CORN Newsletter: 2004-13, May 11, 2004

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C.O.R.N Newsletter 2004-13
May 11, 2004 - May 18, 2004

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Where are Micronutrient Deficiencies Most Likely to Occur?
by Robert Mullen


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With all the attention paid to the big three in soil fertility (N, P, K), micronutrients are sometimes overlooked. Micronutrient levels in Ohio soils are for the most part adequate for maximum crop production. Not to say that micronutrient deficiencies do not reduce yield, but the likelihood of having a micronutrient deficiency in Ohio is generally small. For each micronutrient (and sulfur), field conditions are presented that can enhance the potential for deficiencies.

Sulfur
Sulfur (S) deficiencies would most likely be found in coarser textured soils low in organic matter (S is actually a macronutrient but it is included in this discussion). Because sulfur exists as sulfate (anion – negatively charged) in soil solution, its mobility is similar to nitrate. Sulfur is primarily made plant available by mineralization from the organic fraction and is found readily in rainfall (due to industrial processes). The amount of sulfur found in rainfall varies dramatically across the cornbelt with values as high as 30 lb S/acre and as low as 5 lb S/acre reported. The amount typically used by a crop is approximately 1/10th the amount of N used. If manure application is a part of the fertilizer regimen, the likelihood of seeing a S deficiency is small.

Zinc
Zinc (Zn) deficiencies are primarily confined to areas of the field where erosion has exposed subsoil. Coarser textured soils low in organic matter and high pH soils (> 7) enhance the potential to see Zn deficiencies. Similar to S, if manure is applied regularly as a soil amendment, Zn levels should be adequate for maximum production. Soils with relatively high levels of organic matter are also likely to have adequate levels of Zn. The lower the soil pH the less likely that Zn levels are in the deficient range.

Copper
Copper (Cu) deficiencies are primarily confined to black sands and organic soils (mucks and peats). Mineral soils are rarely deficient in Cu.

Manganese
Manganese (Mn) deficiencies are primarily found in soybeans and oats grown on high pH, high organic matter soils. Mineral soils with pH levels less than 6.5 rarely exhibit Mn deficiencies. Application of high rates of manure can actually enhance the potential of seeing a Mn deficiency, as Mn can be bound in unavailable organic chelates. The likelihood of observing a Mn deficiency in corn or alfalfa is small.

Boron
Boron (B) deficiencies are most likely found in alfalfa grown on coarser textured soils and low organic matter soils. Boron deficiencies are rare in soybeans. Like most micronutrient metals as soil pH decreases B availability increases. Do not apply B as a starter in close proximity to the seed, it can cause seed injury.

Iron
Iron (Fe) availability is strongly tied to soil pH. If soil pH is below 7.3, it is very unlikely that Fe is deficient. Iron deficiency is most probable in calcareous soils or soils with high pH.

Molybdenum
Unlike the other micronutrient metals, molybdenum (Mo) availability increases as soil pH increases. Because of this, Mo deficiencies can be observed on legumes grown in extremely acid soils (pH less than 5.0). However it is more economical to apply lime than to provide Mo as a soil amendment. Molybdenum deficiencies for other non-leguminous crops are extremely rare in this portion of the United States.

Remember, the examples of conditions conducive to deficiency presented above are where deficiencies are most likely to occur, not where they will definitely occur. Generally speaking, soils in this region supply enough micronutrients to satisfy crop needs, thus supplementation of micronutrients by fertilization is unnecessary. Soil testing can indicate whether a micronutrient is deficient or not. If a micronutrient deficiency is suspected, soil and/or plant analysis should be conducted.

Readers can subscribe electronically to this newsletter by signing up at http://agcrops.osu.edu/services/email.html. E-mail labarge.1@osu.edu if you have problems subscribing or no longer wish to receive this newsletter.

C.O.R.N. is a summary of crop observations, related information, and appropriate recommendations for Ohio Crop Producers and Industry. C.O.R.N. is produced by the Ohio State University Extension Agronomy Team, State Specialists at The Ohio State University and Ohio Agricultural Research and Development Center. C.O.R.N. Questions are directed to State Specialists, Extension Associates, and Agents associated with Ohio State University Extension and the Ohio Agricultural Research and Development Center at The Ohio State University.

Information presented above and where trade names are used, they are supplied with the understanding that no discrimination is intended and no endorsement by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.

All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.

Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Keith L. Smith, Director, Ohio State University Extension.

TDD # 1 (800) 589-8292 (Ohio only) or (614) 292-1868


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