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Abstract Based on the reconstructed optimal fertilization algorithm model (NFOA), the effects of applying nitrogen fertilizer on the utilization rate of maize fertilizer and the amount of soil nitrogen absorbed were studied. In 2016, five different nitrogen levels were set up through field experiments. The amount of pure nitrogen was 0, 50, 100, 150 and 200 kg/hm2, respectively, which were expressed as N0, N1, N2, N3 and N4. The changes of nitrogen fertilizer utilization rate, nitrogen fertilizer agronomic efficiency and soil nitrogen uptake by maize were discussed. The 2016 experimental results were validated in adjacent plots in 2017. The experimental results show that: in all 2016 treatments with basal fertilizer only, the yield increased with the increase of nitrogen application rate, but there was no significant difference in agronomic efficiency, and the average value was 21.56 kg/kg; Topdressing agronomic efficiency decreased gradually with the increase of topdressing amount, and was the highest under N1 treatment, which was 14.01 kg/kg. With the increase of nitrogen topdressing, the total nitrogen uptake of maize increased significantly, but the percentage of total nitrogen uptake by soil in maize decreased, and the lowest was 57.15% under N4 treatment. The quadratic curve equation can be used to fit the ratio of nitrogen topdressing utilization rate and nitrogen topdressing rate. With the increase of nitrogen uptake, topdressing utilization rate of maize shows a gradually decreasing trend. In field trials in 2017, the agronomic utilization rate of topdressing for both varieties of maize was higher than that of basic fertilizers; the amount of nitrogen absorbed by maize and the utilization rate of topdressing gradually decreased with the increase of topdressing amount, showing a similar trend to the 2016 test. The amount of nitrogen absorbed by maize from the soil cannot be ignored, and topdressing utilization rate will vary with the amount of topdressing fertilizer. Therefore, we should comprehensively consider the effects of nitrogen topdressing on agronomic efficiency, topdressing efficiency and soil nitrogen uptake, and further provide a theoretical basis for constructing the optimal fertilization algorithm model (NFOA) to achieve precise fertilization.
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