中文摘要：

通过2011,2012连续两年田间定位试验,研究了“小麦/玉米/大豆”套作体系在不同氮用量下（小麦,0,60,120,180,240 kg N/hm2,记为WN1、WN2、WN3、WN4、WN5;玉米,0,97.5,195,292.5,390 kg N/hm2,记为MN1、MN2、MN3、MN4、MN5;大豆SN1、SN2、SN3、SN4、SN5）的干物质积累和产量变化.结果表明,施氮显著提高了作物地上部干物质积累量和籽粒产量（P＜0.01）.小麦各时期的干物质积累量和籽粒产量都随氮用量增加而呈增大趋势,收获期干物质积累量以WN4处理最高,为20610 kg/hm2,产量以WN5处理最高,为8176 kg/hm2,但WN3、WN4、WN5间无显著差异.玉米拔节期、喇叭口期和吐丝期的干物质积累量随氮用量增加而先增大后减小,在MN3时达最大;玉米成熟期干物质积累量和产量随氮用量增加而增大,在MN5处理最高,分别为13143 kg/hm2和6976 kg/hm2,但MN4、MN5间差异不显著.大豆在盛花期、收获期的干物质积累和籽粒产量随氮用量增加而呈先减少再增大的变化趋势,收获期干物质积累和籽粒产量以SN4处理最高,分别为5457 kg/hm2和1977kg/hm2,但MN4、MN5间差异不显著.小麦/玉米/大豆周年体系的总籽粒产量和产值随氮用量增加而增大,在N5处理最高,分别为11959 kg/hm2和27288元/hm2,但总产值减去氮投入的产值效益在N4时最高,为25196元/hm2,N3、N4、N5间无显著差异.小麦、玉米、大豆的产值占体系周年总产值的比重分别为32％,55％,13％,因此,小麦/玉米/大豆周年体系中玉米为主要作物,其次是小麦,再次是大豆.适宜施氮量小麦为120 kg/hm2,玉米为195～292.5 kg/hm2,大豆可据苗情不施或适当追施氮肥,周年体系氮肥用量应为255～382.5 kg/hm2.

英文摘要：

The effects of nitrogen fertilizer （on wheat 0,60,120,180,240 kg N/hm2,marked as WN1,WN2,WN3,WN4,WN5; on maize 0,97.5,195,292.5,390 kg N/hm2,marked as MN1,MN2,MN3,MN4,MN5 ; on soybean as SN1,SN2,SN3,SN4,SN5） on dry matter accumulation （DMA） and grain yield （GY） of three crops in the wheat/maize/soybean relay-cropping system were studied by field experiment in 2011 and 2012.Ⅰ） DMA and GY of the three crops increased significantly with N application （P＜0.01）.Ⅱ） Wheat DMA and GY at the tillering stage （TS）,jointing stage （JS）,flowering stage （FS） and maturity stage （MS）increased with increasing rates of N.DMA at MS was the highest in treatment WN4 （20610 kg/hm2） and GY at MS was the highest in treatment WN5 （8176 kg/hm2） but there was no significant difference between WN3,WN4,and WN5 treatments; Ⅲ） Maize DMA at the jointing stage （JS）,flare opening stage （FS） and silking stage （SS） increased initially,then decreased with increasing rates of N,and was highest in MN3.Maize DMA and GY at MS increased with increasing rates of N and they were both highest in treatment MN5 with 13143 and 6976 kg/hm2,respectively,while there was no significant difference between WN4 and WN5.Ⅳ） Soybean DMA at FS and MS and GY initially decreased then increased with increasing rates of N,and its DMA and GY were the highest in SN4 （5457 and 1977 kg/hm2,respectively）,while there was no significant difference between WN4 and WN5.Ⅴ） Total GY and economic output （TEO） of the wheat/maize/soybean annual relaycropping system rose with increasing rates of N and were the highest in the N5 treatment with 11959 kg/hm2 and 27288 yuan/hm2,respectively.The economic benefit of TEO and N input was highest in N4 treatment with 25196 yuan/hm2 and there was no significant difference between N3,N4,and N5 treatments.The ratio of wheat,maize and soybean economic output to TEO of the system was 32％,55％,13％,respectively.So in the wheat/maize/soybean annual relay-cropping system m