Array ( [0] => {{Short description|Top layer of soil}} [1] => [2] => [[File:Runoff of soil & fertilizer.jpg|thumb|[[Surface runoff]] of topsoil from a field in Iowa during a rain storm]] [3] => [4] => '''Topsoil''' is the upper layer of [[soil]]. It has the highest concentration of [[organic matter]] and [[microorganism]]s and is where most of the [[Earth|Earth's]] [[Biology|biological]] soil activity occurs. [5] => [6] => ==Description== [7] => [8] => Topsoil is composed of mineral particles and organic matter and usually extends to a depth of 5-10 inches (13–25 cm). Together these make a substrate capable of holding water and air which encourages biological activity. [9] => [10] => There are generally a high concentration of roots in topsoil since this is where plants obtain most of their vital [[nutrient]]s. It also plays host to significant [[bacteria]]l, [[Fungus|fungal]] and [[Entomology|entomological]] activity without which [[soil quality]] would degrade and become less suitable for plants. Bacteria and fungi can be essential in facilitating nutrient exchange with plants and in breaking down organic matter into a form that roots can absorb. Insects also play important roles in breaking down material and aerating and rotating the soil. Many species directly contribute to the health of the soil resulting in stronger plants.{{Cite journal |last1=Neher |first1=Deborah A. |last2=Barbercheck |first2=Mary E. |date=14 October 2019 |title=Soil Microarthropods and Soil Health: Intersection of Decomposition and Pest Suppression in Agroecosystems |journal=Insects |language=en |volume=10 |issue=12 |pages=414 |doi=10.3390/insects10120414 |issn=2075-4450 |pmc=6955927 |pmid=31756962|doi-access=free }} A healthy topsoil layer is a very rich [[microbiome]] that hosts a wide array of species.{{Cite journal |last1=Bahram |first1=Mohammad |last2=Hildebrand |first2=Falk |last3=Forslund |first3=Sofia K. |last4=Anderson |first4=Jennifer L. |last5=Soudzilovskaia |first5=Nadejda A. |last6=Bodegom |first6=Peter M. |last7=Bengtsson-Palme |first7=Johan |last8=Anslan |first8=Sten |last9=Coelho |first9=Luis Pedro |last10=Harend |first10=Helery |last11=Huerta-Cepas |first11=Jaime |date=7 March 2017 |title=Structure and function of the global topsoil microbiome |url=http://www.nature.com/articles/s41586-018-0386-6 |journal=Nature |language=en |volume=560 |issue=7717 |pages=233–237 |doi=10.1038/s41586-018-0386-6 |pmid=30069051 |hdl=1887/73861 |s2cid=51892834 |issn=0028-0836|hdl-access=free }} [11] => [12] => [[Organic matter]] provides nutrition for living organisms and varies in quantity between different soils with the strength of the soil structure decreasing when more is present. It condenses and settles over time in different ways depending upon conditions such as beneath roadbeds and foundations vs uncovered and exposed to the elements. The structure becomes affected once the soil is dehydrated. Dehydrated topsoil volume substantially decreases and may suffer [[Aeolian processes|wind erosion]].{{cite book|last1=Marsh|first1=William M.|title=Landscape planning : environmental applications|date=2010|publisher=Wiley|location=Hoboken, NJ|isbn=9780470570814|edition=5th}} [13] => [14] => == Production == [15] => Topsoil is naturally produced in the process of [[soil formation]] or [[pedogenesis]]. Natural topsoil is mined and conditioned for human use and makes up the bulk of commercial topsoil available. The current rate of use and erosion outpaces soil generation.{{cite web |title=Artificial soil: quick and dirty |url=https://www.newscientist.com/article/mg19526161-700-artificial-soil-quick-and-dirty/ |website=New Scientist}} [16] => [17] => It is possible to create artificial topsoil which supports some of the engineering or biological uses of topsoil. More traditional examples of artificial plant-growth media include [[terra preta]] and [[potting mix]]. Manufactured topsoil based on minerals, [[biosolids]], [[compost]] and/or paper mill sludge{{cite journal |last1=Carpenter |first1=Andrew F. |last2=Fernandez |first2=Ivan J. |title=Pulp Sludge as a Component in Manufactured Topsoil |journal=Journal of Environmental Quality |date=March 2000 |volume=29 |issue=2 |pages=387–397 |doi=10.2134/jeq2000.00472425002900020004x}} is available commercially.