Environment affects the corn and soybean rotation effect

Corn (Zea mays L.) and soybean [Glycine max (L.) Merr.], the backbone of Midwestern crop production, respond to rotation, but how growing conditions affect this is not well documented. Our objectives were to determine the effect of various corn and soybean cropping patterns on yields and to evaluate environmental effects on the rotation effect. The study began in 1981 at Lamberton, MN, on a Webster clay loam (fine-loamy, mixed, mesic Typic Endoaquoll), in 1982 at Waseca, MN, on a Nicollet clay loam (fine-loamy, mixed, mesic Aquic Hapludoll), and in 1983 at Arlington, WI, on a Piano silt loam (fine-silty, mixed, mesic Typic Argiudoll). Cropping sequences were (i) continuous monoculture of each crop; (ii) annual rotation of the two crops; and (iii) 1, 2, 3, 4, and 5 yr of each crop following 5 yr of the other crop. Results are based on 11 yr of data at Lamberton, 8 yr (soybean) or 9 yr (corn) at Waseca, and 9 yr at Arlington. Corn rotated annually with soybean yielded 13% more, and 1st-yr corn following multiple years of soybean yielded 15% more titan continuous corn. Soybean annually rotated with corn yielded 10% more, and 1st-yr soybean following multiple years of corn yielded 18% more than continuous soybean. The crops differed in response to increasing years of consecutive planting: 2nd-yr to 5th-yr corn yields were no different from continuous corn yields; 2nd-yr soybean yielded 8% more than continuous soybean, 3rd-yr soybean yielded 3% more, and 4th- and 5th-yr soybean yielded the same as continuous soybean. Relative increase in yields of both crops in annual rotation compared with monoculture was approximately twofold greater in low-yielding than in high-yielding environments. In low-yielding environments, the yield advantage of an annual rotation of corn and soybean compared with monoculture was frequently greater than 25%. The commonly practiced annual rotation of corn and soybean maximized corn yields, but not soybean yields, relative to the other sequences studied.