Micronutrient Deficiencies
in Winter Wheat

Nutrient deficiencies in winter wheat show up most commonly in late April and early May. Cool soils restrict root growth, but the above ground portions of the plant try to grow rapidly whenever there is a warm day, so any shortage in the soil shows up in the plant. The most common deficiency is manganese, but some fields show copper deficiency each year.

Manganese Deficiency

Manganese deficiency symptoms are not as striking in wheat as in soybeans, showing up as yellowing of the upper leaves, or a faint striping on the leaves. Some plants will also show greyish spots between the veins, which may coalesce into larger spots. The patterns of yellowing or stunting in the field are often more diagnostic of manganese deficiency than the symptoms on individual plants.

Manganese availability in the soil is reduced by high pH, high organic matter, and excessive aeration. In rolling fields, it is not uncommon to see Mn deficiency showing up on the eroded knolls and in the muck hollows, but not on the mid-slopes. A very interesting pattern occurs when these fields have received fertilizer, and the tire tracks from the spreader show up as dark green through the yellow areas. The slight compaction in the tire tracks has been enough to create an anaerobic environment, dissolving some of the manganese in the soil.

Foliar applications of manganese are preferred to correct a deficiency, both because it avoids tie up in the soil, and because very small amounts of the nutrient are needed. The product of choice for correcting manganese deficiency is manganese sulphate, applied to provide 2 lb/ac of actual Mn (8 lb/ac of product). This should be applied in high rates of water (40 gal/ac), with a spreader-sticker to help carry the manganese through the cuticle of the leaf. Chelated manganese is much easier to use, and is more compatible with herbicides if they are mixed, but much more expensive. Scientific opinions on the effectiveness of chelates range from about 2X as effective as the sulfate (U. of G.) to equally effective (Michigan State), but the cost is roughly 10X higher for the chelate per pound of manganese. Very low rates of chelated product are not effective.

Soil applied manganese is not effective because the mineral gets tied up in unavailable forms. Adding Mn to the soil simply increases the amount of unavailable Mn. There is some suggestion that on some of the acid sandy soils, which have very low manganese content, that adding slag containing Mn can help overcome a Mn deficiency. This makes sense, for that particular situation, but there have been no trials to confirm this.

Copper Deficiency

Wheat growing in organic (muck) soils will occasionally show copper deficiency symptoms. This appears as leaf tips that die back, and then twist or wrap. Severe copper deficiency will lead to delayed maturity and stunted, misshapen heads. Foliar applications of copper sulphate can be used to correct copper deficiency, but only low rates can be used or there will be excessive leaf burn. Soil applications of copper sulphate in fields with a history of copper deficiency are more effective and safer.

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