How is Base Saturation defined?

Base saturation is defined as the proportion of the cation exchange capacity (CEC) that is occupied by exchangeable base cations. This measurement is important because it indicates the soil's fertility and ability to retain nutrients, which are critical for plant growth. Base cations typically include calcium, magnesium, potassium, and sodium, which all play essential roles in plant nutrition.

High base saturation usually signifies healthy soil that can supply plants with the necessary nutrients, whereas low base saturation may indicate acidic conditions or nutrient deficiencies. Understanding base saturation helps in making informed decisions about soil amendments and fertilization practices to optimize crop production.

The other options do not accurately define base saturation. The proportion of acid cations would focus on those cations that contribute to soil acidity rather than fertility. Total cation exchange capacity refers to the overall ability of the soil to hold cations but does not indicate what portion of this capacity is being used by base cations specifically. Amount of organic matter in soil, while vital for overall soil health, does not relate directly to the concept of base saturation itself.