FERTILITY OF A CHERNOZEMIC CLAY SOIL AFTER 50 YEARS OF CROPPING WITH AND WITHOUT FORAGE CROPS IN THE ROTATION

Abstract

In recent field trials nitrogen–phosphorus fertilizer increased the yield of wheat following summerfallow on a Chernozemic clay soil cropped previously for 50 years in a summerfallow, wheat, wheat rotation. But the fertilizer had no significant effect on wheat yield when the previous cropping system during the 50-year period was summerfallow, wheat, oats, brome–alfalfa for3 years, intertilled corn, wheat, and oats. The beneficial effect of brome–alfalfa in the rotation was reflected in a higher yield of wheat. The average yield of grain per year in the recent trials was 400 kg/ha higher when brome–alfalfa had been included in the rotation.The brome–alfalfa crops produced a better physical condition in the soil. Furthermore, soil samples from the rotation containing brome–alfalfa had higher contents of nitrogen, organic carbon, and total phosphorus than did the samples from the summerfallow, wheat, wheat rotation.