Soil , also commonly referred to as earth , is a mixture of organic matter , minerals , gases , liquids , and organisms that together support the life of plants and soil organisms . Some scientific definitions distinguish dirt from soil by restricting the former term specifically to displaced soil.
141-628: Compost is a mixture of ingredients used as plant fertilizer and to improve soil 's physical, chemical, and biological properties. It is commonly prepared by decomposing plant and food waste, recycling organic materials, and manure. The resulting mixture is rich in plant nutrients and beneficial organisms , such as bacteria, protozoa, nematodes, and fungi. Compost improves soil fertility in gardens , landscaping , horticulture , urban agriculture , and organic farming , reducing dependency on commercial chemical fertilizers. The benefits of compost include providing nutrients to crops as fertilizer , acting as
282-407: A biomass solid fuel and are raw material for producing wood pulp . They may also be used as an organic mulch in gardening , landscaping , and ecosystem restoration ; in bioreactors for denitrification ; and as a substrate for mushroom cultivation . The process of making woodchips is called wood chipping and is done using a wood chipper . The types of woodchips formed following chipping
423-424: A mean prokaryotic density of roughly 10 organisms per gram, whereas the ocean has no more than 10 prokaryotic organisms per milliliter (gram) of seawater. Organic carbon held in soil is eventually returned to the atmosphere through the process of respiration carried out by heterotrophic organisms, but a substantial part is retained in the soil in the form of soil organic matter; tillage usually increases
564-470: A mulch are at least three inches thick. It has a mixed reputation in gardening. It has been promoted for use in habitat restoration projects. As the ramial chipped wood decomposes it improves the soil structure, permeability, bioactivity, and nutrient availability of the soil. Woodchips do not meet American Society for Testing and Materials standards for use as playground surfacing material, and as of 2011 are illegal to use as playground surfacing in
705-513: A soil conditioner , increasing the humus or humic acid contents of the soil, and introducing beneficial microbes that help to suppress pathogens in the soil and reduce soil-borne diseases. At the simplest level, composting requires gathering a mix of "greens" (green waste) and "browns" (brown waste). Greens are materials rich in nitrogen, such as leaves, grass, and food scraps. Browns are woody materials rich in carbon, such as stalks, paper, and wood chips. The materials break down into humus in
846-422: A 'denitrifying woodchip bioreactor ' which has been used for several decades as an emerging biotechnology to treat agricultural wastewater by removing nitrates . It is a subsurface system where denitrification by micro-organisms utilizing a carbon source (as electron donor) reduces the nitrate into a harmless nitrogen gas . Denitrifying woodchip bioreactor have a low construction and operational costs with
987-766: A comparatively long lifespan going up to 15 years. The interest in such a technique has grown in recent years and has expanded into the mining industry. A 2013 experiment showed that after 70 days of startup, a woodchip pile loaded with liquid pig manure at 5 L/m /day removed an average of 90% of nitrate after one month. However, if the environmental conditions do not support complete denitrification, undesirable greenhouse gas such as nitrous oxide gas and methane could be produced. Woodchips have been traditionally used as solid fuel for space heating or in energy plants to generate electric power from renewable energy . The main source of forest chips in Europe and in most of
1128-400: A compost is not recommended due to the speed with which it may dry, the possible presence of phytotoxins in immature compost that may inhibit germination, and the possible tie up of nitrogen by incompletely decomposed lignin. It is very common to see blends of 20–30% compost used for transplanting seedlings . Compost can be used to increase plant immunity to diseases and pests. Compost tea
1269-460: A different use depending on the type of processing the woodchips will undergo. Woodchips used for chemical pulp must be relatively uniform in size and free of bark. The optimum size varies with the wood species. It is important to avoid damage to the wood fibres as this is important for the pulp properties. For roundwood it is most common to use disk chippers. A typical size of the disk is 2.0–3.5 m in diameter, 10–25 cm in thickness and weight
1410-857: A few secondary schools in Northern Ontario as well as a chip-fired boiler at the National Forestry Institute in Petawawa. In the late 1980s, the Ontario provincial government in conjunction with the federal government subsidized building three co-generation plants next to sawmills. The first one was constructed in 1987 in Chapleau followed by a plant built in Cochrane in 1989 and the largest one in Kirkland Lake which
1551-472: A form of cadmium oxide , cadmium silicate (CdSiO 3 ); authors noted that adding it to agricultural or forest soils in the long-term could cause a problem with accumulation of cadmium. Like coal, wood combustion is a known source of mercury emissions, particularly in northern climates during winter. The mercury is both gaseous as elemental mercury (especially when wood pellets are burned) or mercury oxide, and solid PM2.5 particulate matter when untreated wood
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#17327877200141692-594: A habitat for soil organisms , a recycling system for nutrients and organic wastes , a regulator of water quality , a modifier of atmospheric composition , and a medium for plant growth , making it a critically important provider of ecosystem services . Since soil has a tremendous range of available niches and habitats , it contains a prominent part of the Earth's genetic diversity . A gram of soil can contain billions of organisms, belonging to thousands of species, mostly microbial and largely still unexplored. Soil has
1833-446: A higher probability of jamming in small feed mechanisms. Thus, sooner or later, one or more jams is likely to occur. This reduces the reliability of the system, as well as increasing maintenance costs. Despite what some pellet stove manufacturers may say, researchers who are experienced with woodchips, say they are not compatible with the 2 inch (5 cm) auger used in pellet stoves. Woodchips are similar to wood pellets , in that
1974-518: A mouth mask and gloves must be worn to protect from diseases that can be contracted from handling compost, including: Oocytes are rendered unviable by temperatures over 50 °C (122 °F). Compost adds organic matter to the soil and increases the nutrient content and biodiversity of microbes in soil. Composting at home reduces the amount of green waste being hauled to dumps or composting facilities. The reduced volume of materials being picked up by trucks results in fewer trips, which in turn lowers
2115-549: A pH of 9, plant growth is reduced. High pH results in low micro-nutrient mobility, but water-soluble chelates of those nutrients can correct the deficit. Sodium can be reduced by the addition of gypsum (calcium sulphate) as calcium adheres to clay more tightly than does sodium causing sodium to be pushed into the soil water solution where it can be washed out by an abundance of water. There are acid-forming cations (e.g. hydronium, aluminium, iron) and there are base-forming cations (e.g. calcium, magnesium, sodium). The fraction of
2256-468: A pathogen dies depends on the pathogen, how long the temperature is maintained (seconds to weeks), and pH. Compost products such as compost tea and compost extracts have been found to have an inhibitory effect on Fusarium oxysporum , Rhizoctonia species , and Pythium debaryanum , plant pathogens that can cause crop diseases. Aerated compost teas are more effective than compost extracts. The microbiota and enzymes present in compost extracts also have
2397-412: A process taking months. Composting can be a multistep, closely monitored process with measured inputs of water, air, and carbon- and nitrogen-rich materials. The decomposition process is aided by shredding the plant matter, adding water, and ensuring proper aeration by regularly turning the mixture in a process using open piles or windrows . Fungi , earthworms , and other detritivores further break up
