Changes of Grain Yield and Nitrogen Use Efficiency of Maize Hybrids Released in Different Eras in Shaanxi Province

Abstract

Identifying the changes of grain yield and nitrogen use traits will facilitate the development of new maize hybrids with high yield and nitrogen use efficiency. In this study, 12 typical maize hybrids released from 1981 to 2010 in Shaanxi Province were grown in the field under three N rates(0, 120, and 240 kg ha–1) from 2011 to 2012 in Shaanxi, Northwest China. Nitrogen use efficiency and agronomic traits of maize were investigated. The result indicates that grain yield of maize hybrids increased with the increase of nitrogen rates, and the modern maize hybrids(2000s) showed better grain yield than the old ones(1980s) at three nitrogen levels. The yield genetic gains were 46, 65, and 83 kg ha–1 per year at N0, N120, and N240 levels repeat. The modern hybrids showed better biomass and grain yield than the old ones, but there was no clear changing trend in stover yield between hybrids of different ears. Increments of grain yield were achieved mainly through increasing the kernel number per ear, 1000-kernel weight and biomass, and the coefficient of light extinction decreased with the time process of cultivar development from 1981 to 2010. Changes of plant structure would allow the modern maize hybrids to improve light capture resulting in better grain yield than those of the old ones. For nitrogen use point of view, irrespective of nitrogen treatments, nitrogen use efficiency(NUE) of hybrids released increased in responses of time. But nitrogen use efficiency decreased with increasing nitrogen application rates, and nitrogen use efficiency(NUE) was highly correlated with N uptake efficiency(NUpE, r = 0.75), and not with N physiological efficiency(NUtE, r = 0.42). Increased NUE positively correlated with improved N uptake efficiency(NUpE), due to the greater post-anthesis N accumulation. The results indicated that improvements of 1000-kernel weight, kernel number per ear and nitrogen uptake efficiency(NUpE) should be considered during breeding for high yield and high nitrogen use efficiency of maize under low nitrogen and water limited conditions.