陇中旱区农田土壤微量元素特征及其对绿肥休耕的响应

Characteristics of Soil Trace Elements in the Dryland Farming Area of Central Gansu and Their Responses to Green Manure Fallow

研究土壤微量元素对绿肥休耕的响应,为大面积区域农田土壤养分管理和农业生产提供参考。基于陇中旱区3年多点位监测数据,选择土壤有效铁、有效锰、有效铜、有效锌、有效钼和有效硼等6项指标,对比分析休耕种植绿肥前后土壤微量元素差异。结果表明:(1)与基础土壤相比,休耕3年后土壤有效锰、有效铜和有效锌含量分别显著增加18.8%,22.5%,14.3%(p<0.05);有效铁和有效硼含量均显著降低(p<0.05),有效钼无显著变化。(2)回归分析表明,有效铁、有效锰和有效铜的变化幅度与休耕前微量元素基础含量均呈负线性关系,而有效锌和有效钼均呈负对数关系(p<0.05),且对有效锰、有效铜、有效锌和有效钼的基础含量分别小于8.0,0.9,0.3,0.06 mg/kg的农田土壤有显著提高效果;有效铁、有效锰和有效铜变化幅度与休耕前土壤有机质和全氮基础养分含量之间均呈显著负线性关系(p<0.05);有效铁、有效锰、有效铜和有效锌变化幅度与休耕前土壤pH之间均呈显著正线性关系(p<0.05)。(3)进一步对休耕后土壤微量元素和常量元素相关分析表明,休耕后有效铁、有效锰和有效锌均与土壤有机质、全氮、速效磷和速效钾存在显著正相关关系;除有效钼,其他5种微量元素与土壤pH之间均呈显著负相关。综上所述,休耕种植绿肥可不同程度地提高陇中旱农区土壤有效锰、有效铜和有效锌含量,尤其可显著改善土壤缺锰状况,且该模式对土壤养分基础含量较低和偏碱性土壤提高微量元素含量效果更显著。

The responses of soil trace elements to green manure fallow were investigated to provide reference for soil nutrient management and agricultural production in the large region of farmland.Based on the three-year multi-point monitoring data in the dryland farming area of central Gansu,six indexes of soil trace elements,including available Fe,available Mn,available Cu,available Zn,available Mo,and available B,were selected to compare and analyze the differences of soil trace elements before and after fallow planting of green manure.The results showed that:(1)Compared with the basic soil,after three years of fallow,the contents of available Mn,available Cu,and available Zn in soil were significantly increased by 18.8%,22.5%,14.3%,respectively(p<0.05).The contents of available Fe and available B showed significant decreasing trends(p<0.05),while available Mo did not change significantly.(2)Regression analysis showed that the magnitude of variation of available Fe,available Mn and available Cu were all negatively linearly related to the basal content of trace elements before fallow,while effective Zn and effective Mo were all negatively logarithmic(p<0.05),and had a significant enhancement effect on agricultural soils with basal content of available Mn,available Cu,available Zn,and available Mo of less than 8.0,0.9,0.3,0.06 mg/kg,respectively.There were significant negative linear correlations(p<0.05)between the magnitude of changes in available Fe,Mn,Cu and the pre-fallow basic nutrient contents of soil organic matter and total nitrogen.(3)Further correlation analysis of trace elements and macronutrients in the soil after fallowing showed that available Fe,Mn,and Zn were significantly positively correlated with soil organic matter,total nitrogen,available phosphorus and available potassium.Except for available Mo,the other five trace elements were significantly negatively correlated with soil pH.In conclusion,the implementation of fallow mode of green manure planting can improve the contents of available Mn,Cu,and Zn in the dryland farming area of central Gansu to some extent,particularly good for soils of Mn-deficient,and it is more effective for soils with low basic soil nutrient content and alkaline soils.