Steven H. Moore, Maurice C. Wolcott, Dustin L. Harrell, Jim J. Wang and Wayne H. Hudnall
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.
Experiments were conducted on Norwood silt loam soil in areas of known or suspected zinc deficiency at the Dean Lee Research Station in Alexandria
in 2001, 2002 and 2004. Zinc was applied in-furrow using a granular insecticide applicator on the planter at rates of zero, 1, 2, 3, 4 and 6 pounds of elemental zinc per acre using a 35.5 percent zinc sulfate monohydrate material.
Corn plants displayed a remarkable response to supplemental zinc applications in 2001. A comparison of treatments on corn plants at 44 days after planting can be seen in the photo. Zinc concentration in tissue samples collected at this stage increased in response to the 2, 3, 4 and 6-pound application rates. Although the 1-pound rate had a visibly beneficial effect on corn early in the season, the additional zinc supplied by the 1-pound rate may have been exhausted in the leaf tissue by this time.
Yields dramatically increased in response to supplemental in-furrow zinc application in 2001. Yield increased 82 bushels per acre between the zero and 1-pound rates. Optimum yield was closest to the treatment rate of 2 pounds of zinc per acre. Yield response was positively correlated with zinc tissue concentrations.
Subsequent field experiments in 2002 and 2004 revealed a similar response to supplemental zinc, where the largest increase in yield occurred between the zero and 1-pound application rate. In 2004, the optimum rate was 5.1 pounds of zinc per acre, although 95 percent of the yield benefit could be obtained at a 2.3 pound rate. The optimum rate in 2004 was again 5.1 pounds of zinc per acre, although 95 percent of the yield benefit could be obtained at 2.8 pounds of zinc per acre.
Combining results from three years of study, it appears that most of the benefit from supplemental zinc application was obtained with a 2- to-3-pound addition of zinc. Zinc applied in-furrow did not always affect yield in other studies on a Norwood silt loam soil, indicating that supplemental zinc is not always needed on light-textured Red River alluvial soils.
Zinc deficiency can be overcome by applying zinc in the furrow at planting and should be considered by growers. Growers producing corn on light-textured Red River alluvial soils with zinc deficiency are advised to apply at least 2 to 3 pounds per acre to achieve 95 percent of the potential yield increase when using insecticide applicators. Because of problems with material flow through hopper boxes and tubes, growers are advised to obtain the harder material form of the manufactured fertilizer used in this study. Softer zinc fertilizer materials should not be used, and material flow should be evaluated before planting.
Steven H. Moore, Professor, Dean Lee Research Station, Alexandria, La.; Maurice C. Wolcott, Research Associate, LSU AgCenter, Department of Plant Pathology & Crop Physiology, Baton Rouge, La.; Dustin L. Harrell, USDA-NRCS, Corpus Christi, Texas; Jim J. Wang, Assistant Professor, LSU AgCenter, Department of Agronomy & Environmental Management, Baton Rouge, La.; Wayne H. Hudnall, Texas Tech University, Lubbock, Texas
(This article was published in the fall 2006 issue of Louisiana Agriculture.)