ROTATION HELPS TO MAINTAIN FERTILITY 269 



Crop Rotation Helps to Maintain Productive Power of Soils 

 (No soil improvement treatment of any kind made) 



Year the 

 experiment 



Cropping system 



Yield after 36 years, 10-year 

 average 1906-1915 



Per cent greater 



crop value per acre 



over no rotation 



was begun 



Clover 



Corn 



Oats 



(average for 10- 

 year period, 

 1906-1915) 



1879 



Corn continuously 

 Corn and oats in 



rotation 

 Clover, corn and 



oats m rotation 



Tons 

 1.69 



Bus 



28.8 

 37.5* 



57,6 t 



Bus 



38.0* 

 33.4 t 



18 

 36.7 



* Five-year average f Three-year average t Four-year average 



The yieM of corn at the beginning of the experiment was seventy 

 bushels. After thirty-six years of continuous corn culture this 

 yield was reduced nearly 59 per cent; and only 17.7 per cent 

 reduction occurred when corn was grown in rotation with clover 

 and oats. The first twelve years of continuous corn growing 

 reduced the yield to thirty-five bushels, after which the decrease 

 amounted to only eight bushels in sixteen years. It is thought 

 that the rapid reduction in yield during the first twelve years 

 was due, in a large measure, to the destruction, and hence deple- 

 tion, of the soil organic matter. 



The fact that the average annual crop value per acre for the 

 ten-year period, 1906-1915, was 36.7 per cent greater when clover, 

 corn and oats were grown in rotation than when no rotation was 

 practiced is further proof of the advantage of a rotation in main- 

 taining a higher productive power. The higher average crop value 

 for the clover-corn-oat rotation over the corn-oat cropping plan 

 was due largely to the increased yield of corn produced by growing 

 clover in the rotation, and not to the value of the clover as a 

 money crop. 



• Many farmers have experienced more profitable crops when 

 they substituted a rotation for a one-crop system, or when a good 

 rptation coupled with a definite plan of fertihzing is put into 

 practice on a depleted soil. This latter point has been definitely 

 demonstrated in an experiment started in 1894, at the Ohio 

 Station, on silt loam soil which had been previously rented for 

 twenty-five years, and hence badly depleted (Bxilletin 282). 



