杂交水稻

为探究密度和施氮量对再生稻再生季产量和镉积累特性的影响，以创两优669为材料，头季设置2种密度水平(D1，常规密度对照，株行距为16.7 cm×20.0 cm;D2，增密处理，株行距为16.7 cm×16.7 cm)，再生季设置2种施氮水平(N1，常规施肥对照，施纯氮87.00 kg/hm²;N2，减氮15%处理，施纯氮73.95 kg/hm²)，研究其再生季干物质积累量、产量及其构成因素、镉积累特性的差异。结果表明，增密处理虽每穗总粒数和千粒重略有下降，但有效穗数明显增加，结实率提高，因此再生季产量增加；减氮15%处理主要因有效穗数、每穗总粒数明显降低，导致再生季产量显著下降。各处理中，2 a再生季产量均以N1D2处理最高，N2D1处理最低；在D1和D2密度条件下，减氮15%处理分别使再生季平均产量下降17.8%和15.3%，增密处理(D2)可部分缓解减氮导致的产量损失。增密处理明显提高了再生季成熟期地上部各器官的镉积累量，且对各器官镉转运系数影响较小；减氮15%处理则明显降低了各器官镉积累量和镉含量，以及根—茎、根—枝梗、根—糙米、根—叶的镉转运系数。综上，常规施氮+增密处理(N1D2)处理再生季产量及干物质积累量最高，减氮15%处理(N2)的各器官镉含量、镉积累量、镉转运系数均相对较低。

This study aims to explore the effects of density and nitrogen application rate on the yield and cadmium accumulation characteristics of ratoon rice in ratooning season. Chuangliangyou 669 was planted with two densities in the main season(D1, conventional density control, plant-row spacing of 16.7 cm × 20.0 cm; D2, increased density, plant-row spacing of 16.7 cm × 16.7 cm), and two nitrogen application rates in the ratooning season(N1, conventional fertilization control, pure nitrogen of 87.00 kg/hm²; N2, nitrogen reduction by 15%, pure nitrogen of 73.95 kg/hm²). The dry matter accumulation, yield and yield components, and cadmium accumulation characteristics in the ratooning season were studied. The results showed that although the total number of grains per panicle and 1 000-grain weight decreased slightly, the number of effective panicles increased markedly, and seed setting rate increased, and thus the yield in the ratooning season increased in the case of density increasing. Under nitrogen reduction by 15%, however, the yield in the ratooning season decreased significantly due to the marked decreases in the number of effective panicles and total number of grains per panicle. The yield in the ratooning season was the highest in the N1D2 treatment and the lowest in the N2D1 treatment in two years. Under D1 and D2 conditions, nitrogen reduction by 15% decreased the average yield in the ratooning season by 17.8% and 15.3%, respectively. The yield-reducing effect of nitrogen reduction can be partially alleviated by density increasing(D2). Density increasing markedly increased the cadmium accumulation in the aboveground organs at maturity stage in the ratooning season, and it had little effect on the cadmium transport coefficient of each organ. Nitrogen reduction by 15% significantly reduced the cadmium accumulation and cadmium content in various organs and the cadmium transport coefficients of root-stem, root-branch, root-brown rice, and rootleaf. In summary, the yield and dry matter accumulation in the ratooning season were the highest in the treatment with conventional nitrogen application rate + density increasing(N1D2), and the cadmium content, cadmium accumulation, and cadmium transport coefficient of various organs were lower under nitrogen reduction by 15%.