减量施氮对带状套作大豆土壤通气环境及结瘤固氮的影响

为研究种植模式和施氮量对大豆土壤通气环境及结瘤固氮的影响,本研究采用二因素裂区试验设计,主区为种植模式:大豆单作(SS)、玉米/大豆带状套作(MS),副区为不同施氮量:不施氮(NN:0 kg hm^-2)、减量施氮(RN:45kghm^-2)和常量施氮(CN:60kghm^-2),监测了大豆生育期内土壤的O₂含量和土壤呼吸速率的动态变化规律,分析了各处理的土壤水稳性团聚体、容重和孔隙度差异,探讨了大豆生育期内结瘤量、固氮能力的变化特征。2年数据结果表明,与单作大豆相比,带状套作大豆可提高土壤O₂含量、>2 mm粒径团聚体的百分含量、显著增加土壤孔隙度、显著增强后期土壤呼吸的速率,显著降低<1mm粒径团聚体百分含量与土壤孔隙度;R5期根瘤干重差异不显著,但结瘤数量显著增加39.9%,固氮酶活性与固氮潜力也在此时显著高于单作大豆。各施氮量间,土壤O₂含量、0.25～1.00mm粒径的百分含量、带状套作大豆的土壤呼吸速率以RN处理最高,施氮能降低<0...

Effects of reduced nitrogen application on soil aeration and root nodule growth of relay strip intercropping soybean

To study the effects of planting system and nitrogen application rate on soybean soil aeration environment and nodulation and nitrogen fixation,we adopted a two-factor split area experiment design,with the main area of planting pattern[soybean monoculture(SS),maize/soybean relay strip intercropping(MS)],and the sub-regions of different nitrogen application rates[no nitrogen application(NN:0 kg hm^–2),reduced nitrogen application(RN:45 kg hm^–2),and constant nitrogen application(CN:60 kg hm^–2)].The dynamic changes of soil O₂ content and soil respiration rate during soybean growth period was monitored,the differences of soil water-stable aggregates,bulk density,and porosity of each treatment were analyzed,and the variation characteristics of nodulation amount and nitrogen fixation capacity during soybean growth period were discussed.Two years’data showed that,compared with monoculture soybean,relay strip intercropping soybeans increased soil O₂ content,the percentage of aggregates with a particle size>2 mm,significantly increased soil porosity and soil respiration rate during the late growth period in soybean;reduced the percentage of aggregates with a particle size of<1 mm and soil porosity.There was no significant difference in the dry weight of nodules at R5 stage,but the number of nodules was significantly increased by 39.9%.Nitrogenase activity and nitrogen fixation potential were also significantly higher than those of monocrops.Among the various nitrogen application rates,the soil O₂ content,the percentage content of 0.25-1.00 mm particle size,and the soil respiration rate of relay strip intercropping soybean were the highest in RN treatment.Nitrogen application decreased the percentage content of water-stable aggregates with particle size<0.25 mm and soil bulk density;nitrogen application significantly inhibited the nodulation amount,nitrogenase activity and nitrogen fixation potential of monoculture soybean in the early stage,but the inhibitory effect of nitrogen fertilizer was alleviated at R5 stage.Reduced nitrogen application increased nodulation at the late stage of relay strip intercropping soybean,and it could significantly enhance the nitrogenase activity and nitrogen fixation potential of soybeans during the growth period.Relay strip intercropping soybean combined with reduced nitrogen application promoted the formation of large aggregates,increased soil porosity,improved soybean soil aeration environment,maintained higher soil O₂ content,promoted soil respiration,and facilitated the nodulation and nitrogen fixation of soybean at later stages.