2538-614: A raw material for technical wood processing. In industry, processing of bark chips is often separated after peeling the logs due to different chemical properties. Only the heartwood and sapwood are useful for making pulp. Bark contains relatively few useful fibres and is removed and used as fuel to provide steam for use in the pulp mill . Most pulping processes require that the wood be chipped and screened to provide uniform sized chips. Woodchips are also used as landscaping and garden mulch , for water conservation , weed control, and reducing and preventing soil erosion . Woodchips when used as
2679-687: A reduction in the other. The pore space allows for the infiltration and movement of air and water, both of which are critical for life existing in soil. Compaction , a common problem with soils, reduces this space, preventing air and water from reaching plant roots and soil organisms. Given sufficient time, an undifferentiated soil will evolve a soil profile that consists of two or more layers, referred to as soil horizons. These differ in one or more properties such as in their texture , structure , density , porosity, consistency, temperature, color, and reactivity . The horizons differ greatly in thickness and generally lack sharp boundaries; their development
2820-731: A result of a trade-off between toxicity and requirement most nutrients are better available to plants at moderate pH, although most minerals are more soluble in acid soils. Soil organisms are hindered by high acidity, and most agricultural crops do best with mineral soils of pH 6.5 and organic soils of pH 5.5. Given that at low pH toxic metals (e.g. cadmium, zinc, lead) are positively charged as cations and organic pollutants are in non-ionic form, thus both made more available to organisms, it has been suggested that plants, animals and microbes commonly living in acid soils are pre-adapted to every kind of pollution, whether of natural or human origin. In high rainfall areas, soils tend to acidify as
2961-401: A result, layers (horizons) form in the soil profile. The alteration and movement of materials within a soil causes the formation of distinctive soil horizons . However, more recent definitions of soil embrace soils without any organic matter, such as those regoliths that formed on Mars and analogous conditions in planet Earth deserts. An example of the development of a soil would begin with
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#17327877200143102-408: A silt loam soil by percent volume A typical soil is about 50% solids (45% mineral and 5% organic matter), and 50% voids (or pores) of which half is occupied by water and half by gas. The percent soil mineral and organic content can be treated as a constant (in the short term), while the percent soil water and gas content is considered highly variable whereby a rise in one is simultaneously balanced by
3243-412: A soil can be said to be developed, and can be described further in terms of color, porosity, consistency, reaction ( acidity ), etc. Water is a critical agent in soil development due to its involvement in the dissolution, precipitation, erosion, transport, and deposition of the materials of which a soil is composed. The mixture of water and dissolved or suspended materials that occupy the soil pore space
3384-399: A soil determines its ability to supply available plant nutrients and affects its physical properties and the health of its living population. In addition, a soil's chemistry also determines its corrosivity , stability, and ability to absorb pollutants and to filter water. It is the surface chemistry of mineral and organic colloids that determines soil's chemical properties. A colloid
3525-407: A suppressive effect on fungal plant pathogens. Compost is a good source of biocontrol agents like B. subtilis , B. licheniformis, and P. chrysogenum that fight plant pathogens. Sterilizing the compost, compost tea, or compost extracts reduces the effect of pathogen suppression. When turning compost that has not gone through phases where temperatures above 50 °C (122 °F) are reached,
3666-531: A suppressive effect on plant pathogens and soil-borne diseases. The efficacy is influenced by a number of factors, such as the preparation process, the type of source the conditions of the brewing process, and the environment of the crops. Adding nutrients to compost tea can be beneficial for disease suppression, although it can trigger the regrowth of human pathogens like E. coli and Salmonella . Compost extracts are unfermented or non-brewed extracts of leached compost contents dissolved in any solvent. Compost
3807-492: A thermophilic stage for days or weeks. This is hot composting and is the usual method for large-scale municipal facilities and agricultural operations. The Berkeley method produces finished compost in 18 days. It requires assembly of at least 1 cubic metre (35 cu ft) of material at the outset and needs turning every two days after an initial four-day phase. Such short processes involve some changes to traditional methods, including smaller, more homogenized particle sizes in
3948-472: A valence of two, converts to (40 ÷ 2) × 1 milliequivalent = 20 milliequivalents of hydrogen ion per 100 grams of dry soil or 20 meq/100 g. The modern measure of CEC is expressed as centimoles of positive charge per kilogram (cmol/kg) of oven-dry soil. Most of the soil's CEC occurs on clay and humus colloids, and the lack of those in hot, humid, wet climates (such as tropical rainforests ), due to leaching and decomposition, respectively, explains
4089-464: A variety of metals and pharmaceutical compounds. Insufficient processing of biosolids can also lead to problems when the material is applied to land. Urine can be put on compost piles or directly used as fertilizer. Adding urine to compost can increase temperatures, so can increase its ability to destroy pathogens and unwanted seeds. Unlike feces, urine does not attract disease-spreading flies (such as houseflies or blowflies ), and it does not contain
4230-553: Is 0.04%, but in the soil pore space it may range from 10 to 100 times that level, thus potentially contributing to the inhibition of root respiration. Calcareous soils regulate CO 2 concentration by carbonate buffering , contrary to acid soils in which all CO 2 respired accumulates in the soil pore system. At extreme levels, CO 2 is toxic. This suggests a possible negative feedback control of soil CO 2 concentration through its inhibitory effects on root and microbial respiration (also called soil respiration ). In addition,
4371-603: Is a measure of the acidity or alkalinity of the soil. More precisely, it is a measure of hydronium concentration in an aqueous solution and ranges in values from 0 to 14 (acidic to basic) but practically speaking for soils, pH ranges from 3.5 to 9.5, as pH values beyond those extremes are toxic to life forms. At 25 °C an aqueous solution that has a pH of 3.5 has 10 moles H 3 O (hydronium ions) per litre of solution (and also 10 moles per litre OH ). A pH of 7, defined as neutral, has 10 moles of hydronium ions per litre of solution and also 10 moles of OH per litre; since
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4512-509: Is a small, insoluble particle ranging in size from 1 nanometer to 1 micrometer , thus small enough to remain suspended by Brownian motion in a fluid medium without settling. Most soils contain organic colloidal particles called humus as well as the inorganic colloidal particles of clays . The very high specific surface area of colloids and their net electrical charges give soil its ability to hold and release ions . Negatively charged sites on colloids attract and release cations in what
4653-613: Is added after each use. This practice creates air pockets in the human waste to promote aerobic decomposition. This also improves the carbon-to-nitrogen ratio and reduces potential odor . Most composting toilet systems rely on mesophilic composting. Longer retention time in the composting chamber also facilitates pathogen die-off. The end product can also be moved to a secondary system – usually another composting step – to allow more time for mesophilic composting to further reduce pathogens. On open ground for growing wheat , corn , soybeans , and similar crops, compost can be broadcast across
