机械收获模式下直播冬油菜密度与行距的优化

Optimization of Plant Density and Row Spacing for Mechanical Harvest in Winter Rapeseed(Brassica napus L.)

以华油杂62为材料,采用裂区设计,设置密度15万株hm^(–2)(D1)、30万株hm^(–2)(D2)、45万株hm^(–2)(D3)为主区;行距15 cm(R15)、25 cm(R25)、35 cm(R35)为裂区,研究密度及行距变化对油菜群体人工收获产量、叶面积指数(LAI)、角果皮面积指数(PAI)、透光率、抗倒伏、抗裂角性能及机械收获产量的影响,探讨透光率与产量、抗倒性的关系,建立机械化生产模式下油菜密度及行距最优配置。结果表明,密度增加或行距减小,油菜成株率适宜,LAI、PAI值增加,冠层透光率下降,群体生物量及经济系数增加,人工收获产量增加;但单位LAI(PAI)光拦截量、单株生物量及根干重下降,且较低的单位LAI(PAI)光拦截量有利于提高油菜经济系数;密度及行距处理间差异及互作效应显著,与农户习惯种植模式(D2R25)相比,在D3R15处理下可增产14.1%,获得最高人工收获产量。密度或行距增加,地上部鲜重、株高降低及根冠比增加,导致油菜茎秆、根倒角度下降,抗裂角指数增加,机械收获产量变化趋势与人工收获产量一致,与机械收获总损失率相反,表明除通过提高油菜抗倒性和抗裂角性降低机收损失外,较高的人工收获产量是获得较高机械收获产量的前提。由回归方程可知,与常规30万株hm^(–2)密度、25 cm行距配置比,密度43.8万株hm^(–2)和行距21 cm配置可使蕾薹期LAI提高21.02%、透光率及单位LAI光拦截量分别下降32.47%与17.36%,角果期PAI增加15.08%、透光率及单位PAI光拦截量分别下降32.04%与3.30%,获得较高的机械收获产量,进一步提高油菜机械化生产效益。

The field experiment was conducted with the cultivar Huayouza 62, which was seeded at 15（R15）, 25（R15）, and 30（R15） cm in row spacing and 15（D1）, 30（D2）, and 45（D3） ×10~4 plants hm^（–2） in density. The theoretical yield, leaf area index（LAI）, pod area index（PAI）, mechanical-harvested yield and yield loss were measured and calculated. Results showed that plant density and row spacing significantly affected the seed yield of rapeseed. The yield was increased as the plant density increased or row spacing reduced. Compared with the planting patterns used by farmers（D2R25）, D3R15 could achieve 14.1% increase in yield, which was the highest yield among all the treatments because of appropriate mortality, the highest LAI, PAI and the light interception（LI）. Population biomass had the similar trend with yield while harvest index（HI） significantly increased with increasing plant density and row spacing. HI was significantly and negatively correlated with LI/ LAI（PAI）, indicating that lower LI/ LAI（PAI） was favorable for increasing HI. Plant height and aboveground biomass reduced and root/shoot ratio increased with increasing plant density and row spacing, which led to decrease root and stem lodging. Improvement in resistance to pod shattering was also observed as plant density and row spacing increased. These changes all contributed to mechanical harvesting operations, resulting in reducing yield loss. As the regression equations showed, compared with D2R25, 43.8×10~4 plants ha^（–1） in combination with 21 cm row spacing was optimum for rapeseed to maximize seed yield and minimize lodging and pod shattering so as to facilitate mechanical harvest. The combination could make the LAI increase by 21.02%, light transmittance（LT） and LI/LAI decrease by 32.47% and 17.36%; PAI increase by 15.08%, LT and LI/PAI decrease by 32.04% and 3.30%.