496 SOUTIIEUN FIELD CROPS 



of sugar, or injures the quality of sirup. Phosphates tend 

 to hasten the ripening of cane, as also of other plants. 



478. Source of nitrogen. — The demands for a large 

 amount of nitrogen are met Ijy the planters of Louisiana by 

 plowing under, every third or fourth ytux, a luxuriant 

 growth of cowpeas, usually grown in the corn in rotation 

 with sugar-cane. In the pine-belt east of the jMississippi 

 River, nitrogen should be supplied by ploTsdng under, 

 the year before planting cane, a luxuriant growth of vel- 

 vet beans or of the Iron variety of cowpeas. 



479. Fertilizer experiments with cane in the pine-belt. — 

 An e.xtensive series of fertilizer experiments was conducted 

 for two years by the United States Department of Agri- 

 culture on sandy pine land in the southern part of Georgia. 



This field had been in cultivation for a number of years. 

 When cane was not preceded by a soil-improving crop, the 

 results were as follows : — 



(1) The fertilizer formula that can be recommended as the 

 result of these tests consists of 



600 pounds high-grade acid phosphate, 

 100 pounds cotton-seed meal, 

 300 pounds nitrate of soda, 

 100 pounds sulfate or muriate of potash, 

 1100 pounds, total per acre. 



Such a fertilizer would contain about S6 pounds of available 

 phosphoric acid, .50 pounds of nitrogen, and .50 pounds of potash, 

 and would analyze appro.ximately as follows : — 



8.0 per cent, of available phosphoric acid, 

 4.5 per cent of nitrogen, 

 4.5 per cent of potash. 



In these tests 1200 ])ounds, and e\-en 2000 pounds, of a com- 

 plete fertilizer was more profitable than SOO pounds on sandy 



