Abstract: The effects of sowing date［April 15（D1），April 30（D2），May 15（D3），May 30（D4），June 14（D5）］and nitrogen application rate［0 kg/ha（N0），150 kg/ha（N150）and 300 kg/ha（N300）］on population quality，yield and nitrogen absorption and utilization of medium indica hybrid rice Yliangyou 900 were investigated，so as to explore the optimum sowing date and nitrogen application rate in southern Henan rice area. The results showed that the effects of sowing date and nitrogen application rate on yield were significant. The yield increased first and then decreased with the delay of sowing date.The yield of D2 was the highest，and that of D5 was the lowest.The yield of D2 was 126.42% higher than that of D5.The yield of D2 increased with the increase of nitrogen application rate.Overall，D2N300 treatment had the highest yield，followed by D1N300 and D2N150 treatments.The total leaf area index and high⁃efficiency leaf area index both increased first and then decreased with the delay of sowing date，while the total leaf area index and inefficient leaf area index both increased with the increase of nitrogen application rate.Overall，the total leaf area index was the highest under D3N300 treatment，followed by D4N300 and D2N300 treatments；the high⁃efficiency leaf area index was the highest under D3N300 treatment，followed by the D4N300 and D1N300 treatments；the D2N300 treatment had the highest inefficient leaf area index，followed by D4N300 and D3N300 treatments.The ratio of grain number to leaf area and the ratio of grain weight to leaf area both decreased with the delay of sowing date，and decreased with the increase of nitrogen application rate.Overall，the highest ratio of grain number to leaf area was observed under D1N0 treatment，followed by the D2N0 and D3N0 treatments；the highest ratio of grain weight to leaf area was observed under D1N0 treatment，followed by D3N0 and D2N0 treatments.The nitrogen content in stems and leaves of D1，D2 and D3 increased by 12.81%，14.77%，13.02% and 10.64%，25.08%，30.40% respectively compared with D5 at heading and mature stages.Moreover，the nitrogen content in stems and leaves of each sowing date increased with the increase of nitrogen application rate. The nitrogen contents in panicles of D1 and D2 were significantly higher than those of D3，D4 and D5 at heading and mature stages，and nitrogen contents in panicles of N150 and N300 treatments under each sowing date were generally higher than that of N0 treatment.The nitrogen grain production efficiency first increased and then decreased with the delay of sowing date. Both N150 and N300 treatments had the highest nitrogen grain production efficiency under D2 and the lowest nitrogen grain production efficiency under D5，and nitrogen grain production efficiency of N150 treatment was obviously higher than that of N300 treatment. In summary，the sowing date and nitrogen application rate affect yield by adjusting leaf area，ratio of grain to leaf，plant nitrogen content and nitrogen grain production efficiency；the suitable sowing date for high yield and efficiency of medium indica hybrid rice Yliangyou 900 in southern Henan is April 30th（D2），and the appropriate nitrogen application rate is 150—300 kg/ha.

Key words: Medium indica hybrid rice, Sowing date, Nitrogen application rate, Population quality, Yield, Nitrogen absorption and utilization

摘要： 以中籼杂交稻Y两优900为试验材料，研究播期［4月15日（D1）、4月30日（D2）、5月15日（D3）、5月30日（D4）、6月14日（D5）］和施氮量［0 kg/hm²（N0）、150 kg/hm²（N150）和300 kg/hm²（N300）］对中籼杂交稻群体质量、产量和氮素吸收利用的影响，以期探寻豫南稻区最适播期和施氮量。结果表明，播期和施氮量对中籼杂交稻产量的影响均达到显著水平，产量随播期推迟先升高后降低，以D2播期最高，D5播期最低，D2播期产量较D5播期提高126.42%。D2播期产量随着施氮量的增加而升高。整体来看，D2N300处理产量最高，其次是D1N300、D2N150处理。总叶面积指数和高效叶面积指数均随播期推迟先升高后降低，总叶面积指数和低效叶面积指数均随着施氮量的增加而增加。整体来看，总叶面积指数以D3N300处理最高，其次是D4N300、D2N300处理；高效叶面积指数以D3N300处理最高，其次是D4N300、D1N300处理；低效叶面积指数以D2N300处理最高，其次是D4N300、D3N300处理。粒数叶比和粒质量叶比均随着播期的推迟而降低，且随着施氮量的增加而降低。整体来看，粒数叶比以D1N0处理最高，其次是D2N0、D3N0处理；粒质量叶比以D1N0处理最高，其次是D3N0、D2N0处理。D1、D2、D3播期抽穗期和成熟期茎叶氮含量分别较D5 播期增加12.81%、14.77%、13.02% 和10.64%、25.08%、30.40%，且各个播期抽穗期和成熟期茎叶氮含量均随着施氮量增加而增加。抽穗期和成熟期穗氮含量表现为D1、D2播期显著高于D3、D4、D5播期，且各个播期N150、N300处理穗氮含量总体上均高于N0处理。氮素籽粒生产效率随着播期推迟先升高后下降，N150和N300处理均以D2播期最高，D5播期最低，且N150处理氮素籽粒生产效率明显高于N300处理。综上，播期和施氮量通过调节叶面积、粒叶比、植株氮含量和氮素籽粒生产效率影响产量，中籼杂交稻Y两优900在豫南地区丰产高效的适宜播种期是4月30日（D2），适宜施氮量为150~300 kg/hm²。

关键词: 中籼杂交稻, 播期, 施氮量, 群体质量, 产量, 氮素吸收利用