Leaching ( agriculture ) - wikipedia Leaching ( agriculture ) For other uses, see Leaching. In agriculture, leaching refers to the loss of water - soluble plant nutrients from the soil, due to rain and irrigation. Soil structure, crop planting, type and application rates of fertilizers, and other factors are taken into account to avoid excessive nutrient loss. Leaching may also refer to the practice of applying a small amount of excess irrigation where the water has a high salt content to avoid salts from building up in the soil ( salinity control ). Where this is practiced, drainage must also usually be employed, to carry away the excess water. Leaching is an environmental concern when it contributes to groundwater contamination. As water from rain, flooding, or other sources seeps into the ground, it can dissolve chemicals and carry them into the underground water supply. Of particular concern are hazardous waste dumps and landfills, and, in agriculture, excess fertilizer, improperly stored animal manure, and biocides ( e.g. pesticides, fungicides, insecticides and herbicides ). Contents 1 Nitrogen leaching 2 Health impacts 3 See also 4 References 5 External links Nitrogen leaching Nitrogen forms and pathways within an agricultural production system Nitrogen is a common element in nature and an essential plant nutrient. Approximately 78 % of Earth 's atmosphere is nitrogen ( N ). The strong bond between the atoms of N makes this gas quite inert and not directly usable by plants and animals. As nitrogen naturally cycles through the air, water and soil it undergoes various chemical and biological transformations. Nitrogen promotes plant growth. Livestock then eat the crops producing manure, which is returned to the soil, adding organic and mineral forms of nitrogen. The cycle is complete when the next crop uses the amended soil. To increase food production, fertilizers, such as nitrate ( NO ) and ammonium ( NH ), which are easily absorbed by plants, are introduced to the plant root zone. However, soils do not absorb the excess NO ions, which then move downward freely with drainage water, and are leached into groundwater, streams and oceans. The degree of leaching is affected by : soil type and structure. For example, sandy soil holds little water while clay soils have high water - retention rates ; the amount of water used by the plants / crops ; how much nitrate is already present in the soil. The level of nitrous oxide ( N O ) in the Earth 's atmosphere is increasing at a rate of 0.2 to 0.3 % annually. Anthropogenic sources of nitrogen are 50 % greater than from natural sources, such as, soils and oceans. Leached agricultural inputs, i.e. fertilizers and manures, accounts for 75 % of the anthropogenic source of nitrogen. The Food and Agriculture Organization of the United Nations ( FAO ) estimates world demand for nitrogen fertilizers will increase by 1.7 % annually between 2011 and 2015. An increase of 7.5 million tonnes. Regional increases of nitrogen fertilizer use are expected to be 67 % by Asia, 18 % by the Americas, 10 % by Europe, 3 % by Africa, and 1 % by Oceania. Health impacts High levels of NO in water can adversely affect oxygen levels for both humans and aquatic systems. Human health issues include methemoglobinemia and anoxia, commonly referred to as blue baby syndrome. As a result of these toxic effects, regulatory agencies limit the amount of NO permissible in drinking water to 45 -- 50 mg1 - 1. Eutrophication, a decline in oxygen content of water, of aquatic systems can cause the death of fish and other marine species. Finally, leaching of NO from acidic sources can increase the loss of calcium and other soil nutrients, thereby reducing an ecosystem 's productivity. See also Leaching ( pedology ) Leaching model ( soil ) Soil salinity control ( leaching requirement, leaching efficiency ) SahysMod ( spatial agro-hydro salinity, leaching and groundwater model ) References Jump up ^ Ontario Ministry of Agriculture, Food and Rural Affairs. Environmental Impacts of Nitrogen Use in Agriculture ^ Jump up to : Lin, BL ; Sakoda, A ; Shibasaki, R ; Suzuki, M ( 2001 ). `` A modelling approach to global nitrate leaching caused by anthropogenic fertilisation ''. Water research. 35 ( 8 ) : 1961 -- 8. PMID 11337842. doi : 10.1016 / s0043 - 1354 ( 00 ) 00484 - x. Jump up ^ `` WQ262 Nitrogen in the Environment : Leaching University of Missouri Extension ''. Extension.missouri.edu. Retrieved 2013 - 03 - 08. Jump up ^ Mosier, A.R. ; Duxbury, J.M. ; Freney, J.R. ; Heinemeyer, O. ; Minami, K. ( 1996 ). `` Nitrous oxide emissions from agricultural fields : Assessment, measurement and mitigation '' ( PDF ). Plant and Soil. 181 : 95. doi : 10.1007 / BF00011296. Jump up ^ FAO, Current world fertilizer trends and outlook to 2015 External links International Panel on Climate Change ( IPCC ) On line : ( 1 ) R.J. Oosterbaan, Water and salt balances in agricultural hydrology. Lecture notes, International Course on Land Drainage, ILRI, Wageningen, The Netherlands. On line : ( 2 ) R.J. Oosterbaan, 1997. `` SaltMod : A tool for interweaving of irrigation and drainage for salinity control ''. In : W.B. Snellen ( ed. ), Towards