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

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