土壤pH测定的影响因素探讨

Discussion on the influence factors of soil pH determination

为了准确测定土壤pH,对不同检测条件下所测的土壤pH进行了分析比较。结果表明:振荡5 min、静置60 min和振荡30 min或60 min、静置30 min或60 min所测土壤pH趋于一致,悬液静置120 min以内完成检测,检测误差较小。测定搅拌中悬液可提高电极响应速度,测定结果稳定,且用时短,是适宜检测状态。土壤的pH_(氯化钙)、pH_(氯化钾)、pH_(水)有显著差异,但三者可相互转换计算。pH_(水)与pH_(氯化钙)的拟合线性方程为y=0.986x+1.018(R 2=0.990);pH_(水)与pH_(氯化钾)的拟合线性方程为y=1.230x+0.130(R^(2)=0.922);pH_(氯化钾)与pH_(氯化钙)的拟合线性方程为y=0.744x+0.952(R^(2)=0.936)。对于pH为4—9的土壤,pH_(水)受液接电位等因素干扰,精密度低于pH_(氯化钾)和pH_(氯化钙)。pH_(氯化钾)和pH_(氯化钙)测定干扰小,精密度较高。pH_(氯化钙)转换值与pH_(水)的差异较小,两者的可比性良好。对于pH在5—9的土壤,pH_(氯化钾)与pH_(水)差异增大,两者的可比性欠佳。氯化钙浸提液测定土壤pH有利于克服干扰,测定准确稳定,可参比性强,是一种优选的测定方法,可代替水浸提法测定土壤pH。

In order to accurately determine soil pH,the soil pH measured under different detection conditions was analyzed and compared.The results showed that the soil pH values measured by oscillating for 5 min and standing for 60 min,oscillating for 30 min or 60 min and standing for 30 min or 60 min tended to be consistent,and the detection error was small when the suspension was standing within 120 min.The electrode response speed could be improved by measuring the suspension in stirring,the determination result was stable and the time was short,so it was suitable for determination.There were significant differences in soil pH measured by water,potassium chloride and calcium chloride extracts,but they could be calculated by mutual conversion.The fitting linear equation of pH_(water)and pH_(calcium)chloride was y=0.986x+1.018(R^(2)=0.990);the fitting linear equation of pH_(water)and pH_(potassium)chloride was y=1.230x+0.130(R^(2)=0.922);the fitting linear equation of pH_(potassium)chloride and pH_(calcium)chloride was y=0.744x+0.952(R^(2)=0.936).For the soil with pH 4—9,the precision of pH_(water)was lower than those of pH_(potassium)chloride and pH_(calcium)chloride due to the interference of liquid junction potential and other factors.For the soil with pH 5—9,the difference between pH_(potassium)chloride and pH_(water)increased,and their comparability was poor.The determination of soil pH by calcium chloride extract was helpful to overcome the interference,and the determination was accurate and stable with strong reference.It was a preferred method to determine soil pH instead of water extraction method.