12 THE COW PEA. 



restoration of soil fertility. For their growth and develop- 

 ment the soil must have plenty of air. These bacteria require 

 also a soil that is not acid; therefore, land rich in decaying 

 vegetable matter, and hence likely to be acid, should not 

 be planted to cow peas. Such land does not require the 

 humus supplied by the cow peas and could be but little 

 improved thereby. The chief object in cultivating this 

 plant is to add to the fertility of the land and leave it in 

 better shape to produce crops like corn, which subtract 

 from, rather than add, to the supply of plant food in the soil. 

 If the cow pea is to be sown on land with a hard-pan subsoil, 

 the breaking up should be well done with a subsoil plough 

 so as to give it necessary drainage. A water-soaked soil is 

 not well adapted to growing the pea because water cuts off 

 the circulation of air, which is essential to the chemical 

 changes by which nitrogen of the air is taken up by the 

 plant. A poorly prepared soil is also unfavorable for plant 

 development because it prevents the roots from reaching out 

 and obtaining food, no matter how hungry the plant may be. 

 Every means should be employed to improve the .physical 

 condition of the soil so as to enable the crop to absorb the 

 largest possible amount of nitrogen from the air. In deep, 

 mellow and well drained soils the roots act to the best 

 advantage, and, practically free of cost, turn otherwise 

 unavailable atmospheric nitrogen into rich and necessary 

 plant food stored up for future use. On heavy soils, deep 

 ploughing is indispensable, and the seed-bed must be made 

 fine, firm, smooth and level to secure best results. Gener- 



