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Global variation in soil pH. Red = acidic soil. Yellow = neutral soil. Blue = alkaline soil. Black = no data.
Soil pH is a measure of the acidity or basicity (alkalinity) of a soil. Soil pH is a key characteristic that can be used to make informative analysis both qualitative and quantitatively regarding soil characteristics.[1] pH is defined as the negative logarithm (base 10) of the activity of hydronium ions (H+ or, more precisely, H 3O+ aq) in a solution. In soils, it is measured in a slurry of soil mixed with water (or a salt solution, such as 0.01 MCaCl 2), and normally falls between 3 and 10, with 7 being neutral. Acid soils have a pH below 7 and alkaline soils have a pH above 7. Ultra-acidic soils (pH < 3.5) and very strongly alkaline soils (pH > 9) are rare.[2][3]
Soil pH is considered a master variable in soils as it affects many chemical processes. It specifically affects plant nutrient 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;[3] however, many plants have adapted to thrive at pH values outside this range.
^Thomas, G. W. (1996). "Soil pH and soil acidity". In Sparks, D. L.; Page, A. L.; Helmke, P. A.; Loeppert, R. H.; Soltanpour, P. N.; Tabatabai, M. A.; Johnston, C. T.; Sumner, M. E. (eds.). Methods of soil analysis. SSSA Book Series. Madison, Wisconsin: Soil Science Society of America. pp. 475–90. doi:10.2136/sssabookser5.3.c16. ISBN 978-0-89118-866-7. S2CID 93493509. Retrieved 29 January 2023.
^Slessarev, Eric W.; Lin, Yuan; Bingham, Nina L.; Johnson, Jennifer E.; Dai, Yongjiu; Schimel, Joshua P.; Chadwick, Oliver A. (21 November 2016). "Water balance creates a threshold in soil pH at the global scale" (PDF). Nature. 540 (7634): 567–69. Bibcode:2016Natur.540..567S. doi:10.1038/nature20139. PMID 27871089. S2CID 4466063. Retrieved 5 February 2023.
plants and soil organisms. Some scientific definitions distinguish dirt from soil by restricting the former term specifically to displaced soil. Soil consists...
Alkali, or Alkaline, soils are clay soils with high pH (greater than 8.5), a poor soil structure and a low infiltration capacity. Often they have a hard...
the soilpH. For H. macrophylla and H. serrata cultivars, the flower color can be determined by the relative acidity of the soil: an acidic soil (pH below...
means of a pH meter. Knowledge of pH is useful or critical in many situations, including chemical laboratory analyses. pH meters are used for soil measurements...
Soil acidification is the buildup of hydrogen cations, which reduces the soilpH. Chemically, this happens when a proton donor gets added to the soil...
health of vines that all good vineyard soils have. These include calcium which helps to neutralize the soilpH levels, iron which is essential for photosynthesis...
acidic and basic soil conditions. P. sofiense can be found in either soil condition. (For species that grow in only one type of soilpH condition maintaining...
antagonistic effects of soil conditions on lead, zinc, cadmium and copper in radish plants to develop predictive indicators for uptake like soilpH. Calcium absorption...
or horizon O is with sufficient soil organic matter for healthy soil structure and soil moisture retention; SoilpH in the range 5.5 to 7.0 (suitable...
live. Soil acidification refers to the process by which the pH level of soil becomes more acidic over time. SoilpH is a measure of the soil's acidity...
color is affected by soilpH. An acidic soil (pH below 7) will usually produce flower color closer to blue, whereas an alkaline soil (pH above 7) will produce...
modifying soil and water chemistry. Soil biology and chemistry can be seriously damaged by acid rain. Some microbes are unable to tolerate changes to low pH and...
to soilpH. Standards also exist for specialist soils suitable for plants with specific needs including acidic or ericaceous soil and calcareous soil. These...
101.2615.142. PMID 17800488. Nye, P. H. (1981). "Changes of pH across the rhizosphere induced by roots". Plant and Soil. 61 (1–2): 7–26. Bibcode:1981PlSoi...
generally plentiful in the soil solution, except when aluminium over competes calcium on cation exchange sites in very acid soils (pH less than 4), mass flow...
fertility or soil mechanics). It includes soil conservation, soil amendment, and optimal soil health. In agriculture, some amount of soil management is...
colour and resistivity. Soil texture is determined by the relative proportion of the three kinds of soil mineral particles, called soil separates: sand, silt...
specific mineral deficiency in the soil, such as iron, magnesium or zinc deficient nitrogen and/or proteins a soilpH at which minerals become unavailable...
and/or emission properties. Hence, a pH indicator is a chemical detector for hydronium ions (H3O+) or hydrogen ions (H+) in the Arrhenius model. Normally...
(habitat patch size and distance to outside seed sources); bulk density, pH, and soil texture (sand and clay). Secondary succession is the ecological succession...
magnesium, and sulfur. Soil is also assessed for several micronutrients, like zinc and boron. The percentage of organic matter, soilpH, and nutrient holding...
Soil biology is the study of microbial and faunal activity and ecology in soil. Soil life, soil biota, soil fauna, or edaphon is a collective term that...
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