中文摘要：

通过2013-2014年度田间试验,在种植小麦时设置不施氮、低氮、中氮、高氮4个氮肥施用量（0,60,120,180kg/hm2）,同时设置净作大豆（小麦-大豆）和套作大豆（小麦/玉米/大豆）两种种植模式,探究了前作小麦施氮后效及净作、套作两种种植方式对大豆产量和农艺性状的影响。结果表明,1）无论净作或套作,大豆均能利用前作小麦的施氮后效,生物量和籽粒产量均随施氮量增加呈先升高再降低的变化趋势,均在N120处理（纯氮120kg/hm2）时达到最大值,其中套作大豆籽粒产量最高为4133kg/hm2,达高产水平。2）分枝期时大豆地上部生物量为净作显著高于套作,平均高62.3%,而收获期时为套作显著高于净作,平均高57.9%。与净作相比,套作大豆单株粒数、籽粒产量分别高63.9%和55.9%,百粒重二者间相差不大。净作大豆的籽粒重在主茎、分枝上分别占54.2%和45.8%,以在主茎上较多,而套作大豆的籽粒主要分布在分枝上,平均达68.9%。虽然套作大豆的倒伏率比净作大豆高5.2%,但空杆率、瘪荚率却分别低78.0%和25.4%。前作施氮量增加,套作大豆籽粒在分枝上的比例增大。3）大豆主茎长,在分枝期时为套作（平均39.5cm）比净作（平均33.3cm）显著高6.2cm,而收获期时为净作（平均84.8cm）比套作（平均74.4cm）高10.4cm;第一节间长,在分枝期、收获期均为套作（8.3和6.6cm）大于净作（5.6和4.6cm）;分枝数,在分枝期时为净作（平均1.9个）显著高于套作（平均0.7个）1.2个分枝,而收获期时是套作（平均6.1个）高于净作（平均3.5个）2.6个分枝。同时套作大豆分枝数随前作施氮量增加而增加。说明在小麦-大豆和小麦/玉米/大豆体系中大豆能充分利用前作小麦的施氮后效;套作大豆前期虽受玉米的抑制影响,但玉米收获后能加快生长,可以通过合理的前作氮肥调控促进分枝、结荚和鼓粒,提高产量。

英文摘要：

A field experiment was conducted to study the after-effects of nitrogen applied at different rates（0,60,120,180kg/ha）to wheat on the yields and agronomic traits of a subsequent soybean monoculture（wheatsoybean cropping system）and soybean intercrop（wheat/maize/soybean intercropping system）in the 2013-2014 growing season.The results showed that soybean in both monoculture and intercropping systems made full use of the after-effect of nitrogen applied to wheat.The biomass and grain yield of soybean first increased and then decreased as the rate of nitrogen application to wheat increased.The highest biomass and grain yield of monocropped soybean and the highest yield of intercropped soybean（4133kg/ha）were in the N120 treatment.The biomass of monocropped soybean was 62.3% higher than that of intercropped soybean at the branching stage,but the biomass of intercropped soybean was 57.9% higher than that of monocropped soybean at the harvest stage.Compared with monocropped soybean,intercropped soybean showed 63.9% higher grain number per plant and 55.9% higher yield.The 100-grain weight did not differ significantly between intercropped and monocropped soybean.The grain yield from the main stem and branches accounted for 54.2%and45.8%,respectively,of the total yield of monocropped soybean.However,grain yield from the branches accounted for 68.9%of the total grain yield of intercropped soybean.Although the lodging rate was 5.2% higher for intercropped soybean than for monocropped soybean,the empty sticks rate was 78.0%lower and the blighted pod rate was 25.4%lower for intercropped than for monocropped soybean.The percentage of branch grain yield increased with increasing nitrogen application to wheat.The main stem length of intercropped soybean（average,39.5cm）was 6.2cm longer than that of monocropped soybean（average,33.3cm）at the branching stage while that of monocropped soybean（average,84.8cm）was 10.4cm longer than that of intercropped soybean（average,74.4cm）at the harvest stage.The length o