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73-460: Because of regular flooding, floodplains frequently have high soil-fertility since nutrients are deposited with the flood waters. This can encourage farming ; some important agricultural regions, such as the Nile and Mississippi river basins , heavily exploit floodplains. Agricultural and urban regions have developed near or on floodplains to take advantage of the rich soil and freshwater. However,

146-405: A channel. Sediments from the crevasse spread out as delta -shaped deposits with numerous distributary channels. Crevasse formation is most common in sections of rivers where the river bed is accumulating sediments ( aggrading ). Repeated flooding eventually builds up an alluvial ridge, whose natural levees and abandoned meander loops may stand well above most of the floodplain. The alluvial ridge

219-517: A commercial analysis—e.g. 21-0-0-24 which would contain 21% nitrogen and 24% sulfate. Inorganic fertilizers are generally less expensive and have higher concentrations of nutrients than organic fertilizers. Also, since nitrogen, phosphorus and potassium generally must be in the inorganic forms to be taken up by plants, inorganic fertilizers are generally immediately bioavailable to plants without modification. However, studies suggest that chemical fertilizers have adverse health impacts on humans including

292-554: A flood-prone property to qualify for government-subsidized insurance, a local community must adopt an ordinance that protects the floodway and requires that new residential structures built in Special Flood Hazard Areas be elevated to at least the level of the 100-year flood. Commercial structures can be elevated or floodproofed to or above this level. In some areas without detailed study information, structures may be required to be elevated to at least two feet above

365-443: A floodplain. The quantity of sediments in a floodplain greatly exceeds the river load of sediments. Thus, floodplains are an important storage site for sediments during their transport from where they are generated to their ultimate depositional environment. When the rate at which the river is cutting downwards becomes great enough that overbank flows become infrequent, the river is said to have abandoned its floodplain. Portions of

438-452: A limiting factor on plant growth. Peer-reviewed and published scientific studies have shown that increasing CO 2 is highly effective at promoting plant growth up to levels over 300 ppm. Further increases in CO 2 can, to a very small degree, continue to increase net photosynthetic output. Soil depletion occurs when the components which contribute to fertility are removed and not replaced, and

511-487: A number of decisions that depleted the soils, including: allowing herd animals to wander freely, not replenishing soils with manure, and a sequence of events that led to erosion. William Cronon wrote that "...the long-term effect was to put those soils in jeopardy. The removal of the forest, the increase in destructive floods, the soil compaction and close-cropping wrought by grazing animals, ploughing—all served to increase erosion." Cronon continues, explaining, “Where mowing

584-458: Is irrigated with low pH / acidic water , the useful salts (Ca, Mg, K, P, S, etc.) are removed by draining water from the acidic soil and in addition unwanted aluminium and manganese salts to the plants are dissolved from the soil impeding plant growth. When soil is irrigated with high salinity water or sufficient water is not draining out from the irrigated soil, the soil would convert into saline soil or lose its fertility. Saline water enhance

657-414: Is a function of basal shear-stress. Shear stress is increased by factors such as sediment in the water, which increase its density. Shear stress t {\displaystyle t} is proportional to water mass, gravity, and WSS: where t is shear stress (N/m2), ρ is density of flowing water, g is gravity on Earth, D is average water depth, and WSS is Water Surface Slope. This is analogous to

730-542: Is a problem in freshwater systems. Much of the phosphorus in freshwater systems comes from municipal wastewater treatment plants and agricultural runoff. Stream connectivity controls whether phosphorus cycling is mediated by floodplain sediments or by external processes. Under conditions of stream connectivity, phosphorus is better able to be cycled, and sediments and nutrients are more readily retained. Water in freshwater streams ends up in either short-term storage in plants or algae or long-term in sediments. Wet/dry cycling within

803-403: Is advantageous for the rapid colonization of large areas of the floodplain. This allows them to take advantage of shifting floodplain geometry. For example, floodplain trees are fast-growing and tolerant of root disturbance. Opportunists (such as birds) are attracted to the rich food supply provided by the flood pulse. Floodplain ecosystems have distinct biozones. In Europe, as one moves away from

