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Corn Responses to Ammonium- and Nitrate-Nitrogen Fertilization

Texas A&M Univ. Research and Extension Center, Rt. 2, Box 589, Corpus Christi, TX 78410

L. D. Maddux and G. M. Pierzynski

Dep. of Agronomy, Kansas State Univ., Manhattan, KS 66506

D. E. Kissel

Dep. of Agronomy, Univ. of Georgia, Athens, GA 30602

B. R. Bock

Agricultural Research Dep., Tennessee Valley Authority, Muscle Shoals, AL 35660

*Corresponding author.

ABSTRACT

Studies have indicated that, by maintaining relatively high solution culture or soil NH⁺₄/NO^-₃ ratios during the reproductive growth stage, certain corn (Zea mays L.) genotypes have a higher yield potential. Unfortunately, few data on soil NH⁺₄ and NO^-₃ levels have been reported. A 3-yr field experiment was conducted in northeastern Kansas in 1987, 1988, and 1989 to evaluate the effects of time and form of applied N on fertilizer band NH⁺₄/NO^-₃ ratios and on the N nutrition, dry-matter accumulation, and grain yield of two corn hybrids. Urea, urea-NH₄NO₃, urea plus Ca(NO₃)₂, NH₄NO₃, and Ca(NO₃)₂ solutions having NH⁺₄/NO^-₃ ratios of 1:0, 3:1, 1:1, 1:1, and 0:1, respectively, were used at equivalent N rates. The nitrification inhibitors, nitrapyrin [2-chloro-6-(trichloromethyl) pyridine] and dicyandiamide, as well as two-way and three-way timing of application schemes were used to maintain N as NH⁺₄. Split applications of ammoniacal N with a nitrification inhibitor were effective in maintaining elevated soil NH⁺₄ concentrations from planting through early grain fill. In 1988 only, grain yield was increased slightly (3–9% higher) when corn was fertilized with ammoniacal N compared with NO^-₃ only. Overall, manipulation of soil NH⁺₄/NO^-₃ratios had few effects on corn development or yield.

Contribution no. 91-381-J from the Kansas Agric. Exp. Stn. This research was supported by the Fluid Fertilizer Foundation and the Tennessee Valley Authority.

Received for publication March 12, 1991.