水稻秧苗密度对苗质的影响

在合肥先后共用六个组合(品种)进行了三年播种量试验。结果表明,秧苗密度时苗质在三叶期前无显著影响,三叶期后影响日益加大。秧苗单株叶面积、干物重、分蘖数等均与密度呈显著负相关,回归线近似y=1/(a+bx)曲线。3—5、5—7和7—9叶期单株叶面积和地上干重的增长量,较300苗/米~2下降50%以上的临界密度,依次为2000、1200和600苗/米~2左右。单株干重增长速度降低10%,分蘖速度下降12.5—29.5%。5,7,9叶期可发分蘖成蘖率<20%的临界密度依次为2500,1500和600苗/米~2左右。苗质对大田产量的影响随着秧龄延长而加大。在秧大田比保持一定的情况下,苗质对大田产量的影响一般小于秧苗密度对苗质的影响。

THE EFFECTS OF THICKNESS ON QUALITY OF RICE SEEDLINGS

In the year of 1981, 1984, 1985, the seeding rate was successively experimented with 6 varietres in Hefei Ditrict The seeding emergence amounts in the experiments were about 300, 600, 900, 1200, 2500, 5000 and 8000 stem/m~2Before the 3rd leaf-stage no significant impact on seedling quality was observed, but after the stage the impact became gcaduaeeg appacentLeaf-area of individual plant, weight of dry matter and tillering number, etc, are negatively corre-lated with seedeing thinkness Their regression equations are similar to the curve of y=1/a+bx If we, for example, regard increment between leaf-ared of one stem as 300 stem/m~2 and dry matter on the ground as 100, the critial thickneas under the increment of 50 corre-sponding with 3-5, 5-7and 7-9 leaf-stage bacame about 200, 1200 and 600 stems in proper order with the reduction of the growth speed by 10% in dry matter of a trunk, the tillering speed decreased by 12.5%, 14.1% and 29.5% respectivelyThe critical thickness of less than 20% in grown tillering ratio during leaf-stage 5, 7 and 9 were respectively 2500, 1500 and 600 stem/m~2 However, under the condition of approximate proportion between the seedling bed and the fields which retained, per mu yield was less affe-cted than seedling quality by seebling thickness and its affected range was increased as the seedling-ageextended.