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876-678: Is also well documented as a cause of river incision. Stable material on the river bed mitigate erosion, removing this armoring layer of gravel, boulders, etc. exposes the channel bed to the erosive force of the water. "On the Russian River near Healdsburg, California, instream pit mining in the 1950s and 1960s caused channel incision in excess of 3-6 m over an 11-km length of river." Tectonics play an important role in shaping landscapes and rivers, and tectonic uplift and river incision go hand in hand. Over geologic time, as mountains rise higher, water erodes deep gorges and channels, dissecting

949-497: Is any area subject to inundation by a 100-year flood. A problem is that any alteration of the watershed upstream of the point in question can potentially affect the ability of the watershed to handle water, and thus potentially affects the levels of the periodic floods. A large shopping center and parking lot, for example, may raise the levels of 5-year, 100-year, and other floods, but the maps are rarely adjusted and are frequently rendered obsolete by subsequent development. In order for

1022-542: Is becoming increasingly harder to find and its reserves are starting to be depleted due to the excessive use as a fertilizer. The widespread use of phosphorus in fertilizers has led to pollution and eutrophication . Recently the term peak phosphorus has been coined, due to the limited occurrence of rock phosphate in the world. A wide variety of materials have been described as soil conditioners due to their ability to improve soil quality , including biochar , offering multiple soil health benefits. Food waste compost

1095-463: Is common after tectonic uplift of the landscape. Incision by multiple rivers result in a dissected landscape, for example a dissected plateau . River incision is the natural process by which a river cuts downward into its bed, deepening the active channel. Though it is a natural process, it can be accelerated rapidly by human factors including land use changes such as timber harvest, mining, agriculture, and road and dam construction. The rate of incision

1168-422: Is defined as the part of the river valley that is regularly flooded and dried. Floods bring in detrital material rich in nutrients and release nutrients from dry soil as it is flooded. The decomposition of terrestrial plants submerged by the floodwaters adds to the nutrient supply. The flooded littoral zone of the river (the zone closest to the river bank) provides an ideal environment for many aquatic species, so

1241-513: Is eroded or depleted of its original organic material. The Dust Bowl in the Great Plains of North America is a great example of this with about one-half of the original topsoil of the great plains having disappeared since the beginning of agricultural production there in the 1880s. Outside of the context of colonialism topsoil depletion can historically be attributed to many past civilizations' collapses. As historian David Silkenat explains,

1314-559: Is largely a result of flood control, hydroelectric development (such as reservoirs), and conversion of floodplains to agriculture use. Transportation and waste disposal also have detrimental effects. The result is the fragmentation of these ecosystems, resulting in loss of populations and diversity and endangering the remaining fragments of the ecosystem. Flood control creates a sharper boundary between water and land than in undisturbed floodplains, reducing physical diversity. Floodplain forests protect waterways from erosion and pollution and reduce

1387-470: Is that, as the river meanders, it creates a level flood plain composed mostly of point bar deposits. The rate at which the channel shifts varies greatly, with reported rates ranging from too slow to measure to as much as 2,400 feet (730 m) per year for the Kosi River of India. Overbank flow takes place when the river is flooded with more water than can be accommodated by the river channel. Flow over

1460-421: Is the element in soil that is most often lacking. Nitrogen and potassium are also needed in substantial amounts. For this reason these three elements are always identified on a commercial fertilizer analysis. For example, a 10-10-15 fertilizer has 10 percent nitrogen, 10 percent available phosphorus (P 2 O 5 ) and 15 percent water-soluble potassium (K 2 O). Sulfur is the fourth element that may be identified in

1533-707: Is topped by a channel belt formed by successive generations of channel migration and meander cutoff. At much longer intervals, the river may abandon the channel belt and build a new one at another position on the floodplain. This process is called avulsion and occurs at intervals of 10–1000 years. Historical avulsions leading to catastrophic flooding include the 1855 Yellow River flood and the 2008 Kosi River flood . Floodplains can form around rivers of any kind or size. Even relatively straight stretches of river are capable of producing floodplains. Mid-channel bars in braided rivers migrate downstream through processes resembling those in point bars of meandering rivers and can build up

