25O THE FORAGE AND FIBER CROPS IN AMERICA 



A low and irregular yield of cowpeas in 1899 was attributed 

 by the Arkansas Station partly to the unimproved condition of 

 the soil, and partly to the absence or limited number of tubercle- 

 producing organisms in the soil. 1 At the Delaware Station 

 plants grown in sterilized soil produced no tubercles, and made 

 a weak growth. 2 Under favorable conditions, tubercles develop 

 when plants are only a few inches high. 



309. Rotations. On account of the ease and variety of con- 

 ditions under which different varieties will grow, and the 

 rapidity with which they will develop, cowpeas are admirably 

 adapted to simple or elaborate rotations. (C. A. 396) They 

 are usually planted in the southern states between the maize 

 rows at the last or next to the last cultivation, or follow oats, 

 wheat, or rye as a second crop, thus adding to the number of 

 crops which may be taken from the land during a rotation. 

 A desirable rotation for the cotton states is: maize and cow- 

 peas, one year; oats followed by cowpeas harvested for hay, 

 one year; cotton one or two years. In the more closely and 

 thickly planted maize fields of the North Atlantic and the North 

 Central states cowpeas do not develop sufficiently to be of value 

 either for forage or for fertilizers. 



310. FERTILIZERS. In general, nitrogen has not been found a profitable 

 constituent of fertilizers for cowpeas. The Alabama Station, however, found 

 on a soil previously liberally fertilized with phosphates and potash an increase 

 of about four bushels of seed or about 27 per cent, from the use of complete 

 commercial fertilizer, with practically no increase from mineral fertilizers. 

 In another experiment there was an increase of 4.5 bushels or 48 per cent. 

 from the use of 240 pounds of Florida soft (rock) phosphate per acre, and 

 an increase of 5.8 bushels or 60 per cent, from the same quantity of acid 

 phosphate. 3 The Tennessee Station found that nitrate of soda had apparently 

 no effect on the growth and yield of the crop, while muriate of potash and 

 lime used singly increased the green yield about one ton per acre. The 

 experience of this station has been that acid phosphate used alone has given 



i Arkansas Sta. Bui. No. 70 (1901), p. 93. 

 'Delaware Sta. Rpt. (1896), p. 108. 

 'Alabama Sta. Bui. No. 118 (1902), p. 21. 



