| Improving nitrogen use efficiency in crops has become increasingly important not only for reducing cost, but also for protecting environment. This research was undertaken to evaluate systematically genotypic differences among various wheat varieties, explore physi-ecological mechanism in nitrogen utilization, determine cultural regulation approaches for efficient nitrogen management. The present study was conducted under soil conditions provided by pot and field experiments.In prder to evaluate genotypic and environmental variation of five nitrogen use efficiency (NUE) parameters, a field experiment was carried out using 40 wheat (Triticum aestivum L.) genotypes grown in two sites (Xuzhou and Nanjing). Relationship between nitrogen nutrition characteristics and NUE parameters were also studied. The results showed that genotypic variation of all parameters was significant except NHL NRE and NFE were slightly affected by environmental factors compared with other parameters, whereas all parameters were significantly influenced by interaction of genotype X environment. NFE , correlated positively and significantly with NRE and NFS, may be more reliable for evaluation of nitrogen utilization in wheat because it's an integrated index of grain protein and yield. NFE could be improved by increasing N assimilation and translocation after anthesis to increase effectively N utilization in wheat. These varieties were divided into three different groups according to their NFE performance.On the basis of the above studies, four wheat varieties with different nitrogen flow efficiency (NFE) were selected. Pot experiment was conducted under three nitrogen levels to compare genetic differences in nitrogen assimilation and translocation. Significant differences of wheat varieties in plant growth, nitrogen accumulation, C/N translocation and photosynthetic characteristics at late growth stages were found. Compared with low NFE genotypes (Yanfu 188 and Wanmai 18), wheat genotypes with high NFE (Xuzhou 26 and Huaimai 18) exhibited superior nitrogen accumulation capacity, and R/S corresponded orderly over growth period. High NFE was mainly related to better postanthesis performance, which are reflected as root activity, leaf area, photosynthetic ability duration, and ability in transferring C/N matter to grain during late growth period. At low N level, the small genotypic variation in NFE was mainly associated with nitrogen translocation ability. Yet at higher N level, both nitrogen uptake efficiency and transfer efficiency played animportant role. Higher nitrogen use efficiency could be obtained by enhancing C/N metabolism ability during grain filling stage. We suggest that nitrogen fertilizer management during late growth period should be strengthened.To demonstrate an effective approach of regulation on NUE under the field conditions, the effects of nitrogen application level, basal/dressing ratio and wheat genotypes on carbon and nitrogen assimilation and transfer, yield and nitrogen use efficiency were observed. Two wheat cultivars Xuzhou 26 (with high NFE and high grain protein content) and Huaimai 18 (with high NFE and low grain protein content) were used. The results showed that wheat responded better to nitrogen ratio of 34/66 under high nitrogen level and 66/34 under low nitrogen level. Huaimai 18 was promoted more significantly by increased nitrogen application. While Xumai 26 got a higher yield than Huaimai 18 under low nitrogen level. It also showed that high NFE of Huaimai 18 was mostly due to its increased total matter accumulation and high assimilation ability during late growth period, but Xumai 26 transferred more reserved carbohydrate and amino acid from the vegetative organs to the grain.Pot culture experiments were conducted to investigate the effects of different nitrogen forms on growth and nitrogen accumulation under different N levels (0.05, 0.15, 0.30 g N /kg soil) .Dry weight of total plant, grain yield, nitrogen uptake, leaf area and NRA were significantly enhanced by EAN treatment (N^N...
|
PDF Full Text Request