红壤不同利用方式下的剖面酸度特征

Acidity characteristics of red soil profile under different land use patterns

【目的】作物类型及其管理模式是影响红壤酸化的主要因素之一,研究不同利用方式下红壤剖面酸度的变化特征,对红壤酸化防治具有重要指导意义。【方法】选取由红砂岩母质发育红壤的4种主要利用方式(水田、旱地、果园和林地),通过分层(0—20、20—40、40—60、60—80 cm和80—100 cm)测定pH、交换性酸、交换性盐基总量和盐基饱和度,定量比较不同利用方式下各酸度指标在剖面上的变化特征及程度。【结果】在不同利用方式下,红壤剖面pH为水田(5.69)>旱地(4.71)≈果园(4.74)>林地(4.49);交换性酸含量为林地(6.54 cmol/kg)≈旱地(6.52 cmol/kg)>果园(3.51 cmol/kg)>水田(0.79 cmol/kg);交换性盐基总量为水田(4.47 cmol/kg)>旱地(1.97 cmol/kg)>果园(1.26 cmol/kg)>林地(0.48 cmol/kg);盐基饱和度为水田(53.14%)>旱地(20.87%)>果园(15.41%)>林地(4.67%)。随着土层深度的增加,红壤剖面pH值逐渐升高;不同层次间交换性酸含量无显著差异;交换性盐基总量随土壤深度增加逐渐升高,为60—100 cm (2.34 cmol/kg)> 40—60 cm(2.05 cmol/kg)> 0—40 cm (1.75 cmol/kg);水田利用方式下红壤盐基饱和度随土壤深度增加逐渐升高,为80—100 cm (33.95%)> 60—80 cm (32.27%)> 40—60 cm (31.31%)> 20—40 cm (25.47%)> 0—20 cm (21.08%)。水田、果园利用方式下红壤pH与交换性酸含量呈显著负相关,与交换性盐基总量和盐基饱和度呈显著正相关;旱地利用方式下红壤pH与交换性盐基总量呈显著正相关;林地利用方式下pH与交换性酸含量呈显著负相关。【结论】4种利用方式下,在0—40 cm土层,林地红壤酸度最高,其次是果园和旱地,水田红壤酸度最低,在40—100 cm土层酸度变异较小。通过改变土地利用方式,降低红壤交换性酸含量、增加交换性盐基总量和盐基饱和度可以有效降低红壤酸度。

[ Objectives ] Crop types and management modes are main factors influencing red soil acidification. Study of the acidify characteristics of red soil profiles under different land uses will provide reference for mitigating acidification of red soil in hilly regions. [ Methods ] Soil samples developed from red sandstone under 4 land uses （paddy field, dry land, orchard, and forest land） were collected from different depths （0-20, 20-40, 40-60, 60-80 cm and 80-100 cm）. The soil pH, exchangeable acid, amount of exchangeable base and salt base saturation were measured, quantitative comparison was conducted on acidification characteristics and their variation with depth and land use. [ Results ] pH of red soil followed the following order： paddy soil （5.69） 〉 dryland （4.71）≈ orchard （4.74） 〉 woodland （4.49）. Exchangeable acid followed the order： woodland （6.54 cmol/kg）, dry land （6.52 cmol/kg） 〉 orchard （3.51 cmol/kg） 〉 paddy （0.79 cmol/kg）. Exchangeable base followed the order： paddy （4.47 cmol/kg） 〉 dry land （1.97 cmol/kg） 〉 orchard （1.26 cmol/kg） 〉 woodland （0.48 cmol/kg）. Salt base saturation followed the order： paddy （53.14%） 〉 dry land （20.87%） 〉 orchard （15.41%） 〉 woodland （4.67%）. With the increase of soil depth, soil pH increased gradually, but exchangeable acid did not change. Exchangeable base increased with soil depth, following the order： 60-100 cm （2.34 cmol/kg） 〉 40-60 cm （2.05 cmol/kg） 〉 0-40 cm （1.75 cmol/kg）. Salt base saturation of paddy soil increased with depth, with 33.95% at 80-100 cm, 32.27% at 60-80 cm, 31.31% at 40-60 cm, 25.47% at 20-40 cm and 21.08% at 0-20 cm. Soil pH under paddy and orchard uses had a significant negative correlation with exchangeable acid, but a significant positive correlation with exchangeable base and salt base saturation. Soil pH under dry land use had a significant positive correlation with exchangeable base. Soil pH under woodland use had a significant negative correlation with exchangeable acid. [ Conclusions ] At 0-40 cm soil depth, red soil acidity of woodland is the highest, followed by orchards and the dry land, while that of paddy is the lowest under four land uses. Red soil acidity has small variation at 40-100 cm depth. Red soil acidity can be improved by changing land use patterns, decreasing exchangeable acid content, and increasing total exchangeable base content and salt base saturation.