Micronutrient Management Dorivar Ruiz Diaz Soil Fertility and Nutrient Management

Outline  Overview micronutrients  Factors to be considered  S, Zn, Cl, and Fe  Deficiency symptoms  Fertilization strategies and management  Current studies

Essential Micronutrients  Minor elements or trace elements  Increased interest in micronutrients – Higher crop yields and micronutrient removal rates – Declining soil organic matter, a major source of most micronutrients – N, P and K fertilizers contain lower amounts of micronutrient impurities  Excessive levels can cause toxic effects on plants  In Kansas: Fe, S, Zn, and Cl.  Other micronutrients: B, Mg, Cu, Mn, and Ni.

Organic Matter  Important source of most micronutrients.  Simple organic compounds as chelates.  S, Zn and B deficiencies are more likely to occur in soils low in O.M.  Deficiencies of Cu and Mn are most common in peat soils.

Soil pH and micronutrient availability  Soil pH affects availability of micronutrients.  In general the solubility and availability of micronutrients are greatest in acid soils and lowest in high pH calcareous soils.  Exception is Mo.  In some soils, high levels of soluble Fe, Al and Mn may be toxic to plants.

Sulfur (S) Photos by Brian Lang, IA

 Soil situations and climatic conditions aggravating deficiency symptoms – Coarse textured soils (sandy soils) – Low organic matter soils – Cold, wet soils – Slow release of S from organic matter – Low atmospheric deposition  No application from – Manure – Other fertilizers Sulfur Deficiencies

S N

10 kg SO 4 /ha = 3 lb S/acre Sulfur Deposition

Corn Response to Sulfur J. Sawyer, 2007

Wheat S Rec. (Lb/A) = (0.6 × Y Goal) – (2.5 × % OM) – Profile Sulfur – Other Sulfur Credits Corn and Sorghum S Rec. (Lb/A) = (0.2 × Y Goal) – (2.5 × % OM) – Profile Sulfur – Other Sulfur Credits Soybean S Rec. (Lb/A) = (0.4 × Y Goal) – (2.5 × % OM) – Profile Sulfur – Other Sulfur Credits Subsoil S may be significant. Profile soil test for S, 0-24 inches, also good for nitrate and Cl. Sulfur Fertilizer Recommendation

Zinc (Zn)

Zinc  Frequently deficient micronutrient  Absorbed by plant roots as Zn ++  Involved in the production of chlorophyll, protein, and several plant enzymes  Deficiency symptoms –Most distinctive in corn with new leaves out of whorl turning yellow to white in a band between the leaf midvein and margin

 Sensitive crops – Corn, sorghum  Soil Situation – Low organic matter, high pH (>7.4), eroded soil – Coarse texture, restricted rooting –High P application in conjunction with borderline or low zinc availability – High soil P alone does not create deficiency  Climatic Conditions – Cool and wet soil Zinc Deficiencies

Phosphorus and Zinc  Zn deficiency impairs plant P regulation.  Large amounts of starter applied P can enhance Zn deficiency if soil Zn is low and no Zn fertilizer is applied. P2O5P2O5 ZnYieldLeaf tissue lb/acrebu/acreP, %Zn, ppm Adriano and Murphy, KSU

P and Zn Effects On Corn Yields P2O5P2O5 Zn B’castStarter Lb / A Corn Yield (Bu/A) St. Mary’s, KS – Kansas State University

Wheat response to foliar Zn and Cu western Kansas 1 lb/acre Zn 1 lb/acre Cu Control B. Olson, 2009 Soil Test YearSiteVarietyCopperZinc ppm Danby Jagalene1.0 3Wesley Jagalene Jagalene Ike TAM

Wheat response to foliar Zn and Cu western Kansas B. Olson, 2009 TreatmentYield bu/acre Zinc6342 Copper6540 Control6342 LSD (0.05)NS

Zinc Fertilizer Recommendation Corn, Sorghum and Soybeans Zinc Recommendation Zn Rate = 11.5 – (11.25 × ppm DTPA Zn) If DTPA Zn > 1.0 ppm then Zn Rec = 0 If DTPA Zn <= 1.0 ppm then Minimum Zn Rec = 1

Application Methods  Broadcast –Preferred to correct a low Zn soil test –5 to 15 pound will increase soil test for a number of years –Inorganic Zn is more economical than chelates at these rates  Band –Very efficient method of applying Zn –0.5 lb Zn/Acre of inorganic Zn is generally sufficient –Annual applications will be needed for low testing soils

Chloride (Cl)

 Wheat, corn, sorghum deficiencies in Kansas  Deficiencies most likely in higher rainfall areas with no K application history - central and eastern part of state  Soluble, mobile anion  Addition of KCl – Increased yields with high levels of available K – Reduced incidence of plant disease – Internal water relationships, osmotic regulation, enzyme activation and other plant processes

