Overlap areas whether in the middle of the field or in the headlands for some soybean fields has shown an interesting coloration. Often when we see yellowing beans in a field we think of micro nutrient deficiencies such as manganese. Those appear as areas in the field circular or semi circular areas. The linear patterns and location of yellow patches being seen happen after applications of glyphosate about 3 weeks ago. The areas where sprayers were turned on and off are most pronounced.
Yellow flash is the name given to this phenomenon. This has been noted in other areas of the midwest in previous growing seasons. The conditions leading to this tend to be:
- Rapid soybean growth after application
- Sprayer overlap or other application conditions that lead to higher product application.
- Areas prone to micro nutrient deficiencies primarily manganese or iron.
The yellowing is a by product of the level of AMPA in the leaf which is a breakdown product of glyphosate which reduces chlorophyll levels in the newly developing leaf give the yellow appearance. If you want more information, Dr Mark Loux has a couple of links posted at http://corn.osu.edu/newsletters/2011/2011-26/yellow-soybeans-in-response-to-glyphosate-applications