LDSF Topsoil PH
This map shows the distribution of predicted topsoil pH (0-20cm) illustrating only a few areas of extremely acidic or akaline soils. Soil acidity, a primary determinant of the soils potential to support vegetation is measured by the concentration of H+ ions in soil solution. Above pH 5.5 soil acidity is not generally considered as a constraint to plant growth, below pH 5.5 aluminum ions in solution drive soil acidity and can be toxic for plant growth, and below pH 3.5 H+ ions can be toxic to some plants. Soil pH affects the availability of several cations; at low pH the availability of Ca, Mg, K, P, N and S can be lowered but levels of Fe, Mn, Al increase and can be toxic to plant growth. In soils with high pH levels, or alkaline soils, nutrient deficiencies can be induced including phosphorus deficiency and micronutrient deficiencies (Fe, Mn, B, Cu, Zn).
The pH values across the watershed ranged dramatically but did not differ by LULC class. They were however on average significantly lower pH values (p<0.001) in the upper watershed with an overall mean value of 6.7 for topsoil and 6.6 for subsoil. In the lower watershed topsoils had an average pH of 7.3 and subsoils 7.2. There were not any statistical differences for pH values for slope gradient. Soil pH on average is unlikely to negatively impact plant growth and productivity either in the upper or lower watershed.
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