| In order to provide a theoretical basis for increasing the yield of local crops and efficient utilization of fertilizer resources, this study explored the optimum amount of nitrogen fertilizer applied to the farmland with straw incorporation in semi-arid areas. In this study, Xinong 979 was used as the experimental material. Under the condition of straw incorporation to the field(9 000 kg·hm-2), five kinds of pure nitrogen application levels were set up(N0:0 kg·hm-2；N75:75 kg·hm-2；N150:150 kg·hm-2；N225:225 kg·hm-2； N300:300 kg·hm-2). Among them, no nitrogen fertilizer(N0) was used as a blank control. According to the survey on the average amount of fertilizer applied by farmers in the Guanzhong area of Shaanxi Province,N300 treatment was used as the traditional fertilization amount of farmers. On the basis of traditional fertilization by farmers, the amount of nitrogen applied was reduced to study the effects of different nitrogen fertilizers applied on the soil moisture, photosynthetic characteristics of flag leaves of winter wheat during flowering stage, nitrogen utilization, yield and economic benefits. The results showed that as the amount of nitrogen is increased, the water consumption of each treatment is gradually increased. The grain water use efficiency(WUE) increased at first,and then dcreased with the increase of nitrgen rate.Compared with N300, WUEs under N150 and N225 were higher,and increased by 0.60% and 2.71%, respectively, and WUE under N0 and N75 was decreased by 17.74% and 3.90%(P<0.05), respectively. The photosynthesis ability of the flag leaves under each treatment during flowering stage was increased first and then decreased with the increase of nitrogen application rate, and that under N225 was the best. Compared with N300, the intercellular CO2 concentration under N225 was significantly reduced by 13.36%, and the net photosynthetic rate, transpiration rate and stomatal conductance were significantly increased by 16.36%, 11.81% and 18.39%, respectively. The photosynthetic performance under other treatments were significantly lower than that under N300. For yield and its components, compared with N300, the number of spikes per hectare under N225 decreased significantly by 2.56%(P<0.05); while the number of kernels per spike and 1 000-grain weight increased by 2.48% and 1.35%, respectively, and the final yield increased by 1.36%. The grain yield under N150 was slightly lower than that under N300, but the difference was not significant. Compared with N300, the yield under N0 and N75 decreased significantly by 21.62% and 7.74%(P<0.05). The contribution rate of nitrogen fertilizer reached the highest under N225, and increased significantly by 4.95% compared with that under N300. The difference between N150 and N300 was not significant(P<0.05). Compared with N300, the nitrogen partial productivity under N75, N150 and N225 was significantly increased by 269.08%, 98.25% and 35.16%, respectively(P<0.05), and the agronomic efficiency of nitrogen fertilizer increased by 166.52%, 95.74% and 42.00%, respectively. Compared with N300, the economic benefits under N0 and N75 reduced by 2 841.44 yuan·hm-2 and 828.54 yuan·hm-2, respectively, and that under N150 and N225 increased by 169.20 yuan·hm-2 and 332.40 yuan·hm-2, respectively. Straw incorporation combined with nitrogen fertilizer can improve crop water use efficiency, enhance photosynthetic ability of winter wheat, increase soil nitrogen use efficiency, maintain high yield of crops, and increase economic benefits. Considering comprehensively, the effect of the full amount of straw incorporation to the field with nitrogen fertilizer 150-225 kg·hm-2 is better. |
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