Cover crops, double-crop soybean, and nitrogen rates affect productivity and profitability of a no-till rotation

Double crops and cover crops can increase cropping intensity and diversity, which are associated with productive, sustainable cropping systems. However, adoption of cover crops remains low. A long-term study with a no-till, sorghum [Sorghum bicolor (L.) Moench]–soybean [Glycine max (L.) Merr.]–wheat (Triticum aestivum L.) rotation intensified with double crops or cover crops was used to evaluate the effect of fallow management and nitrogen fertilizer applications to sorghum on system productivity and net returns. The experiment was established near Manhattan, KS, in 2007 and contained all three crops every year. Treatments included fallow management between wheat and sorghum as whole plots (chemical fallow, double-crop soybean [DSB], summer legume cover crop [SL], summer non-legume cover crop [SNL], winter legume cover crop, and winter non-legume cover crop) and nitrogen fertilizer rates applied to sorghum as subplots (0, 45, 90, 135, and 180 kg ha⁻¹) in a randomized complete block with four replications. Net returns were calculated as gross revenue less input and operating costs. Across three iterations of three cycles of the rotation from 2007 through 2018, total rotation yields increased with greater nitrogen rates, but the amount required to maximize yield varied, ranging from 90 kg ha⁻¹ with DSB and SL to 180 kg ha⁻¹ with SNL. The DSB treatment with 90 kg nitrogen ha⁻¹ applied to sorghum maximized system yields and net returns. Intensifying a cropping system with double or cover crops can increase system productivity and profits, but the system must be managed carefully to achieve positive outcomes.