Starting last week, the annual June “Yellow Flash” or IDC (iron deficiency chlorosis) started to really show up in soybean fields across the province. The excess moisture being experienced across much of the province certainly isn’t helping. Time for a quick review.
Symptoms of IDC (iron deficiency chlorosis) include interveinal yellowing (chlorosis) of new growth, where leaf veins remain green. In extreme cases, interveinal browning (necrosis) can occur. Symptoms show up in soybeans as early as V1 (1st trifoliate).
Prior to V1, cotyledons supply stored iron (Fe) to the soybean plant. Once this source of Fe is depleted, plants must acidify their root zone to access it in a plant-available form from the soil. Despite the abundance of Fe in Manitoba soils, factors such as excess calcium carbonates, soil moisture, soluble salts and/or high nitrate levels can impede Fe uptake into the plant and increase the risk of IDC. Wet years can bring soluble salts to the upper soil profile. If dry conditions follow, it is expected that these salts remain in place, increasing the risk of IDC.
Producers should monitor the patterns, persistence and severity of IDC in your fields. While it seems that some IDC shows up on most soybean fields in Manitoba every year, the condition should be transitory, relatively short in duration (a week or two) and plants should fully recover. In fields where severe symptoms persist over multiple weeks, changes in management should be considered.