{{cite web |last1=Pettinelli |first1=Dawn |last2=Luce |first2=Harvey D |url=https://portal.ct.gov/-/media/Departments-and-Agencies/DPH/dph/environmental_health/eoha/pdf/051215PurchasingTopsoilpdf.pdf |title=Purchasing Topsoil |publisher=Soil Nutrient Analysis Laboratory}} A [[Victoria, Australia|Victorian]] [[open-cut]] coal mine was rehabilitated with low-quality artificial topsoil made from local materials.{{cite journal |last1=Birjak |first1=Anna |last2=Walmsley |first2=Alena |last3=Anderson |first3=Nicole |last4=Missen |first4=Jon |last5=Yellishetty |first5=Mohan |title=Field Scale Assessment of Artificial Topsoil: A Victorian Coal Mine Experience |journal=Proceedings of the 28th International Symposium on Mine Planning and Equipment Selection - MPES 2019 |series=Springer Series in Geomechanics and Geoengineering |date=2020 |pages=376–389 |doi=10.1007/978-3-030-33954-8_45 |isbn=978-3-030-33953-1 |s2cid=212959835 |url=https://www.researchgate.net/publication/337653300}} [18] => [19] => ==Classification== [20] => In soil classification systems, topsoil is known as the O Horizon or A Horizon.U.S. Department of Agriculture (USDA), Soil Survey Division Staff (1993). [http://soils.usda.gov/technical/manual/ "Soil Survey Manual."] {{webarchive|url=https://web.archive.org/web/20070207044212/http://soils.usda.gov/technical/manual/ |date=2007-02-07 }} USDA Handbook 18. Chapter 3.{{Cite book |author=National Committee on Soil and Terrain |title=Australian soil and land survey field handbook. Third edition. |publisher=CSIRO, Melbourne |year=2009}} [[Soil horizon]]s are layers parallel to the soil surface whose physical, chemical and biological characteristics differ from the layers above and beneath. The depth of the topsoil layer is measured as the depth of the surface to the first densely packed soil layer, known as [[subsoil]]. [21] => [22] => In the [[United States]], there is no federal, legal definition of the word topsoil when used in commerce. [23] => [24] => ==Evaluation== [25] => Organisations such as the [[BSI Group|British Standards Institution (BSI)]] and the [[North Carolina Department of Agriculture and Consumer Services|North Carolina Department of Agriculture]] publish guidelines for soil quality and the desired levels of topsoil nutrients broadly suitable for many plants.{{cite web|url=http://www.ncagr.gov/agronomi/pdffiles/sfn14.pdf|title=Topsoil . North Carolina Department of Agriculture(July, 1995)|website=ncagr.gov}} [26] => {| class="wikitable" [27] => |+Topsoil guideline according to North Carolina Department of Agriculture [28] => |- [29] => ! Category !! Desired Results [30] => |- [31] => | pH Level || 5.0 to 6.2 [32] => |- [33] => | Phosphorus (P-I) || Index of 50 [34] => |- [35] => | Potassium (K-I)|| Index of 50 [36] => |- [37] => | Calcium (Ca%)|| 40-60% of Cation Exchange Capacity (CEC) [38] => |- [39] => | Magnesium (Mg%)|| 8-10% of CEC [40] => |- [41] => | [[Base saturation]] (BS%)|| 35-80% of CEC [42] => |- [43] => | Manganese (Mn-I)|| Index > 25 [44] => |- [45] => | Zinc (Zn-I)|| Index > 25 [46] => |- [47] => | Copper (Cu-I)|| Index > 25 [48] => |} [49] => [50] => Two common types of commercial topsoil are Bulk and Bagged Topsoil. The following table illustrates major differences between the two. [51] => {| class="wikitable" [52] => |+Typical analysis of bulk and bagged topsoil, NCDA [53] => |- [54] => ! Topsoil Type !! [[Humus|HM]]%{{efn|1=Percent humic matter is a measure of the portion of organic matter that has decomposed to form [[humic acid|humic]] and [[fulvic acid]]s. HM% represents the portion of organic matter that is chemically reactive. This value affects determinations of lime and herbicide rates. [http://www.ncagr.gov/agronomi/obpart1.htm]}} !! BS% !! pH !! P-I !! K-I !! Ca% !! Mg% [55] => |- [56] => | Bulk|| 0.3|| 69 || 5.2 || 009 || 026 || 45 || 10 [57] => |- [58] => | Bagged|| 0.7 || 78 || 5.8 || 166+ || 178 || 56 || 12.3 [59] => |} [60] => [61] => Alternatively the [[BSI Group|BSI]] relates the following values: [62] => [63] => {| class="wikitable" [64] => |+Topsoil guideline according to BS 3882 [65] => |- [66] => ! Category !! Desired Results [67] => |- [68] => | pH Level || 5.5 to 8.5 [69] => |- [70] => | Phosphate (PO4) || 16 to 140 mg/L [71] => |- [72] => | Potassium (K)|| 121 to 1500 mg/L [73] => |- [74] => | Magnesium (Mg)|| 51 to 600 mg/L [75] => |- [76] => | Nickel (Ni)|| from <60 mg/kg [77] => |- [78] => | Zinc (Zn)|| from <200 mg/kg [79] => |- [80] => | Copper (Cu)|| from <100 mg/kg [81] => |} [82] => [83] => The preceding