| Field experiments were conducted at two locations to evaluate the effect of pre-harvest herbicides applied at growth stages R5 to R8 on soybean seed production and viability. Two soybean cultivars, a mid-Group IV (NK 4260) and a glyphosate-tolerant mid-Group IV (AG4701RR), were evaluated. Sodium chlorate tank-mixed with glyphosate or paraquat reduced yield, seed weight, germination, emergence, and seedling growth when applied at R5 or R6 to either soybean cultivar. In 'AG 4701RR', glyphosate + sodium chlorate at R7 reduced normal germination and at R6 and R7 decreased seedling length compared to paraquat + sodium chlorate. These results indicate that pre-harvest desiccant applications, particularly those containing glyphosate, should not be made prior to soybean maturity.; Field research was conducted to evaluate the effect of soybean cultivar, early-season weed control, and pre-harvest desiccation on weed seed production and viability. Use of an earlier-maturing soybean cultivar reduced seed production, weight, and vigor of pitted morningglory, and reduced seed weight, germination, emergence, and vigor in hemp sesbania. Use of tall-stature soybean decreased weed seed production and weight of both species. Early-season weed control also reduced seed weight, germination, and vigor by killing the initial weed population, allowing soybean to gain a competitive advantage.; Pitted morningglory, sicklepod, and hemp sesbania seed production and viability in early-maturing soybean were evaluated following a number of pre-harvest desiccants. Tank-mixtures of glyphosate plus sodium chlorate, paraquat plus sodium chlorate, and oxyfluorfen plus sodium chlorate were good desiccants that in most cases also reduced seed production and emergence of pitted morningglory, and germination, emergence, and growth of sicklepod. Hemp sesbania germination, emergence, and growth were all affected by herbicides that desiccated vegetation effectively. Decreasing application volume of treatments containing paraquat resulted in decreased germination and growth of sicklepod was reduced.; Efficacy of reduced rates of glufosinate, and their effect on common cocklebur emergence and growth was evaluated. Reduced rates of glufosinate desiccated weeds effectively, and were comparable to paraquat or glyphosate plus sodium chlorate. All treatments reduced common cocklebur bur production and weight. All tank-mixtures containing glyphosate or glufosinate reduced common cocklebur growth. |