4794-424: Is also a net sink of methane (CH 4 ) but a net producer of methane (a strong heat-absorbing greenhouse gas ) when soils are depleted of oxygen and subject to elevated temperatures. Soil atmosphere is also the seat of emissions of volatiles other than carbon and nitrogen oxides from various soil organisms, e.g. roots, bacteria, fungi, animals. These volatiles are used as chemical cues, making soil atmosphere
4935-421: Is an aerobic method of decomposing organic solid wastes, so it can be used to recycle organic material. The process involves decomposing organic material into a humus-like material, known as compost, which is a good fertilizer for plants. Composting organisms require four equally important ingredients to work effectively: Certain ratios of these materials allow microorganisms to work at a rate that will heat up
5076-418: Is an ongoing and dynamic process; adding new sources of carbon and nitrogen consistently, as well as active management, is important. Organisms can break down organic matter in compost if provided with the correct mixture of water, oxygen, carbon, and nitrogen. They fall into two broad categories: chemical decomposers, which perform chemical processes on the organic waste, and physical decomposers, which process
5217-464: Is assumed acid-forming cations). Base saturation is almost in direct proportion to pH (it increases with increasing pH). It is of use in calculating the amount of lime needed to neutralise an acid soil (lime requirement). The amount of lime needed to neutralize a soil must take account of the amount of acid forming ions on the colloids (exchangeable acidity), not just those in the soil water solution (free acidity). The addition of enough lime to neutralize
5358-401: Is called the soil solution. Since soil water is never pure water, but contains hundreds of dissolved organic and mineral substances, it may be more accurately called the soil solution. Water is central to the dissolution , precipitation and leaching of minerals from the soil profile . Finally, water affects the type of vegetation that grows in a soil, which in turn affects the development of
5499-548: Is cost, the advantage of wood pellets is the controlled fuel value. The use of woodchips in automated heating systems, is based on a robust technology. The size of the woodchips, moisture content, and the raw material from which the chips are made are particularly important when burning wood chips in small plants. Unfortunately, there are not many standards to decide the fractions of woodchip. However, as of March 2018, The American National Standards Institute approved AD17225-4 Wood Chip Heating Fuel Quality Standard. The full title of
5640-421: Is dependent on the type of parent material , the processes that modify those parent materials, and the soil-forming factors that influence those processes. The biological influences on soil properties are strongest near the surface, though the geochemical influences on soil properties increase with depth. Mature soil profiles typically include three basic master horizons: A, B, and C. The solum normally includes
5781-652: Is dependent on the type of wood chipper used and the material from which they are made. Woodchip varieties include: forest chips (from forested areas), wood residue chips (from untreated wood residues, recycled wood and off-cuts), sawing residue chips (from sawmill residues), and short rotation forestry chips (from energy crops). The raw materials of woodchips can be pulpwood , waste wood, and residual wood from agriculture , landscaping , logging , and sawmills . Woodchips can also be produced from remaining forestry materials including tree crowns , branches, unsaleable materials or undersized trees. Forestry operations provide
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5922-414: Is found in solid human waste. Phosphorus, which helps plants convert sunlight into energy in the form of ATP, can be found in liquid human waste. Solid human waste can be collected directly in composting toilets , or indirectly in the form of sewage sludge after it has undergone treatment in a sewage treatment plant . Both processes require capable design, as potential health risks need to be managed. In
6063-580: Is generally considered a source of nitrogen and includes pre- and post-consumer food waste , grass clippings, garden trimmings, and fresh leaves. Animal carcasses, roadkill, and butcher residue can also be composted, and these are considered nitrogen sources. Brown waste is a carbon source. Typical examples are dried vegetation and woody material such as fallen leaves, straw, woodchips, limbs, logs, pine needles, sawdust, and wood ash, but not charcoal ash. Products derived from wood such as paper and plain cardboard are also considered carbon sources. On many farms,
6204-424: Is in effect creating a nurse log that is covered with soil. Benefits of Hügelkultur garden beds include water retention and warming of soil. Buried wood acts like a sponge as it decomposes, able to capture water and store it for later use by crops planted on top of the bed. A composting toilet is a type of dry toilet that treats human waste by a biological process called composting. This process leads to
6345-649: Is included in the broader concept of regolith , which also includes other loose material that lies above the bedrock, as can be found on the Moon and other celestial objects . Soil is a major component of the Earth 's ecosystem . The world's ecosystems are impacted in far-reaching ways by the processes carried out in the soil, with effects ranging from ozone depletion and global warming to rainforest destruction and water pollution . With respect to Earth's carbon cycle , soil acts as an important carbon reservoir , and it
6486-401: Is induced. Capillary action is responsible for moving groundwater from wet regions of the soil to dry areas. Subirrigation designs (e.g., wicking beds , sub-irrigated planters ) rely on capillarity to supply water to plant roots. Capillary action can result in an evaporative concentration of salts, causing land degradation through salination . Soil moisture measurement —measuring
6627-531: Is likely home to 59 ± 15% of the species on Earth. Enchytraeidae (worms) have the greatest percentage of species in soil (98.6%), followed by fungi (90%), plants (85.5%), and termites ( Isoptera ) (84.2%). Many other groups of animals have substantial fractions of species living in soil, e.g. about 30% of insects , and close to 50% of arachnids . While most vertebrates live above ground (ignoring aquatic species), many species are fossorial , that is, they live in soil, such as most blind snakes . The chemistry of
6768-591: Is low in Quebec due to low hydroelectricity rates but a small town is using wood chips as an alternative to road salt for icy roads. EMC3 Technologies started producing wood chips coated with magnesium chloride in November 2017 for the town and has claimed it maintains traction in -30 degrees Celsius compared to regular road salt at -15 degrees Celsius. In Ontario, wood chip operations include a college in Brockville,
6909-463: Is made up of extracts of fermented water leached from composted materials. Composts can be either aerated or non-aerated depending on its fermentation process. Compost teas are generally produced from adding compost to water in a ratio of 1:4–1:10, occasionally stirring to release microbes . There is debate about the benefits of aerating the mixture. Non-aerated compost tea is cheaper and less labor-intensive, but there are conflicting studies regarding
7050-477: Is more advanced. Most plant nutrients, with the exception of nitrogen , originate from the minerals that make up the soil parent material. Some nitrogen originates from rain as dilute nitric acid and ammonia , but most of the nitrogen is available in soils as a result of nitrogen fixation by bacteria . Once in the soil-plant system, most nutrients are recycled through living organisms, plant and microbial residues (soil organic matter), mineral-bound forms, and
7191-581: Is not necessary with cold composting, although a risk exists that parts of the pile may go anaerobic as it becomes compacted or waterlogged. Composting can destroy some pathogens and seeds , by reaching temperatures above 50 °C (122 °F). Dealing with stabilized compost – i.e. composted material in which microorganisms have finished digesting the organic matter and the temperature has reached between 50 and 70 °C (122 and 158 °F) – poses very little risk, as these temperatures kill pathogens and even make oocysts unviable. The temperature at which
