中文摘要：

为明确秸秆还田条件下稻茬小麦高产高效栽培的适宜播种密度和氮肥运筹方式，采用大田试验，以济麦22号为材料，研究了稻秸还田下不同播种密度（播量120kg·hm^-2、180kg·hm^-2）、施氮量（180、225和270kgN·hm^-2）及氮肥基追比（基肥；拔节肥：孕穗肥为6：3：1、5：3：2和4：3：3）对小麦产量和氮素利用效率的影响。结果表明，在施氮量180kg·hm^-2（低氮）和225kg·hm^-2（适氮）下，提高播种密度显著提高了小麦叶面积指数、开花期旗叶光合速率、花后干物质积累量和籽粒产量；而在施氮量270kg·hm^-2（高氮）下，提高播种密度显著降低了小麦生育后期叶面积指数、开花期旗叶光合速率、花后干物质积累量和籽粒产量。提高播种密度、降低施氮量均降低了土壤中无机氮的盈余量，氮肥吸收效率和氮肥农学效率显著提高。产量、氮肥吸收效率及氮肥农学效率均在氮肥基追比为基肥：拔节肥：孕穗肥=6：3：1时最大。因此，稻秸还田条件下提高小麦播种密度、适当降低施氮量并提高基肥比例，可以实现小麦产量和氮素利用效率的同步提高。

英文摘要：

To explore the effects of planting density and nitrogen（N） fertilizer management on grain yield and N use efficiency of wheat under rice straw returning, field experiment was conducted to study the effects of planting density（120 kg·hm^-2 and 180 kg ·hm^-2） ,N rate（180,225 and 300 kg·hm^-2） and the ratio of basal to top-dressing（basal fertilizer ＂ jointing fertilizer ＂ booting fertilizer=6 ： 3 ： 1,5 ： 3 ： 2 and 4 ： 3： 3,respectively） on grain yield and N utilization in wheat under rice straw returning,with Jimai 22 as material. Results showed that increasing planting density improved leaf area index, photosynthetic rate of flag leaf at anthesis stage and dry matter accumulation from anthesis to maturity stage under low N rate（180 kg·hm^-2） and appropriate N rate（225 kg·hm^-2） ,therefore grain yield was improved significantly. However,under excessive N rate（270 kg·hm^-2）,increasing planting density decreased leaf area index at the late growth stage, photosynthetic rate of the flag leaf at anthesis stage and dry matter accumulation post-anthesis significantly, which resulted in reduction of grain yield. In addition,increasing planting density with reduced N rate decreasedsoil inorganic N surplus amount, but improved N agronomy efficiency and N uptake efficiency significantly. The optimal ratio of basal to top-dressing was 6 ： 3 ： 1,which could simultaneously improve grain yield and N use efficiency. In conclusion,increasing planting density with reduced N rate properly and increased the ratio of basal fertilizer under rice straw returning could improve grain yield and N use efficiency.