Nutrient Diagnosis in Corn Grown on Hydric Dystrandepts: I. Optimum Tissue Nutrient Concentrations

The Benchmark Soils Project is an internationally based research project testing the hypothesis that agricultural technology can be transferred from one location in the tropics to another in soils of the same family. Environmental conditions and maize hybrids used in the tropics differ from those in temperature and subtropical regions. These factors can Influence the “adequate range” or “critical” tissue nutrient concentrations at which acceptable crop growth is obtained. The use of incorrect criteria for diagnosis of nutrient deficiencies from plant tissue analyses could result in inaccurate fertilizer recommendations. The objectives of this study were to evaluate several methods of determining adequate ranges and critical earleaf concentrations for a single maize hybrid grown on Hydric Dystrandepts in Hawaii and to compare the results with published data for other locations. Four methods of determining the optimum ranges of tissue nutrient concentrations were compared using data from eight N × P and seven CaCO₃ × P fertilizer experiments. Optimum concentrations or ranges were calculated as follows: (A) the range of nutrient concentrations associated with the highest 5% of all plot grain yields; (B) the range of nutrient concentrations within one standard deviation of the mean concentration of the highest 15% of all plot yields; (C) the nutrient concentration at 95% of the maximum yield; and (D) the nutrient concentration which, when used as the critical concentration, resulted in the highest percentage of correct diagnoses of nutrient deficiencies. Methods (A) and (B) were used to determine optimum concentrations and ranges of N, P, K, Ca, Mg, S, Al, Mn, Fe, Cu, and Zn. Methods (C) and (D) were used for N and P only. Except for N, Mg, and S, the optimum ranges calculated by methods (A) and (B) were similar and were within previously reported sufficiency ranges for malze (Zea mays L.). For N, Mg, and S, high maize grain yields were found at concentrations slightly lower than those previously reported. The optimum concentrations of N and P obtained by methods (C) and (D) were similar and fell well within published ranges. In seven N × P experiments, highly significant positive correlations were found between both tissue N and P concentrations and grain yield. Likewise, the concentrations of tissue K, S, Cu, and Zn were often positively correlated with tissue N and P concentrations and with grain yield. Only Mn had a consistent negative correlation with grain yield and earleaf N concentration.