bone meal. 



3. 100 pounds cotton seed hull ashes. 



100 pounds slag meal (or 150 pounds acid phosphate), 



or in any other combination that will furnish about 

 the same quantity of potash and phosphoric acid. 



