以两系杂交稻两优培九为试材，研究不同N肥用量(纯N 0、112.5、225.0、337.5 kg/hm2)和栽插密度（22.5×104、27.0×104、31.5×104穴/hm2）对产量形成及N素吸收利用的影响。结果表明，(1)栽插密度对结实率和千粒重影响较小，对单位面积穗数和每穗粒数影响较大，在22.5×104~31.5×104穴/hm2的密度范围内，穗数与每穗粒数之间具有良好的互补性，因而产量差异未达显著水平。(2)N肥用量对每穗粒数影响较小，对穗数、结实率和千粒重影响较大，纯N用量为337.5 kg/hm2时，增穗作用不显著，反而极显著降低结实率和千粒重，导致减产。(3)稻株吸N量随供N水平的提高而增加，但植株含N率和N素累积量过高不利于叶鞘茎中的N素向穗部运转，降低籽粒N素积累量，导致结实率和千粒重显著下降而减产。(4)在中等肥力土壤上，施纯N 225.0 kg/hm2，栽插密度22.5×104穴/hm2，高峰苗控制在500.0万/hm2左右，有利于两优培九抽穗前茎鞘叶N素积累和抽穗后向穗部运转，能较好地协调穗数、结实率和千粒重的关系而获得高产。
A field experiment was conducted with different transplanting densities (22.5×104，27×104，31.5×104 hole/ha) and nitrogen fertilizer rates (0，112.5，225.0，337.5 kg/ha) using an intersubspecific hybrid rice, Liangyoupeijiu. The main results were as follows: (1) Influence of transplanting density on panicle per unit area and grain number per panicle was higher than that on seed-setting rate and 1000-grain weight. There was no significant difference in yield between treatments with transplanting densities ranging from 22.5×104 to 31.5×104 holes per hectare. (2) Effect of nitrogen fertilizer on grain number per panicle was lower than that on panicle number, seed-setting rate and 1000-grain weight. Seed-setting rate and 1000-grain weight were decreased significantly in the treatment with 337.5 kg/ha nitrogen fertilizer. (3) The amount of N-uptake was increased with the increment of nitrogen fertilizer rate. But excessive N-content and nitrogen accumulation were not of benefit to the transfer of nitrogen from vegetative organs (leaf, sheath and stem) to panicle, resulting in the reduction of N-accumulation amount in seeds, seed-setting percentage, 1000-grain weight and yield. (4) The better N accumulation of stem, sheath and leaf before heading, the better N transfer of nitrogen from stem, sheath and leaf to panicle after heading, the better coordinate relationship among panicle number, seed setting rate and 1000-grain weight and higher yield would be obtained under medium-fertility field with nitrogen application of 225.0 kg/ha, transplanting density of 22.5×104 hole/ha and high peak seedlings of 500.0×104/ha.
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