COWPEAS AND SOIL RENOVATION, 



A field of cowpeas has been very happily designated ' ' the poor 

 man's bank," for in common with all its leguminous congeners, the 

 field pea, clovers, alfalfa, and a score of others, this crop has the 

 power of increasing the fertility of the soil upon which it grows. This 

 fact has long been accepted by farmers and students of agriculture, 

 but until recent discoveries in Germany and America it was believed 

 that the chief function of these plants was to pump up nitrogen from 

 the subsoil reservoir to the surface by means of their long roots for 

 the use and benefit of succeeding crops. 



But experiments in the field and laboratory for the purpose of 

 determining the causes of natural phenomena have taken the place 

 of class-room philosophy and speculative reasoning. Within the last 

 twenty years scientific workers have discovered that minute micro- 

 organisms, or bacteria, which live within the tissues of the roots of 

 leguminous plants take up free nitrogen from the gases in the soil, 

 just as the higher plants and animals utilize the oxygen of the air. 

 This nitrogen enters into combination to form nitric acid, which unites 

 with the mineral elements of the soil to form nitrates, a kind of plant 

 food exceedingly valuable to the growing crop. Nitrogen, when in 

 combination with other elements, is an indispensable form of plant 

 and animal food, but the free element can not be utilized by any 

 of the higher organisms. Small amounts of nitrous acid are formed 

 as a result of lightning discharges and are washed out of the air by 

 the rains, to be in part absorbed by the soil, and in part carried by 

 rivers and drainage waters into the sea. Free nitrogen exists only 

 in the air and in the gases of the soil, but as ammonia, nitrous and 

 nitric acid, nitrites and nitrates, it is present in varying quantities in 

 the soil, the unbroken rocks, and the waters of continents and oceans. 



The most available purchasable nitrogen is obtained either as salt- 

 peter or nitrate of soda from the extensive deposits in the Peruvian 

 deserts, or from some form of animal wastes, such as freshly ground 

 bone, dried blood, guano, tankage, and fish scrap, and from cotton- 

 seed meal and other like by-products of the oil mills. These fertil- 

 izers are all expensive, so much so that they can be profitably employed 

 by the farmer only in extensive farming with specialized crops. The 

 gain in yield with low-priced crops, such as corn, cotton, tobacco, 

 cowpeas, and the grasses, using high-grade and costly fertilizers, is 

 not commensurate with the additional expense. But every farmer, 

 rich and poor, has over three thousand tons of atmospheric nitrogen 

 resting on every acre of his farm, a certain quantity of which can be 

 transformed into available plant food every time he grows a crop of 

 cowpeas, red clover, or alfalfa. 



