After reading this article you will learn about the relationship between percentage base saturation of soil and its ph.
The determination of soil pH is comparatively more easier than that of determining base saturation. If pH is determined the base saturation can then be estimated approximately. A low percentage base saturation means acidity, whereas a percentage base saturation approaching 100 will result in neutrality or alkalinity.
As the base saturation is reduced due to leaching loss of calcium, the pH is also decreased (Due to development of acidity) in a definite proportion. Within the range of soil pH 5-6, the ratio for humid temperate region mineral soils is roughly at 5 per cent base saturation change for every 0.10 unit change in pH.
Thus, – if the percentage base saturation is 50 per cent at pH 5.5, it should be 25 per cent and 75 per cent at pH 5.0 and 6.0 respectively.
The percentage base saturation does provide numerical values of the amount of exchangeable hydrogen and aluminium ion species and this helps in predicting and amount of lime needed to neutralize the soil acidity. A relationship between the soil pH and the approximate proportions of various cations on the exchange complex are presented graphically (Fig. 9.12).
Kind of adsorbed cations also affects the soil pH for an example two soils possess same per cent base saturation but varied with the adsorbed cations. One soil is dominated by sodium and the other one by calcium and magnesium. Then the pH of the soil will be more in the former soil (Na-dominated soil) than that of latter soil.