磷酸钾影响酸化茶园土壤pH及其交换性阳离子路径研究

Effects of potassium phosphate on acidified tea garden soil pH and its approach of exchangeable cations

【目的】明确施用磷酸钾对酸化茶园土壤pH及其交换性阳离子的影响,以探索便捷高效的茶园土壤酸化改良方法。【方法】分别选取pH 3.53和pH 4.16的茶园土壤,以磷酸钾作为钾肥,分别设置4种不同浓度水平的施钾处理(50、100、150、200 mg/kg),并以不施肥为对照(CK),在恒温恒湿条件下进行室内培养试验。每隔1、5、10、20、30、45、60 d取出1次土样晾干并测定土壤pH、交换性阳离子K^(+)、Na^(+)、Ca^(2+)、Mg^(2+)、H^(+)、Al^(3+)、铵态氮、硝态氮。【结果】①在2种受试土壤中,添加磷酸钾均可显著(P<0.05)提高酸化茶园土壤pH和交换性K^(+)含量,提高幅度与磷酸钾的添加量呈正比,其中添加200 mg/kg磷酸钾处理对土壤pH和交换性K^(+)的增幅最大,与CK相比,2种受试土壤pH分别提高0.17、0.19个单位,交换性K^(+)的增幅分别为26.84%~104.97%,32.56%~100.98%;②交换性Al^(3+)含量在添加磷酸钾处理下显著降低,且与pH呈显著负相关;③结构方程分析表明,施用磷酸钾主要通过增加土壤中交换性K^(+)和降低交换性Al^(3+)两条路径提高土壤pH。在pH 3.53和pH 4.16的受试土壤中,这两条路径的直接效应绝对值之和分别为0.848、0.817,分别占总直接效应系数的67.4%、65.2%。【结论】施用磷酸钾可以改良茶园土壤酸化,且改良效果随施用浓度而递增,其中200 mg/kg的高浓度水平对pH提高最为显著,在培养20 d后其改良效果最佳;且通过构建结构方程模型发现酸化改良的主要作用路径是土壤中交换性K^(+)含量的增加和交换性Al^(3+)含量的降低。

【Objective】The purpose of the present study was to clarify the effect of potassium phosphate application on pH and exchangeable cations of acidified tea garden soil,and to explore a convenient and efficient acidification improvement mechanism of tea garden soil.【Method】The tea garden soil with pH 3.53 and pH 4.16 were selected for the study,and potassium phosphate was used as potash fertilizer.Four different potassium application rates(50,100,150,200 mg/kg)were set.At the same time,with no fertilizer as control(CK),the indoor culture experiment was carried out under the condition of constant temperature and humidity.The soil samples were dried every 1,5,10,20,30,45 and 60 days.The soil pH,the exchangeable cations K^(+),Na^(+),Ca^(2+),Mg^(2+),H^(+),Al^(3+),ammonium nitrogen and nitrate nitrogen were determined.【Result】(i)In the tested soils,the addition of potassium phosphate could significantly increase(P<0.05)the pH and exchangeable K^(+)content of acidified soil.Compared with CK soil,the addition of 200 mg/kg potassium phosphate treatment had the largest increase in soil pH and exchangeable K^(+),soil pH increased by 0.17 and 0.19 units,and exchangeable K^(+)increased by 26.84%-104.97%and 32.56%-100.98%,respectively.(ii)The exchangeable Al^(3+)content was significantly reduced under the treatment of adding potassium phosphate,and had a significant negative correlation with pH;(iii)The analysis of structural equation showed that the application of potassium phosphate increased soil pH mainly by increasing the exchangeable K^(+)and reducing the exchangeable Al^(3+)in the soil.In the tested soil at pH 3.53 and pH 4.16,the sum of the absolute values of the direct effects of these two paths was 0.848 and 0.817,respectively,accounting for 67.4%and 65.2%of the total direct effect coefficients,respectively.【Conclusion】Therefore,soil acidification in tea garden can be improved by potassium phosphate,and the improvement effect increases with the application concentration.Among them,the high concentration of 200 mg/kg has the most obvious improvement effect on pH,and the improvement effect is the best after 20 days of cultivation.By constructing the structural equation finds its routes becoming operative through the increasing exchangeable K^(+)and reducing exchangeable Al^(3+).