218 FIELD CROPS FOR THE COTTON-BELT 



continuous corn growing with rotations of corn and oats; 

 and corn, oats, and clover with the following results: 



TABLE 15. SHOWING AVERAGE CORN YIELDS FOR LAST THREE YEARS 

 WHERE THREE SYSTEMS OF CROPPING ARE COMPARED. (!LL. 



STA.) * 



The yield of corn on this land before the experiment was 

 started was 70 bushels an acre. The one-crop system has 

 decreased the yield 35 bushels an acre in thirteen years 

 and 43 bushels in twenty-nine years. The yields have also 

 decreased, though less rapidly, where the rotations were 

 practiced. As all crops were removed from the land, it is 

 probable that neither rotation supplied organic matter 

 in sufficient amounts to liberate the mineral matter re- 

 quired by a 70-bushel crop of corn. When all crops are re- 

 moved, rotation will not maintain soil productiveness. 



On soils that are quite deficient in mineral matter, or 

 where all crops are removed from the land, the rotation 

 must be supplemented by manures or fertilizers. This fact 

 is well illustrated by the results of an experiment conducted 

 by the Louisiana Station on hill land originally covered 

 with pine trees and much exhausted by from seventy to 

 eighty years of cotton culture. The experiment consisted 

 of six one-acre plots arranged in three series of two plots 

 each, one unfertilized and the other fertilized for each 



1 111. Agr. Exp. Sta., Bui. 125, 1908. 



