水稻机插中苗双膜育秧落谷密度对苗质和产量影响的研究

Effects of Sowing Density on Quality of Medium-seedling Nursed with Two-layer Plastic Film and Grain Yield in Mechanical Transplanting Rice

以半直立穗型、强秆高产粳稻品种武运粳 7号为材料 ,研究双膜育秧中不同落谷密度 (催芽种谷 170 7、2 2 9 4、2 85 4、342 7和 4 0 0 1粒 /dm2 )对机插秧苗素质及产量的影响。结果表明 ,秧龄在 3叶 1心初期移栽 ,田间发根力、单位苗高干重、地上部干重和苗基粗等苗质指标均随落谷密度增大而变劣。落谷密度最稀的处理 (170 7粒 /dm2 )苗质显著 (或明显 )优于其他处理 ,但机插缺穴率高和每穴苗数少 ,稻谷产量反而低于其他处理。落谷密度在 2 2 9 4～ 4 0 0 1粒 /dm2 之间 ,苗质虽随落谷密度增加而呈下降的趋势 ,但大田稻谷产量处理间差异不显著。从提高秧龄弹性的要求出发 ,双膜育秧中苗移栽的落谷密度在 2 2 9粒 /dm2 左右为宜。除 170 7粒 /dm2 外 ,其他处理秧苗地上部干重的峰值出现在播后 2 0d ,叶龄为 3 8～ 4 1时 ,其后秧苗干重下降或不增长 ,苗质变劣 ,苗质下降的速率随落谷密度的增大而加大 ,表明其超秧龄的临界期在叶龄 3 8～ 4 1。

Wuyunjing 7, a semi-erect panicle, high-yield and lodging-resistant japonica cultivar, was used to investigate the effects of five sowing densities (170.7, 229.4, 285.4, 342.7 and 400.1 germinated grains per dm 2) on quality of medium-seedling nursed with two-layer plastic film and grain yield in mechanical transplanting. The results showed that the main indices of seedling quality, root-developing ability in field, the ratio of dry weight to seedling height, above ground dry weight and the base stem thickness, became worse with the increase of the sowing density when the seedlings were transplanted at 3-leaf age. The indices for the least density (170.7 grains/dm 2) treatment were significantly or obviously superior to other treatments, but its grain yield was significantly lower than others due to higher empty hill percentage and less seedlings per hill in the field. Although there existed a decreasing trend in seedling quality with the increase of the sowing densities from 229.4 grains/dm 2 to 400.1 grains/dm 2, the differences among the treatments were not significant for grain yields. It suggested that the most suitable sowing density for nursing the strongest seedlings was not the density for mechanical transplanting. The reasonable sowing density for mechanical transplanting was around 229 grains/dm 2 due to extended suitable seedling age. The peak seedling dry weight appeared at 20th day after sowing when the leaf age of the seedling was 3.8-4.1 for all the density treatments except for 170.7 grains/dm 2 treatment. The seedling quality 20 days after sowing declined with increasing of sowing density, which indicated that the critical suitable transplanting time was at 20th day after sowing and a critical leaf age of seedlings was 3.8-4.1.