Effects of side deep placement of nitrogen on rice yield and nitrogen use efficiency

: Lateral deep fertilization is an efficient, high-quality, and safe cultivation technology of rice mechanical transplanting. In order to improve the technical system of lateral deep fertilization, we investigated the effects of different fertilization methods on rice yield and nitrogen use efficiency under the condition of lateral deep fertilization. In this study, Nanjing 9108 and Nanjing 5718, the representative varieties of quality and delicious rice of Jiangsu, were used as materials. Four different lateral deep fertilization methods were arranged, including 100% base fertilizer side deep application FM1 (fertilization method 1), 70% base fertilizer side deep application + 30% tillering fertilizer FM2 (fertilization method 2), 70% base fertilizer side deep application + 30% panicle fertilizer FM3 (fertilization method 3), and 35% base fertilizer side deep application + 35% tillering fertilizer + 30% panicle fertilizer FM4 (fertilization method 4). In addition, the conventional fertilization method and no nitrogen treatment were added. The effects of different treatments on rice yield, leaf area index, photosynthetic potential, dry matter accumulation, population growth rate, and nitrogen use efficiency were compared. The results revealed that the yield of FM3 and FM4 were higher than those of other treatments. The main reason was that the spikelet number of the population was significantly higher than that of other treatments on the basis of stable panicle number. The leaf area index and dry matter accumulation of FM3 treatment were higher in the middle and late growth stages, especially from heading to maturity stage. Nitrogen accumulation of FM3 was less before jointing stage, but nitrogen accumulation after jointing stage and the total nitrogen uptake during the whole growth period were significantly higher than those of other treatments. Moreover, the nitrogen agronomic utilization rate, nitrogen physiological utilization rate, nitrogen absorption utilization rate, and nitrogen partial productivity of FM3 were significantly higher than those of the other treatments. At the same time, compared with CFM and FM4, FM3 can reduce fertilization times by 1–2 times, save labor and cost, and is conducive to large-scale production. It is a high-yield, simple and efficient fertilization method for rice.