Row Width and Weed Management Systems for Early Soybean Production System Plantings in the Midsouthern USA

Abstract

Management inputs that maximize economic return from the early soybean [Glycine max (L.) Merr.] production system (ESPS) in the midsouthern USA have not been evaluated fully. Field studies were conducted at Stoneville, MS (33°26′ N lat) to determine effect of weed management on yield and net return from maturity group (MG) IV and MG V cultivars grown in the ESPS in narrow rows (NRs; 50‐cm width) and wide rows (WRs; 100‐cm width) in nonirrigated (NI) and irrigated (IRR) environments. Use of NRs vs. WRs resulted in less weed cover at soybean maturity, but this was associated with greater weed management costs in NRs. In NI, choice of MG for ESPS plantings and choice of row width for MG V cultivars was arbitrary, but the MG IV cultivar did best in NR. Use of both pre‐emergent (PRE) and postemergent (POST) broadleaf weed management in both NRs and WRs resulted in lower net returns. In IRR, NRs outyielded WRs, the MG IV cultivar yield equaled or exceeded the MG V yield in NRs, and the MG V cultivar outyielded the MG IV cultivar in WRs in both years. Differences in net returns followed yield differences. Use of POST‐only broadleaf and grass weed management resulted in the highest net returns across the 2 yr. Thus, a MG IV cultivar planted in NRs with POST weed management appears to be the most profitable option in IRR‐ESPS plantings. If WRs are required for management reasons in the ESPS, a MG V cultivar should be used.