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Breeding for higher concentrations of minerals in food crops is one option for improving the health of humans suffering from the consequences of mineral deficiency. The plant breeding approach requires that varietal differences are stable across different environmental conditions. The main objective of our research was, therefore, to determine whether differences in the concentration of grain minerals (P, K, Mg, Ca, Mn, Zn, and Cu) among tropical maize varieties are affected by the level of water and N supply. A 3‐yr study with two water regimes (preanthesis drought vs. irrigation throughout the vegetation cycle), three levels of N fertilization (0, 80, 160 kg N ha−1, applied as ammonium sulfate), and four varieties (Suwan 1, La Posta Sequia, KTX2602, DK888) was conducted in the tropical lowlands of Thailand. The water regime did not affect the mineral composition of the grains. Application of N fertilizer reduced the concentrations of Ca and Zn, and increased the concentration of Mn in the grains. The top yielder, DK888, had the lowest concentrations of N, P, Mg, and Cu in the grain. The varietal differences in the concentrations of grain N and minerals were fairly stable across the levels of N and preanthesis water supply. The varieties that differed most in the grain N and P concentrations (DK888 and KTX2602) had almost the same endosperm/germ dry weight ratio. It remains to be determined whether breeding for high grain yield inevitably lowers the concentrations of grain minerals and protein.

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The measurement of agronomical parameters of maize (Zea mays L.) indicating its biomass and nutritional status provides important information to understand its responses to the environment. The detection of significant differences among maize hybrids would be very useful in plant breeding programs screening for N uptake and drought tolerance. The aim of the study was to assess the efficacy of high‐throughput sensing measurements to determine the aerial biomass and N uptake of tropical maize hybrids grown in well‐watered (control) and drought stress treatments. Experiments were conducted at the National Corn and Sorghum Research Center in Thailand in the years 2007 through 2009. High‐throughput canopy reflectance measurements using spectral indices from the literature and newly developed for this study were performed regularly along with biomass samplings until flowering. The relationship of the spectral indices with each of aerial biomass and N uptake had coefficients of determination of up to 0.8 and were also able to distinguish between drought stress levels. Through most sampling dates and stress levels, varieties were similarly classified in their amount of aerial biomass and N uptake by destructive and noncontacting measurements. Our results support the possibility of incorporating these methods in the development of high‐throughput phenotyping techniques that could prove to be potentially useful for future plant breeding.