Relay-intercropping soybean and winter wheat in Wisconsin

Relay intercropping (RIC) of soft red winter wheat (SRWW, Triticum aestivum L.) and soybean [Glycine max (L.) Merr.] offers potential benefits but requires optimized management. This 2-year study (2022–2023) evaluated the effects of soybean planting date and strip-tillage vs. no-tillage (ST vs. NT) on RIC soybean yield and assessed the impact of ST on wheat yield. Later-planted RIC soybean (May 19, 2022, and May 30, 2023) outyielded earlier-planted RIC soybean (April 29, 2022, and May 11, 2023) by 18.8 bushels per acre in 2022 and 20.1 bushels per acre in 2023. However, sole crop soybean yielded higher (∼50 bushels per acre) and had better economic returns. ST increased RIC soybean yield by 8.3 bushels per acre in 2022 and 1.8 in 2023 compared to NT. The experiment was also designed to isolate the effect of ST on wheat yield in RIC to help establish soybean rows. NT wheat outperformed ST wheat in both years, with yield reductions of 5.4 bushels per acre in 2022 and 14.8 bushels per acre in 2023 when ST was used. These results indicate that while ST benefits RIC soybean yield, it negatively affects wheat yield, highlighting a tradeoff in the system. Our findings suggest that later planting dates improve RIC soybean yield by reducing competition with wheat, but overall, sole crop soybean remains more productive and profitable.