Micronutrient Management in Glyphosate Tolerant Crops

Glyphosate tolerant crops have become widespread in soybeans, alfalfa, cotton and corn, making weed control much easier to manage.  However, early in its use, glyphosate applications over the top of crops caused manganese flash in soybeans. Manganese flash occurs as glyphosate ties up manganese in the plant making it unavailable, which induces a micronutrient deficiency.  Glyphosate is an excellent chelator that not only ties up manganese in the plant, but also does the same in the soil.  Roots of weeds and crops exude glyphosate into the soil, tying  up the manganese and making it unavailable to the crop.  Although the relationships are not completely understood, glyphosate is also known to affect uptake and distribution of iron and zinc.

Tank mixing a manganese nutrient with the herbicide application was a solution developed to mitigate the effects of glyphosate on manganese uptake and distribution.  When tank mixed with glyphosate, it was discovered that non-chelated forms of manganese decreased weed control and did not mitigate the manganese flash.  However, when chelated forms of manganese were applied, weed control was not affected and the deficiency was mitigated.  This is because the glyphosate was tying up the non-chelated manganese in the spray tank and was not able to provide acceptable weed control.  By using  EDTA-chelated manganese, both weed control and nutrient delivery were excellent.

Helena’s broad line of Axilo products consists of 100% EDTA–chelated dry micronutrients. The soluble micro-granules in Axilo prevent and treat a wide range of micronutrient deficiencies. The rates for these products on glyphosate tolerant corn, cotton or alfalfa are 0.5 to 1.0 lb/a and compatible with glyphosate.  Axilo products are excellent options to mitigate the effects of glyphosate on micronutrient nutrition in these crops.

- Matt Beene, SJV Products Manager