TILLAGE AND CROP-ROTATION AFFECT CORN, SOYBEAN, AND WINTER-WHEAT YIELDS

There is little research in northern regions on tillage systems in cor n (Zea mays L.), soybean [Glycine max (L.) Merr], and wheat (Triticum aestivum L.) rotations. The objectives of this study were to (i) evalu ate the influence of tillage on performance of corn, soybean, and wint er wheat in rotations with each other, and (ii) determine whether corn or soybean yields could be increased in 3-yr rotations with wheat com pared with an annual rotation with each other. Field studies were cond ucted near Arlington, WI, for 3 yr (1989 to 1991) on a Plano silt loam soil (fine-silty, mixed, mesic Typic Argiudoll) under both moldboard plow (MP) and no-till (NT). Six crop sequences evaluated were: corn/so ybean, corn/soybean/wheat, corn/wheat/soybean, and continuous corn, so ybean, or wheat. Grain yields for both corn and soybean were similar r egardless of crop sequence when these crops were in rotation, with no advantage for 3-yr vs. 2-yr sequences. Average yields were reduced 10% (corn) and 15% (soybean) for continuous cropping compared with rotati ons, with greater yield reductions under NT than MP. Tillage did not i nfluence grain yield for soybean or corn in rotation, but yields were reduced under NT for both crops with monocropping. Grain yields for NT continuous corn were 8% lower than MP, and continuous soybean yields were 7% less with NT than MP. Wheat yields were low and response to ti llage and rotation was inconsistent. In this study we found no clear a dvantage for three-crop corn, soybean, and wheat rotations compared wi th an annual rotation of corn and soybean.