Tillage management for doublecropped soybean grown in narrow and wide row width culture

Leaving residues on the soil surface and deep tillage may reduce the severity of yield-reducing, plant water stress on the southeastern Coastal Plain. For narrow (<75 cm) row width culture, little is known about the seed-yield response of doublecropped soybean [Glycine max (L.) Merr.] to surface tillage or deep tillage, We conducted a 2-yr field study on a Goldsboro sandy loam soil to (i) determine the seed-yield response of doublecropped soybean to surface tillage and deep tillage when grown using 19- and 76-cm-row widths and (ii) determine the effects of surface tillage and deep tillage on branch and mainstem yield components. Doublecropped soybean was grown following winter wheat (Triticum aestivum L.) harvest using all combinations of surface tillage (disked or no surface tillage), spring deep tillage (deep tilled or no deep tillage before soybean planting), rove width culture (production practices for row widths of 19 or 76 cm), and fall deep tillage (no deep tillage or deep tilled before wheat planting) treatments. Averaged across years and all other treatments, the soybean grown with the 19-cm-row width had a 53 and 83% greater seed yield than the soybean grown with the 76-cm-row width in the dished and no-surface-tillage plots, respectively. When deep tilled, soybean yields were consistently higher with no surface tillage, compared with dishing, only when the 19-cm-row width was used, Seed-yield increases due to deep tillage were greatest when plots were deep tilled before planting both crops and when no surface tillage and the narrow row width culture were used. Across all treatments and Sears, seed yield was highly correlated with seed number per square meter (r = 0.93), but less so with individual seed weight (r = 0.52), Results indicate that seed-yield increases due to deep tillage and no surface tillage are greater when doublecropped soybean is planted using production practices established for narrow row width culture.