Harvest aid applied at soybean growth stage R7 rarely impacted seed, protein, or oil yield

Abstract

Harvest aids, such as foliar-applied crop defoliants or desiccants, are tools available to soybean [Glycine max (L.) Merr.] farmers that can homogenize maturity and help facilitate earlier soybean harvest, particularly when extreme weather events are forecasted. Prior research has shown soybean harvest aids increase harvest efficiency but has been limited primarily to states in the southern United States. Further investigation on the utility of harvest aids across the majority of US soybean production is warranted as incorrect desiccation timing can significantly reduce seed, protein, and oil yield. In 2024, a study was conducted at 19 sites across 13 US states to test the effect of planting date, maturity group, and desiccation timing on soybean seed yield, protein and oil yield, green stem incidence, and harvest timing. Seed yield reductions were rare when desiccation occurred at R7 but were common at R6.5 applications. Seed protein and oil yield was not affected by desiccation at R7 but was reduced with some R6.5 applications. Desiccation at R6.5 and R7 reduced green stem incidence 50% of the time. Harvest could occur 15 days earlier in the southern United States when desiccation occurred at R6.5 or R7, while harvest could occur 4 and 3 days earlier in the northern United States, respectively. Overall, the data show a harvest aid applied at soybean R7 can allow farmers to harvest earlier with low risk of seed, protein, or oil yield reductions.