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The Effect of Crop Rotations and Soil Treatments on Soil Productivity¹

ABSTRACT

Permanent fertility studies were set up on the Agronomy Farm of Kansas State College in 1909 to determine the long-time effects of crop rotations and of soil treatments on the productive capacity of the soil. Trends in soil productivity induced by the different rotations and the different soil treatments were analyzed for the 42-year period 1911 through 1952.

The analysis showed that, despite improved wheat varieties used during the investigations, the yields of unfertilized wheat and of unfertilized corn were maintained only in a 16-year rotation. Legume yields were not maintained in any rotation studied.

Wheat yields indicate how various combinations of commercial fertilizers, rock phosphate, lime, and manure increased the productive capacity of the soil. Corn yields indicate that only treatments including nitrogen increased soil productivity for this crop. Soil treatments increased alfalfa yields. Alfalfa yields, however, were not maintained at the original level by any soil treatment.

¹ Contribution No. 498, Department of Agronomy, Kansas Agr. Exp. Sta., Manhattan, Kans. Presented before Div. IV of the Soil Science Society of America, Dallas, Texas, Nov. 19, 1953.

² Associate Professor of Soils, Kansas State College.

Received for publication December 3, 1954.