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1606-557: The Yellow River in China – see list of deadliest floods . The worst of these, and the worst natural disaster (excluding famine and epidemics), was the 1931 China floods , estimated to have killed millions. This had been preceded by the 1887 Yellow River flood , which killed around one million people and is the second-worst natural disaster in history. The extent of floodplain inundation depends partly on flood magnitude, defined by

1679-545: The basal shear stress commonly used in glaciology. Increases in slope, depth, or density of water increase the water's potential to cause erosion. Traditional logging in the West coast of the United States included many practices which increased river incision. Timber removal and the associated road construction facilitate runoff and thus increased erosion and sediment delivery to streams. Increases in sediment increases

1752-684: The return period . In the United States, the Federal Emergency Management Agency (FEMA) manages the National Flood Insurance Program (NFIP). The NFIP offers insurance to properties located within a flood-prone area, as defined by the Flood Insurance Rate Map (FIRM), which depicts various flood risks for a community. The FIRM typically focuses on the delineation of the 100-year flood inundation area, also known within

1825-425: The risk of inundation has led to increasing efforts to control flooding . Most floodplains are formed by deposition on the inside of river meanders and by overbank flow. Wherever the river meanders, the flowing water erodes the river bank on the outside of the meander. At the same time, sediments are simultaneously deposited in a bar on the inside of the meander. This is described as lateral accretion since

1898-523: The turgor pressure or osmotic pressure requirement which impedes the off take of water and nutrients by the plant roots. Top soil loss takes place in alkali soils due to erosion by rain water surface flows or drainage as they form colloids (fine mud) in contact with water. Plants absorb water-soluble inorganic salts only from the soil for their growth. Soil as such does not lose fertility just by growing crops but it lose its fertility due to accumulation of unwanted and depletion of wanted inorganic salts from

1971-521: The Amazon was strongly influenced by the formation of Dark Earth. As a result, Amazonian societies benefitted from the dark earth in terms of agricultural success and enhanced food production. Soil analyses have been completed on the modern and ancient Kuikuro Indigenous Territory in the Upper Xingu River basin in southeastern Amazonia through archaeological and ethnographic research to determine

2044-728: The Amazonian regions of South America, particularly the size of the communities and the depth of interactions with the environment, are continually debated. Central to the debate is the influence of Dark Earth. Dark Earth is a type of soil found in the Amazon that has a darker color, higher organic carbon content, and higher fertility than soil in other regions of South America which makes it highly coveted even today. Dark Earth deposits have been found, through ethnographic and archaeological studies, to have been created through ancient Indigenous practices by intentional soil management. Ethnoarchaeologist Morgan Schmidt outlines how this carbon-rich soil

2117-526: The Middle East for example, many countries find it difficult to grow produce because of droughts, lack of soil, and lack of irrigation. The Middle East has three countries that indicate a decline in crop production, the highest rates of productivity decline are found in hilly and dryland areas. Many countries in Africa also undergo a depletion of fertile soil. In regions of dry climate like Sudan and

2190-560: The NFIP as the Special Flood Hazard Area. Where a detailed study of a waterway has been done, the 100-year floodplain will also include the floodway, the critical portion of the floodplain which includes the stream channel and any adjacent areas that must be kept free of encroachments that might block flood flows or restrict storage of flood waters. Another commonly encountered term is the Special Flood Hazard Area, which

2263-421: The abandoned floodplain may be preserved as fluvial terraces . Floodplains support diverse and productive ecosystems . They are characterized by considerable variability in space and time, which in turn produces some of the most species-rich of ecosystems. From the ecological perspective, the most distinctive aspect of floodplains is the flood pulse associated with annual floods, and so the floodplain ecosystem

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2336-531: The ability of soil to sustain agricultural plant growth , i.e. to provide plant habitat and result in sustained and consistent yields of high quality. It also refers to the soil's ability to supply plant/crop nutrients in the right quantities and qualities over a sustained period of time. A fertile soil has the following properties: The following properties contribute to soil fertility in most situations: In lands used for agriculture and other human activities, maintenance of soil fertility typically requires

