Abstract: 【Objective】Ridge-furrow irrigation has been promoted widely in northwestern China, but short in alternative nitrogen application. This article described the effects of different nitrogen application methods on root growth, yield and nitrogen use efficiency of spring maize under field condition in conventional furrow irrigation situation, in order to reveal the pattern of root growth and distribution, yield, and nitrogen use under different nitrogen application methods and explore the reasonable nitrogen applications fitting to arid and semi-arid region in northwestern China.【Method】Spring maize variety Jinsui 4 was used as the experimental materials and was planted with ridge-furrow irrigation for two consecutive years. There were three treatments: conventional nitrogen supply (CN, nitrogen was applied evenly on both furrows), alternate nitrogen supply (AN, nitrogen was applied alternately in one of the furrows) and fixed nitrogen supply (FN, nitrogen was applied fixed in one furrow). Nitrogen was applied at 200 kg N•hm-2 in each treatment. Urea nitrogen was selected and applied at three times: 50%, 25% and 25% with basal application in sowing, topdressing in spike formation and tasseling stages, respectively. Calcium superphosphate was applied as a base fertilizer, evenly spreaded at the rate of 45 kg P2O5•hm-2. The irrigation norm was 3 750 m3•hm-2 was conducted after sowing and at the stages of jointing, spike formation, tasseling and filling, respectively. Root lengths under the plant, in the right and left of the plant of maize in the soil layers of 0-100 cm were measured at the growth stages of maize tasselling, filling and maturity stages of maize, and each 20 cm as one layer. Root length density was calculated through the body of the sampling. Yield and the total nitrogen of the plant were measured after harvest and the nitrogen use efficiency was calculated. 【Result】The results showed that, maize roots were mainly gathered under the plant in the soil layer of 0-40 cm. Root length density showed a decreasing trend with the soil depth increasing. In general, the root length density of maize was the largest in CN, the second place was in AN and smallest in FN during the monitoring period. Root length density was larger in CN in the soil layer of 0-40 cm while was larger in FN in the soil layer 60-100 cm. As in FN, root length density had a significant difference between right and left sides of the plant. The root length densities were nearly the same between right and left side of the plant in CN. The average nitrogen uptake rate, yield and nitrogen use efficiency in CN in two years was 217.8 kg N•hm-2, 10 318 kg•hm-2 and 47.3 kg•kg-1N, respectively. Compared with FN and AN, the nitrogen uptake rate in CN improved averagely by 4.28% and 2.50%, respectively; the yield improved averagely by 8.45% and 4.42%, respectively; the nitrogen use efficiency improved averagely by 4.08% and 1.87%, respectively. 【Conclusion】 Obviously, CN could maintain a larger root mass and had a most uniform distribution of roots between right and left sides of the plant during the monitoring period. Roots distribution between right and left sides of the plant had a significant difference under FN. The AN was located between CN and FN in maintaining root growth. As maintaining of the root growth and yield formation in three treatments, the CN was the best, AN was the second and FN was the worst. It was suggested that in condition of conventional furrow irrigation, nitrogen fertilizer should be applied evenly on both furrows and it is a good way for nitrogen applications.

Key words: nitrogen application methods , root length density , yield , nitrogen use efficiency , maize