68 INDIAN CORN CULTURE. 



for this purpose, such as the clovers in the 

 North and the cowpea in the South, increase 

 the soil fertility" by returning to it additional 

 plant food secured from the atmosphere or soil. 

 The clover plant, it has been demonstrated, 

 adds materially to the fertility of the surfafce 

 soil by securing nitrogen from the atmosphere 

 and holding it, and also by absorbing and hold- 

 ing nitric acid from below the cultivated sur- 

 face, so that clover plowed under decidedly 

 increases soil fertility. In the Southern States 

 the cowpea plowed under is a recognized reno- 

 vator of worn-out lands. 



According to Sir J. B. Lawes,* "the leguminous 

 (clovers, peas, beans, etc.) are the only plants 

 which can be said distinctly to enrich the sur- 

 face soil when plowed in, and I may mention 

 that in a case where a crop of red clover was 

 grown by us, and twice mown for hay, the in- 

 crease of nitrogen in the surface soil was suffi- 

 cient to be measurable by analysis when com- 

 pared with another part of the field where the 

 grain crop was grown." 



Green manure is especially valuable on light 

 soils or heavy impoverished clay land. The 

 crop should be plowed in at about the time of 

 well-advanced bloom, before seed formation. 



The plowing under of sod or stubble is in a 

 measure a form of green manuring, for much 



* The Country Gentleman, March 12, 1885. 



