GENOTYPE VARIATION IN GRAIN NUTRIENT CONCENTRATION IN TROPICAL MAIZE GROWN DURING A RAINY AND A DRY SEASON

A set of 12 tropical maize cultivars was screened for grain nitrogen, phosphorus, and potassium concentration (GNC, GPC and GKC). The experiments were conducted at the National Corn and Sorghum Research Centre, Farm Suwan, Pakchong, Thailand during a rainy and a dry season. The genotypic variability in GNC, GPC and GKC was considerable. There was no inverse relationship between grain yield and grain nutrient concentration. The hybrids KUH 2301 and KUH 2602 were identified as high yielding, high GNC cultivars. However, due to positive correlations between GNC and GPC, both cultivars exported much more phosphorus from the field than the high yielding low GNC cultivars, Pi hybrid 6181 and CP hybrid. The cultivation of the latter 2 should be recommended to Thai cash crop farmers as a means of reducing the need for large amounts of scarce and costly mineral fertilizers and because decreases in GNC, GPC and GKC are not necessarily a disadvantage for utilization in animal husbandry in developed countries.