菌根与间作对紫色土-水界面氮流失的削减效应

揭示土著丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)与间作对紫色土-水界面各形态氮流失的削减效应,可为保护水环境、减缓紫色土坡耕地氮流失带来的农业面源污染提供理论依据。通过自然降雨条件下的径流模拟试验,设置不同种植模式(单作玉米、玉米/大豆间作、单作大豆)和不同菌根处理(抑菌、未抑菌),在雨季不同时间采集7次径流和侧渗水样,分析比较各不同处理下径流及侧渗各氮形态变化迁移特征。研究结果表明,侧渗即壤中流为紫色土-水界面氮素流失的主要途径,硝态氮为紫色土-水界面氮素流失的主要形态。随取样时间后延,径流总氮、硝态氮浓度均呈现出波浪式上升的趋势,而铵态氮浓度整体表现出先上升再下降的趋势;侧渗总氮浓度趋势则呈现先下降后上升再下降的趋势,硝态氮浓度整体表现出下降后趋于平缓的趋势,铵态氮浓度则表现出先上升后下降并趋于平缓的趋势。所有复合处理中,未抑菌—间作处理的径流、侧渗及总流失量中总氮、铵态氮浓度均最低,且其径流、总流失量中硝态氮浓度也明显低于其他处理。在未抑菌处理下,与单作玉米、单作大豆处理相比,间作处理使径流和侧渗总氮浓度分别下降约13.4%、20.3%和56.5%、48.7%,总流失量中总氮浓度分别下降约50.1%和43.5%;使径流和总流失量中的硝态氮浓度分别降低约10.0%、16.7%和51.3%、42.9%;并使径流和总流失量中铵态氮浓度分别显著降低约10.5%、26.0%和21.7%、30.2%,侧渗铵态氮浓度也相应降低约29.6%和33.7%。可见土著菌根真菌与玉米/大豆间作体系对协同削减紫色土-水界面氮素的流失表现出了较大的潜力。

Effects of Native AMF and Intercropping Reducing Nitrogen Loss from Soil-Water Interface in Purple Soil

[Objective] In order to explore the reduction effects of native arbuscular mycorrhizal fungi (AMF) and intercropping reducing on the N loss from of nitrogen forms in purple soil-water interface in purple soil, a field experiment of runoff simulation under natural rainfalls was carried out in a field of purple soil, in an attempt so that to provide a theoretical basis for protecting the water environment and mitigating slowing the agricultural non-point source pollution caused by the nitrogen loss of from purple soil slope farmlands.[Method] The experiment was designed to have different planting patterns or mode[monocropping of maize (MM), maize/soybean intercropping (MSI), and monocropping of soybean (MS)] and different mycorrhizal treatments[inhibited (MI) and non-inhibited (NM)] . Samples of runoff and lateral infiltration were collected seven times during the rainy season for analysis of forms of Nitrogen (N) and their concentrations therein, and further for comparison between the treatments in effect on changes in form and translocation of Nitrogen.[Result] Results show that lateral infiltration or subsoil flow was the main path of N loss from soil-water interface in the purple soil, and nitrate N was the main form of N lost with the subsoil flow With sampling going on, the concentrations of total N and nitrate N in runoff fluctuated along a rising trend, while the concentration of ammonium N rose firstly and then declined. The concentration of total N concentration in lateral infiltration exhibited a trend of descending firstly, and then ascending and descending again, while the concentration of nitrate N did a gentle descending trend, but the concentration of ammonium N did a gentle trend of increasing first and then decreasing. Among all the composite treatments, Treatment NM+MSI was the lowest in concentration of total N and ammonium N in runoff and lateral infiltration and hence in total N loss, and significantly lower than all the other treatments. Treatment NM+MSI was 13.4% and 20.3%, respectively, lower than Treatment NM and Treatment MI in concentration of total N in runoff, 56.5% and 48.7%, respectively, lower in concentration of total N in lateral infiltration, 50.1% and 43.5%, respectively, lower in total N loss, 10.0% and 16.7%, respectively, lower in concentration of nitrate N in runoff, 51.3% and 42.9%, respectively, lower in concentration of nitrate N in total N loss with runoff, 10.5% and 26.0%, respectively, lower in concentration of ammonium N in runoff, 21.7% and 30.2%, respectively, lower in concentration of ammonium N in lateral infiltration, and 29.6% and 33.7%, respectively, lower in concentration of ammonium N in total N loss with lateral infiltration.[Conclusion] All the findings indicate that native AMF and maize/soybean intercropping has a certain potential to reduce nitrogen loss from the purple soil via soil-water interface.