tables are for a multipurpose grade and certain levels can alter with regard to [[soil pH]]. [84] => [85] => Standards also exist for specialist soils suitable for plants with specific needs including acidic or [[Ericaceous bed|ericaceous]] soil and [[calcareous]] soil. These have different pH levels to typical soil and are meant for growing different plant species. Low fertility, low fertility acidic and low fertility calcareous are other soil classifications designed for plants which thrive in nutrient sparse soil. [86] => [87] => Examples of specialist plants include the [[Venus flytrap]] which is found in low [[nitrogen]] and [[phosphorus]] environments so is less tolerant of highly nutrient rich environments than other plants and less able to compete in them. Whereas blueberries require ericaceous soil to grow well and clover grows well in calcareous soil. Soils must therefore be selected to suit the plants which are intended to be grown and hence standards are required. [88] => [89] => ==Carbon to nitrogen ratio== [90] => [91] => Topsoil is the primary resource for plants to grow and crops to thrive. The main two parameters for this are carbon and nitrogen. The carbon provides energy and nitrogen is required for plants to build proteins and hence tissues. Plants require them in a range of ratios to enable suitable growth. An optimum figure for topsoil in the UK is a C:N ratio of less than 20:1. A sawdust base typically has a high C:N ratio in the order of 400:1 while an alfalfa hay has a low [[carbon]]aceous content and can typically have a C:N ratio around 12:1.Understanding the Carbon Nitrogen Ratio by Crow Miller ACRES https://www.ecofarmingdaily.com/build-soil/soil-inputs/minerals-nutrients/carbon-nitrogen-ratio/ [92] => [93] => ==Commercial application== [94] => A variety of soil mixtures are sold [[commerce|commercially]] as topsoil. Typical uses for this product are improving [[garden]]s and [[lawn]]s or for use in [[container garden]]s. [[Potting soil]], [[compost]], [[manure]] and [[peat]] are also sold for domestic uses with each having specific intended purposes. Topsoil products typically are not as suitable for potting plants or growing fruit and veg as potting soil or compost. Using it for this purpose can also work out prohibitively expensive compared to other alternatives. [95] => [96] => Topsoil is also used for proper surface [[grade (slope)|grading]] near residential buildings. In order to protect against flooding the [[International Building Code|International Residential Code]] requires a 2% slope ({{cvt|2.4|in}}) for the first ten feet away from the home.{{Cite web |title=Final Grade Slopes Away from Foundation {{!}} Building America Solution Center |url=https://basc.pnnl.gov/resource-guides/final-grade-slopes-away-foundation |access-date=2022-05-15 |website=basc.pnnl.gov}}[[Energy Star]] requires a rate of {{cvt|0.5|in/ft}}. [97] => [98] => Commercially available topsoil (manufactured or naturally occurring) in the United Kingdom must be classified to British Standard BS 3882, with the current version dated 2015. The standard has several classifications of topsoil with the final classification requiring material to meet certain threshold criteria such as nutrient content, extractable phytotoxic elements, particle size distribution, organic matter content, carbon:nitrogen ratio, electrical conductivity, loss on ignition, pH, chemical and physical contamination. The topsoil must be sampled in accordance with the British Standard and European Norm BS EN 12579:2013 Soil improvers and growing media – Sampling.BS 3882:2015 Specification for Topsoil [99] => [100] => ==Erosion== [101] => Topsoil [[erosion]] occurs when the topsoil layer is blown or washed away. The estimated annual costs of public and environmental health losses related to soil erosion in the United States exceed $45 billion.