Tillage erosion is a form of soil erosion occurring in cultivated fields due to the movement of soil by tillage. [1] [2] There is growing evidence that tillage erosion is a major soil erosion process in agricultural lands, surpassing water and wind erosion in many fields all around the world, especially on sloping and hilly lands [3] [4] [5] A signature spatial pattern of soil erosion shown in many water erosion handbooks and pamphlets, the eroded hilltops, is actually caused by tillage erosion as water erosion mainly causes soil losses in the midslope and lowerslope segments of a slope, not the hilltops. [6] [1] [3] Tillage erosion results in soil degradation, which can lead to significant reduction in crop yield and, therefore, economic losses for the farm. [7] [8]
Conceptually, the process of tillage erosion (ETi) can be described as a function of tillage erosivity (ET) and landscape erodibility (EL): [9]
ETi = f(ET, EL)
Tillage erosivity (ET) is defined as the propensity of a tillage operation, or a sequence of operations, to erode soil and is affected by the design and operation of the tillage implement (e.g., the size, arrangement and shape of tillage tools, tillage speed and depth). Landscape erodibility (EL) is defined as the propensity of a landscape to be eroded by tillage and is affected by the landscape topography (e.g., slope gradient and slope curvature) and soil properties (e.g., texture, structure, bulk density and soil moisture content).
Tillage erosion occurs as a result of changes in tillage translocation (soil movement by tillage) across the field. Tillage translocation is expressed as a linear function of slope gradient (θ) and slope curvature (φ): [9]
TM = α + β θ + γ φ
where TM is tillage translocation; α is the tillage translocation on flat soil surface; β and γ are coefficients which describe the additional translocation resulting from slope gradient and slope curvature, respectively. Tillage erosion, which is the net tillage translocation, is then calculated as:
TMNet = ΔTM = β Δθ + γ Δφ
For a unit area A in a cultivated field, tillage erosion rate for a tillage operation can be calculated as:
ETi = (TMout – TMin) / A = [β (θout - θin) + γ (φout - φin)] / A
where ETi is tillage erosion rate for the tillage operation; TMout is the outgoing tillage translocation or the amount of soil moving out from A; and TMin is the incoming tillage translocation or the amount of soil moving into A; θout is the outgoing slope gradient along the tillage direction, θin is the incoming slope gradient along the tillage direction; φout is the outgoing slope curvature along the tillage direction, φin is the incoming slope curvature along the tillage direction.
Typical spatial patterns of tillage erosion observed in cultivated field are either local topography related: soil loss from hilltops (convexities) and soil accumulation in depressions (concavities); or field boundary related: soil loss from the downside of a field boundary and soil accumulation in the upper-side of a field boundary. [3] [6] Local topography related tillage erosion is most pronounced in hummocky landscapes with eroded hilltops that often exhibit a light soil color due to the loss of organic-rich topsoil, a phenomenon often mistakenly assumed to be the result of water erosion. Field boundary related tillage erosion is determined by not only topography but also tillage directions and it is responsible for the forming of tillage banks and terraces. [10] [11]
Tillage erosion can be measured via the measurement of tillage translocation or the measurement of soil loss and accumulation. [12] Tillage translocation is normally measured with a tracer that is incorporated into the soil in plots. The distributions of the tracer before and after tillage are used to calculate tillage translocation. Two types of tracers, point tracers, [13] [14] [15] [16] and bulk tracers [17] [18] [19] [20] [21] are being used. Whereas point tracers are easy to implement, bulk tracers can provide more information regarding the dispersion of the soil during the translocation process. Soil loss and accumulation by tillage erosion can be estimated from changes in surface elevation. For example, elevation of a tilled field can be compared to an adjacent reference object that has not been eroded such as a fence line or hedgerow. Decreases in surface elevation indicate soil losses while increases in elevation are evidence of soil accumulations. Elevation change can also be determined by taking repeated measurements of the soil surface elevations with high accuracy topographic survey techniques such as RTK GPS, total station and close range photogrammetry. Another way to estimate soil loss and accumulation is to measure the changes in soil properties , such as soil organic matter content. However, soil organic matter can be affected by many factors so it is not a very reliable method. Since 1980s, radioisotopes such as Cs-137 and Pb-210 have been used to provide much more accurate soil erosion estimates. [22] [23] [24] [25]
Tillage erosion causes loss of fertile top soil from the eroding portion of the field. [3] [34] As the top soil layer is getting thinner, subsequent tillage operations will bring up sublayer soil and mix it into the tillage layer. This vertical mixing results in soil degradation in the eroding portion of the field. Moreover, the degraded soil in the eroding portion of the field will be horizontally mixed into adjacent areas through tillage translocation. [28] Over time, with the vertical and horizontal mixing, tillage translocation will cause the spread the subsoil from the eroding portion to over the entire field, including areas of tillage accumulation.
