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. pH is defined as the negative logarithm (base 10) of the activity of hydronium ions (H+ or, more precisely, H3O+aq) in a solution. In soils, it is measured in a slurry of soil mixed with water (or a salt solution, such as 0.01M CaCl2), 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. 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; however, many plants have adapted to thrive at pH values outside this range. The United States Department of Agriculture Natural Resources Conservation Service classifies soil pH ranges as follows: 0 to 6=acidic,7=neutral and 8 and above alkalinity Methods of determining pH include: Observation of soil profile: certain profile characteristics can be indicators of either acid, saline, or sodic conditions. Examples are: Poor incorporation of the organic surface layer with the underlying mineral layer – this can indicate strongly acidic soils; The classic podzol horizon sequence, since podzols are strongly acidic: in these soils, a pale eluvial (E) horizon lies under the organic surface layer and overlies a dark B horizon; Presence of a caliche layer indicates the presence of calcium carbonates, which are present in alkaline conditions; Columnar structure can be an indicator of sodic condition. Observation of predominant flora. Calcifuge plants (those that prefer an acidic soil) include Erica, Rhododendron and nearly all other Ericaceae species, many birch (Betula), foxglove (Digitalis), gorse (Ulex spp.

About this result
This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.
Related courses (27)
CIVIL-203: Soil mechanics and flow through porous media
The course introduces students to the fundamentals of the mechanics of soils and fluid-infiltrated porous media. The first part is devoted to the constitutive behavior of soils in dry conditions, whil
ENV-222: Soil sciences
Le cours est une introduction aux Sciences du sol. Il a pour but de présenter les principales caractéristiques, propriétés et fonctions des sols. Il fait appel à des notions théoriques mais également
ENV-367: Environmental and construction law
Ce cours donne aux étudiant-e-s les connaissances de base nécessaires pour comprendre les dimensions juridiques de leur activité professionnelle concernant l'aménagement du territoire et la protection
Show more
Related publications (305)
Related concepts (21)
Alkali soil
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 calcareous layer at 0.5 to 1 metre depth. Alkali soils owe their unfavorable physico-chemical properties mainly to the dominating presence of sodium carbonate, which causes the soil to swell and difficult to clarify/settle. They derive their name from the alkali metal group of elements, to which sodium belongs, and which can induce basicity.
Soil horizon
A soil horizon is a layer parallel to the soil surface whose physical, chemical and biological characteristics differ from the layers above and beneath. Horizons are defined in many cases by obvious physical features, mainly colour and texture. These may be described both in absolute terms (particle size distribution for texture, for instance) and in terms relative to the surrounding material, i.e. 'coarser' or 'sandier' than the horizons above and below. The identified horizons are indicated with symbols, which are mostly used in a hierarchical way.
Soil structure
In geotechnical engineering, soil structure describes the arrangement of the solid parts of the soil and of the pore space located between them. It is determined by how individual soil granules clump, bind together, and aggregate, resulting in the arrangement of soil pores between them. Soil has a major influence on water and air movement, biological activity, root growth and seedling emergence. There are several different types of soil structure. It is inherently a dynamic and complex system that is affected by different factors.
Show more
Related MOOCs (1)
Water quality and the biogeochemical engine
Learn about how the quality of water is a direct result of complex bio-geo-chemical interactions, and about how to use these processes to mitigate water quality issues.

Graph Chatbot

Chat with Graph Search

Ask any question about EPFL courses, lectures, exercises, research, news, etc. or try the example questions below.

DISCLAIMER: The Graph Chatbot is not programmed to provide explicit or categorical answers to your questions. Rather, it transforms your questions into API requests that are distributed across the various IT services officially administered by EPFL. Its purpose is solely to collect and recommend relevant references to content that you can explore to help you answer your questions.