Surface runoff, also called nonpoint source pollution, from a farm field in Iowa during a rain storm.
Topsoil as well as farm fertilizers and other potential pollutants run off unprotected farm fields when heavy rains occur.

Topsoil is the upper, outermost layer of soil, usually the top 2 inches (5.1 cm) to 8 inches (20 cm). It has the highest concentration of organic matter and microorganisms and is where most of the Earth's biological soil activity occurs.



Plants generally concentrate their roots in and obtain most of their nutrients from this layer. The actual depth of the topsoil layer can be measured as the depth from the surface to the first densely packed soil layer known as subsoil.


In soil classification systems, topsoil is known as the "A Horizon," therefore, it is the very top layer.[1]

Commercial application

A variety of soil mixtures are sold commercially as topsoil, usually for use in improving gardens and lawns, e.g. container gardens, potting soil and peat.


A major environmental concern known as topsoil erosion occurs when the topsoil layer is blown or washed away. Without topsoil, little plant life is possible. The estimated annual costs of public and environmental health losses related to soil erosion exceed $45 billion.[2] Conventional agriculture encourages the depletion of topsoil because the soil must be plowed and replanted each year. Sustainable techniques attempt to slow erosion through the use of cover crops in order to build organic matter in the soil. The United States alone loses 2 billion tons of topsoil per year[citation needed]. This is of great ecological concern as one inch of topsoil can take 500 years to form naturally.[3] However, farmer and engineer P. A. Yeomans developed a technique known as Keyline design, which has been proven to convert subsoil into topsoil much faster; Yeomans published a book, called Water For Every Farm, in 1954 about the technique[citation needed].

See also


External links

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Look at other dictionaries:

  • Topsoil — Top soil , n. The upper layer of soil; surface soil. [1913 Webster] …   The Collaborative International Dictionary of English

  • topsoil — (n.) 1836, from TOP (Cf. top) (n.1) + SOIL (Cf. soil) (n.) …   Etymology dictionary

  • topsoil — ► NOUN ▪ the top layer of soil …   English terms dictionary

  • topsoil — ☆ topsoil [täp′soil΄ ] n. the upper layer of soil, usually darker and richer than the subsoil; surface soil …   English World dictionary

  • topsoil — /top soyl /, n. 1. the fertile, upper part of the soil. v.t. 2. to cover (land) with topsoil. [1860 65; TOP1 + SOIL1] * * * …   Universalium

  • topsoil — noun The most fertile soil, easiest to start new plants in. Little grew on the farm, after the floods from the hurricane washed away the topsoil …   Wiktionary

  • topsoil — [[t]tɒ̱psɔɪl[/t]] N UNCOUNT Topsoil is the layer of soil nearest the surface of the ground …   English dictionary

  • topsoil — /ˈtɒpsɔɪl / (say topsoyl) noun 1. the surface or upper part of the soil. –verb (t) 2. to cover (land) with topsoil. {top1 + soil1} …   Australian English dictionary

  • topsoil — dirvožemio armuo statusas Aprobuotas sritis žemdirbystė apibrėžtis Viršutinis dirbamosios žemės sluoksnis, daugiausia tamsios spalvos, kuriame yra daugiau organinių ir maisto medžiagų negu podirvyje. atitikmenys: angl. topsoil vok.… …   Lithuanian dictionary (lietuvių žodynas)

  • topsoil — noun Date: 1836 surface soil usually including the organic layer in which plants have most of their roots and which the farmer turns over in plowing …   New Collegiate Dictionary

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