The Comparative Effect of Corn and Sorghums on the Yield of Succeeding Crops

T deleterious effect of sorghums on the growth of succeeding crops under certain conditions has resulted in the popular belief that sorghums are hard on the soil. In many instances land owners will not permit the planting of sorghums on their soil. This prevailing idea has tended to restrict the acreage of sorghums in areas where they are adapted in spite of the known advantages that the crop offers for both grain and forage purposes. For many years the Kansas Agricultural Experiment Station and the Bureau of Plant Industry of the U. S. Dept, of Agriculture have had work under way which has made possible a direct comparison of the effect of corn and sorghum on the yield of subsequent crops under greatly varied conditions. In this work attention has been directed toward the possible cause or causes of the frequently observed deleterious effects. Several suggested reasons for the harmful effect of sorghums on succeeding crops are to be found in the published literature. These include depletion of mineral nutrients, depletion of moisture, toxic root excretions, toxic products of decay, unfavorable physical condition of the soil, and the limited nitrate nitrogen accumulation as a result of the decomposition of the sorghum roots which contain a relatively large quantity of sugar and other easily decomposed carbonaceous compounds. Since the publication of the original paper by Conrad (2), considerable evidence has been accumulated which suggests that the low nitrate nitrogen supply following sorghums is at least one factor involved on many soils.