Row spacing and weed management systems for nonirrigated early soybean production system plantings in the midsouthern USA

The new paradigm for soybean [Glycine mar (L.) Merr.] production in the mid southern USA is the Early Soybean Production System (ESPS), which involves planting early-maturing cultivars in April. Field studies were conducted fo r 3 yr at Stoneville, MS, on Sharkey clay (very-fine, smectitic, thermic ch romic Epiaquert) with a MG IV soybean cultivar grown in 0.5-m-wide rows (NR ) and a MG V cultivar grown in 1-m-wide rows (WR), both with varying weed m anagement inputs, to determine the most profitable system for nonirrigated ESPS plantings. Weed management in NR consisted of broadcast application of herbicides. Weed management in WR included band (0.5-m-wide) application o f herbicides plus two to three between-row cultivations. Total weed cover a t harvest in all treatments was below 10% in the first 2 yr. In the third y ear, browntop millet [Brachiaria ramosa (L.) Stapf.] plus pitted morningglo ry (Ipomoea lacunosa L.) percentages exceeded 10% in 3 of 10 treatments in NR and in I of 10 treatments in WR, but these treatments were among those p roducing the highest yield and net return. Soybean treated for preemergence (PRE) broadleaf management, PRE broadleaf plus PRE grass management, PRE b roadleaf plus postemergence (POST) grass management, and PRE and POST broad leaf plus PRE and POST grass management were among the highest yielding tre atments, but only the treatment of PRE broadleaf management provided the hi ghest net return across both NR and WR. Soybean with PRE and POST broadleaf plus PRE grass management provided the lowest net returns across both NR a nd WR. These results indicate that only a broadcast PRE broadleaf herbicide in NR and a PRE banded broadleaf herbicide plus POST cultivation in WR in an ESPS planting that is not irrigated will produce yield and net return th at are among the highest, and weed management cost that is among the lowest of less than or equal to $62 ha(-1).