增苗节氮对早稻抛秧群体质量及光合参数的影响

为了探明增苗节氮技术高产群体的适宜群体指标，在大田裂区试验下比较了3个氮肥水平N₁：105 kg/hm²(节氮)、N₂：135 kg/hm²(节氮)、N₃：165 kg/hm²(常氮)]和3个抛秧密度M₁：27万穴/hm²(常苗)、M₂：31.5万穴/hm²(增苗)、M₃：36万穴/hm²(增苗)]对‘湘早籼45号’抛秧群体质量及光合参数的影响。结果表明：在不影响产量的前提下，氮肥用量能比当前习惯施氮量减少18.2%，但进一步降低施氮量（减少36.4%）存在减产风险；氮肥、密度对作物生长率、净同化率、叶面积指数、叶面积衰减率、叶面积比率、表观转运率、光合势、粒叶比等群体指标均有一定影响，产量最高组合(N₂M₃)各项指标值位于中间范围内；N₂M₃的净光合速率、气孔导度、蒸腾速率、水分利用率也处于适中水平。综上所述：“增苗节氮”下早稻抛秧高产群体各项群体指标应该在适中范围内，实行合理搭配，以构建适宜群体来实现高产，而不是为了追求高产而盲目地增加氮肥用量，从而减少过度施用氮肥对生态环境所带来的危害。

Performance on Population Quality and Photosynthetic Parameters of Early Rice of Throwing Transplanting Under Seedling-increase and Nitrogen-reduction Measures

The Population quality and photosynthetic parameters of rice ＇Xiangzhaoxian 45＇ of throwing transplanting under three nitrogen levels N1：105 kg/hm2 （low nitrogen dose）; N2：135 kg/hm2 （low nitrogen dose）; N3：165 kg/hm2 （regular nitrogen dose）] combined with 3 seedling densities MI： 0.27 million hills per hectare （regular seedling rate）; ME： 0.315 million hills per hectare （high seedling rate）; M3：0.36 million hills per hectare （high seedling rate）] in a split-plot trial field were compared to verify suitable population index of high-yielding groups under seedlings-increase and nitrogen-reduction measures. The results showed that： under the premise of not affecting production, nitrogen fertilizer could reduce 18.2% when compared with current habitual amount, but the risk of reducing production would arise when nitrogen fertilizer reduced further （reduce 36.4%）. Nitrogen and density had certain influence on population index of crop growth rate, net assimilation rate, leaf area index, leaf area decay rate, leaf area ratio, export rate, photosynthetic potential and grain leaf ratio etc., each population index value of N2M3 was in the moderate range; net photosynthetic rate, stomatal conductance, transpiration rate and water use efficiency of the highest yield combination （N2M3） were also at a moderate level. In summary, the population index value of high-yielding groups of early rice by throwing transplanting ought to be moderate level under seedling-increase and nitrogen-reduction measures, building suitable groups could reach high yield through reasonable collocation between nitrogen fertilizer and density, rather than increased nitrogen fertilizer blindly to pursue high-yielding, thus reduced the harm to environment on account of excessive nitrogen fertilizer application.