Effects of Crop Rotation and Irrigation on Soybean and Wheat Doublecropping on Clay Soil: An Economic Analysis

Field experiments were conducted from 1984 to 1991 to determine and compare the yields and economic returns of soybean [Glycine max (L.)] monocrops, continuous wheat [Triticum aestivum (L.)]-soybean doublecrops, and 2-year rotations of com [Zea mays (L.)]/wheat soybean and sorghum [Sorghum bicolor (L.) Moench]/ wheat-soybean in irrigated and nonirrigated environments on Tunica clay (clayey over loamy, montmorillonitic, nonacid, thermic Vertic Haplaquept). Yields, production records, and commodity prices were used to calculate annual net returns above specified costs for each cropping system. In the irrigated study, the highest overall net returns per acre were produced by the corn/wheat-soybean ($136.29) and the wheat-soybean doublecrop ($123.47) systems, whereas the lowest overall net returns per acre were from soybean monocrops ($52.85). In the nonirrigated study, the highest overall net returns per acre were from the sorghum/wheat-soybean rotation ($63.65) and the wheat-soybean doublecrops ($47.79). The lowest overall net returns per acre were from the nonirrigated corn/wheat-soybean rotation ($15.47). Supplemental irrigation of the summer crops increased the overall net returns per acre of soybean monocrops ($28.12), wheat soybean doublecrops ($75.68), com/wheat-soybean rotations ($120.82), and sorghum/wheat-soybean rotations ($31 .67). The average net returns per acre of wheat were high for all cropping systems, whereas the average net returns per acre of nonirrigated soybean in all cropping systems were not sufficient to cover land rental charges.