Tillage Effect on Soil Water Content and Corn Yield in a Strip Intercropping System

A three-crop strip intercropping system including corn (Zea mays L.), soybean [Glycine max (L.) Merr.], and oat (Avena sativa L.) interseeded with nondormant alfalfa (Medicago sativa L.), was established in south-central Iowa on a poorly drained Haig soil (fine, smectitic, mesic Vertic Argiaquoll). In 1989 (a dry year) and 1990 (a wet year), we studied the effect of tillage treatment (conventional, CT; reduced, RT; and no-till, NT) and row position on soil water content, canopy and air temperatures, corn grain yield, and yield components. No-till resulted in the most favorable soil water status, plant water status, and grain yield in 1989. No-till had the poorest performance in 1990, mainly because of excessive soil water. The opposite was true for conventional till in both years. Reduced till yield equaled that for the most productive tillage treatment in both years. Conventional and reduced tillage resulted in lower corn grain yield at the border with oat-alfalfa than with soybean because oat depleted soil water more than soybean in both years. In contrast, for no-till the corn grain yield at the border with oat-alfalfa was 6% greater than corn yield bordering soybean in 1989 and 13% greater in 1990. When water was not limiting, in 1990, both corn borders outyielded the center rows by an average of 14% in NT, 27% in RT, and 28% in CT. Soil water content rankings throughout the 1989 season were NT > RT > CT and row position rankings were soybean border > center > oats-alfalfa border. In 1990, there were no soil water content differences between tillage treatments and row positions. Reduced tillage is the most suitable soil management system for corn production with three-crop strip intercropping on this soil, considering consistently high relative yields for both wet and dry years. Journal Paper no. J-16919 of the Iowa Agric. and Home Economics Exp. Stn., Ames. Project no. 2910.