In 1994, system, WTRT, and the system x WTRT interaction significantly affected yield and net return.
In 1995, yield was not significantly affected by either system, WTRT, or their interaction (Table 4).
Average seed yield for MG IV soybean grown in narrow rows (NR) and MG V soybean grown in wide rows (WR) under varying weed management (WTRT) in 1994, 1995, and 1996 at Stoneville, MS.
In both NR and WR, the addition of either PRE or POST grass herbicides to either PRE of POST broadleaf herbicides (WTRT 4 and WTRT 5 vs.
In NR, soybean with PRE and POST broadleaf plus PRE grass management (WTRT 8) had yield similar to that from the PRE and POST broadleaf management only treatment (WTRT 3), but net return was usually lower.
For example, the PRE broadleaf plus POST grass management treatment (WTRT 5) averaged 2065 kg [ha.sup.-1] across the 3 yr with weed management costs of $96, $59, and $59 [ha.sup.-1], respectively.
Abbreviations: CSPS, conventional soybean production system; DAP, days after planting; ESPS, early soybean production system; MG, maturity group; NR, narrow-row system; NETRET, net return; PFA, preplant foliar-applied; POST, postemergence; PRE, preemergence; WR, wide-row system; WTRT, weed management treatment.
Uncontrolled weeds will reduce yield of soybean; thus, there was no comparison of the selected WTRTs to a weedy check.
The selected WTRTs assumed that broadleaf weeds but not necessarily grass weeds in a dryland environment must be controlled.
The intent in selecting the WTRTs was to have weed management options that differ in cost, and broadcasting of herbicides in NR vs.
In WR, yield differences among WTRTs were small and usually not significant (Table 4).