Effect of nitrogen fertilizer managements on rice yield and nitrogen uptake in medium and low yield fields under the conditions of straw turnover

A field experiment was carried out to study the effect of different nitrogen fertilizer ratios of basal∶dressing in tillering-panicle period of rice in Hubei Province in 2011 and 2012 on the yield and nitrogen uptake in the experiment. Rice cultivar, Liangyoupei 9, was used as material. The rice straw were completely turnover into paddy fields after harvest and the total nitrogen input was N 180 kg/ha for all the treatments in both the medium and low yield paddy fields, and the yield and yield components, leaf SPAD, nitrogen uptake and utilization were determined. The results show that the highest rice yield in both low and medium yield fields are achieved in the N application ratio of 40-30-30 for basal-tillering-panicle among the four treatments, the yield is increased by 15.9%-8. 6% compared with the ratio of 80-0-20, and 6.7%-5.5% with the ratio of 60-20-20. Meanwhile, higher nitrogen harvest index and partial fertilizer productivity of nitrogen are also obtained in the ratio of 40-30-30. The descant order of the yield in both the low and medium yield fields is 40-30-3050-20-3060-20-2080-0-20. Comprehensively considering the yield and its components, SPAD value, nitrogen uptake and utilization, we conclude that the application ratio of 40-30-30 for nitrogen fertilizer used at basal, tillering and heading stage in rice is a reasonable N fertilization management in medium\| and low\| yield fields.