2409-510: The advantages provided by the richness of the alluvial soil of the floodplain are severely offset by frequent floods brought on by cyclones and annual monsoon rains. These extreme weather events cause severe economic disruption and loss of human life in the densely-populated region. Floodplain soil composition is unique and varies widely based on microtopography. Floodplain forests have high topographic heterogeneity which creates variation in localized hydrologic conditions. Soil moisture within

2482-497: The banks of the river deposits a thin veneer of sediments that is coarsest and thickest close to the channel. This is described as vertical accretion , since the deposits build upwards. In undisturbed river systems, overbank flow is frequent, typically occurring every one to two years, regardless of climate or topography. Sedimentation rates for a three-day flood of the Meuse and Rhine Rivers in 1993 found average sedimentation rates in

2555-622: The conditions which support soil's fertility are not maintained. This leads to poor crop yields. In agriculture, depletion can be due to excessively intense cultivation and inadequate soil management . Depletion may occur through a variety of other effects, including overtillage (which damages soil structure), underuse of nutrient inputs which leads to mining of the soil nutrient bank, and salinization of soil. Soil fertility can be severely challenged when land-use changes rapidly. For example, in Colonial New England , colonists made

2628-499: The countries that make up the Sahara Desert , droughts and soil degradation is common. Cash crops such as teas, maize, and beans require a variety of nutrients in order to grow healthy. Soil fertility has declined in the farming regions of Africa and the use of artificial and natural fertilizers has been used to regain the nutrients of ground soil. The details of Indigenous societies prior to European colonization in 1492 within

2701-444: The deposition builds the point bar laterally into the river channel. Erosion on the outside of the meander usually closely balances deposition on the inside so that the channel shifts in the direction of the meander without changing significantly in width. The point bar is built up to a level very close to that of the river banks. Significant net erosion of sediments occurs only when the meander cuts into higher ground. The overall effect

2774-495: The development of chronic disease from the toxins. As for the environment, over-reliance on inorganic fertilizers disrupts the natural nutrient balance in the soil, resulting in lower soil quality, loss of organic matter, and higher chances for erosion in the soil. Additionally, the water-soluble nitrogen in inorganic fertilizers does not provide for the long-term needs of the plant and creates water pollution. Slow-release fertilizers may reduce leaching loss of nutrients and may make

2847-463: The environment naturally intersect in complex and powerful ways, leaving lasting effects from the period of emancipation through modern-day reckonings with racial justice…the land too fell victim to the slave owner’s lash”. One of the most widespread occurrences of soil depletion as of 2008 is in tropical zones where nutrient content of soils is low. The depletion of soil has affected the state of plant life and crops in agriculture in many countries. In

2920-414: The environment. Soil fertility and depletion have different origins and consequences in various parts of the world. The intentional creation of dark earth in the Amazon promotes the important relationship between indigenous communities and their land. In African and Middle Eastern regions, humans and the environment are also altered due to soil depletion. Bioavailable phosphorus (available to soil life)

2993-459: The floodplain has a big impact on phosphorus availability because it alters water level, redox state, pH, and physical properties of minerals. Dry soils that were previously inundated have reduced availability of phosphorus and increased affinity for obtaining phosphorus. Human floodplain alterations also impact the phosphorus cycle. Particulate phosphorus and soluble reactive phosphorus (SRP) can contribute to algal blooms and toxicity in waterways when

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3066-401: The floodplain of between 0.57 and 1.0 kg/m. Higher rates were found on the levees (4 kg/m or more) and on low-lying areas (1.6 kg/m). Sedimentation from the overbank flow is concentrated on natural levees, crevasse splays , and in wetlands and shallow lakes of flood basins. Natural levees are ridges along river banks that form from rapid deposition from the overbank flow. Most of

3139-507: The floodplain. Normally, floods are allowed to spread out across the floodplain, allowing deposition of sediment and slowing water speeds, reducing the erosive potential of the water. Channelization concentrates flood flows down the active channel, increasing erosion. River incision due to agriculture is well-documented throughout the agricultural regions of the world, such as the Central Valley of California. In-stream gravel mining