Chloride fertilization for wheat and sorghum, in Kansas Chloride rateWheat yield (Var. 2145) lb/acrebu/acre LSD(0.05)= 3 B. Gordon, 2009

Wheat response to Cl and fungicide application Overley wheat yield Chloride rateNo fungicideFungicide lb/acre bu/acre LSD(0.05)= 3 B. Gordon, 2009

Grain Yield ChlorideMarion Co.Saline CoStafford Co. Rate Site ASite BSite ASite BSite CSite DSite ASite BAvg. lb/a bu/a Soil test Cl, lb/a (0-24") *Average over either 12 or 16 varieties. Soil test Cl, lb/a (0-24") Chloride Fertilization on Wheat

Cl Fertilizer Recommendation Profile soil ChlorideChloride recommendation ppmlb/acrelb Cl/acre < 4< > 6> 450 Wheat, corn and sorghum

Iron (Fe)  Iron in the plant – Catalyst in the production of chlorophyll – Involved with several enzyme systems  Deficiency symptoms – Yellow to white leaf color – Symptoms first appear on the younger leaves – Wide range of susceptibility of different crops Sorghum, field beans and soybeans are more sensitive than corn and alfalfa Varieties differ within crops

Iron Deficiency

Iron Deficiency - Causes  Iron deficiency is caused by a combination of stresses rather than a simple deficiency of available soil Fe  Soil Chemical Factors –pH, carbonates, salinity (EC), available Fe (DTPA- Fe), high nitrate-N. –Cool, wet soils  Biotic factors –Variety, SCN, root rotting fungi, interplant competition.

Effect of soil nitrate?

The nitrate theory  Iron is part of the chlorophyll molecule  Iron taken up as Fe +++ (ferric)  Iron in chlorophyll exists as Fe ++ (ferrous)  High concentrations of nitrate-nitrogen inhibit conversion of Fe +++ to Fe ++

Irrigated soybean

Nitrogen application and iron chlorosis G. Rehm, 2007

Soybean population and iron chlorosis Iron chlorosis score 5= Dead; 1=Green Neave, 2004

Soybean population – yield Neave, 2004 Loc.1Loc bu/acre

Soybean Fe Study  Varieties (2): high and low IDC tolerance.  Seed treatment: with and without 0.6 lb/acre of EDDHA Fe (6.0%).  Foliar treatments: – 0.1 lb/acre EDDHA Fe (6.0%) – 0.1 lb/acre HEDTA Fe (4.5%) – No foliar treatment  4 locations with 5 replications

Objectives  Evaluate fertilization strategies.  Determine soil parameters (diagnostic): – Fe, Mg, P, K, Ca, OM, OC, TN, pH, EC, Carbonates, nitrate-N.  Determine “optimum” plant tissue level.  Evaluate possible interaction of parameters, both in soil and plant. – Possible Fe-Mn interaction?

Soybean seed treatment with Fe chelate

Seed coating treatment

Chlorophyll meter readings

Plant height at maturity

Treatment Average yield W/O Seed coating39 6% Foliar40 4.5% Foliar37 No39 W/ seed coating50 6% Foliar52 4.5% Foliar49 No49 Var AG3205: Low IC tolerance Soybean grain yield

Var AG2906: Very Good IC tolerance Treatment Average yield W/O Seed coating36 6% Foliar35 4.5% Foliar38 No35 W seed coating50 6% Foliar47 4.5% Foliar52 No52

Are these yield values significantly different? EffectF ValuePr > FSignificance Variety NS Seed trt69.6<.0001S Foliar NS Var*Seedtrt NS Var*Foliar NS Seedtrt*Foliar NS Var*Seed*Foliar NS

Common Iron Fertilizers Fertilizer Source Iron Sulfate Iron Chelates Other Organics Manure - best Fe (%) ??

Manure source IronManganeseBoronZincCopper lb/wet ton Dairy solid Swine solid Poultry lb/1000 gal Dairy liquid Swine liquid Average animal manure micronutrient content

Summary  Fe deficiency potential can not be explained well by a single soil parameter.  Development of an “ soil index” may be the best alternative.  Foliar treatment seems to increase the “greenness” effectively. But seed coating provides higher yield increases.  Select a soybean variety that is tolerant to Fe chlorosis.  Avoid excessive application of nitrogen fertilizer to the crop that precedes soybeans in the rotation.

Summary  Increased interest for foliar application of nutrients.  Tissue test can provide good indication for micronutrient needs.  Increased interest for mixing micronutrients with fluid fertilizer for band application.  Seed coating with micronutrients is an alternative.

Questions? Dorivar Ruiz Diaz