Short‐Term Crop Rotation Systems for Soybean Production

Abstract

AbstractContinuous monocrop soybean [Glycine max (L.) Merr.] production has been common in Louisiana for 20 yr. This field study was undertaken to determine if, and how, short‐term crop rotations could increase soybean yield on a Providence silt loam (fine‐silty, mixed, thermic Typic Fragiudalfs) in southeast Louisiana. Eight 2‐yr rotations were evaluated in a field following 15 yr of continuous soybean production. Rotations investigated were: continuous soybean; soybean rotated with grain sorghum (Sorghum bicolor L.); soybean rotated with fallow; soybean doublecropped with winter wheat (Triticum aestivum L.); soybean alternated with winter wheat underseeded with alfalfa (Medicago sativa L.); and three additional rotations, identical to the first three listed with the addition of a winter ryegrass (Lolium multiflorum L.) cover crop. Two soybean cultivars, Centennial and Davis, with different plant parasitic nematode susceptibility, were evaluated in each rotation. Over four complete rotation cycles, Centennial consistently out‐yielded Davis. Soybean grown after either grain sorghum or fallow consistently out‐yielded soybean grown following soybean. This difference existed during favorable and unfavorable growing seasons and was greater for Davis than for Centennial. Insect populations were not high at the study site and did not have a major impact on crop yields. Soybean cyst nematode (Heterodera glycines Inchinohe) populations were higher under Davis than Centennial soybean, increased each year, and were greater with continuous soybean than with rotation. Control of cyst nematode populations appeared to be the main reason for the beneficial rotation effect observed in this study.