【Objective】In this experiment, the mixed controlled-release nitrogen (N) fertilizer (composed of two controlled-release N fertilizers with different release periods) and conventional N fertilizer were mixed and then applied as base fertilizers at one time under mechanical pot-seedling transplanting, with a view to select the optimal mixed controlled-release N fertilizer treatment that matched the nutrient absorption of late mid-season japonica rice with good taste quality, so as to provide a scientific basis for high-yield and simplified fertilization of that type of rice under mechanical pot-seedling transplanting.【Method】The experiment was carried out in the rice season of 2018-2019 (May-October). The two late mid-season japonica rice and more panicles cultivars with good taste quality, including Nanjing 9108 and Fengjing 1606, were used as materials under the pure nitrogen condition of 270 kg·hm -2. A mixed controlled-release N fertilizer and a conventional nitrogen fertilizer were combined at a ratio of 5﹕5, and the mixed controlled-release N fertilizer consists of two kinds of controlled-release fertilizers with different release period at a ratio of 4﹕1. Six combinations were set up, including 60 d + 40 d, 60 d + 80 d, 80 d + 60 d, 80 d + 100 d, 100 d + 80 d, and 100 d + 120 d, and conventional urea split fertilization (CK) was used as a control. Then, the yield, population quality index and characteristics of nitrogen absorption and utilization were measured.【Result】The results showed that, compared with CK, the yield of Nanjing 9108 and Fengjing1606 under 100 d+80 d treatment were increased by 4.66% and 4.29% on average for two years, respectively. The increase of grain yield was due to the significant increase in effective panicles per unit area and total spikelet per unit area, and grain number per panicle and filled-grain percentage had no significant difference between 100 d+80 d, 100 d+120 d treatments and CK. The grain yield under 100 d+120 d treatment was next to 100 d+80 d treatment, except for the 100 d+120 d treatment of Nanjing9108 in 2019. There was no significant difference in yield between 80 d+60 d, 80 d+100 d treatments and CK for two years. Compared with CK, the yield under 60 d+40 d and 60 d+80 d treatments was significantly reduced. From sowing to jointing, the group N accumulation under the mixed controlled-release N fertilizer treatments increased, compared with CK, with an average increase of 14.86%, which promoted the occurrence of group tillers and the simultaneous increase in LAI and net assimilation rate, improved photosynthetic productivity, and then increased dry matter accumulation. From jointing to heading, the N accumulation and dry matter accumulation of only 100 d+80 d, 100 d+ 120 d treatments were at the highest level with CK, which increased by 47.02%-55.01% and 14.52%-18.15% respectively, compared with the lowest 60 d+40 d treatment. Compared with the treatments of 100 d+80 d and 100 d+120 d, the net assimilation rate under CK was increased relatively, but the LAI at heading stage decreased significantly. From heading to maturity, the nitrogen accumulation under 100 d+120 d treatment was significantly higher than other treatments, which was increased by 9.23%-22.03% compared with CK. However, the dry matter accumulation under 100 d+80 d and 100 d+120 d treatments was at the highest level, which was significantly increased by 5.44%-8.58% compared with CK, which might be due to that N release under 100 d+80 d and 100 d+120 d treatments, and it could improve photosynthetic leaf area and net assimilation rate relatively coordinately, resulting in relatively sufficient photosynthetic production after heading; While the net assimilation rate of CK was relatively high, but the photosynthetic leaf area was relatively insufficient. With regard to N use efficiency, N partial factor productivity (NPFP) and N agronomy efficiency (NAE) under 100 d+80 d treatment respectively was increased by 3.90%-4.92% and 9.42%-11.93%, compared with CK; The apparent N use efficiency (ANE) under 100 d+80 d and 100 d+120 d treatments was increased by 5.29%-7.21% and 5.79%-8.51%, respectively, compared with CK.【Conclusion】The N release under the 100 d + 80 d and 100 d + 120 d treatments was most consistent with nutrient absorption of Nanjing 9108 and Fengjing 1606, which led to the formation of high-yield population and could be used as a nitrogen fertilizer management method for high-yield and simplified fertilization of late mid-season japonica rice with good taste quality by mechanical pot-seedling transplanting.
