Abstract: To further study  the characteristics of nitrogen absorption, utilization, transport and nitrogen use efficiency of new Indica hybrid rice varieties with different grain weight types bred in Southwest China under different density of bowl-seedling-mechanical-transplanting, the representative large grain-weight variety Nei 6 You 107 and the medium grain-weight variety Jingyouhuazhen were selected and transplanted with pot seedling mechanical transplanting LD, MD and HD of 3 constant gradient densities in space configuration of 24 , 16 and 12 cm, and with  hand method  in conventional local planting density as control. The effects of different planting densities on nitrogen uptake, accumulation, translocation, and nitrogen use efficiency of 2 new varieties were studied on the basis of less than the total nitrogen application rate of local custom. The results showed that: compared with the large grain weight variety Nei 6 You 107, the 1 000-grain weight of Jingyouhuazhen was lower, but its effective panicles, grains per spike and seed-setting percentage and grain yield were higher. Meanwhile, there was little difference of nitrogen content rate between the two varieties at the main growth stages, but the plant nitrogen uptake, plant nitrogen uptake at each growth stage and partial factor productivity of Jingyouhuazhen were higher than Nei 6 You 107, and the nitrogen translocation efficiency, nitrogen translocation conversion, nitrogen dry matter production efficiency and nitrogen harvest index of Jingyouhuazhen were lower than those of Nei 6 You 107. There were significant differences in the yield of different grain-weight varieties under different planting density of bowl seedling mechanical transplanting, and the yield of MD treatment was the highest yield of both varieties. The yield of large grain weight variety Nei 6 You 107 was 15.81%, 4.29% and 29.08% higher than that of LD, HD and CK, respectively. While under MD treatment, and the yield of medium grain weight variety Jingyouhuazhen was 8.78%, 503% and 27.6 % higher than that of LD, HD and CK, respectively. The effects of mechanical transplanting density on nitrogen uptake and nitrogen use efficiency of the two varieties were basically consistent with different mechanical transplanting densities. There was no significant difference on the nitrogen content at the early growth stage, but it increased significantly with the increase of mechanical transplanting density at the late growth stage. At the early stage, the nitrogen uptake increased with the increase of the transplanting density, but at the late growth stage, the nitrogen uptake was higher under MD treatment, and the nitrogen uptake at the growth stage was HD>MD>LD>CK, with significant difference. The nitrogen translocation of LD treatment was the least, partial factor productivity increased at first and then decreased, while plant nitrogen translocation efficiency, nitrogen dry matter production efficiency and nitrogen harvest index  decreased with the increase of mechanical transplanting density. It was suggested that mechanical transplanting of bowl seedling with 16 cm conducive to nitrogen accumulation different growth stages, increase nitrogen translocation from full heading stage to mature stage, and achieve synergistic improvement of yield and nitrogen use efficiency. Above results was of great significance to the breeding of rice green varieties and cultivation techniques and theories of high efficiency and high yield.

Key words: Indica hybrid rice, bowl-seedling-mechanical-transplanting, planting densities, nitrogen use efficiency

摘要： 为进一步分析我国西南区域不同粒重类型杂交籼稻新品种在不同钵苗机插密度配置下氮肥吸收、利用、转运情况及氮肥利用效率与产量的特征，选取代表性大粒型品种内6优107和中粒型品种旌优华珍，以钵苗插秧机配置24、16和12 cm株距构建3个等梯度密度处理LD、MD和HD，并以当地常用人工手插宽行窄株栽培模式为对照（CK），在总施氮量比习惯用量减少的基础上，研究钵苗机插密度对新品种的氮肥吸收、转运和利用的影响。结果表明：与大粒型品种内6优107相比，中粒型品种旌优华珍的千粒重较低，但其有效穗数、穗粒数和结实率较高，产量较优；同时，两品种主要生育时期植株含氮率差异较小，但旌优华珍主要生育时期植株吸氮量、植株各阶段吸氮量以及氮肥偏生产力均较高，而其氮素表观转运率、氮素贡献率、氮肥干物质生产效率和氮肥收获指数低于内6优107。钵苗机插密度对不同粒重类型品种的产量具有显著影响，且均以MD处理产量最高，大粒型品种内6优107在MD处理下分别较LD、HD和CK增产15.81%、4.29%和29.08%，而中粒型品种旌优华珍分别增产8.78%、5.03%和27.69%。两个品种的植株吸氮能力和氮肥利用能力受机插密度的影响表现基本一致：不同机插密度处理间，植株含氮率在水稻生长前期差异不明显，但在生育后期随着机插密度增加而显著增加；植株阶段吸氮量在前期主要随机插密度增加而增加，但在生育后期均以MD处理较高，且主要生育时期植株吸氮量均表现为HD>MD>LD>CK，差异达到显著水平；氮素转运量均以LD处理最小，氮肥偏生产力随着机插密度增加表现为先增加后降低，而叶茎鞘氮素转运率、氮肥干物质生产效率和氮肥收获指数均随机插密度增加而降低。钵苗机插可显著提高水稻产量和氮肥吸收能力，且通过适量增加密度能够显著提高不同粒重类型杂交籼稻新品种的产量和氮肥利用效率。钵苗机插株距16 cm配置，有利于各生育时期氮素积累，提高齐穗期至成熟期的氮素转运量，实现产量和氮肥利用效率协同提升。上述结果对高产高效绿色水稻品种选育和栽培技术与理论具有重要意义。

关键词: 杂交籼稻, 钵苗机插, 密度, 氮肥利用效率