The effect of cation–anion interactions on soil pH and solubility of organic carbon

Abstract

Summary Alkaline soil is widely distributed and cultivated throughout the agricultural regions of the world. Organic carbon (OC) concentrations in alkaline soil are often small, partly because of the limitations of a high pH on the productivity of crops and pastures together with the effects of high pH on the chemistry of soil OC. Soil pH is often hypothesized to be a major factor in regulating OC turnover in agricultural soil, but there are few detailed studies on the effects of high pH on carbon cycling in alkaline soil. Sodium, K+, Mg2+ and Ca2+ are the major cations in alkaline soil, whereas Cl−, SO42prefix−, normalHnormalCnormalO3− and normalCnormalO32prefix− are the major anions. The effect of different combinations of these cations and anions on soil pH and OC is not well described in the literature. The objectives of this study were to evaluate the effect of cations and anions on soil pH and to quantify the dissolution of OC in relation to these changes in pH. The results showed that normalHnormalCnormalO3− (Na+, K+ and Mg2+) salts and CaCO3 dominate in the pH range 7.0–8.5, and normalCnormalO32prefix− salts of Na+ and K+ dominate above pH 8.5. The amount of dissolved OC (DOC) increased significantly as pH increased. Therefore, the presence of large concentrations of normalHnormalCnormalO3− and normalCnormalO32prefix− not only increased pH but also promoted the dissolution of soil OC. The concentration of Ca2+ modified this effect; large concentrations of Ca2+ increased the adsorption and reduced the concentration of DOC.

Рослини роду Robinia як індикатор оптимізуючої дії зоогенного механізму екосистемних сервісів в умовах урбоекосистем

“…Отже, пошук нових механізмів зоогенних екосистемних сервісів (Vasilyuk, 2016a(Vasilyuk, , 2016b(Vasilyuk, , 2016c) за умов урбоекосистем, має прикладне значення. Визначення видового різноманіття, як основоположного чинника надійності та сталості екосистем (Bulakhov, Pakhomov, 2006;Caceres et al, 2015;Sanyal et al, 2015a;Ao et al, 2016;Vanguelova et al, 2017), що запобігає (регулюючі екосистемні сервіси) зміні клімату (Dee, Ahn, 2014), забезпечує (забезпечуючі екосистемні послуги) карбонатні цикли (Tavakkoli et al, 2015;Garland et al, 2016;Hardy et al, 2016), досить актуально. Визначається вплив і землекористування на рослинність, ґрунт та воду (Sanyal et al, 2015b;Njue et al, 2016) та розраховуються платежі за користування екосистемними послугами.…”

Soil Chemistry Factors Confounding Crop Salinity Tolerance—A Review

“…The measurement of pH using electrodes indicates the activity of hydrogen ions rather than their concentration. Hydrolysis of water molecules by cations and anions changes the pH of soil solutions to be either acidic or alkaline [21]. In addition, ionic strength determined by the concentration and valence of the ions influences the activity of hydrogen ions.…”

“…The acidic pH (<6) of highly weathered soils with low basic exchangeable cations like Ca 2+ , Mg 2+ , K + , and Na + arises mainly because of the hydrolysis of the cations Fe and Al [21]. By contrast, the soils of arid regions usually have alkaline pH (>7) and contain mainly Ca 2+ , Mg 2+ , K + , and Na + as exchangeable cations.…”

“…Brady and Weil et al 2008 described them as "non-acid cations" different from acid cations such as H + and Al 3+ [25]. Tavakkoli et al 2015 showed that when a soil with >90% exchangeable Na + had near neutral pH when accompanying anions were Cl − and SO 4 2− and alkaline pH (>8) when accompanying anions were HCO 3 − and CO 3 2− [21]. The weak hydrolysis reactions of Cl − and SO 4 2− result in a small change from neutral pH.…”

“…Strong adsorption of Fe and Al species by organic matter can effectively reduce proton concentration (H + ) in soil solution [35]. Dissolved organic carbon in soil solution is highly influenced by soil pH; higher dissolution of organic carbon is observed in high pH soils containing HCO 3 -and CO 3 2− ions [21]. Charged fractions of organic matter can contribute to the anion or cation exchange capacity of soils in a similar manner to of clay minerals.…”