Kationvahetusvaegud

Kationvahetusvaegud, also known as cation exchange capacity (CEC), is a fundamental property of soil that describes its ability to hold and exchange positively charged ions, or cations. These cations include essential plant nutrients such as calcium (Ca2+), magnesium (Mg2+), potassium (K+), and ammonium (NH4+). The CEC is typically expressed in centimoles of charge per kilogram of soil (cmolc/kg) or milliequivalents per 100 grams of soil (meq/100g).

Soils with higher CEC values have a greater capacity to retain these nutrients, making them less susceptible to leaching by rainfall or irrigation. This retention is primarily due to the presence of negatively charged sites on soil particles, particularly clay minerals and organic matter. These negatively charged sites attract and bind cations from the soil solution. When plants require specific nutrients, they can release hydrogen ions (H+) or aluminum ions (Al3+) from their root surfaces, which then displace the nutrient cations held on the soil exchange sites.

Factors influencing CEC include soil texture, with finer-textured soils (clays) generally having higher CEC than coarser-textured soils (sands). The amount and type of clay minerals present, as well as the organic matter content, are also critical. Soils rich in organic matter tend to have a higher CEC because organic molecules possess many negative charges. Soil pH also plays a role; as pH increases, more negative charges become available on clay and organic matter surfaces, thus increasing CEC. Understanding CEC is crucial for effective soil management, as it helps predict nutrient availability, soil buffering capacity, and the potential for contaminant retention.