密度和氮肥用量对油菜产量及氮肥利用率的影响?

 为机械化种植油菜，研究不同施氮水平下密度对直播油菜生长发育和氮肥利用效率的影响。以甘蓝型油菜品种中双11号为材料，在低密（15万株/hm2）和高密（45万株/hm2）两种密度下，设施氮0、90、180和270kg/hm2处理，分析施氮量与密度对油菜农学性状、产量、氮肥利用效率的影响，并对比分析了密度与油菜需氮量之间的关系。结果表明，增密后油菜的株高、分枝数、单株角果数和每角粒数显著降低，分枝高度和千粒重显著增加。高密油菜群体株型结构整齐均一，更能满足机械化收获需要。高密处理油菜籽粒产量高于低密处理。施氮0～180kg/hm2时，两个密度下的籽粒产量均随施氮量增加而显著提高，但在270kg/hm2时两密度下油菜产量均有所下降。油菜氮肥表观利用率随着施氮量的增加而下降，但是又随种植密度的增加而增加。说明增加密度能促进氮素向油菜籽粒转移，降低每生产100kg籽粒油菜需氮量，提高氮肥表观利用率。在相同的目标产量（低密下的经济产量、湖北省油菜平均单产和全国油菜平均单产）下，油菜增密后可以节约氮肥用量22.9%~30.6%，增密减氮效果明显。 

Effects of planting density and nitrogen application rate on rapeseed yield and nitrogen use efficiency

For rapeseed mechanization production, effects of rape density and nitrogen (N) application rate on growth and N use efficiency were investigated under field condition. Two planting density (15?104 and 45?104 plant per hectare) and four N rates (0, 90, 180 and 270kg per hectare) were applied to study the interaction between N and density on agronomic characteristics, yield, N use efficiency and N fertilizer requirements for Zhongshuang 11. Results showed that plant height, branch number, effective siliques per plant and seeds per pod significantly decreased at higher density, but branch height and 1 000-seeds weight increased significantly. Under higher density, the plant-type was uniform and ideal for mechanized harvesting. Yield of high density rape was higher. Both yields on high and low density increased at 0 to 180kg/hm2 N rates. But when N rates were up to 270kg/hm2, both yields decreased. N use efficiency decreased at higher N rates and lower density. It indicated that higher density could promote seed N accumulation, decrease N fertilizer requirement and improve the N use efficiency. For the same targets yield (compared to the top economic yield at low density, the average yield of Hubei Province and that of China), the N fertilizer requirement significantly decreased by 22.9% to 30.6% after increasing planting density.
Key words: Rapeseed (Brassica napus L.); Planting density; Nitrogen fertilizer; Yield; Nitrogen use efficiency