integration of irrigation, and drainage management. ILRI Special report, p. 41 -- 43. On line : ( 3 ) Natural resources Air Pollution / quality Ambient standards ( USA ) Index Indoor developing nations Law Clean Air Act ( USA ) Ozone depletion Emissions Airshed Trading Deforestation ( REDD ) Energy Law Resources Fossil fuels ( peak oil ) Geothermal Nuclear Solar sunlight shade Tidal Wave Wind Land Arable peak farmland Degradation Law property Management habitat conservation Minerals mining law sand peak rights Soil conservation fertility health resilience Use planning reserve Life Biodiversity Bioprospecting Biosphere Bushfood Bushmeat Fisheries law management Food Forests genetic resources law management Game law Gene bank Herbalist plants Marine conservation Non-timber forest products Rangeland Seed bank Wildlife conservation management Wood Water Types / location Aquifer storage and recovery Drinking Fresh Groundwater pollution recharge remediation Hydrosphere Ice bergs glacial polar Irrigation Rain harvesting Stormwater Surface water Wastewater reclaimed Aspects Desalination Floods Law Leaching Sanitation Conflict Conservation Peak water Pollution Privatization Quality Right Resources management policy Related Commons enclosure global land tragedy of Economics ecological Ecosystem services Exploitation overexploitation Earth Overshoot Day Management adaptive Natural capital accounting Nature reserve Systems ecology Urban ecology Wilderness Resource Common - pool Conflict ( perpetuation ) Curse Depletion Extraction Nationalism Renewable / Non-renewable Portals Agriculture and agronomy Energy Environment Fishing Forestry Mining Water Wetlands agencies law management ministries organizations Colleges Natural resources Topics in soil science Main fields Pedology Edaphology Soil physics Soil mechanics Soil chemistry Soil biology Soil zoology Soil ecology Soil morphology Environmental soil science Agricultural soil science ‎ Soil topics Soil Pedosphere Pedodiversity Pedogenesis Soil erosion Soil contamination Soil retrogression and degradation Soil compaction Soil compaction ( agriculture ) Soil salinity Alkali soil Soil pH Soil acidification Soil health Soil life Soil biodiversity Soil quality Soil value Soil fertility Soil resilience Soil color Soil texture Soil structure Pore space in soil Pore water pressure Soil crust Soil horizon Soil biomantle Soil carbon Soil gas Soil respiration Soil organic matter Soil moisture Soil water ( retention ) Soil type Soil classification USDA soil taxonomy Alfisols Andisols Aridisols Entisols Gelisols Histosols Inceptisols Mollisols Oxisols Spodosols Ultisols Vertisols World Reference Base for Soil Resources ( 1998 -- ) Acrisols Albeluvisols Alisols Andosols Anthrosols Arenosols Calcisols Cambisols Chernozem Cryosols Durisols Ferralsols Fluvisols Gleysols Gypsisols Histosol Kastanozems Leptosols Lixisols Luvisols Nitisols Phaeozems Planosols Plinthosols Podzols Regosols Solonchaks Solonetz Stagnosol Technosols Umbrisols Vertisols Other systems FAO soil classification ( 1974 -- 98 ) Unified Soil Classification System AASHTO Soil Classification System Référentiel pédologique ( French classification system ) Canadian system of soil classification Australian Soil Classification Polish Soil Classification 1938 USDA soil taxonomy List of U.S. state soils List of vineyard soil types Types of soil Applications Soil conservation Soil management Soil guideline value Soil survey Soil test Soil governance Soil value Soil salinity control Erosion control Soil policy Soil policy ( Victoria, Australia ) Agroecology Liming ( soil ) Related fields Geology Geochemistry Petrology Geomorphology Geotechnical engineering Hydrology Hydrogeology Biogeography Earth materials Archaeology Agricultural science Agrology Societies, Initiatives International Union of Soil Sciences Soil and Water Conservation Society National Society of Consulting Soil Scientists Soil Science Society of America National Society of Consulting Soil Scientists Australian Society of Soil Science Incorporated International Year of Soil World Congress of Soil Science See also Land use Land conversion Land management Vegetation Infiltration ( hydrology ) Groundwater Crust ( geology ) Impervious surface / Surface runoff Wikipedia : WikiProject Soil Category soil Category soil science Index of soil - related articles List of soil scientists Retrieved from `` https://en.wikipedia.org/w/index.php?title=Leaching_(agriculture)&oldid=785853415 '' Categories : Horticulture and gardening Soil Talk Contents About Wikipedia Català Dansk Deutsch Français Svenska Edit links This page was last edited on 15 June 2017, at 19 : 50. Text is available under the Creative Commons Attribution - ShareAlike License ; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia ® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization. About Wikipedia

Question: what is leaching and why is it a problem
Answer: leaching refers to the loss of water-soluble plant nutrients from the soil, due to rain and irrigation. Soil structure, crop planting, type and application rates of fertilizers, and other factors are taken into account to avoid excessive nutrient loss.