[目的]以红壤区典型县域祁阳为例,分析不同母质发育的水田改为旱地和菜地后土壤酸度和养分含量变化特征,为该区合理利用土地防治酸化提供科学依据.[方法]选取 18 个点位,采集水田及相邻的旱地和菜地,分析土壤pH、交换性酸、交换性盐基离子、有机质、阳离子交换量和养分含量的变化及其相互关系.[结果]碱性母质发育的土壤 pH 均显著高于酸性母质发育的土壤.酸性母质发育的水田改为菜地后土壤 pH 降低了 0.48 个单位;碱性母质发育的水田改为旱地和菜地后土壤pH分别降低了 0.74 和 0.53 个单位.双直线模型拟合分析表明,当水田、旱地和菜地的土壤pH分别低于 5.88、5.78 和 5.63 时,土壤交换性铝含量快速升高,且降低一个 pH 单位土壤交换性铝含量分别增加 1.09、2.33和 2.93 cmol(+)·kg-1.酸性母质发育的水田改为旱地土壤有机质和全氮含量分别降低了 11.06 和 0.42 g·kg-1,而菜地无显著变化;碱性母质发育的水田改为旱地和菜地后土壤有机质和全氮含量均显著下降,降幅分别为 13.88-17.28 和 0.57-0.71 g·kg-1.碱性母质发育的水田改为旱地和菜地后土壤有效氮含量分别降低了 47.66 和 42.34 mg·kg-1.两种母质发育的水田改为菜地后土壤全磷、有效磷含量均显著增加,增幅分别为 0.41-0.48 g·kg-1 和 26.79-28.69 mg·kg-1.两种母质发育的水田改为旱地和菜地土壤全钾含量无显著变化;碱性母质发育的水田改为旱地和菜地后土壤有效钾含量显著升高,分别升高了 36.69 和 65.76 mg·kg-1.相关分析表明,土壤pH与土壤交换性钙和镁、阳离子交换量、有机质含量和全氮含量呈显著正相关(P＜0.01);土壤交换性酸和铝与有效磷含量显著正相关(P＜0.05),与土壤交换性钙和镁、阳离子交换量、有机质含量和全氮含量呈显著负相关(P＜0.01).[结论]酸性母质和碱性母质发育的水田改为旱地后土壤有机质、全氮含量均显著降低,而土壤全磷、有效磷含量呈增加趋势;酸性母质发育的水田只有改为菜地后土壤才酸化,而碱性母质发育的水田改为旱地和菜地后土壤均酸化;水田改为旱地和菜地后土壤硝化作用增强和盐基离子淋失增加可能是其酸化的主要原因之一.
[Objective]The aim of this study was to analyze the characteristics of changes in soil acidity and nutrient content after the conversion of paddy fields with different parent material development into dryland and vegetable fields in Qiyang,a typical county in the red soil area,so as to provide a scientific basis for the rational use of land to prevent acidification in the area.[Method]18 sites were selected and collected from paddy fields and adjacent dryland and vegetable fields to analyze the changes of soil pH,exchangeable acid,exchangeable salt-based ions,organic matter,cation exchange,and nutrient content and their interrelationships.[Result]The pH of all the soils developed with alkaline parent material was significantly higher than that of the soils developed with acidic parent material.Soil pH decreased by 0.48 units after the conversion of acidic parent material developed paddy fields to vegetable fields;soil pH decreased by 0.74 and 0.53 units after the conversion of alkaline parent material developed paddy fields to drylands and vegetable fields,respectively.The bilinear model fit analysis showed that the soil exchangeable aluminum content increased rapidly when the soil pH was below 5.88,5.78 and 5.63 in the paddy field,dryland and vegetable field,respectively,and the increment of soil exchangeable aluminum content increased by 1.09,2.33 and 2.93 cmol(+)·kg-1 by one pH unit,respectively.Soil organic matter and total nitrogen content decreased by 11.06 and 0.42 g·kg-1,respectively,in the acidic matrices developed paddy fields converted to drylands,while no significant changes were observed in vegetable fields;soil organic matter and total nitrogen content decreased significantly in the alkaline matrices developed paddy fields converted to drylands and vegetable fields,by 13.88-17.28 and 0.57-0.71 g·kg-1,respectively.The total and effective phosphorus content of the soil increased significantly from 0.41-0.48 g·kg-1 and 26.79-28.69 mg·kg-1 after the conversion of the paddy field with alkaline parent material to dryland and vegetable field,respectively.Correlation analysis showed that soil pH was significantly and positively correlated with soil exchangeable calcium and magnesium,cation exchange,organic matter content and total nitrogen content(P＜0.01);soil exchangeable acid and aluminum were significantly correlated with effective phosphorus content(P＜0.05)and negative correlation(P＜0.01)with soil exchangeable calcium and magnesium,cation exchange,organic matter and total nitrogen.[Conclusion]Soil organic matter and total nitrogen content decreased significantly after the conversion of acidic and alkaline parent material developed paddy fields to drylands,while soil total phosphorus and effective phosphorus content tended to increase.Soil acidification was observed after the conversion of paddy fields to vegetable fields for acidic parent materials or to drylands and vegetable fields for alkaline parent materials;the increased nitrification and increased leaching of salt-based ions from paddy fields to drylands and vegetable fields might be one of the main reasons for soil acidification.
邱海华;蒯磊鑫;张璐;刘立生;文石林;蔡泽江
中国农业科学院农业资源与农业区划研究所/北方干旱半干旱耕地高效利用全国重点实验室,北京 100081||中国农业科学院衡阳红壤实验站/湖南祁阳农田生态系统国家野外科学观测研究站,湖南祁阳 426182
母质;红壤;水田改旱地和菜地;土壤酸度;养分特征
parent material;red soil;conversion of paddy fields to dry land and vegetable field;soil acidity;nutrient characteristics
《中国农业科学》 2024 (003)
525-538 / 14
国家自然科学基金(U19A2046,41977104)
10.3864/j.issn.0578-1752.2024.03.008
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