Harvest Aids and Soybean Seed Quality
On Aug. 18, 2018, I received an email inquiring about whether or not products that are commonly used as harvest aids for soybeans will affect quality of harvested soybean seeds following the application of these products.
After a thorough search of major soybean information sources, I found an article titled “Effect of three different desiccant herbicides on soybean seed quality” (Weed Science, Vol. 32:484-490, 1982). The content of the article dealt with germination of and fungal populations on harvested seed following applications of glyphosate, paraquat, or sodium chlorate:sodium borate at growth stages R5.5, R6.0, and R7 (defined in article as 50% defoliation or beginning maturity). The R7 application would be the only one that was applied at the appropriate time according to recent results of research reported here; i.e. newer research indicates that a harvest aid applied before R6.5 will reduce yield and subsequently should not be applied at earlier stages.
Results reported in the above-cited article indicate the following when soybean seeds were sampled 15 days after spraying paraquat as a desiccant at stage R7 (paraquat has a 15-day PHI).
• There was no increase in total fungi (Fusarium, Alternaria, Phomopsis) present on seed, or in percentage of fungi-infected seeds.
• Germination of harvested seed was not affected.
• Seed weight was not affected.
• Delayed harvest increased the levels of seedborne fungi and decreased germination regardless of desiccant application.
• Temperature and rainfall patterns/conditions at seed maturation are more important than the rate of tissue senescence in affecting seed infection by fungi following desiccant application.
I was unable to find any information on soybean seed composition following application of harvest aids/desiccants. Evidently, there has been no research conducted to determine how harvest aid products may or may not affect the chemical composition of soybean seeds that are harvested following their application.
With a significant acreage of ESPS soybeans receiving harvest aid products in the Midsouth, research conducted to determine if these products do affect the chemical composition of harvested soybean seed is warranted. The results of such research will be especially important if/when soybean seed composition is rewarded at the delivery point, or if soybeans are grown for seed for future plantings.
Composed by Larry G. Heatherly, Aug. 2018, larryheatherly@bellsouth.net