Abstract:

【Objective】 Soil acid and alkali buffer capacity, as a major indicator for evaluating the vulnerability and resistibility to soil acidification and alkalization, is an important factor impacting the sustainable development of agricultural soils, through which soil acidification process can be predicted and modified. 【Method】 In this study, titration curve method was adopted to investigate the pHBC, and separate titration curves were established by adding incremental amounts of either standardized hydrochloric acid (HCl) (0.12 mol?L-1) or sodium hydroxide (NaOH) (0.10 mol?L-1) to soil suspended in deionized water (soil﹕solution = 1﹕5). Soil pH was measured after 7d resuspension and isothermal equilibrium (t =25℃). Linear regressions were fitted to the linear portion of each titration curve and the slopes of these lines were used as the determination of pHBC. 【Result】 The results showed that great significance of correlations between the amounts of adding acid or alkali and the pH drop or increase were presented, and the coefficients of relativity were higher than the similar researches on acid soils (R2 = 0.97). The slope-derived pHBC of acid and alkali were 158.71 mmol?kg-1 and 25.02 mmol?kg-1, respectively. 【Conclusion】Titration technique was applicable in determination of pHBC on typical fluvor-aquic soil in Huang-Huai-Hai Plain. According to the classification of soil buffer systems, the soil studied belongs to the calcium carbonate buffer system, and in contrast to the soil organic matter, the carbonates contribute the most to pHBC.

Key words: fuvor-aquic soil')">fuvor-aquic soil, Huang-Huai-Hai plain, pH buffer capacity (pHBC)