Relay Intercropping Soybeans into Winter Wheat and Spring Oats1

Abstract

AbstractRelay intercropping of soybeans [Glycine max (L.) Merr.] into small grains might allow the two‐crops‐in‐1 year concept to be moved further northward in the U.S. Corn Belt. The small grain crops in such a system might also provide protection against soil erosion on sloping soils currently in conventional soybean production. The objective of this study was to compare monoculture oat (Avena saliva L.), wheat (Triticum aestivum L.), and soybean yields with soybeans relay intercropped into spring oats or winter wheat. Variables considered included small grain and soybean row widths, soybean planting date, and soybean cultivar. Field experiments were conducted on Typic Haploquoll and Typic Argiudoll soils in central Illinois.Interseeding soybeans into small grains did not affect small grain yields. In three of four environments tested, small grain yields in rows 41, 61, and 81‐cm wide averaged yields of 91, 72, and 58%, respectively, of small grains in 21‐cm row widths. In a fourth experiment, where winter wheat rows wider than 21‐cm were created by spring removal of intervening rows, yield reductions were greater than for those planted in wider rows. Monoculture soybeans produced significantly higher yields and taller plants than intercropped soybeans. Reduced growth of intercropped soybeans, especially in narrow rows, was associated with below normal precipitation during both years of experimentation. Soybeans intercropped between 41 and 61‐cm small grain rows yielded between 7 and 93% of monoculture soybeans grown in similar row widths. Soybeans aerially seeded into small grain stands failed to establish a stand, but soybeans conventionally placed in the soil produced acceptable stands. A short determinate soybean cultivar did not appear to withstand early season stress associated with intercropping as well as a tall indeterminate cultivar. In years with normal early season precipitation, successful relay intercropping of soybeans into small grains should be possible.