Soil pH

<p>Soil pH is a measure of the <a href="/facts/Acidity/FySU18n1">acidity</a> or <a href="/facts/Basicity/M9wA7qeM">basicity</a> (alkalinity) of a <a href="/facts/Soil/5Ddpr3QM">soil</a>. Soil pH is a key characteristic that can be used to make informative analysis both qualitative and quantitatively regarding soil characteristics. <a href="/facts/PH/RnSv8D7y">pH</a> is defined as the negative <a href="/facts/Logarithm/QeXaV97q">logarithm</a> (base 10) of the <a href="/facts/Activity_(chemistry)/kGUf85XI">activity</a> of <a href="/facts/Hydronium/HzE3BGYJ">hydronium</a> ions (H+ or, more precisely, H3O+aq) in a <a href="/facts/Aqueous_solution/eRNr3MH2">solution</a>. In soils, it is measured in a slurry of soil mixed with water (or a salt solution, such as 0.01 <a href="/facts/Molarity/P2WL5b9q">M</a> CaCl2), and normally falls between 3 and 10, with 7 being neutral. Acid soils have a pH below 7 and <a href="/facts/Alkali_soil/XRLYuHtu">alkaline soils</a> have a pH above 7. Ultra-acidic soils (pH < 3.5) and very strongly alkaline soils (pH > 9) are rare.
</p><p>Soil pH is considered a master variable in soils as it affects many chemical processes. It specifically affects <a href="/facts/Plant_nutrition/hXWLy7Sc">plant nutrient</a> availability by controlling the chemical forms of the different nutrients and influencing the chemical reactions they undergo. The optimum pH range for most plants is between 5.5 and 7.5; however, many plants have adapted to thrive at pH values outside this range.
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Soil pH open-in-new

Soil pH