What is the quantity of humic acid applied to soil to decrease the soil pH and effect of humic acid on other soil properties like Lime, OC and nutrients availability. please share any dat available in this regard
The impact of adding humic acid on soil pH is generally subtle and not a primary method for pH adjustment. Humic acid is primarily used to enhance soil structure, nutrient availability, and microbial activity. Its effect on pH can vary based on factors such as the type of humic acid, soil properties, and initial pH levels. If you're aiming to lower soil pH, other materials like sulfur or acidic fertilizers are more commonly recommended. The quantity of humic acid needed to induce a specific pH change would depend on multiple variables and is not a straightforward process. It's important to consult experts or perform soil testing for accurate guidance on adjusting soil pH effectively and safely.
Please take a look at Pertusatti, J,, and Prado, A. 2007. Buffer Capacity of Humic Acid: Thermodynamic Approach. J. Collodi Interface Science
Humic acid should not be seen as a pH change agent but rather a strong buffering action.
Strong buffering of pH is found from pH 5.8 to 8.0. The maximum buffering is at 6.0. At a pH of 6.0 the toxicity of Fe, AL, and Mn is not an issue. In addition the optimal pH for Phosphorus availability is about 6.0 to 6.7.
For changing an acid soil the use of calcitic when Magnesium is well available and dolomitic lime would be the choice of adjusting pH.
In a alkaline solution the use of sulfur and ammoniated nitrogen sources would drive down pH to 7.3 and the use of calcium sulfate might aid in removeing excess salt.
In both the acid and alkaline origninal soil condition the ability to raise soil organic to 3 to 5 percent will optimize many issues with the soil.
A majority of cultivated soils have soil organic at less than 2% and many less than 1%. Under such a condition the soil dynamics from a biological physical or chemical sense will be compromised.
Building soil organic matter requires some long term effort and systematic actions.
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