Subsoil often has undesirable soil properties for crop growth (e.g., less organic carbon, poor structure). When subsoil is mixed into the tillage layer due to tillage erosion, crop productivity will be negatively impacted. The loss due to such crop productivity loss is enormous given that the damage is long lasting and it takes great effort to restore the soil quality to its original level. [7] [8]
As soil is degraded due to tillage erosion, it can lead to some environmental issues such as increased nutrient losses and GHG emissions. [35] [36] [37] For carbon sequestration in particular, although degraded soil in the eroding portion may reduce carbon sequestration, the burial of top soil in the soil accumulation regions create a large sink for carbon sequestration [38]
Tillage erosion is a dominant process for landform evolution in many agricultural fields. [39] [1] It flattens convexities and concavities and creates tillage walls and banks along field boundaries [10] [40] With a consistent pattern, it can even create topographic features in flat fields. For example, when a one way throw tillage equipment (e.g., mouldboard plough) is used in a circular pattern over many years, it can create a “>--<” pattern ditch in the middle of the field. [32]
Cultivated fields are subject to not only tillage erosion but also water and wind erosion. [1] [7] There are linkages and interactions between these erosion processes. [41] [31] Linkages and interactions refer to the additive and non-additive effects, respectively, between different erosion processes. Total soil erosion may be increased or decreased due to positive and negative linkages, respectively, between different erosion processes. [6] [37] Interactions occur when one erosion process changes the erodibility of the landscape for another erosion process, or when one process works as a delivery mechanism for another erosion process. For example, soil degradation caused by tillage erosion likely will increase the erodibility of the soil to water and wind erosion. Another example is the interactions between tillage and water erosion around water eroded channels, especially ephemeral gullies. Tillage is often used to eliminate these channels and ephemeral gullies, in which tillage translocation essentially serves as a delivery mechanism to transport soil to areas most susceptible to water erosion. [4]
Tillage erosion can be mitigated by reducing the intensity of tillage. [4] This includes reducing the frequency of tillage, the speed and depth of tillage, and the size of the tillage implement. However, conservation tillage equipment designed to reduce water erosion may not be able to reduce tillage erosion and field operations traditionally not considered tillage operations may cause significant amount of tillage erosion (e.g., harvesting for potato). [42] Contour tillage will reduce the variation of tillage speed and depth, resulting in reduced changes in tillage translocation across the field. This will also lead to lower tillage erosion. In addition, downslope movement of soil can be compensated by using a reversible moldboard plough to throw the furrow upslope. [43] [1] Physically moving soil from accumulation areas (e.g., depressions) to the eroding portion of the field (e.g., hilltops), a practice termed soil landscape restoration, can mitigate the impact of tillage erosion by restoring soil productivity at the eroding portion of the field. [43] [1]
Erosion is the action of surface processes that removes soil, rock, or dissolved material from one location on the Earth's crust and then transports it to another location where it is deposited. Erosion is distinct from weathering which involves no movement. Removal of rock or soil as clastic sediment is referred to as physical or mechanical erosion; this contrasts with chemical erosion, where soil or rock material is removed from an area by dissolution. Eroded sediment or solutes may be transported just a few millimetres, or for thousands of kilometres.
A glacier is a persistent body of dense ice that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires distinguishing features, such as crevasses and seracs, as it slowly flows and deforms under stresses induced by its weight. As it moves, it abrades rock and debris from its substrate to create landforms such as cirques, moraines, or fjords. Although a glacier may flow into a body of water, it forms only on land and is distinct from the much thinner sea ice and lake ice that form on the surface of bodies of water.
Tillage is the agricultural preparation of soil by mechanical agitation of various types, such as digging, stirring, and overturning. Examples of human-powered tilling methods using hand tools include shoveling, picking, mattock work, hoeing, and raking. Examples of draft-animal-powered or mechanized work include ploughing, rototilling, rolling with cultipackers or other rollers, harrowing, and cultivating with cultivator shanks (teeth).
Crop rotation is the practice of growing a series of different types of crops in the same area across a sequence of growing seasons. This practice reduces the reliance of crops on one set of nutrients, pest and weed pressure, along with the probability of developing resistant pests and weeds.
Soil erosion is the denudation or wearing away of the upper layer of soil. It is a form of soil degradation. This natural process is caused by the dynamic activity of erosive agents, that is, water, ice (glaciers), snow, air (wind), plants, and animals. In accordance with these agents, erosion is sometimes divided into water erosion, glacial erosion, snow erosion, wind (aeolian) erosion, zoogenic erosion and anthropogenic erosion such as tillage erosion. Soil erosion may be a slow process that continues relatively unnoticed, or it may occur at an alarming rate causing a serious loss of topsoil. The loss of soil from farmland may be reflected in reduced crop production potential, lower surface water quality and damaged drainage networks. Soil erosion could also cause sinkholes.
Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand and silt can be carried in suspension in river water and on reaching the sea bed deposited by sedimentation; if buried, they may eventually become sandstone and siltstone through lithification.
A gully is a landform created by running water, mass movement, or commonly a combination of both eroding sharply into soil or other relatively erodible material, typically on a hillside or in river floodplains or terraces.
No-till farming is an agricultural technique for growing crops or pasture without disturbing the soil through tillage. No-till farming decreases the amount of soil erosion tillage causes in certain soils, especially in sandy and dry soils on sloping terrain. Other possible benefits include an increase in the amount of water that infiltrates into the soil, soil retention of organic matter, and nutrient cycling. These methods may increase the amount and variety of life in and on the soil. While conventional no-tillage systems use herbicides to control weeds, organic systems use a combination of strategies, such as planting cover crops as mulch to suppress weeds.
Nutrient management is the science and practice directed to link soil, crop, weather, and hydrologic factors with cultural, irrigation, and soil and water conservation practices to achieve optimal nutrient use efficiency, crop yields, crop quality, and economic returns, while reducing off-site transport of nutrients (fertilizer) that may impact the environment. It involves matching a specific field soil, climate, and crop management conditions to rate, source, timing, and place of nutrient application.
There are dozens of erosion prediction models. Some models focus on long-term erosion, as a component of landscape evolution. However, many erosion models were developed to quantify the effects of accelerated soil erosion i.e. soil erosion as influenced by human activity.
Contour plowing or contour farming is the farming practice of plowing and/or planting across a slope following its elevation contour lines. These contour line furrows create a water break, reducing the formation of rills and gullies during heavy precipitation and allowing more time for the water to settle into the soil. In contour plowing, the ruts made by the plow run perpendicular rather than parallel to the slopes, generally furrows that curve around the land and are level. This method is also known for preventing tillage erosion. Tillage erosion is the soil movement and erosion by tilling a given plot of land. A similar practice is contour bunding where stones are placed around the contours of slopes. Contour plowing has been proven to reduce fertilizer loss, power, time consumption, and wear on machines, as well as to increase crop yields and reduce soil erosion.
Soil conservation is the prevention of loss of the topmost layer of the soil from erosion or prevention of reduced fertility caused by over usage, acidification, salinization or other chemical soil contamination.
In agriculture, a living mulch is a cover crop interplanted or undersown with a main crop, and intended to serve the purposes of a mulch, such as weed suppression and regulation of soil temperature. Living mulches grow for a long time with the main crops, whereas cover crops are incorporated into the soil or killed with herbicides.
Erosion control is the practice of preventing or controlling wind or water erosion in agriculture, land development, coastal areas, river banks and construction. Effective erosion controls handle surface runoff and are important techniques in preventing water pollution, soil loss, wildlife habitat loss and human property loss.
In hillslope geomorphology, a rill is a shallow channel cut into soil by the erosive action of flowing surface water. Similar but smaller incised channels are known as microrills; larger incised channels are known as gullies.
The Universal Soil Loss Equation (USLE) is a widely used mathematical model that describes soil erosion processes.
The Accona Desert refers to a hilly area in the Siena province of Italy, within the municipality of Asciano [43°14'4.30"N; 11°33'37.48"E]. The term is often used to include the Biancana site of Le Fiorentine - Leonina [ 43°17'32.95”N; 11°26'54.07"E]. Despite its name, its climate is Mediterranean, with a hot, dry summer and almost 800 mm/y of rain.
The environmental impact of agriculture is the effect that different farming practices have on the ecosystems around them, and how those effects can be traced back to those practices. The environmental impact of agriculture varies widely based on practices employed by farmers and by the scale of practice. Farming communities that try to reduce environmental impacts through modifying their practices will adopt sustainable agriculture practices. The negative impact of agriculture is an old issue that remains a concern even as experts design innovative means to reduce destruction and enhance eco-efficiency. Animal agriculture practices tend to be more environmentally destructive than agricultural practices focused on fruits, vegetables and other biomass. The emissions of ammonia from cattle waste continue to raise concerns over environmental pollution.
A catena in soil science (pedology) is a series of distinct but co-evolving soils arrayed down a slope. Each soil type or "facet" differs somewhat from its neighbours, but all occur in the same climate and on the same underlying parent material. A mature catena is in equilibrium as the processes of deposition and erosion are in balance.
Soil compaction, also known as soil structure degradation, is the increase of bulk density or decrease in porosity of soil due to externally or internally applied loads. Compaction can adversely affect nearly all physical, chemical and biological properties and functions of soil. Together with soil erosion, it is regarded as the "costliest and most serious environmental problem caused by conventional agriculture."
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