Responsesofgrainyield And Nitrogrn Use Efficiency Of Wheat Cultivars Released In Different Decades To Soil Fertility In Shaanxi Guangzhong Plain

Wheat is a major food crop in the world. Improving wheat yield potential and its nitrogen use efficiency isof a vital important option to solve the global food security problem and protect the environment. Cultivar improvement is probably the most important way to achievesuch a goal. Therefore, clarifyingthe relationship between cultivar evolution and soil fertility and how their interaction affects nitrogen efficiency of wheat varieties is of paramount importance for directive breeding and efficient utilization of limited resources. We evaluated the performance of three representative leading wheat cultivars released during 1980 s to 2010 s under a gradient of soil fertility levels, which had been built up by receiving diverse fertilization treatments for 33 years. The winter wheat cultivars are cultivar Xiaoyan 6 in 1980 s, cultivar Xiaoyan 22 at the end of 1990 s and cultivar Xinong 979 after 2005. The fertilization treatments including different quantities and/or types of mineral fertilizers and organic manure, they are control(CK, no nutrient input), two rates of organic manure(M1, M2), combination of two rates of nitrogen and phosphorus fertilizers(N1P1, N2P2) and their combination with two doses of organic manure(M1N1P1, M1N2P2, M2N1P1, M2N2P2). The main results were summarized as follows:1)The soil fertility and cultivar showed a significant interaction effect on grain yield and harvest index of wheat. In general, the grain yield and harvest index of winter wheat tended tobe increased with improving wheat cultivar under same soil fertility level, particularly so under high fertility soils. The grain yield of wheat increased with the improving soil fertility and the amount of fertilizers supplied, and the range of yield increase for old cultivar is less than the new one, but the improvement of wheat cultivar showed no effect on lower fertility soils.2) Wheat cultivar evolution had no significant effects on aboveground biomass at all growth stages in Guanzhong Plain, but the biomass of Xiaoyan 22 was higher than that of Xiaoyan 6 and Xinong 979 at nearly all growth stages. Biomass of winter wheatincreased with the development of wheat growth, and reached its maximum at filling stage on lower fertility soils, but at mature stage on high fertility soils. The biomass of wheat increased with the improving soil fertility and the amount of fertilizers applied. Cultivar Xiaoyan 6 and Xiaoyan 22 accumulated more biomass before anthesis, and Cultivar Xinong 979 after anthesis. The biomass accumulation either before or after anthesis on high fertility soils was significantly higher than that on low fertility soils in the process of cultivar evolution.3) The nitrogen uptake by plant was increased with the development of wheat growth for all three wheat cultivars, but no difference between them at any growth stages. However, the nitrogen uptake is differed from soil fertility, it increased slowly from the seedling stage to the flowering stage, and from thenon increased rapidly until the filling stage, then showed a decreasing trend to the mature stage on lower fertility soils. By contrast, it increased linearly with the development of the growth stage forall wheat cultivars selected on high fertility soils, where nitrogen accumulation was also higher during period of before anthesis than that of after anthesis.4) The nitrogen physiological efficiency, nitrogen agronomic efficiency and nitrogen partial factor productivity showed an increasing trend with cultivar evolution, but nitrogen recovery efficiency had no difference. The former three parameters decreased with the improving soil fertility and the amount of fertilizers supplied.5) Nitrogen budget results showed that nitrogen consumption increased with cultivar evolution on high fertility soils. Nitrogen surplus of three wheat cultivars were increased with the improving soil fertility and the amount of fertilizers supplied.The updated wheat varieties could achieve an improvingly higher grain yield potential and increased nitrogen efficiencies only under high soil fertility conditions where the nutrients are sufficiently supplied in Shaanxi Guanzhong Plain. With high soil fertility and adequate nutrient inputs, the cultivar evolution showed the high yield and high nitrogen efficiency.Therefore, cultivation of new varieties should be synchronized with the improving soil fertility to assure food security and reach a sustainable agricultural production.