Manganese deficiency in winter wheat

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.  

Many stands of winter wheat in the state have taken a good beating this spring due to early growth followed by a mid-April cold spell. The variable weather affecting wheat growth has also prompted the appearance of manganese (Mn) deficiency in some fields. Manganese deficiency is the most common micronutrient problem in Michigan, and wheat is highly responsive to Mn. Manganese exists in many forms in the soil, most of which are unavailable to the growing crop. An adequate level of Mn2+, the primary plant-available source in our soils, is influenced closely by soil pH. Manganese issues most often occur on organic peats or mucks with pH >5.8, but can occur on mineral lakebed and glacial outwash soils with pH > 6.5. Manganese deficiency in wheat generally shows up in patchy areas within a field, and appears as generally stunted plants with yellowing of the upper leaves, slight striping of the leaves and whitish or colorless spots. In some wheat fields, sprayer or tractor tracks will appear noticeably healthier through an area of Mn deficient plants. This phenomenon results from the slightly compacted, more anaerobic (wetter) conditions under the tracks where bacteria convert Mn oxide to plant-available Mn2+. Often times, Mn deficiency shows up early in the spring as a result of limited root activity from environmental conditions (weather, compaction, disease, N deficiency, etc.), even though there may be sufficient Mn2+ in the soil. If limited root growth is driving the deficiency, the crop will often grow out of the Mn deficiency when conditions become more favorable. If you’re not willing to wait and see, foliar applications of Mn fertilizer can be effective at correcting the deficiency. Spray grade carriers of Mn sulfate are the recommended source, applied at a rate of 1 to 2 lbs of actual Mn per acre with 30 gallons of water and a sticker. (Always be sure products are compatible prior to tank mixing.) Chelated sources of Mn generally tank mix better, but are much more expensive and are generally no more effective than inorganic sources.

A detailed discussion of Mn deficiency in wheat, including deficiency photos, can be found at:      http://www.omafra.gov.on.ca/english/crops/field/news/croppest/2005/04cpo05a2.htm

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