Relationships between Grain Nitrogen Concentrations and the Nitrogen Status of Corn
1990
Cerrato, M. E. | Blackmer, A. M.
Grain analysis is frequently used to determine the N status of corn (Zea mays L.). The objective of this study was to assess the reliability of N concentration in grain as an indicator of the N status of corn. The study involved 12 site-years of data, each having 10 rates of N applied preplanting. Nitrogen concentrations in grain tended to increase with increases in rates of N application. Nitrogen concentrations also tended to increase with increases in relative yields, but the relationships often were C-shaped, and there was no basis for establishing critical N concentrations. The relationships between N concentrations in grain and adjusted rates of N fertilization (i.e., rates of fertilization expressed relative to economic optimum) were statistically significant, but they had low predictability. For example, only 19% of the variability in N concentrations could be explained by a model that considered only data between ± 100 kg N ha⁻¹ from economic optimum rates of fertilization. Only 1% of the variability could be explained by a model that considered only data between ±50 kg N ha⁻¹ from economic optimum. These observations indicate that, especially where the availability of N is near or above optimal, N concentration in grain does not provide a reliable indicator of the N status of corn. Journal Paper no. J-13515 of the Iowa Agric. and Home Econ. Exp. Stn., Ames, IA. Project 2741. This work was supported in part from the Fertilizer Trust Account of the Iowa Dep. of Agric. and Land Stewardship and in part by the Integrated Farm Management Demonstration Program of The Agricultural Energy Management Fund, State of Iowa, through the Iowa Dep. of Agric. and Land Stewardship.
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