减氮对甜玉米//大豆间作系统大豆结瘤固氮特性的影响

Effect of reduced nitrogen application on nodulation characteristics of soybean in sweet maize//soybean intercropping system

为了探讨减氮和甜玉米//大豆间作对大豆结瘤和固氮特性的影响,通过大田定位试验(2015年春-2018年秋,共8季)对比了三种施氮水平:不施氮(N0,0 kg·hm^(-2))、减量施氮(N1,300 kg·hm^(-2))、常规施氮(N2,360 kg·hm^(-2)),两种间作模式:甜玉米//大豆2∶3间作(S2B3)、甜玉米//大豆2∶4间作(S2B4),以及不施肥单作大豆(SB)对大豆结瘤数、根瘤干重、固氮效率和固氮量及其稳定性的影响。结果表明:1)大豆根瘤数、根瘤干重、固氮效率和固氮量随着年季变化呈现明显的动态变化,春季大豆根瘤数和根瘤干重显著高于秋季,但秋季固氮效率和固氮量显著高于春季。2)施氮水平与种植模式极显著影响大豆固氮效率和固氮量,不施肥处理大豆固氮效率为S2B4(69.87%)>S2B3(60.64%)、SB(56.3%),但生物固氮量为SB(142.31 kg·hm^(-2))>S2B4(109.50 kg·hm^(-2))>S2B3(86.12 kg·hm^(-2))。3)间作甜玉米显著提高了大豆的固氮效率且随大豆种植比例的增加而增加,S2B4-N0、N1及N2的固氮效率分别比S2B3-N0、N1及N2高9.47%、3.41%、1.83%,但是,相同施氮水平下不同间作模式之间均无差异。4)减氮和间作甜玉米可显著提高大豆固氮率和固氮量的稳定性。总之,减氮和间作甜玉米均能促进大豆结瘤、提高生物固氮量及固氮效率。

In order to explore the effects of reduced nitrogen application and intercropping on soybean biological nitrogen fixation characteristics,a field experiment was conducted at Experimental Center of South China Agriculture University for four years(8 seasons,from spring 2015 to autumn 2018)to investigate the dynamic changes of soybean nodule number,nodule dry weight,nitrogen fixation amount and nitrogen fixation efficiency in maize//soybean intercropping system under three nitrogen levels[nitrogen dose of 0 kg·hm^(-2)(N0),reduced nitrogen dose of 300 kg·hm^(-2)(N1)and conventional nitrogen dose of 360 kg·hm^(-2)(N2)]and two intercropping patterns[sweet maize/soybean intercropping with sweet maize to soybean line ratios of 2:3(S2B3),2:4(S2B4)]and soybean monocropping with no fertilizers(SB).Results showed that:1)the soybean nodule number,nodule dry weight,nitrogen fixation amount and nitrogen fixation efficiency in maize/soybean intercropping system under different treatment showed obvious seasonal dynamic changes and were significantly affected by different seasons and planting patterns.Soybean nodule number and nodule dry weight were generally higher in spring than in autumn,and nitrogen fixation efficiency and amount of nitrogen fixation were higher in autumn than in spring.2)The nitrogen fixation efficiency and nitrogen fixation amount of soybeans were also significantly affected both by the chemical nitrogen application level and planting mode.The nitrogen fixation efficiency of N0 treatments was S2B4(69.87%)>S2B3(60.64%)and SB(56.3%),but for the nitrogen fixation amount was SB(142.31kg·hm^(-2))>S2B4(109.50kg·hm^(-2))>S2B3(86.12 kg·hm^(-2)).3)Intercropping sweet maize significantly improved the nitrogen fixation efficiency of soybeans.The nitrogen fixation efficiency of S2B4-N0,N1and N2 was 9.47%,3.41%and 1.83%high than that of S2B3-N0,N1and N2 separately.4)Nitrogen reduction and intercropping sweet maize could significantly increase the rate of nitrogen fixation and the stability of nitrogen fixation in soybeans.In short,nitrogen reduction and intercropping can promote the nodulation and nitrogen fixation ability of soybeans.