Micronutrient Deficiencies in Wheat Kurt Steinke, Ph.D. Soil Fertility & Nutrient Mgmt. Dept. of Plant, Soil, and Microbial Sciences Michigan State University

General Comments on Micronutrients Micronutrients defined as: Nutrients required by a plant for growth Amount needed is very small (<100 mg/kg) compared to macronutrients (primary & secondary) Deficiency can be just as yield limiting as a deficiency of a macronutrient K. Steinke, MSU

The Eight Micronutrients Boron (B) Chloride (Cl) Copper (Cu) Iron (Fe) Manganese (Mn) Molybdenum (Mo) Nickel (Ni) Zinc (Zn) K. Steinke, MSU

Micronutrient Use is Increasing Because of: Higher crop yields Widespread use of N-P-K fertilizers Higher analysis fertilizers containing less micronutrients Sales gimmick ($$) K. Steinke, MSU

Micronutrients ARE NOT miracle workers nor magic pills in a bottle K. Steinke, MSU

Soil pH Has the Greatest Impact on Nutrient Use Efficiency 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 extreme strong slight acidity acidity acidity slight alkalinity strong alkalinity nitrogen phosphorus potassium sulfur calcium magnesium iron manganese boron copper and zinc molybdenum K. Steinke, MSU

Micronutrients - Mn Healthy leaves: 40 – 100 ppm Mn (40-60 target) Conc. decreases as season progresses < 20 ppm: deficient Immobile in plant Young leaves affected (shadow effect) Interveinal chlorosis (many field crops) Wheat: Yellow, dis-colored, colorless spots (Similar to disease) Causes: high soil pH (>6.5), imbalance with other nutrients (Ca, Mg, Fe, Zn) For every 1 pH unit ↑, 100x decrease in soil [Mn2+]

K. Steinke, MSU

Micronutrients - Mn Corrective Measures Most effective as starter applications Soil or foliar Soil banded: 4 – 18 lbs Mn/A (Mn sulfate) Soil b-cast: >20 lbs Mn/A (not recommended) Mn oxides and chelates not effective for soil application Foliar: 1-2.5 lb Mn/A in 30 gal H2O Mn sulfate or chelates work best Do not apply to chelate to soil as other cations (e.g., Ca or Fe) often replace Mn in the chelate and convert to unavailable forms

Micronutrients - Cu Healthy leaves: 8 – 50 ppm Cu (target 8-20 ppm) Conc. often increases as season progresses (incr root area) < 6 ppm: deficient Immobile in plant Young leaves affected (shadow effect) Wilting, lack or turgor, bluish-green tip Often confused with disease symptoms Grain loses pigmentation Eventually chlorotic leaf tips and death (may be confused with cold damage) Causes: Peaty/muck soils, imbalance with other nutrients (Zn, P, Fe Rare on most Michigan mineral soils Where present: acid soils, heavily cropped with N, P, and K

Yellow, stunted necrosis along edges K. Steinke, MSU

Micronutrients - Cu Corrective Measures Soil or foliar Soil: 1 – 20 lbs Cu/A based on soil test (Cu sulfate or oxide) Muck/Peat: 20-40 lb/A for low or high responsive crop Chelates not effective for soil application Foliar: 0.5 – 1.0 lb Cu/A in 30 gal H2O Cu sulfate or chelates work best Do not apply chelate to soil as other cations (e.g., Ca or Fe) often replace Cu in the chelate and convert to unavailable forms Beware: Cu doesn’t leach; If apply too much, toxicity problems are difficult to correct

116 101 K. Steinke, MSU

Wheat – Whole Plant – GS 5 K. Steinke, MSU

Wheat – Flag Leaf – GS 9 K. Steinke, MSU

Take Home Points Tissue Deficiencies Some is good, more is not better Something will be deficient at some point in the season Does NOT equate to yield-limiting factor Collect BOTH soil and plant tissue Collect from good AND poor areas Good area = reference point Transitional area may be sampled to determine why issue occurred Some is good, more is not better Beware of large bulk nutrient application Cation/anion interference Ex. : High Ca interfering with Mn Are you creating your own problem?

Thank You for the Support! K. Steinke, MSU