苜蓿后茬冬小麦对氮素的响应及土壤氮素动态研究

Study on the response of Triticum aestivum to nitrogen application after a four year Medicago sativa phase and soil nitrogen dynamics

2001至2004年,在甘肃庆阳黄土高原定位研究了施氮和不施氮对比条件下,4龄苜蓿后茬冬小麦对氮素的响应.结果表明,4龄苜蓿后茬冬小麦产量对氮连续3年有响应,至第3茬,施氮显著增加籽粒产量(P<0.05),促进了第1茬冬小麦对氮的吸收,与产量的变化趋势一致;第2茬冬小麦对氮肥的利用率最高,达47%,不施氮下土壤氮素处于亏缺状态,第1年的亏缺量最大、第2年最小;施氮明显增加第2茬冬小麦0～60 cm 土层中硝态氮的含量,且硝态氮的累积峰从2003年的0～60 cm土层,转移到2004年的60～200 cm, 表明氮有一定程度的向下淋溶.在黄土高原,4龄苜蓿后茬种植头茬作物可不施氮肥.

A field trial was carried out to assess the response of three successive Triticum aestivum crops to nitrogen application that were grown after four years of Medicago sativa at the Qingyang Loess Plateau, Gansu province, from 2001 to 2004. Nitrogen application was shown to increase the T. aestivum yield for three harvests, with a significant N effect on grain yield for the third T. aestivum crop （P〈0.05）. Nitrogen use efficiency was highest for the second T. aestivum crop at 47.22 %. Soil nitrate-N deficiency was found to occur when N was not applied. Nitrogen application accelerated the N uptake by the crop. After N application, soil nitrate-N accumulated in the 0--60 cm soil layer for the second crop, and in the 60--200 cm layer for the third crop. This suggests there was nitrate-N leaching through the soil profile during the wet year. Based on the results it is recommended that N fertilizer should have been applied for the second T. aestivum crop following the M. sativa phase.