NET RETURNS FROM 8 IRRIGATED CROPPING SYSTEMS ON CLAY SOIL

Considerable research has been conducted on the agronomic relationships of cropping systems adapted to the clayey soils of the lower Mississippi River flood plain; however, only a few studies included the determination and evaluation of net returns. An 8-yr study (1984-1991) was conducted on a Tunica clay (clayey over loamy, montmorillonitic, nonacid, thermic Vertic Haplaquept) to determine net returns from eight irrigated cropping systems. The cropping systems included (1) monocrop corn (Zea mays L.), (2) monocrop soybean [Glycine max (L.) Merr.], (3) monocrop sorghum [Sorghum bicolor (L.) Moench.], (4) biennial rotation of corn and soybean, (5) biennial rotation of sorghum and soybean, (6) continuous wheat (Triticum aestivum L.)-soybean doublecrop, (7) biennial rotation of corn and wheat-soybean doublecrop, and (8) biennial rotation of sorghum and wheat-soybean doublecrop. Average net returns per acre from the biennial rotation of corn and wheat-soybean doublecrop ($136) and the continuous wheat-soybean doublecrop systems ($123) were similar and slightly higher than average net returns from the biennial rotation of corn-soybean ($110). Average net returns from the biennial rotation of sorghum and wheat-soybean doublecrop ($95), sorghum-soybean biennial rotation ($84), and monocrop corn ($79) systems were similar and higher than average net returns from monocrop soybean ($53) and monocrop sorghum ($19) systems. Average net returns from monocrop systems of com, soybean, and sorghum were all lower than net returns from cropping systems where the crops were grown in a biennial rotation with each other or with a wheat-soybean doublecrop sequence.