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#17327877200147332-437: Is potentially one of the most reactive to human disturbance and climate change . As the planet warms, it has been predicted that soils will add carbon dioxide to the atmosphere due to increased biological activity at higher temperatures, a positive feedback (amplification). This prediction has, however, been questioned on consideration of more recent knowledge on soil carbon turnover. Soil acts as an engineering medium,
7473-479: Is rarely used alone, plants can flourish from mixed soil that includes a mix of compost with other additives such as sand , grit, bark chips, vermiculite , perlite , or clay granules to produce loam . Compost can be tilled directly into the soil or growing medium to boost the level of organic matter and the overall fertility of the soil. Compost that is ready to be used as an additive is dark brown or even black with an earthy smell. Generally, direct seeding into
7614-409: Is referred to as cation exchange . Cation-exchange capacity is the amount of exchangeable cations per unit weight of dry soil and is expressed in terms of milliequivalents of positively charged ions per 100 grams of soil (or centimoles of positive charge per kilogram of soil; cmol c /kg ). Similarly, positively charged sites on colloids can attract and release anions in the soil, giving
7755-514: Is regulated in Canada and Australia as well. Soil Soil consists of a solid phase of minerals and organic matter (the soil matrix), as well as a porous phase that holds gases (the soil atmosphere) and water (the soil solution). Accordingly, soil is a three- state system of solids, liquids, and gases. Soil is a product of several factors: the influence of climate , relief (elevation, orientation, and slope of terrain), organisms, and
7896-764: Is sold as bagged potting mixes in garden centers and other outlets. This may include composted materials such as manure and peat but is also likely to contain loam, fertilizers, sand, grit, etc. Varieties include multi-purpose composts designed for most aspects of planting, John Innes formulations, grow bags, designed to have crops such as tomatoes directly planted into them. There are also a range of specialist composts available, e.g. for vegetables, orchids, houseplants, hanging baskets, roses, ericaceous plants, seedlings, potting on, etc. Compost can also be used for land and stream reclamation, wetland construction , and landfill cover. The temperatures generated by compost can be used to heat greenhouses , such as by being placed around
8037-459: Is up to 30 tons. The disk is fitted with 4 to 16 knives and driven with motors of ½ –2 MW. Drum chippers are normally used for wood residuals from saw mills or other wood industry. There are four potential methods to move woodchips: pneumatic , conveyor belt , hopper with direct chute, and batch system (manual conveyance). A disk wood chipper features a flywheel made of steel and chopping blades with slotted disks. The blades slice through
8178-473: Is used. When wood burning is used for space heating, indoor emissions of 1,3-butadiene , benzene , formaldehyde and acetaldehyde , which are suspected or known carcinogenic compounds, are elevated. The cancer risk from these after exposure to wood smoke is estimated to be low in developed countries. Certain techniques for burning woodchips result in the production of biochar – effectively charcoal – which can be either utilised as charcoal, or returned to
8319-545: Is very little organic material. Basaltic minerals commonly weather relatively quickly, according to the Goldich dissolution series . The plants are supported by the porous rock as it is filled with nutrient-bearing water that carries minerals dissolved from the rocks. Crevasses and pockets, local topography of the rocks, would hold fine materials and harbour plant roots. The developing plant roots are associated with mineral-weathering mycorrhizal fungi that assist in breaking up
8460-427: Is very wet and usually not mixed with bedding material, must be mixed with straw or similar raw materials. Poultry manure must be blended with high-carbon, low-nitrogen materials. Human excreta , sometimes called "humanure" in the composting context, can be added as an input to the composting process since it is a nutrient-rich organic material. Nitrogen, which serves as a building block for important plant amino acids,
8601-490: The aeration of the soil and the ability of water to infiltrate and to be held within the soil. Soil water content can be measured as volume or weight . Soil moisture levels, in order of decreasing water content, are saturation, field capacity , wilting point , air dry, and oven dry. Field capacity describes a drained wet soil at the point water content reaches equilibrium with gravity. Irrigating soil above field capacity risks percolation losses. Wilting point describes
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#17327877200148742-444: The atmosphere , and the biosphere . Soil has four important functions : All of these functions, in their turn, modify the soil and its properties. Soil science has two basic branches of study: edaphology and pedology . Edaphology studies the influence of soils on living things. Pedology focuses on the formation, description (morphology), and classification of soils in their natural environment. In engineering terms, soil
8883-400: The decomposition of organic matter and turns human waste into compost-like material. Composting is carried out by microorganisms (mainly bacteria and fungi ) under controlled aerobic conditions. Most composting toilets use no water for flushing and are therefore called " dry toilets ". In many composting toilet designs, a carbon additive such as sawdust , coconut coir , or peat moss
9024-561: The humus form ), the copedon (in intermediary position, where most weathering of minerals takes place) and the lithopedon (in contact with the subsoil). The soil texture is determined by the relative proportions of the individual particles of sand , silt , and clay that make up the soil. The interaction of the individual mineral particles with organic matter, water, gases via biotic and abiotic processes causes those particles to flocculate (stick together) to form aggregates or peds . Where these aggregates can be identified,
9165-425: The mineralogy of those particles can strongly modify those properties. The mineralogy of the finest soil particles, clay, is especially important. Large numbers of microbes , animals , plants and fungi are living in soil. However, biodiversity in soil is much harder to study as most of this life is invisible, hence estimates about soil biodiversity have been unsatisfactory. A recent study suggested that soil
9306-613: The water-holding capacity of soils is vital for plant survival. Soils can effectively remove impurities, kill disease agents, and degrade contaminants , this latter property being called natural attenuation . Typically, soils maintain a net absorption of oxygen and methane and undergo a net release of carbon dioxide and nitrous oxide . Soils offer plants physical support, air, water, temperature moderation, nutrients, and protection from toxins. Soils provide readily available nutrients to plants and animals by converting dead organic matter into various nutrient forms. Components of
9447-424: The (powerplant) station by truck are less expensive than those delivered ... and shipped by railcar. The range of prices is typically between US$ 18 to US$ 30 per (wet)-ton delivered. In 2006, prices were US$ 15 and US$ 30 per wet-ton in the northeast. In the 20 years leading up to 2008, prices have fluctuated between US$ 60–70/oven-dry metric ton (odmt) in the southern states, and between US$ 60/odmt and US$ 160/odmt in
9588-448: The A and B horizons. The living component of the soil is largely confined to the solum, and is generally more prominent in the A horizon. It has been suggested that the pedon , a column of soil extending vertically from the surface to the underlying parent material and large enough to show the characteristics of all its horizons, could be subdivided in the humipedon (the living part, where most soil organisms are dwelling, corresponding to
