Abstract:

Application of nitrogen (N) fertilizer is one of the most important cultivated measures to increase wheat (Triticum aestivum L.) yield in production. However, abuse of N fertilizer will not only reduce grain yield and economic profit but also cause environmental problems. The proper amount of N fertilizer applied in high-yielding production of winter wheat has been studied at the yield level of 9000 kg ha^-1. The objective of this study was to determine the effects of several N fertilizer rates on uptake, distribution, and translocation of nitrogen as well as grain yield, therefore, to suggest a reasonable application rate of N fertilizer in wheat production. Three rates of N fertilizer application (0, 180, and 240 kg ha^-1) without manure before sowing were designed in Experiment I in 2005–2006, only one treatment of N fertilizer (260 kg ha^-1) with 3 750 kg ha^-1 manure before sowing in Experiment II in 2005–2006, and six N fertilizer rates (0, 210, 240, 270, 300, and 330 kg ha^-1) with 3 750 kg ha^-1 manure in 2006–2007. Two wheat cultivars with medium protein content, Taishan 23 and Jimai 22, were used in the three experiments, i.e., Taishan 23 in Experiment I, Jimai 22 in the other two experiments. The results showed that the application of manure before sowing had minor effect in this study, and three experiments showed similar changing trends in N accumulation and translocation among various organs and growth stages as well as the grain yield. Take the example of Experiment III, with more input of N fertilizer, the grain yield first increased and later decreased during growth period compared with the control (no N fertilizer treatment), and the grain yields of N240 (240 kg ha^-1) and N270 (270 kg ha^-1) treatments were 9 954.73 and 10 647.02 kg ha^-1, respectively, by the increase percentages of 11.20% and 18.93%. Compared with the control, the nitrogen accumulation amount in plant and grain and the nitrogen translocation amount (nitrogen accumulation in vegetative organs at anthesis stage minus the nitrogen accumulation in vegetative organs at maturity, NTA) from vegetative organs to grains after anthesis significantly increased in treatments with N fertilizer application. With the increase of N fertilizer rate, the nitrogen accumulation amount in wheat plant showed a changing trend of first up and then down. The N270 treatment had the highest nitrogen accumulation amount at maturity. The NTA and nitrogen translocation efficiency (NTA/ nitrogen accumulation in vegetative organs at anthesis stage, TE) from vegetative organs to grain after anthesis also increased at first and then decreased. The N270 treatment had the highest nitrogen translocation amount, which was 213.78 kg ha^-1. The N 240 treatment had the highest TE of 67.98%. Similarly, the dry matter accumulation amount in various vegetative organs of wheat at maturity, the dry matter redistribution amount from vegetative organs to grain after anthesis, and the dry matter redistribution efficiency after anthesis were all largest in N270 treatment. Among the six N fertilizer treatments, the contribution of dry matter accumulation amount from vegetative organs to grains after anthesis was the largest in N240 treatment. The results of this study suggested that N fertilizer supplied at 240–270 kg ha^-1 is optimal in wheat production under similar conditions to those of the experiments to obtain the high-yielding level of 10 000 kg ha^-1.

Key words: Nitrogen fertilizer rate, Wheat, Yield, Nitrogen accumulation and distribution