【目的】 机插秧是当前我国水稻种植发展的主要方向,探索不同秧龄下机插方式与密度对杂交稻根系生长及氮素利用特征的影响,对提高水稻产量和氮肥利用率,加快水稻机械化高产高效栽培技术的集成具有重要意义。【方法】 以超级杂交稻F优498为材料,采用两因素裂区试验设计,在25 d和40 d秧龄下,通过“钵苗机插+高密度”、“钵苗机插+中密度”、“钵苗机插+低密度”、“毯苗机插+高密度”、“毯苗机插+中密度”、“毯苗机插+低密度”6种机插方式与密度配合的处理,研究其对氮素利用特征、根系生长特性的影响,并探讨根系生长与氮素利用及产量的关系。【结果】 各生育时期氮素吸收与各阶段氮素积累量,齐穗至成熟期氮素吸收速率、茎和叶的氮素转运量、穗部氮素增加量、氮素偏生产力、拔节后根系干质量以及产量,25 d秧龄均较40 d秧龄优势明显。在相同秧龄下,与毯苗机插相比,钵苗机插可促进杂交稻各生育时期根系生长,提高氮素积累及吸收速率,增加结实期各器官氮素的转运量,从而提高稻谷产量;尤其在秧龄25 d、钵苗机插株距为15.5 cm时,较其他处理优势明显,为本研究最优处理。毯苗机插在25 d秧龄与株距为12 cm时,也能够获得较高产量;密度降低,提高了根冠比及茎叶转运率,但降低了各时期的氮素积累量、吸收速率以及结实期茎叶的转运量,产量较低。相关性分析表明,不同秧龄机插方式与密度配合下,主要生育时期根干质量与产量及氮素吸收利用均存在极显著正相关( r = 0.47**~ 0.83**),齐穗和成熟期根冠比与产量及氮素吸收利用均极显著负相关( r = -0.52**和-0.79**)。【结论】 机插杂交稻25 d秧龄根系生长及氮素利用特性均优于40 d秧龄,且钵苗较毯苗机插能优化水稻个体与群体关系,但其机插密度不宜过高或过低,行距与株距以33 cm×15.5 cm为宜,可促进氮素吸收利用及产量同步提高;且拔节与成熟期根系的生长对产量影响显著。研究结果可为水稻钵苗机插秧高产高效栽培技术集成及应用提供技术和实践依据。

【Objective】Mechanical transplanting is the main development direction of the rice planting in China, and it has important significance for increasing rice yield, nitrogen (N) use efficiency and accelerating integration of high yield and efficient cultivation techniques of rice mechanization by researching the effects of mechanical-transplanted modes and density on root growth and characteristics of N utilization in hybrid rice at different seedling-ages. 【Method】A split plot design was used with the super hybrid rice F you 498 as material to analyze the effects of six mechanical-transplanted modes and density combined treatments of “bowl mechanical-transplanting with high density, bowl mechanical-transplanting with middle density, bowl mechanical-transplanting with low density, carpet mechanical-transplanting with high density carpet mechanical-transplanting with middle density, and carpet mechanical-transplanting with low density” on characteristics of N utilization, root growth, and to recover the relationship between root growth with N utilization and yield at different seedling-ages. 【Result】The N uptake of main growth period, N accumulation at growth and development stage, N absorption rate, N translocation amount of stem and leaf from full-heading to maturity, N increase in panicle, N partial factor productivity and root dry weight after jointing stage, and yield of 25-day-old seedlings have an obvious advantage over that of 40-day-old seedlings. Compared with carpet mechanical-transplanting, the bowl mechanical-transplanting can improve the root growth at different growth stages, enhance N accumulation and uptake rate, increase the amount of N translocation to various organs during grain filling stage, so as to increase the grain yield. Especially the best treatment, the bowl mechanical-transplanting with a plant spacing of 15.5 and 25-day-old seedlings has obvious advantages than other treatments. And carpet mechanical-transplanting can also help get a higher yield with the plant spacing of 12 cm and 25-day-old seedlings, but the yield will be reduced when density decreased even though it improved the root to shoot ratio, transport rate of leaf and stem, but decreased N accumulation of each period, absorption rate, and the leaf and stem translocation amount during grain filling stage. Correlation analysis showed that grain yield and N uptake and utilization were significantly correlated with root dry weight of main growth period (r=0.47**~0.83**), but significantly negatively correlated with root-shoot-ratio of full-heading and maturity period (r=-0.52**~ -0.79**). 【Conclusion】For root growth and N uptake and utilization characteristics, 25-day-old seedlings were better than 40-day-old seedlings and bowl mechanical-transplanting can optimize the relationship between individuals and population, but seedling density should be moderate, the most suitable spacing is 33 cm × 15.5 cm. It can promote the absorption and utilization of N and grain yield. Furthermore, the findings suggested that attention should be paid to the root growth from jointing stage and maturity stage, because of its significant effect on yield. The result laid a technical and practical basis for the high yield and high efficiency cultivation technology of bowl mechanical-transplanting.