9729-778: The CEC increases. Hence, pure sand has almost no buffering ability, though soils high in colloids (whether mineral or organic) have high buffering capacity . Buffering occurs by cation exchange and neutralisation . However, colloids are not the only regulators of soil pH. The role of carbonates should be underlined, too. More generally, according to pH levels, several buffer systems take precedence over each other, from calcium carbonate buffer range to iron buffer range. Wood chips Woodchips are small- to medium-sized pieces of wood formed by cutting or chipping larger pieces of wood such as trees , branches , logging residues, stumps , roots , and wood waste. Woodchips may be used as
9870-458: The Northwest. Wood chips have been used as a source of single-dwelling heating in Canada since the early days of settling but the development of oil and natural gas has dramatically decreased its usage. Most of the wood chip usage is by installations such as schools, hospitals and prisons. Prince Edward Island (PEI) has the most wood-chip plants due to high electricity rates and subsidies from
10011-527: The US, not being ADA-approved according to US department of Justice guidelines. Woodchips can also be used to infuse flavor and enhance the smoky taste to barbecued meats and vegetables. Several different species of wood can be used depending on the type of flavor wanted. For a mild, sweet fruity flavor, apple wood can be used while hickory gives a smoky, bacon-like flavor. Other different types of wood used are cherry, mesquite and pecan. Woodchips can be loaded into
10152-733: The United States, on-farm use is relatively rare since rates over 4 tons/acre may not be affordable. This results from an over-emphasis on "recycling organic matter" than on "sustainable nutrients." In countries such as Germany, where compost distribution and spreading are partially subsidized in the original waste fees, compost is used more frequently on open ground on the premise of nutrient "sustainability". In plasticulture , strawberries , tomatoes , peppers , melons , and other fruits and vegetables are grown under plastic to control temperature, retain moisture and control weeds. Compost may be banded (applied in strips along rows) and worked into
10293-406: The acronym CROPT. The physical properties of soils, in order of decreasing importance for ecosystem services such as crop production , are texture , structure , bulk density , porosity , consistency, temperature , colour and resistivity . Soil texture is determined by the relative proportion of the three kinds of soil mineral particles, called soil separates: sand , silt , and clay . At
10434-446: The addition of any more hydronium ions or aluminum hydroxyl cations drives the pH even lower (more acidic) as the soil has been left with no buffering capacity. In areas of extreme rainfall and high temperatures, the clay and humus may be washed out, further reducing the buffering capacity of the soil. In low rainfall areas, unleached calcium pushes pH to 8.5 and with the addition of exchangeable sodium, soils may reach pH 10. Beyond
10575-452: The apparent sterility of tropical soils. Live plant roots also have some CEC, linked to their specific surface area. Anion exchange capacity is the soil's ability to remove anions (such as nitrate , phosphate ) from the soil water solution and sequester those for later exchange as the plant roots release carbonate anions to the soil water solution. Those colloids which have low CEC tend to have some AEC. Amorphous and sesquioxide clays have
10716-426: The basic cations are forced off the soil colloids by the mass action of hydronium ions from usual or unusual rain acidity against those attached to the colloids. High rainfall rates can then wash the nutrients out, leaving the soil inhabited only by those organisms which are particularly efficient to uptake nutrients in very acid conditions, like in tropical rainforests . Once the colloids are saturated with H 3 O ,
10857-602: The basic composting ingredients are animal manure generated on the farm as a nitrogen source, and bedding as the carbon source. Straw and sawdust are common bedding materials. Nontraditional bedding materials are also used, including newspaper and chopped cardboard. The amount of manure composted on a livestock farm is often determined by cleaning schedules, land availability, and weather conditions. Each type of manure has its own physical, chemical, and biological characteristics. Cattle and horse manures, when mixed with bedding, possess good qualities for composting. Swine manure, which
10998-451: The case of home composting, a wide range of microorganisms, including bacteria, viruses, and parasitic worms, can be present in feces, and improper processing can pose significant health risks. In the case of large sewage treatment facilities that collect wastewater from a range of residential, commercial and industrial sources, there are additional considerations. The composted sewage sludge, referred to as biosolids , can be contaminated with
11139-572: The chute by gravity and the rotation of the drum where it is broken up by the steel blades. The drum type is noisy and creates large uneven chips but are more energy efficient than the disk type. A screw-type wood chipper contains a conical, screw-shaped blade {citation needed}. The blade rotation is set parallel to the opening so wood is pulled into the chipper by the spiral motion. Screw-type, also called high-torque rollers, are popular for residential use due to being quiet, easy to use and safer than disk and drum types. Woodchips are used primarily as
11280-426: The compost pile. Active management of the pile (e.g., turning over the compost heap) is needed to maintain sufficient oxygen and the right moisture level. The air/water balance is critical to maintaining high temperatures 130–160 °F (54–71 °C) until the materials are broken down. Composting is most efficient with a carbon-to-nitrogen ratio of about 25:1. Hot composting focuses on retaining heat to increase
11421-474: The composting of livestock. In-vessel composting generally describes a group of methods that confine the composting materials within a building, container, or vessel. In-vessel composting systems can consist of metal or plastic tanks or concrete bunkers in which air flow and temperature can be controlled, using the principles of a " bioreactor ". Generally the air circulation is metered in via buried tubes that allow fresh air to be injected under pressure, with
11562-407: The cost of woodchip fuel is comparable to coal . Solid biomass is an attractive fuel for addressing the concerns of the energy crisis and climate change , since the fuel is affordable, widely available, close to carbon neutral and thus climate-neutral in terms of carbon dioxide (CO 2 ), since in the ideal case only the carbon dioxide which was drawn in during the tree's growth and stored in
11703-586: The countries have been logging residues. It is expected that the shares of stumps and roundwood will increase in the future. As of 2013 in the EU, the estimates for biomass potential for energy, available under current 2018 conditions including sustainable use of the forest as well as providing wood to the traditional forest sectors, are: 277 million m , for above ground biomass and 585 million m for total biomass. The newer fuel systems for heating use either woodchips or wood pellets . The advantage of woodchips
11844-494: The decomposition rate, thus producing compost more quickly. Rapid composting is favored by having a carbon-to-nitrogen ratio of about 30 carbon units or less. Above 30, the substrate is nitrogen starved. Below 15, it is likely to outgas a portion of nitrogen as ammonia. Nearly all dead plant and animal materials have both carbon and nitrogen in different amounts. Fresh grass clippings have an average ratio of about 15:1 and dry autumn leaves about 50:1 depending upon species. Composting
11985-436: The dry limit for growing plants. During growing season, soil moisture is unaffected by functional groups or specie richness. Available water capacity is the amount of water held in a soil profile available to plants. As water content drops, plants have to work against increasing forces of adhesion and sorptivity to withdraw water. Irrigation scheduling avoids moisture stress by replenishing depleted water before stress
