种植密度对冬小麦根系时空分布和氮素利用效率的影响

在大田条件下,以大穗型品种泰农18和中穗型品种山农15为材料,研究不同种植密度(泰农18:每公顷135、270、405万株；山农15:每公顷172.5、345、517.5万株)对冬小麦根系时空分布和氮素利用效率的影响.结果表明:在整个生育期,随种植密度的增加,泰农18的根长密度、根系总吸收面积和活跃吸收面积均显著增加；在生育后期,山农15的根长密度、根系总吸收面积和活跃吸收面积在种植密度为每公顷345万株时最大.泰农18的籽粒产量、氮肥吸收利用效率、氮肥偏生产力和氮素利用效率在种植密度为每公顷405万株时最高,山农15在种植密度为每公顷345万株时最高,但与种植密度为每公顷517.5万株的处理差异不显著.随种植密度的增加,冬小麦成熟期土壤硝态氮、铵态氮和无机态氮在不同土层的积累量均降低.泰农18和山农15种植密度分别为每公顷405万株和345万株时,是兼顾高产和高效利用氮素的适宜种植密度.

Effects of planting density on root spatiotemporal distribution and plant nitrogen use efficiency of winter wheat

Taking winter wheat cultivars Tainong 18(TN18) and Shannong 15(SN15) as test materials,a field experiment was conducted to study the effects of planting density(135×104,270×104,and 405×104 plants·hm-2 for TN18;172.5×104,345×104,and 517.5 ×104 plants·hm-2 for SN15) on the root spatiotemporal distribution and plant nitrogen use efficiency of the varieties.For TN18,its root length density,total root absorbing area,and active root absorbing area increased with increasing planting density,and peaked at planting density 405×104 plants·hm-2 during the whole growth period.For SN15,its root length density,total root absorbing area,and active root absorbing area achieved the highest values at planting density 345×104 plants·hm-2 at booting and late grain-filling stages.The grain yield,nitrogen uptake efficiency,nitrogen partial factor productivity,and nitrogen use efficiency of TN18 were the highest at planting density 405×104 plants·hm-2,and those of SN were the highest at planting density 345×104 plants·hm-2 but had less differences between the densities 345×104 and 517.5×104 plants·hm-2.The inorganic nitrogen accumulation in different soil layers decreased with increasing planting density at maturity stage.Taking grain yield and nitrogen use efficiency into consideration,the appropriate planting density of TN18 and SN15 would be 405×104 and 345×104 plants·hm-2,respectively.