CORN FERTILIZERS 153 



This places corn on one third of the cultivated area 

 each year. When this rotation is repeated through the 

 fourth, fifth, and sixth years, it is plain that cowpeas or 

 cowpea stubble, following the small grains, is plowed under 

 just a full year before corn occupies the land. 



141. A four-year rotation. The above scheme may 

 readily be changed into a four-year rotation by growing 

 two successive crops of cotton, the first of which may well 

 be followed by a catch crop of crimson clover, plowed under 

 about April 1, as fertilizer. This places corn on.one fourth 

 of the cultivated land and on fields where cowpeas were 

 plowed under two years before and where, perhaps, crimson 

 clover was plowed under one year before the corn was 

 planted. 



FERTILIZERS 



142. Need for a fertilizer rich in nitrogen. Corn must 

 make a rapid development of stalk, leaf, and ear, and for 

 this purpose there must be present in soil or fertilizer a 

 large amount of plant-food. The rapid growth seems to 

 make especially necessary large supplies of nitrogen. Those 

 soils richest in nitrogen almost invariably produce the 

 largest yields of corn. 



In unpublished experiments made on a wide variety of poor 

 soils in Alabama, nitrogenous fertilizers have increased the crop to 

 a much greater extent than any other kinds. In these tests, 

 potash was usually of far less value than when applied to the 

 cotton plant. Acid phosphate was intermediate in value be- 

 tween the nitrogenous and phosphatic fertilizers. However, 

 the results of fertilizer experiments vary greatly according to the 

 nature and previous history of the soil. 



