BUFFERING CAPACITY OF SOILS
Features
· Various minerals in soil help to buffer against changes in pH when an acid or base is added. At high pH, calcium, magnesium and potassium oxides, together with carbonates, help to buffer pH changes; at acidic pH, aluminum oxides and iron hydroxides act as buffering agents; at intermediate pH levels, soil organic matter, mineral weathering and exchange reactions help to buffer the soil.
Function
· A higher buffer capacity means that the soil can absorb more acid and/or base without a significant change in pH. In general, clay soils have higher buffer capacity than sandy soils, and a higher organic matter content tends to increase buffering capacity.
Significance
· Buffering capacity is important because it helps to stabilize the pH. Changes in pH can affect plants in a variety of ways, especially by diminishing the fraction of nutrients in soil that are available to the plants and increasing uptake of undesirable minerals like aluminum.
Soil pH is a useful indicator of the relative acidity or alkalinity of a soil. The pH scale ranges from 0 to 14, and the soil is assigned a value from the pH scale to describe the acidity or alkalinity. Since pH 7 falls midway along the scale, pH values that are equal to 7 are said to be neutral. However, pH values that fall below 7 are acidic, while pH values above 7 are alkaline.
By definition, the pH of a soil is the measurement of the concentration of hydrogen ions in soil water. Recall that the hydrogen ion is an acid cation. The greater the concentration of hydrogen ions in the soil water solution, the lower the pH. In return, the lower the pH value, the greater the acidity of the soil will be. The concentration of hydrogen ions in the soil solution is directly proportionate to and in equilibrium with the hydrogen ions retained on the soil’s cation exchange complex. Thus, the hydrogen ions retained by clay particles replenish, or buffer, the hydrogen ions in soil water.
· Various minerals in soil help to buffer against changes in pH when an acid or base is added. At high pH, calcium, magnesium and potassium oxides, together with carbonates, help to buffer pH changes; at acidic pH, aluminum oxides and iron hydroxides act as buffering agents; at intermediate pH levels, soil organic matter, mineral weathering and exchange reactions help to buffer the soil.
Function
· A higher buffer capacity means that the soil can absorb more acid and/or base without a significant change in pH. In general, clay soils have higher buffer capacity than sandy soils, and a higher organic matter content tends to increase buffering capacity.
Significance
· Buffering capacity is important because it helps to stabilize the pH. Changes in pH can affect plants in a variety of ways, especially by diminishing the fraction of nutrients in soil that are available to the plants and increasing uptake of undesirable minerals like aluminum.
Soil pH is a useful indicator of the relative acidity or alkalinity of a soil. The pH scale ranges from 0 to 14, and the soil is assigned a value from the pH scale to describe the acidity or alkalinity. Since pH 7 falls midway along the scale, pH values that are equal to 7 are said to be neutral. However, pH values that fall below 7 are acidic, while pH values above 7 are alkaline.
By definition, the pH of a soil is the measurement of the concentration of hydrogen ions in soil water. Recall that the hydrogen ion is an acid cation. The greater the concentration of hydrogen ions in the soil water solution, the lower the pH. In return, the lower the pH value, the greater the acidity of the soil will be. The concentration of hydrogen ions in the soil solution is directly proportionate to and in equilibrium with the hydrogen ions retained on the soil’s cation exchange complex. Thus, the hydrogen ions retained by clay particles replenish, or buffer, the hydrogen ions in soil water.