ARS | Publication request: SURFACE AND DEEP TILLAGE EFFECT ON DOUBLE-CROPPED SOYBEAN

Submitted to: Annual Southern Conservation Tillage Conference for Sustainable Agriculture
Publication Type: Proceedings
Publication Acceptance Date: March 30, 1996
Publication Date: N/A

Interpretive Summary: A large proportion of the acres of soybeans in the southeastern United States are planted after winter wheat. After the wheat is harvested, farmers used to burn the wheat stubble or till their fields to bury the wheat residues before planting the soybeans. More and more, farmers are trying conservation tillage methods that keep the wheat residues on the surface. They are looking for ways to increase the yield and profitability of soybeans when using conservation tillage. Traditionally, soybeans are grown in 30- to 38-in.-wide rows with deep tillage to loosen the soil with little surface disruption. We found that for soybeans grown in 30-in. rows, deep tillage did not increase yield and there was no yield difference between conventional and conservation surface tillage. But we also found that growing soybeans in 7.5-in.-wide rows had higher yields than the traditional 30-in.-row spacing, that conservation tillage was superior to conventional surface tillage in the 7.5-in.-row spacing, and that using deep tillage increased yield in the 7.5-in.-row spacing. This information is important to the USDA-NRCS, extension, and farmers because it provides an improved conservation tillage method of growing soybeans after wheat.

Technical Abstract: Information is needed on optimum conservation tillage soybean production management when the soybean is planted following a wheat grain crop. Our objective was to determine the effect of surface tillage, deep tillage, and row width on double-cropped soybean growth and yield. Surface tillage treatments were disked or not disked. Row width treatments were 7.5 in. or 30 in. Deep tillage treatments consisted of fall paratilling before seeding wheat or not paratilling. In the spring, half of the 30-in. plots were in-row subsoiled and half of the 7.5-in. plots were paratilled, and these were compared to no spring deep tillage. Soybeans were planted in early June in 1994 and 1995. Surface tillage and spring deep tillage impacted plant height at some measurement times through each season, but row width and fall deep tillage did not. Averaged over all treatment combinations, soybeans grown in 7.5-in. rows yielded 30.1 bu/ac (1994) and 21.2 bu/ac (1995) more than soybeans grown in 30-in. rows. Surface tillage and deep tillage had no effect on yield when the 30-in.-row width was used. When the 7.5-in-row width was used, both fall and spring deep tillage increased yield. Disking before planting the 7.5-in.-row width soybeans resulted in yield reductions of 14.2 bu/ac in 1994 and 9.8 bu/ac in 1995, compared to the no surface tillage treatment. Conservation tillage, combined with narrow-row culture and deep tillage, should improve double-crop soybean production in the Coastal Plain.