Intensifying a no‐till sorghum–soybean–wheat rotation with double‐crop soybean and cover crops

Abstract A central strategy of sustainable intensification is increasing cropping intensity. The fourth cycle of a long‐term, no‐till sorghum [ Sorghum bicolor (L.) Moench]–soybean [ Glycine max (L.) Merr.]–wheat ( Triticum aestivum L.) rotation established in 2007 near Manhattan, KS, was intensified with both double‐crop soybean (DCB) and cover crops. Crop phases were present every year as whole plots with six intensification treatments: chemical fallow (CF), DSB, plus four treatments consisting of different combinations of DSB and cover crops, imposed in subplots. Five nitrogen rates applied to sorghum—0, 45, 90, 135, or 180 kg ha −1 —were imposed in sub‐subplots and some cover crops occasionally reduced the amount of fertilizer N required to maximize sorghum yield compared to CF. However, yield reductions of 6%–54% for sorghum and up to 6% for soybean occurred when cover crop growth was substantial in the spring preceding planting of each crop. Yield reductions were greatest in dry years. Wheat yields tended to increase as cropping intensity increased with the most intense treatment yielding 4%–10% more than in the CF treatment. Intensifying with DSB and/or cover crops maintained or increased total rotation yield compared to CF with adequate nitrogen applied to sorghum, except in 1 year when a dry winter and spring before sorghum planting resulted in severe sorghum yield reductions after the spring cover crop. Maintaining enough flexibility to adjust cropping strategies in response to changing soil moisture availability is essential for successful cropping system intensification in this region.