472 FIELD CROPS 



this crop is often planted on the same field for several years 

 'in succession. This practice, however, is much less com- 

 mon now than it was a few years ago. Because of the con- 

 stant growing of the same crop on the land with little or no 

 effort to keep up the supply of vegetable matter and plant 

 food, many of the fields are now in a more or less exhausted 

 condition, so that they must be highly fertilized to produce 

 a good crop. Whenever possible, a regular rotation should 

 be followed which includes a leguminous crop to supply 

 vegetable matter rich in nitrogen. A number of excellent 

 crops for this purpose are available, including the cowpea, 

 soy bean, crimson clover, and velvet bean. Increasing the 

 supply of vegetable matter and adopting a proper system of 

 crop rotation are the most effective methods of increasing 

 cotton yields. 



When the nitrogen is supplied by a leguminous crop which 

 precedes cotton, less of this element need be added m the 

 form of commercial fertilizers. The use of a complete fer- 

 tilizer is advised in all cases when the soil shows a tendency 

 to become exhausted and when leguminous crops are not 

 grown. Cotton seed was formerly largely used, but the 

 ready market for it afforded by the oil mills has led to the 

 substitution of other materials. As the oil in the seed is of 

 no value as a fertilizer, the use of whole seed for this purpose 

 is wasteful. At the present time, the most popular ferti- 

 lizing material is cotton-seed meal, as it contains a good 

 supply of nitrogen and some potash and phosphoric acid. 

 It should generally be supplemented with acid phosphate 

 and muriate of potash, while a small quantity of nitrate of 

 soda helps the early growth of the crop. 



Barnyard manure is used to some extent for cotton, but 

 the available supply is usually limited, as the number of 

 live stock kept on Southern farms is relatively small and those 



