浙江省红层母质发育土壤的酸缓冲性及其在人为利用下的酸化特点

Acid Buffering Characteristics of Soils Developed from Red Beds in Zhejiang Province and Its Acidification under Agricultural Utilization

为了解由红层坡地改成梯田后,在稳定的成土环境与施肥条件下土壤酸碱度的变化特点,从浙江省采集了240个不同利用方式和利用时间的红层母质发育的农地土壤样本,探讨了不同类型红层母质发育土壤的酸缓冲性,分析了在水耕和旱耕条件下红层母质发育土壤酸碱度随利用时间的变化特点。结果表明,研究土壤酸缓冲曲线可分为pH值>6.5、pH值介于3.5~6.5之间和pH值<3.5等3个阶段,pH值>6.5和<3.5时,土壤pH值随酸加入量的变化较缓慢,对酸具有较强的缓冲性;pH值介于3.5~6.5时,土壤pH值随酸量增加呈现快速下降的趋势,容易发生土壤酸化。红层母质发育土壤的酸缓冲容量与缓冲强度有很大的变化,分别介于65.09~663.31、38.98~160.61 mmol/kg之间,平均值分别为232.64、81.60 mmol/kg;其酸缓冲容量明显高于自然红壤。土壤酸缓冲容量和土壤酸缓冲强度主要与土壤初始pH值、CaCO_(3)含量、CEC和盐基饱和度有关。水耕和旱耕后的红层母质发育土壤均随利用时间的延长而发生酸化,红紫砂土的pH值下降主要发生在利用时间25 a内,紫砂土的pH值下降主要发生在利用时间25 a后;而酸性紫砂土的pH值持续缓慢地下降,水耕对紫砂土的酸化作用较旱耕更明显,但对红紫砂土和酸性紫砂土的酸化作用比旱耕弱。

To understand the evolution characteristics of soil pH under stable soil formation environment and fertilization conditions after changing red bed slope land to terrace agricultural land,240 soils developed from different red beds with different land use ways and times were collected from Zhejiang province,and the acid buffering properties of the soils were discussed.The pH evolution of the soils with utilization time under the conditions of both paddy and dry tillage was analyzed.The results showed that the soil acid buffer curve could be divided into three stages:greater than 6.5,pH 6.5~3.5 and lower than 3.5.At the stage of pH greater than 6.5 and lower than 3.5,the soil pH changed slowly with increasing addition of acid,and had strong buffer against acid.At pH 6.5~3.5,the soil pH value decreased rapidly with the increase of acid addition,and soil acidification was easy to occur.The acid buffer capacity and buffer strength of the soils developed from different red beds varied greatly,ranging from 65.09 to 663.31 mmol/kg and 38.98 to 160.61 mmol/kg,with their averages of 232.64 mmol/kg and 81.60 mmol/kg,respectively.Its acid buffer capacity was significantly higher than that of natural red soil.Soil acid buffer capacity and soil acid buffer strength were mainly related to soil initial pH value,CaCO_(3) content,CEC and base saturation.After continuous paddy or dry tillage,all of the soils developed from different red beds were acidified with the utilization time.The decrease of pH value of red purple sandy soil mainly occurred within 25 years,and that of purple sandy soil mainly occurred after 25 years,while the pH value of acid purple sandy soil showed a slow and continuous decline with utilization time.Compared with dry tillage,the acidification of paddy tillage on purple sandy soil was more obvious.The acidification of red purple sandy soil and acid purple sandy soil under paddy tillage was weaker than that under dry tillage.