12126-695: The exhaust being extracted through a biofilter , with temperature and moisture conditions monitored using probes in the mass to allow maintenance of optimum aerobic decomposition conditions. Aerated static pile (ASP) composting refers to any of a number of systems used to biodegrade organic material without physical manipulation during primary composting . The blended admixture is usually placed on perforated piping, providing air circulation for controlled aeration . It may be in windrows , open or covered, or in closed containers . With regard to complexity and cost, aerated systems are most commonly used by larger, professionally managed composting facilities, although
12267-464: The expense and emissions impact of trucking, storing and/or shipping the wood. Woodchips are less expensive than cord wood , because the harvesting is faster and more highly automated. Woodchips are of greater supply, partly because all parts of a tree can be chipped, whereas small limbs and branches can require substantial labor to convert to cord wood. Cord wood generally needs to be "seasoned" or "dry" before it can be burned cleanly and efficiently. On
12408-436: The federal government. Nova Scotia has a 2.5 MW wood chip burning system that provides power to a textile factory as well as systems that provide power to a poultry processing plant, two hospitals and an agricultural college. The University of New Brunswick operates a wood chip burning furnace system to supply heat to the university, several industrial buildings, an apartment complex and a hospital. Usage of wood chips for heat
12549-419: The highest AEC, followed by the iron oxides. Levels of AEC are much lower than for CEC, because of the generally higher rate of positively (versus negatively) charged surfaces on soil colloids, to the exception of variable-charge soils. Phosphates tend to be held at anion exchange sites. Iron and aluminum hydroxide clays are able to exchange their hydroxide anions (OH ) for other anions. The order reflecting
12690-466: The input materials, controlling carbon-to-nitrogen ratio (C:N) at 30:1 or less, and careful monitoring of the moisture level. Cold composting is a slower process that can take up to a year to complete. It results from smaller piles, including many residential compost piles that receive small amounts of kitchen and garden waste over extended periods. Piles smaller than 1 cubic metre (35 cu ft) tend not to reach and maintain high temperatures. Turning
12831-644: The lost nutrients back into the soil. If woodchips are harvested as a by-product of sustainable forestry practices, then this is considered a source of renewable energy . Theoretically, whole-tree chip harvesting does not have as high a solar energy efficiency compared to short rotation coppice ; however, it can be an energy-efficient and low-cost method of harvesting. Woodchips and bark chips can be used as bulking agents in industrial composting of municipal biodegradable waste, particularly biosolids . Woodchip harvesting can be used in concert with creating man-made firebreaks , which are used as barriers to
12972-402: The most hardy of pathogens, such as parasitic worm eggs. Animal carcasses may be composted as a disposal option. Such material is rich in nitrogen. Human composting (also known as soil transformation) is a process for the final disposition of human remains in which microbes convert a deceased body into compost. It is also called natural organic reduction (NOR) or terramation. Although
13113-502: The movement and handling is more amenable to automation than cord wood, particularly for smaller systems. Woodchips are less expensive to produce than wood pellets, which must be processed in specialized facilities. While avoiding the costs associated with refinement, the lower density and higher moisture content of woodchips reduces their calorific value , substantially increasing the feedstock needed to generate an equivalent amount of heat. Greater physical volume requirements also increase
13254-428: The natural decomposition of human corpses into soil is a long-standing practice, a more rapid process that was developed in the early 21st century by Katrina Spade, entails encasing human corpses in wood chips, straw, and alfalfa until thermophile microbes decompose the body. In this manner, the transformation can be sped up to as little as 1–2 months. The accelerated process is based in part on techniques developed for
13395-429: The negatively charged colloids resist being washed downward by water and are out of reach of plant roots, thereby preserving the soil fertility in areas of moderate rainfall and low temperatures. There is a hierarchy in the process of cation exchange on colloids, as cations differ in the strength of adsorption by the colloid and hence their ability to replace one another ( ion exchange ). If present in equal amounts in
13536-412: The negatively-charged soil colloid exchange sites (CEC) that are occupied by base-forming cations is called base saturation . If a soil has a CEC of 20 meq and 5 meq are aluminium and hydronium cations (acid-forming), the remainder of positions on the colloids ( 20 − 5 = 15 meq ) are assumed occupied by base-forming cations, so that the base saturation is 15 ÷ 20 × 100% = 75% (the compliment 25%
13677-419: The next larger scale, soil structures called peds or more commonly soil aggregates are created from the soil separates when iron oxides , carbonates , clay, silica and humus , coat particles and cause them to adhere into larger, relatively stable secondary structures. Soil bulk density , when determined at standardized moisture conditions, is an estimate of soil compaction . Soil porosity consists of
13818-518: The only planting substrate. The particular crop and the seeds' sensitivity to nutrients, salts, etc. dictates the ratio of the blend, and maturity is important to insure that oxygen deprivation will not occur or that no lingering phyto-toxins remain. Compost can be added to soil, coir , or peat , as a tilth improver, supplying humus and nutrients. It provides a rich growing medium as absorbent material. This material contains moisture and soluble minerals, which provide support and nutrients . Although it
13959-736: The organic material. Aerobic bacteria and fungi manage the chemical process by converting the inputs into heat, carbon dioxide , and ammonium ions. Composting is an important part of waste management, since food and other compostable materials make up about 20% of waste in landfills, and due to anaerobic conditions, these materials take longer to biodegrade in the landfill. Composting offers an environmentally superior alternative to using organic material for landfill because composting reduces methane emissions due to anaerobic conditions, and provides economic and environmental co-benefits. For example, compost can also be used for land and stream reclamation, wetland construction, and landfill cover. Composting
14100-635: The other cations more weakly bound to colloids are pushed into solution as hydrogen ions occupy exchange sites ( protonation ). A low pH may cause the hydrogen of hydroxyl groups to be pulled into solution, leaving charged sites on the colloid available to be occupied by other cations. This ionisation of hydroxy groups on the surface of soil colloids creates what is described as pH-dependent surface charges. Unlike permanent charges developed by isomorphous substitution , pH-dependent charges are variable and increase with increasing pH. Freed cations can be made available to plants but are also prone to be leached from
14241-406: The other hand, woodchip systems are typically designed to cleanly and efficiently burn "green chips" with very high moisture content of 43–47% (wet basis). (see gasification and woodgas ) Compared to conventional timber harvesting, woodchip harvesting has a greater impact on the environment, since a larger proportion of biomass is removed. Increased use of woodchips can have negative effects on
14382-539: The outside edges. There are process and product guidelines in Europe that date to the early 1980s (Germany, the Netherlands, Switzerland) and only more recently in the UK and the US. In both these countries, private trade associations within the industry have established loose standards, some say as a stop-gap measure to discourage independent government agencies from establishing tougher consumer-friendly standards. Compost
14523-486: The overall emissions from the waste-management fleet. Potential sources of compostable materials, or feedstocks, include residential, agricultural, and commercial waste streams. Residential food or yard waste can be composted at home, or collected for inclusion in a large-scale municipal composting facility. In some regions, it could also be included in a local or neighborhood composting project. The two broad categories of organic solid waste are green and brown. Green waste