3212-599: The floodplain. Other smaller-scale mitigation efforts include acquiring and demolishing flood-prone buildings or flood-proofing them. In some floodplains, such as the Inner Niger Delta of Mali , annual flooding events are a natural part of the local ecology and rural economy , allowing for the raising of crops through recessional agriculture . However, in Bangladesh , which occupies the Ganges Delta ,

3285-562: The goals of Southern plantation and slave owners, instead of measuring productivity based on outputs per acre, were to maximize the amount of labor that could be extracted from the enslaved workforce. The landscape was seen as disposable, and the African slaves were seen as expendable. Once these Southern farmers forced slaves to leach soils and engage in mass deforestation, they would discard the land and move towards more fertile prospects. The forced slave practices created extensive destruction on

3358-503: The human relation to the soil. The “results demonstrate the intentional creation of dark earth, highlighting how Indigenous knowledge can provide strategies for sustainable rainforest management”. In Egypt, earthworms of the Nile River Valley contributed to the significant fertility of the soils. As a result, Cleopatra declared the earthworm and sacred animal to recognize the animal’s positive impact. No one, including farmers,

3431-420: The human-caused disconnect between floodplains and rivers exacerbates the phosphorus overload. Floodplain soils tend to be high in eco-pollutants, especially persistent organic pollutant (POP) deposition. Proper understanding of the distribution of soil contaminants is difficult because of high variation in microtopography and soil texture within floodplains. Soil fertility Soil fertility refers to

3504-462: The impact of floodwaters. The disturbance by humans of temperate floodplain ecosystems frustrates attempts to understand their natural behavior. Tropical rivers are less impacted by humans and provide models for temperate floodplain ecosystems, which are thought to share many of their ecological attributes. Excluding famines and epidemics , some of the worst natural disasters in history (measured by fatalities) have been river floods, particularly in

3577-438: The intensity, seasonality, and frequency of the burns, the conservation of biodiversity and the overall health of the soil can be negatively impacted by fire. In addition to soil erosion through using too much or too little fire, colonial agriculture also resulted in topsoil depletion. Topsoil depletion occurs when the nutrient-rich organic topsoil , which takes hundreds to thousands of years to build up under natural conditions,

3650-448: The land. The environmental impact included draining swamps, clearing forests for monocropping and fuel steamships, and introducing invasive species, all leading to fragile ecosystems. In the aftermath, these ecosystems left hillsides eroded, rivers clogged with sterile soil, and extinction of native species. Silkenat summarizes this phenomenon of the relationship between enslavement and soil, “Although typically treated separately, slavery and

3723-626: The landscape. In some instances, such as the Sierra Nevada mountains of California, up to 1 km of incision has been shown to have occurred over the last 5 million years. "River erosion is one of the primary agents of landscape evolution. Outside of glaciated regions, rivers are responsible for sculpting uplifted terrain into arborescent valley networks and creating the relief that drives gravitational transport processes such as landsliding". Rivers and streams that cross tectonic boundaries are subject to immense geomorphic change. When an area in

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3796-613: The makeup towards ash (49%) with maple increasing to 14% and oak decreasing to 25%. Semiarid floodplains have a much lower species diversity. Species are adapted to alternating drought and flood. Extreme drying can destroy the ability of the floodplain ecosystem to shift to a healthy wet phase when flooded. Floodplain forests constituted 1% of the landscape of Europe in the 1800s. Much of this has been cleared by human activity, though floodplain forests have been impacted less than other kinds of forests. This makes them important refugia for biodiversity. Human destruction of floodplain ecosystems

3869-758: The nitrogen-to-phosphorus ratios are altered farther upstream. In areas where the phosphorus load is primarily particulate phosphorus, like the Mississippi River, the most effective ways of removing phosphorus upstream are sedimentation, soil accretion, and burial. In basins where SRP is the primary form of phosphorus, biological uptake in floodplain forests is the best way of removing nutrients. Phosphorus can transform between SRP and particulate phosphorus depending on ambient conditions or processes like decomposition, biological uptake, redoximorphic release, and sedimentation and accretion. In either phosphorus form, floodplain forests are beneficial as phosphorus sinks, and

