Herbicides used as harvest aids are applied at crop maturity to desiccateweed and crop foliage. Weeds present in the harvested crop can increasemoisture content and foreign material, reducing grade and market price.Weeds can also delay the harvest operation and reduce harvest efficiency.Glyphosate can be used to desiccate weeds in glyphosate-resistant cropswithout concern for crop injury. Carfentrazone and pyraflufen-ethyl used asharvest aids can be effective in desiccating broadleaf weeds in corn andsoybean. Paraquat, although effective on grass and broadleaf weeds whenapplied late season, can cause significant crop injury if applied too early.With expanded production of early maturing soybean cultivars in themid-South (Arkansas, Louisiana, Mississippi, Missouri bootheel, and westTennessee), presence of green stems, green pods, or green leaf retention, orcombinations of these at harvest has increased. Interest in harvest aids hasshifted to use as a crop desiccant. Paraquat also is an effective soybeandesiccant, but application timing differs for indeterminate and determinatecultivars. Paraquat applied after soybean seed reached physiologicalmaturity reduced number of green stems, pods, and retained green leavespresent, allowing harvest to proceed 1 to 2 wk earlier than nontreatedsoybean. Seed moisture, foreign material, and seed damage also were reducedwhen paraquat was applied.

Research was conducted over 2 yr to evaluate soybean response to harvest aid herbicide treatments paraquat at 0.28 kg ai ha−1, paraquat with carfentrazone at 0.014 kg ai ha−1, and sodium chlorate at 6.72 kg ai ha−1. Indeterminate and determinate soybean cultivars were treated when moisture of seed collected from the uppermost four nodes of plants averaged 60, 50, 40, 30, and 20% (± 2%). For each soybean cultivar, the harvest aid treatment by application timing interaction was not significant, and data for harvest aid treatments were averaged. Application of harvest aid at 60% average seed moisture reduced yield for the maturity group (MG) IV indeterminate cultivar 15.4% compared with the nontreated; 100-seed weight was reduced 12.4%. Yield and seed weight were not negatively affected when harvest aid was applied at 50% average seed moisture and soybean was harvested 14 and 15 d before the nontreated control. Although planting date in the 2 yr for the indeterminate cultivar differed by 26 d, number of days from planting to harvest aid application at 50% average seed moisture was 112 and 116 d. For MG V and MG VI determinate cultivars, application of harvest aid at 60% average seed moisture reduced yield compared with the nontreated control 22 and 18.1%, respectively, and at 50% average seed moisture 15.6 and 4%, respectively; seed weight reductions of 8.9 to 33.3% accompanied the yield reductions of the two cultivars. Reduction in soybean yield and seed weight was not observed when harvest aid was applied at 40% average seed moisture, and harvest for the 2 yr was 8 and 9 d earlier for the MG V cultivar and 10 and 14 d earlier for the MG VI cultivar.