14664-492: The plant roots release hydrogen ions to the solution. CEC is the amount of exchangeable hydrogen cation (H ) that will combine with 100 grams dry weight of soil and whose measure is one milliequivalents per 100 grams of soil (1 meq/100 g). Hydrogen ions have a single charge and one-thousandth of a gram of hydrogen ions per 100 grams dry soil gives a measure of one milliequivalent of hydrogen ion. Calcium, with an atomic weight 40 times that of hydrogen and with
14805-486: The porous lava, and by these means organic matter and a finer mineral soil accumulate with time. Such initial stages of soil development have been described on volcanoes, inselbergs, and glacial moraines. How soil formation proceeds is influenced by at least five classic factors that are intertwined in the evolution of a soil: parent material, climate, topography (relief), organisms, and time. When reordered to climate, relief, organisms, parent material, and time, they form
14946-434: The rate of soil respiration , leading to the depletion of soil organic matter. Since plant roots need oxygen, aeration is an important characteristic of soil. This ventilation can be accomplished via networks of interconnected soil pores , which also absorb and hold rainwater making it readily available for uptake by plants. Since plants require a nearly continuous supply of water, but most regions receive sporadic rainfall,
15087-414: The rate of diffusion of gases into and out of soil. Platy soil structure and soil compaction (low porosity) impede gas flow, and a deficiency of oxygen may encourage anaerobic bacteria to reduce (strip oxygen) from nitrate NO 3 to the gases N 2 , N 2 O, and NO, which are then lost to the atmosphere, thereby depleting the soil of nitrogen, a detrimental process called denitrification . Aerated soil
15228-491: The raw materials needed for woodchip production. Almost any tree can be converted into woodchips, however, the type and quality of the wood used to produce woodchips depends largely on the market. Softwood species, for instance, tend to be more versatile for use as woodchips than hardwood species because they are less dense and faster growing. A wood chipper is a machine used for cutting wood into smaller pieces (chips). There are several types of wood chippers, each having
15369-432: The risks of phytotoxicity and human pathogen regrowth. Aerated compost tea brews faster and generates more microbes, but has potential for human pathogen regrowth, particularly when one adds additional nutrients to the mixture. Field studies have shown the benefits of adding compost teas to crops due to organic matter input, increased nutrient availability, and increased microbial activity. They have also been shown to have
15510-442: The seat of interaction networks playing a decisive role in the stability, dynamics and evolution of soil ecosystems. Biogenic soil volatile organic compounds are exchanged with the aboveground atmosphere, in which they are just 1–2 orders of magnitude lower than those from aboveground vegetation. Humans can get some idea of the soil atmosphere through the well-known 'after-the-rain' scent, when infiltering rainwater flushes out
15651-575: The soil particle density is much higher, in the range of 2.6 to 2.7 g/cm . Little of the soil of planet Earth is older than the Pleistocene and none is older than the Cenozoic , although fossilized soils are preserved from as far back as the Archean . Collectively the Earth's body of soil is called the pedosphere . The pedosphere interfaces with the lithosphere , the hydrosphere ,
15792-441: The soil anion exchange capacity. The cation exchange, that takes place between colloids and soil water, buffers (moderates) soil pH, alters soil structure, and purifies percolating water by adsorbing cations of all types, both useful and harmful. The negative or positive charges on colloid particles make them able to hold cations or anions, respectively, to their surfaces. The charges result from four sources. Cations held to
15933-538: The soil by volatilisation (loss to the atmosphere as gases) or leaching. Soil is said to be formed when organic matter has accumulated and colloids are washed downward, leaving deposits of clay, humus , iron oxide , carbonate , and gypsum , producing a distinct layer called the B horizon. This is a somewhat arbitrary definition as mixtures of sand, silt, clay and humus will support biological and agricultural activity before that time. These constituents are moved from one level to another by water and animal activity. As
16074-416: The soil prior to bedding and planting, be applied at the same time the beds are constructed and plastic laid down, or used as a top dressing. Many crops are not seeded directly in the field but are started in seed trays in a greenhouse. When the seedlings reach a certain stage of growth, they are transplanted in the field. Compost may be part of the mix used to grow the seedlings, but is not normally used as
16215-420: The soil solution composition (attenuate changes in the soil solution) as soils wet up or dry out, as plants take up nutrients, as salts are leached, or as acids or alkalis are added. Plant nutrient availability is affected by soil pH , which is a measure of the hydrogen ion activity in the soil solution. Soil pH is a function of many soil forming factors, and is generally lower (more acidic) where weathering
16356-402: The soil solution. Both living soil organisms (microbes, animals and plant roots) and soil organic matter are of critical importance to this recycling, and thereby to soil formation and soil fertility . Microbial soil enzymes may release nutrients from minerals or organic matter for use by plants and other microorganisms, sequester (incorporate) them into living cells, or cause their loss from
16497-473: The soil voids are saturated with water vapour, at least until the point of maximal hygroscopicity , beyond which a vapour-pressure deficit occurs in the soil pore space. Adequate porosity is necessary, not just to allow the penetration of water, but also to allow gases to diffuse in and out. Movement of gases is by diffusion from high concentrations to lower, the diffusion coefficient decreasing with soil compaction . Oxygen from above atmosphere diffuses in
16638-430: The soil water solution will be insufficient to change the pH, as the acid forming cations stored on the soil colloids will tend to restore the original pH condition as they are pushed off those colloids by the calcium of the added lime. The resistance of soil to change in pH, as a result of the addition of acid or basic material, is a measure of the buffering capacity of a soil and (for a particular soil type) increases as
16779-433: The soil water solution: Al replaces H replaces Ca replaces Mg replaces K same as NH 4 replaces Na If one cation is added in large amounts, it may replace the others by the sheer force of its numbers. This is called law of mass action . This is largely what occurs with the addition of cationic fertilisers ( potash , lime ). As the soil solution becomes more acidic (low pH , meaning an abundance of H ),
16920-462: The soil where it is consumed and levels of carbon dioxide in excess of above atmosphere diffuse out with other gases (including greenhouse gases ) as well as water. Soil texture and structure strongly affect soil porosity and gas diffusion. It is the total pore space ( porosity ) of soil, not the pore size, and the degree of pore interconnection (or conversely pore sealing), together with water content, air turbulence and temperature, that determine
17061-468: The soil's parent materials (original minerals) interacting over time. It continually undergoes development by way of numerous physical, chemical and biological processes, which include weathering with associated erosion . Given its complexity and strong internal connectedness , soil ecologists regard soil as an ecosystem . Most soils have a dry bulk density (density of soil taking into account voids when dry) between 1.1 and 1.6 g/cm , though
17202-502: The soil, a complex feedback which is exemplified in the dynamics of banded vegetation patterns in semi-arid regions. Soils supply plants with nutrients , most of which are held in place by particles of clay and organic matter ( colloids ) The nutrients may be adsorbed on clay mineral surfaces, bound within clay minerals ( absorbed ), or bound within organic compounds as part of the living organisms or dead soil organic matter. These bound nutrients interact with soil water to buffer
