Effects of Nitrogen and Potassium on Growth and Cation Composition of Corn Genotypes Differing in Average Ear Number
1987
Ebelhar, S. A. | Kamprath, E. J. | Moll, R. H.
Genetic improvements for increased grain yield through selection for prolificacy in corn (Zea mays L.) may affect plant responses to fertilizers. A field study was conducted on a Dothan loamy sand (Typic Plinthic Paleudult) to determine the effects of N and K rates on growth, grain yield, and concentrations of N, K, Ca, and Mg in the leaves of corn genotypes differing in average ear production. Nitrogen rates of 50, 150, and 250 kg N ha⁻¹ and K rates of 0, 50, and 100 kg K ha⁻¹ were used in factorial combination with prolific (Pr), semi-prolific (SP), and nonprolific (NP) genotypes at plant densities of 34 000 and 68 000 plants ha⁻¹. Leaf weight and grain yield of all three genotypes were increased with N fertilization. Response above 150 kg N ha⁻¹ was relatively small. Yield response to K was obtained at 150 kg N ha~' but not at 250 kg N ha⁻¹ in a year with optimum conditions for yield. Lack of K response at the high N rate was a result of greater uptake of soil K. Nitrogen rate had a greater effect on K uptake than K rate. Leaf concentrations of Ca, Mg, and K increased with N rates and were greatest with the Pr and SP genotypes. The Pr and SP genotypes had considerably higher leaf concentrations of Ca and Mg and total cation concentration than the NP genotype. However, the NP genotype had the highest leaf N concentration. Increasing K rates decreased Ca and Mg concentrations in the leaves but had little effect on total cation concentration.
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