Corn and soybean yields and returns are greater in rotations with wheat

Simple rotations containing only corn ( Zea mays L.) and/or soybean ( Glycine max L.) dominate landscapes despite agronomic, soil health, and environmental benefits associated with diversification. We hypothesize that inclusion of wheat ( Triticum aestivum L.) in corn–soybean (CS) rotations increases yield and net returns and that this benefit is becoming larger over time. Yields from rotation–tillage trials located near Elora and Ridgetown, ON, Canada, respectively, were used to investigate the yield and return effects of diversifying CS rotation using wheat with/without red clover ( Trifolium pratense L). At Elora, wheat inclusion increased rate of yield increase in corn and soybean over 36 yr. During the latter 16 yr, adding wheat to CS rotation increased conventional tillage (CT) 1st and 2nd‐year corn yields (with red clover) by 0.43 Mg ha −1 (4.2%) and 0.98 Mg ha −1 (11.8%), respectively, no‐till 1st and 2nd‐year corn yields (no red clover) by 0.78 Mg ha −1 (9.9%) and 0.45 Mg ha −1 (5.3%), respectively, and 1st‐year soybean yield by 0.34 Mg ha −1 (11.8%). At Elora, net returns in the 4‐yr wheat‐containing rotations were 10% greater compared to the CS rotation. Similar corn and soybean yield responses including wheat in 2 or 3 yr rotations also occurred at the greater‐yielding Ridgetown trial, however net returns were not increased relative to the CS rotation. Inclusion of wheat in CS rotation once every 4–5 yr may provide the optimal balance between accruing higher net returns from corn and soybean while minimizing direct net revenue reductions associated with wheat.