17343-414: The soil, possibly making the soil less fertile. Plants are able to excrete H into the soil through the synthesis of organic acids and by that means, change the pH of the soil near the root and push cations off the colloids, thus making those available to the plant. Cation exchange capacity is the soil's ability to remove cations from the soil water solution and sequester those to be exchanged later as
17484-408: The soil, since wood ash can be used as a mineral-rich plant fertilizer . The latter method can result in an effectively carbon-negative system, as well as acting as a very effective soil conditioner, enhancing water and nutrient retention in poor soils. Unlike the smooth, uniform shape of manufactured wood pellets , woodchip sizes vary and are often mixed with twigs and sawdust . This mixture has
17625-431: The spread of wildfire . Undergrowth coppice is ideal for chipping, and larger trees may be left in place to shade the forest floor and reduce the rate of fuel accumulation. Woodchip costs usually depend on such factors as the distance from the point of delivery, the type of material (such as bark, sawmill residue or whole-tree chips), demand by other markets and how the wood fuel is transported. Chips delivered directly to
17766-427: The stability and long-term growth of the forests in which they're removed from. For instance, chipping of trees from forests has been shown to increase the removal of plant nutrients and organic matter from an ecosystem, thereby reducing both the nutrients and humus content of the soil. One option to balance the negative effects of woodchip harvesting is to return the woodchip ash to the forest which would restore some of
17907-454: The standard is: ANSI/ASABE AD17225-4:2014 FEB2018 Solid Biofuels—Fuel Specifications and classes—Part 4: Graded wood chips. One common chip category is the GF60 which is commonly used in smaller plants, including small industries, villas, and apartment buildings. "GF60" is known as "Fine, dry, small chips". The requirements for GF60 are that the moisture is between 10 and 30% and the fractions of
18048-409: The strength of anion adhesion is as follows: The amount of exchangeable anions is of a magnitude of tenths to a few milliequivalents per 100 g dry soil. As pH rises, there are relatively more hydroxyls, which will displace anions from the colloids and force them into solution and out of storage; hence AEC decreases with increasing pH (alkalinity). Soil reactivity is expressed in terms of pH and
18189-430: The summer (with teas in the bark and covered so rain can't reach to them), and is then chipped in the fall, the woodchips' moisture content will be approximately 20–25%. The energy content, then, is approximately 3.5–4.5kWh/kg (~150–250 kg/cubic metre). Coal power plants have been converted to run on woodchips, which is fairly straightforward to do, since they both use an identical steam turbine heat engine , and
18330-485: The technique may range from very small, simple systems to very large, capital intensive, industrial installations. In agriculture , windrow composting is the production of compost by piling organic matter or biodegradable waste , such as animal manure and crop residues, in long rows – windrow . The practice of making raised garden beds or mounds filled with rotting wood is also called Hügelkultur in German. It
18471-406: The top of the soil using spreader trucks or spreaders pulled behind a tractor. It is expected that the spread layer is very thin (approximately 6 mm (0.24 in)) and worked into the soil prior to planting. Application rates of 25 mm (0.98 in) or more are not unusual when trying to rebuild poor soils or control erosion. Due to the extremely high cost of compost per unit of nutrients in
18612-491: The two concentrations are equal, they are said to neutralise each other. A pH of 9.5 has 10 moles hydronium ions per litre of solution (and also 10 moles per litre OH ). A pH of 3.5 has one million times more hydronium ions per litre than a solution with pH of 9.5 ( 9.5 − 3.5 = 6 or 10 ) and is more acidic. The effect of pH on a soil is to remove from the soil or to make available certain ions. Soils with high acidity tend to have toxic amounts of aluminium and manganese . As
18753-473: The void part of the soil volume and is occupied by gases or water. Soil consistency is the ability of soil materials to stick together. Soil temperature and colour are self-defining. Resistivity refers to the resistance to conduction of electric currents and affects the rate of corrosion of metal and concrete structures which are buried in soil. These properties vary through the depth of a soil profile, i.e. through soil horizons . Most of these properties determine
18894-433: The waste into smaller pieces through methods such as grinding, tearing, chewing, and digesting. Under ideal conditions, composting proceeds through three major phases: The time required to compost material relates to the volume of material, the particle size of the inputs (e.g. wood chips break down faster than branches), and the amount of mixing and aeration. Generally, larger piles reach higher temperatures and remain in
19035-553: The water content of the soil, as can be expressed in terms of volume or weight—can be based on in situ probes (e.g., capacitance probes , neutron probes ), or remote sensing methods. Soil moisture measurement is an important factor in determining changes in soil activity. The atmosphere of soil, or soil gas , is very different from the atmosphere above. The consumption of oxygen by microbes and plant roots, and their release of carbon dioxide, decreases oxygen and increases carbon dioxide concentration. Atmospheric CO 2 concentration
19176-461: The weathering of lava flow bedrock, which would produce the purely mineral-based parent material from which the soil texture forms. Soil development would proceed most rapidly from bare rock of recent flows in a warm climate, under heavy and frequent rainfall. Under such conditions, plants (in a first stage nitrogen-fixing lichens and cyanobacteria then epilithic higher plants ) become established very quickly on basaltic lava, even though there
19317-476: The whole soil atmosphere after a drought period, or when soil is excavated, a bulk property attributed in a reductionist manner to particular biochemical compounds such as petrichor or geosmin . Soil particles can be classified by their chemical composition ( mineralogy ) as well as their size. The particle size distribution of a soil, its texture, determines many of the properties of that soil, in particular hydraulic conductivity and water potential , but
19458-410: The wood as the material is fed through the chute. Knives located in the throat of the chipper cuts the wood in the opposite direction. The design is not as energy efficient as other styles but produces consistent shapes and sizes of woodchips. A drum wood chipper has a rotating parallel-sided drum attached to the engine with reinforced steel blades attached in a horizontal direction. Wood is drawn into
19599-414: The wood is released into the atmosphere again. Compared to the solid waste disposal problems of coal and nuclear fuels, woodchip fuel's waste disposal problems are less grave; in a study from 2001 fly ash from woodchip combustion had 28.6 mg cadmium/kg dry matter. Compared to fly ash from burning of straw, cadmium was bound more heavily, with only small amounts of cadmium leached. It was speciated as
19740-411: The woodchips are distributed as follows: 0–3.5mm: <8%, 3.5–30mm: <7%, 30–60 mm: 80–100%, 60–100 mm: <3%, 100–120 mm: <2%. The energy content in one cubic metre is normally higher than in one cubic metre wood logs, but can vary greatly depending on moisture. The moisture is decided by the handling of the raw material. If the trees are taken down in the winter and left to dry for
19881-471: Was built in 1991. In several well wooded European countries (e.g. Austria, Finland, Germany, Sweden) woodchips are becoming an alternative fuel for family homes and larger buildings due to the abundant availability of woodchips, which result in low fuel costs. The European Union is promoting woodchips for energy production in the EU Forest action plan 2007–2011. The total long term potential of woodchips in
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