3942-417: The nutrients in microbial biomass , a process often called immobilization . The balance between immobilization and mineralization processes depends on the balance and availability of major nutrients and organic carbon to soil microorganisms. Natural processes such as lightning strikes may fix atmospheric nitrogen by converting it to (NO 2 ). Denitrification may occur under anaerobic conditions (flooding) in

4015-651: The nutrients that they provide available over a longer period of time. Soil fertility is a complex process that involves the constant cycling of nutrients between organic and inorganic forms. As plant material and animal wastes are decomposed by micro-organisms, they release inorganic nutrients to the soil solution, a process referred to as mineralization . Those nutrients may then undergo further transformations which may be aided or enabled by soil micro-organisms. Like plants, many micro-organisms require or preferentially use inorganic forms of nitrogen, phosphorus or potassium and will compete with plants for these nutrients, tying up

4088-402: The path of a river is uplifted, the river must either divert, or slowly incise into the uplifted area, creating a gorge or canyon. As a channel bed drops, the water in the surrounding aquifer runs into the stream, lowering the water table. This modifies the flow regime of a stream, and can lead to a large reduction in summer flows. Prolonged incision can lower the water table to the point where

4161-450: The presence of denitrifying bacteria. Nutrient cations, including potassium and many micronutrients, are held in relatively strong bonds with the negatively charged portions of the soil in a process known as cation exchange . Phosphorus is a primary factor of soil fertility as it is an element of plant nutrients in the soil. It is essential for cell division and plant development, especially in seedlings and young plants. However, phosphorus

4234-509: The river, the successive plant communities are bank vegetation (usually annuals); sedge and reeds; willow shrubs; willow-poplar forest; oak-ash forest; and broadleaf forest. Human disturbance creates wet meadows that replace much of the original ecosystem. The biozones reflect a soil moisture and oxygen gradient that in turn corresponds to a flooding frequency gradient. The primeval floodplain forests of Europe were dominated by oak (60%) elm (20%) and hornbeam (13%), but human disturbance has shifted

4307-496: The roots of the riparian vegetation can no longer access it for water, causing the death of the riparian forest and thus a loss of soil stability, contributing to increased sedimentation. Riparian forests are some of the most productive and diverse ecosystems on the planet and are for this reason the focus of many restoration projects throughout the United States. At low erosion rates increased stream incision may make gentle slopes to erode creating convex-up forms. Convex slopes around

4380-428: The soil by improper irrigation and acid rain water (quantity and quality of water). The fertility of many soils which are not suitable for plant growth can be enhanced many times gradually by providing adequate irrigation water of suitable quality and good drainage from the soil. River incision River incision is the narrow erosion caused by a river or stream that is far from its base level . River incision

4453-509: The soil for the benefit of the human and non-human world. He continues that industrial agriculture disrupts the delicate balance of nature and irrevocably robs the soil of its fertility. Irrigation is a process by which crops are watered by man-made means, such as bringing in water from pipes, canals, or sprinklers. Irrigation is used when the natural rainfall patterns of a region are not sustainable enough to maintain crops. Ancient civilizations heavily relied on irrigation and today about 18% of

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4526-418: The soil. This must be gotten into good condition first of all and then the reaction of the soil, the plant, animal, and man observed. Many diseases will then automatically disappear...Soil fertility is the basis of the public health system of the future...”. Howard connects the health crises of crops to the impacts of livestock and human health, ultimately spreading the message that humans must respect and restore

4599-407: The spawning season for fish often coincides with the onset of flooding. Fish must grow quickly during the flood to survive the subsequent drop in water level. As the floodwaters recede, the littoral experiences blooms of microorganisms, while the banks of the river dry out and terrestrial plants germinate to stabilize the bank. The biota of floodplains has high annual growth and mortality rates, which

4672-458: The surrounding grade. Many State and local governments have, in addition, adopted floodplain construction regulations which are more restrictive than those mandated by the NFIP. The US government also sponsors flood hazard mitigation efforts to reduce flood impacts. California 's Hazard Mitigation Program is one funding source for mitigation projects. A number of whole towns such as English, Indiana , have been completely relocated to remove them from

