Utilization of drilling sodium bentonite to improve acidity and aluminum–iron toxicity in acid sulfate soil beneath water storage pond base

Abstract

Improvement of acidity and aluminum-iron toxicity in water pond-based acid-sulfate soil (ASS) by drilling sodium bentonite (NaB) has not been proven. Therefore, we aimed to apply drilling NaB with and without dolomite (DL) to reduce acidity and aluminum-iron toxicity in Thai active ASS beneath the water storage pond base. The three treatments include (i) Control, (ii) NaB rate of 320 g NaB kg−1 soil, and (iii) NaB rate of 160 g NaB kg−1 soil + DL rate of 6 g kg−1 soil, were mixed with pond-based ASS subsoil, and aligned as randomized block design. We analyzed soil chemical properties at the initial time (baseline) (t0), after pond excavation (t1), after treatment applied (t2), and once a month after mixing for three months (t3, t4, t5). We filled tap water (initial pH = 6.7) into the ponds and kept the water level at 1 m depth. The results revealed that applying NaB with and without dolomite improved severe pH to normal pH and reduced pH buffering capacity, aluminum-iron toxicity, potential acidity, and excess Al and Fe released from the ASS. In addition, Na+ in NaB can be exchanged by Al3+ and H+ in ASS, making Na more soluble and easier to leach and liming.

Keywords

• Aluminum toxicity
• Acid sulfate soils
• pH buffering capacity
• Drilling mud
• Disposal management