Adjustment of Soil pH and Redox Potential Using KOH and KMnO4 in Acidic Soils Applied with Immature Compost

pH and pe are very helpful values for understanding soil environmental conditions. Particularly, it has a great influence on the form of nutrients such as nitrogen. When pH+pe is less than 14.32, NO2- increases and NO2 (g) produced from NO2- harms crops. In this study, KOH, KMnO4, and sodium percarbonate (sp) were used to raise pH and pe to above the appropriate range (pH 6-7). While the pH was around 5 before the test, the pH was maintained at 6 or higher by all treatments until the end of the test (pH increment (ΔpH) after 5 days 1.0-2.5). pH+pe values were able to be corrected to 14.32 or more by KOH+KMnO4 treatments and sp treatment in drip irrigation and excessive treatment was good at furrow irrigation with easily reductive condition. Potassium (K), which is one of soil cation exchange capacity (CEC), acts as a strong base to increase the pH, so it is necessary to carry out the CEC measurement and titration test before the KOH+KMnO4 treatment. Mn2+ is decreased by the precipitation reaction with phosphate ion (H2PO4-) in the soil. Phosphate input will be helpful to supply phosphate necessary for crop growth and to prevent Mn excess. In addition, when determining the amount of reagent treated, it is considered that the soil osmotic pressure should be lower than the plant osmotic pressure so as not to cause wilted plant. Temporal variation of pH+pe in soils added with KOH+KMnO4 solution and Na2CO3•1.5 H2O2 solution. (a), (b) : Field A soils; (c),(d) : Field B soils.