{{Cite web|url=http://www.ce.cmu.edu/~gdrg/readings/2007/02/20/Pimental_EnvironmentalEnergeticAndEconomicComparisonsOfOrganicAndConventionalFarmingSystems.pdf|archive-url=https://web.archive.org/web/20100624180924/http://www.ce.cmu.edu/~gdrg/readings/2007/02/20/Pimental_EnvironmentalEnergeticAndEconomicComparisonsOfOrganicAndConventionalFarmingSystems.pdf|url-status=dead|archive-date=June 24, 2010|title = Welcome to Civil and Environmental Engineering at CMU - Civil and Environmental Engineering - Carnegie Mellon University}} Conventional [[industrial agriculture]] practices such as [[plough]]ing and spraying high quantities of synthetic liquid [[Fertilizer|fertilisers]] can degrade the quality of the soil. [[Intensive farming]] methods to satisfy high food demands with high [[crop yield]]s and growing crops in [[monoculture]]s can deplete the soil nutrients and damage the soil [[microbiome]]. These factors can affect the consistency and quality of the soil resulting in increased erosion. [102] => [103] => [[Surface runoff]] from farm fields is a type of [[nonpoint source pollution]]. Topsoil as well as farm [[fertilizer]]s and other potential [[Water pollution|pollutants]] run off unprotected farm fields when heavy rains occur. This can result in polluting waterways and [[groundwater]] and may potentially contaminate drinking water sources. [[Algal bloom|Algae blooms]] can occur when high quantities of nutrients flood rivers, lakes or oceans often as a result of farm runoff or from sewage. These [[harmful algal bloom]]s can be toxic and have devastating impacts on ecosystems and wildlife. They are often referred to as red tides due to the presence of toxic red algae which can impact human food sources by contaminating seafood.{{Cite web |title=Red Tide (Paralytic Shellfish Poisoning) {{!}} Mass.gov |url=https://www.mass.gov/info-details/red-tide-paralytic-shellfish-poisoning |access-date=2022-07-11 |website=www.mass.gov |language=en}} [104] => [105] => Sustainable techniques attempt to slow erosion through the use of [[cover crops]] in order to build organic matter in the soil. The United States loses almost 3 tons of topsoil per acre per year.{{cite web |url=https://www.nrcs.usda.gov/technical/nri |title=Summary Report, 2007 Natural Resources Inventory |publisher= Natural Resources Conservation Services, U. S. Department of Agriculture |date=December 2009 |page= 97}} {{convert|1|in|cm}} of topsoil can take between 500{{cite news|title=Eating Locally|url=http://discovermagazine.com/2001/may/feateatlocal|access-date= May 1, 2001|newspaper=Discover |date= May 1, 2001 |author=James Smolka}} and 1,000 years{{cite news|url= http://www.scientificamerican.com/article/only-60-years-of-farming-left-if-soil-degradation-continues/|title= Only 60 Years of Farming Left If Soil Degradation Continues | work=Scientific American| date=December 5, 2014}} to form naturally, making the rate of topsoil erosion a serious ecological concern. Based on 2014 trends, the world has about 60 years of topsoil left.{{cite magazine|url= http://world.time.com/2012/12/14/what-if-the-worlds-soil-runs-out/|title= What If the World's Soil Runs Out? | magazine=Time | date=December 14, 2012}} [106] => [107] => ==Conservation== [108] => {{excerpt|soil conservation}} [109] => [110] => ==See also== [111] => {{Portal|Ecology}} [112] => {{div col|colwidth=22em}} [113] => * [[Agricultural wastewater]] [114] => * [[Desertification]] [115] => * [[Dust Bowl]] [116] => * [[Erosion control]] [117] => * [[No-till farming]] [118] => * [[Sustainable agriculture]] [119] => * [[Waterway degradation]] [120] => {{div col end}} [121] => [122] => ==References== [123] => {{notelist}} [124] => {{Reflist}} [125] => [126] => ===Further reading=== [127] => {{refbegin}} [128] => * [http://www.seattlepi.com/local/348200_dirt22.html The lowdown on topsoil: It's disappearing] [129] => * {{cite journal|journal=[[National Geographic Magazine]]|title=Our Good Earth|url=http://ngm.nationalgeographic.com/2008/09/soil/mann-text|author=Mann, C|year=2008|volume=214|issue=3|pages=80–107|url-status=dead|archive-url=https://web.archive.org/web/20130121122149/http://ngm.nationalgeographic.com/2008/09/soil/mann-text|archive-date=2013-01-21}} [130] => {{refend}} [131] => [132] => ==External links== [133] => * [https://www.nrcs.usda.gov/technical/efotg/ USDA Electronic Field Office Technical Guide] - Detailed soil conservation guides tailored to individual states/counties [134] => [135] => {{Authority control}} [136] => [137] => [[Category:Soil]] [138] => [[Category:Horticulture]] [139] => [[Category:Soil improvers]] [140] => [[Category:Lawn care]] [141] => [[Category:Types of soil]] [] => )
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Topsoil

Topsoil is the upper layer of soil. It has the highest concentration of organic matter and microorganisms and is where most of the Earth's biological soil activity occurs.

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