58 



DRY FARMING 



year period more than double what the unfertilized land 

 was capable of at the beginning. The rotations alone, 

 therefore, would not maintain yields without fertiliza- 

 tion. Plants as well as animals require food. 



41. Illinois Experiment. — The Illinois Agricultural Ex- 

 periment Station is conducting an experiment on the 

 typical brown silt loam prairie land of the Corn Belt. 

 Five fields are under cultivation, "wheat, corn, oats and 

 clover being rotated for five years on four fields, while 

 alfalfa occupies the fifth field, which is then brought 

 under the four-crop system to make place for alfalfa 

 on one of the other fields for another five-year period, 

 and so on*". Sixteen years' results have been publishedf, 

 the averages appearing in table XIV. 



Table "KIV .—Illinois Experiment: Urbana Field. Brown silt 

 loam prairie: Early Wisconsin Glaciation. 



1. Figures in parenthesis represent tons of bay. 



2. Soy-beans planted wben clover failed. 



By comparing plots 2, 4, and 6 with 3, 5, and 7 re- 

 spectively, we have direct comparisons between two 



♦ Hopkins, et al, Soil Report No. 18 Champaign (bounty Soils, 

 t Hopkins, et al, Illinois Agricultural Experiment Station Bulletin 

 219. Illinois crop yields from Soil Experiment Fields. 



