The increasing cost of micronutrients zinc and manganese may dampen the euphoria that has led some analysts to predict a large bump nationwide in corn acreage in 2007.

A 10-year high in corn prices, combined with myriad questions over the future of cotton, tobacco and peanut production in the Southeast, have stimulated increased interest in corn production.

Cotton, peanuts and tobacco aren’t going away in the Southeast, but it is no secret projected increases in corn will cut into 2007 acreage in these traditional Southern crops.

To take full advantage of the record high corn prices, growers will have to more carefully manage the purchase and application of zinc and manganese micronutrients.

Corn must have zinc and needs manganese in many soil types in the Southeast. Worldwide there is a shortage of zinc, and to a lesser degree, manganese. Zinc that sold in 2006 for less than a dollar per pound may reach $5 per pound and manganese may top $3 per pound, according to Alan Robinett, a representative of Tetra Micronutrients.

High prices may also drive down availability of both zinc and manganese. Lack of availability and cost will demand that growers be more efficient on when and how they apply these micronutrients in 2007.

Zinc can be a miracle micronutrient for corn. An acre of corn typically needs only two ounces, but these two ounces can increase yields by over 60 bushels per acre. Zinc is a growth promoting substance that controls the development of the shoot. It also forms enzyme systems which regulate plant life and auxins that can reduce pest damage.

Zinc deficiencies in corn appear to be increasing with sometimes severe effects on yield. The increase may be due to declining soil organic matter, where a little decrease can significantly affect micro-nutrient availability. Zinc-deficient young corn seedlings exhibit purple or red coloring on leaf tips, yellow or white striping and shortened internodes.

Zinc deficiency can be overcome in corn by applying granular or liquid formulations of zinc in the furrow at planting or liquid or foliar applications after the crop emerges. Softer zinc fertilizer materials should not be used, and material flow should be evaluated before planting.

In tests conducted in 2004 and 2005 across the Southeast corn plants displayed a strong response to supplemental zinc applications at 2-3 pounds per acre. Some tests indicate a one pound per acre rate may be sufficient in some soils, but on lighter soils with lower levels of crop nutrients, the lower levels of zinc were not adequate to sustain maximum yields.

The impact of zinc on corn is directly tied to a number of soil and climatic conditions. Cool soil temperatures in early spring can intensify the need for zinc. When soils are cold, the organic matter does not decompose and zinc is not released and is unavailable for crop growth.

Fine-textured soils, characteristic of the Coastal Plain soils dominant in the Southeast are likely to produce the most response to zinc. On sandier soils a response to zinc is most likely to occur when high yields are grown on sandy soils that have a low organic matter content.

The response of corn to zinc fertilization increases where topsoil has been removed or eroded away. When soils are eroded, the amount of free calcium carbonate on the soil surface increases. The probability of the need for zinc in a fertilizer program increases as the percentage of free calcium carbonate increases.

There is a known relationship between phosphorus (P) and zinc in soils. Excessive applications of phosphate fertilizers have caused a zinc deficiency in corn and reduced yields.

Manganese deficiency can cause up to a 50-percent reduction in soybean yield potential. Corn losses can range from 20 to 50 percent.

For corn growers in the Southeast in 2007, careful monitoring of soil test samples is critical to maximizing yield and to take advantage of current high corn prices.

Manganese deficiency in corn causes streaking on the uppermost leaves of mature corn. Such deficiencies are rare in corn on soils with a pH of 6.0 to 6.3. Most crops deficient in manganese become yellowish to olive-green. In corn the yellow-green discoloration creates a pin-striping of the leaves that is sometimes calls interveinal chlorosis.

When the pH is above 6.2, the best way to correct a manganese deficiency is to spray a liquid manganese fertilizer on the leaves. Use a highly water-soluble source of manganese at a rate of 0.5 pound per acre in enough water to cover the leaves thoroughly. In severe cases, several applications may be necessary during a growing season, but the increase in yield will usually more than pay for the cost of treatment.

Damage caused by manganese deficiency is rare in corn but does occur in the upper Southeast on soils extremely low in the trace nutrient. Damage is most often found where soil pH is excessively high as a result of improper liming.

Though a small cost of the production of corn, projected dramatic increases in zinc and manganese in 2007 could drive profits down and failure to address deficiencies in these micronutrients could further reduce profits by negatively affecting yield.

e-mail: rroberson@farmpress.com