4745-414: The suspended sand is deposited on the levees, leaving the silt and clay sediments to be deposited as floodplain mud further from the river. Levees are typically built up enough to be relatively well-drained compared with nearby wetlands, and levees in non-arid climates are often heavily vegetated. Crevasses are formed by breakout events from the main river channel. The river bank fails, and floodwaters scour

4818-666: The upper 30 cm of the soil profile also varies widely based on microtopography which affects oxygen availability. Floodplain soil stays aerated for long stretches of time in between flooding events, but during flooding, saturated soil can become oxygen-depleted if it stands stagnant for long enough. More soil oxygen is available at higher elevations farther from the river. Floodplain forests generally experience alternating periods of aerobic and anaerobic soil microbe activity which affects fine root development and desiccation. Floodplains have high buffering capacity for phosphorus to prevent nutrient loss to river outputs. Phosphorus nutrient loading

4891-501: The use of soil conservation practices. This is because soil erosion and other forms of soil degradation generally result in a decline in quality with respect to one or more of the aspects indicated above. Soil fertility and quality of land have been impacted by the effects of colonialism and slavery both in the U.S. and globally. The introduction of harmful land practices such as intensive and non-prescribed burnings and deforestation by colonists created long-lasting negative results to

4964-539: The water's stream power, increasing the stream's ability to do geomorphic work on the bed and banks. This leads to scouring of the bed material, exposing the bedrock channel bed to erosion and thus faster rates of channel incision. The scoured bed material consists of finer sediments such as silts, sands, and gravels. The removal of these removes important aquatic habitats for salmonid species and other aquatic organisms. In many agricultural areas, rivers have been straightened and dyked for flood control and to plant crops in

5037-466: The world's cropland is irrigated. The quality of irrigation water is very important to maintain soil fertility and tilth , and for using more soil depth by the plants. When soil is irrigated with high alkaline water, unwanted sodium salts build up in the soil which would make soil draining capacity very poor. So plant roots can not penetrate deep into the soil for optimum growth in Alkali soils . When soil

5110-417: Was found to have better soil improvement than manure based compost. Photosynthesis is the process whereby plants use light energy to drive chemical reactions which convert CO 2 into sugars. As such, all plants require access to both light and carbon dioxide to produce energy, grow and reproduce. While typically limited by nitrogen, phosphorus and potassium, low levels of carbon dioxide can also act as

5183-468: Was intentionally created by communities in the Amazon. While Dark Earth, and other anthropic soils, can be found all throughout the world, Amazonian Dark Earth is particularly significant because “it contrasts too sharply with the especially poor fertility of typical highly weathered tropical upland soils in the Amazon”. There is much evidence to suggest that the development of ancient agricultural societies in

5256-1148: Was unnecessary and grazing among living trees was possible, settlers saved labor by simply burning the forest undergrowth...and turning loose their cattle...In at least one ill-favored area, the inhabitants of neighboring towns burned so frequently and graze so intensively that…the timber was greatly injured, and the land became hard to subdue...In the long run, cattle tended to encourage the growth of woody, thorn-bearing plants which they could not eat and which, once established, were very difficult to remove”. These practices were methods of simplifying labor for colonial settlers in new lands when they were not familiar with traditional Indigenous agricultural methods. Those Indigenous communities were not consulted but rather forced out of their homelands so European settlers could commodify their resources. The practice of intensive land burning and turning loose cattle ruined soil fertility and prohibited sustainable crop growth. While colonists utilized fire to clear land, certain prescribed burning practices are common and valuable to increase biodiversity and in turn, benefit soil fertility. Without consideration of

5329-536: Was “allowed to harm or remove an earthworm for fear of offending the deity of fertility”. In Ghana and Liberia, it is a long-withstanding practice to combine different types of waste to create fertile soil that is referred to as African Dark Earths. This soil, contains high concentrations of calcium, phosphorus, and carbon. Albert Howard is credited as the first Westerner to publish Native techniques of sustainable agriculture. As noted by Howard in 1944, “In all future studies of disease we must, therefore, always begin with

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