不同年限有机栽培对土壤生物固氮活性的影响

氮是对作物生长和产量维持最重要的元素。有机农业无化学肥料投入，生物固氮是氮素最重要的来源之一。然而到目前为止，有机栽培对农田土壤微生物固氮活性的影响尚不清楚。本文以20年常规栽培花椰菜农田土壤为对照，比较经10年、14年、20年有机栽培后土壤微生物固氮活性的变化，并通过多元统计分析探究了影响土壤生物固氮活性的因素。研究结果表明，在7天的测定周期中，与常规栽培相比，10年和14年有机栽培降低了前期土壤生物固氮速率，但整个周期累积固氮在量各处理间无显著差异。不同年限有机栽培对土壤生物固氮速率和累积固氮量影响显著，整体而言14年有机栽培的最低，10年和20年有机栽培间的差异因培养时间而异。培养结束时，常规栽培土壤固氮速率接近于0，有机栽培的花椰菜土壤则仍保持较高活性。皮尔森相关分析和冗余分析（RDA）表明，NH₄+、NO₃?及Olsen P含量是影响有机栽培土壤生物固氮活性的关键因素；其中，NO₃?对固氮有抑制作用，Olsen P则促进了土壤生物固氮活性的增加。

Soil Biological Nitrogen Fixation under Organic Management in Different Years

Nitrogen (N) is the most important element for the growth and yield of crops. Biological N fixation plays an essential role in N supply in organic agriculture without chemical fertilizer input. However, the effect of organic management years on biological N fixation activity is still unclear. This study compared the dynamics of N fixation rate and cumulative N fixation in soils under the organic management of cauliflower for 10 years, 14 years, 20 years and its conventional management for 20 years. And the factors influencing N fixation were explored using multivariate statistical analysis. The results showed that during the 7-day incubation, 10-year and 14-year organic managements reduced the N fixation rate compared with conventional management. However, the accumulative N fixation over the incubation showed no significant difference among all treatments. The N fixation rate and cumulative N fixation amount were significantly affected by organic management years and were the lowest in 14-year organic management. At the end of incubation, the soil N fixation rate under conventional management was near zero, whereas N fixation activity remained high under organic managements. Pearson correlation and redundancy analysis showed that the N fixation activity was primarily affected by the contents of NH₄+, NO₃? and Olsen P. NO₃? suppressed the N fixation, while Olsen P increased the N fixation activity.