Conservation Tillage Systems in the Southeast

Glossary

Overview

ACCase inhibitors. Herbicides belonging to Aryloxyphenoxypropionate (FOPs), cyclohexanedione (DIMs), and phenylprazolin (DENs) chemistries. These herbicides inhibit the enzyme acetyl-CoA carboxylase (ACCase), which catalyzes the first step in fatty acid synthesis and is important for membrane synthesis.

Actinobacteria. Most are found in soil; they include some of the most common soil life and play important roles in decomposition and humus formation.

Adjusted gross income. Defined by the income tax system as gross income minus specific deductions to income.

Aflatoxin. Toxic metabolites produced by certain fungi in or on foods and feeds. Aflatoxins have been associated with various diseases in livestock, domestic animals and humans.

Aggregate stability. A measure of the proportion of the aggregates in a soil that do not easily slake, crumble or disintegrate.

Aggregates. The structures, or clumps, formed when soil minerals and organic matter are bound together with the help of organic molecules, plant roots, fungi and clays.

Allelopathy. Suppression of the germination or growth of one plant by another. The chemicals responsible for this effect are produced during the growth of a plant or during its decomposition.

ALS inhibitors. Acetolactate synthase (ALS)-inhibiting herbicides inhibit the enzyme common to the biosynthesis of branched-chain amino acids. ALS-inhibiting herbicides affect vascular plants (i.e., those with conducting tissue that can move water and minerals throughout the plant), bacteria, fungi, yeasts and algae.

Alter-row spacing. To space crops apart with another crop in order to establish better and more-productive plants.

Amortized annual cost. The accumulated portion of the recorded cost of a fixed asset that has been charged to expense through either depreciation or amortization.

Anaerobic. Growing in the absence of molecular oxygen (such as anaerobic bacteria).

Anion. Atoms or molecules that have a negative charge due to the presence of more valence electrons than protons. These types of ions include chlorine, nitrate, sulfate and phosphate.

Anion exchange site. The site of the chemical process in which anions are exchanged or removed.

Base saturation. The ratio of the quantity of exchangeable bases to the cation exchange capacity. The value of the base saturation varies according to whether the cation exchange capacity includes only the salt extractable acidity or the total acidity determined at pH 7 or 8. Often expressed as a percent.

Beneficial insects. Insects that prey on pests, thereby reducing insect damage to crops.

Bioenergy. Energy derived from the conversion of biomass where biomass may be used directly as fuel or processed into liquids and gases.

Biofuels. Fuel composed of or produced from biological raw materials as opposed to fossil fuels.

Biomass. Biological material derived from living or recently living organisms.

Biorefinery. A facility that converts biomass to energy.

Bt corn. A variant of maize that has been genetically altered to express one or more proteins from the bacterium Bacillus thuringiensis, including Delta endotoxins. The protein is poisonous to certain insect pests and is widely used in organic gardening.

Bulk density. The dry weight of soil per unit volume of soil. Bulk density considers both the solids and the pore space, whereas particle density considers only the mineral solids. It is an indicator of compaction and is typically expressed in grams per cubic centimeter (g/cm3).

Capillary action. The movement of water within the spaces of porous material due to the forces of adhesion, cohesion and surface tension.

Capital recovery method. A process to estimate the amount required to regain the cost of an asset.

Carbon sequestration. The process by which atmospheric carbon dioxide is taken up by trees, grasses and other plants through photosynthesis and stored as carbon in biomass (trunks, branches, foliage and roots) and soils.

Carbon-to-nitrogen ratio (C:N). The amount of carbon in a residue divided by the amount of nitrogen. A high ratio results in low rates of decomposition and can also result in a temporary decrease in nitrogen nutrition for plants, as microorganisms use much of the available nitrogen.

Catch crop. A crop that reaches maturity in a relatively short time, often planted as a substitute for a crop that has failed or at a time when the ground would ordinarily lie fallow, as between the planting of two staple crops.

Cation. Atoms or molecules that have a positive charge due to the presence of less valence electrons than protons. These types of ions include calcium, magnesium, potassium, ammonium, hydrogen and sodium.

Cation exchange capacity (CEC). The amount of negative charge that exists on humus and clays, allowing them to hold onto positively charged chemicals (cations). This process helps keep nutrients in place and in a form easily exchangeable with plant roots.

Cellulose. An inert carbohydrate and the chief constituent of the cell walls of plants and of wood, cotton, hemp, paper, etc.

Chaff. The seed covering and other debris separated from the seed when threshing grain.

Chisel plowing. A tillage system that fractures the plow layer with a minimum amount of incorporation of surface residue.

Clean tillage. Any system that leaves the soil surface more or less free of residue.

Compaction. Soil compaction occurs when soil particles are pressed together, reducing pore space between them. Heavily compacted soils have a reduced rate of both water infiltration and drainage from the compacted later.

Compost extract. Liquid versions of solid compost material, commonly known as compost teas. They contain soluble plant nutrients and a complex community of beneficial microorganisms.

Cone index. A parameter of soil strength that measures the bearing capabilities of the soil. A soil’s cone index is greatly influenced by tillage types and is related to soil density.

Cover crop. A crop grown for the purpose of protecting the soil from erosion during the time of the year when the soil would otherwise be bare. It is sometimes called a green manure crop.

Deep Banding. The placement of immobile nutrients in a band at a depth of 4–6 inches below the soil surface. This placement is frequently used in conservation tillage systems.

Denitrification. The process by which microorganisms convert nitrate to a gas, causing nitrogen losses from the soil into the atmosphere. This occurs when soils are water saturated and oxygen is low.

Dicotyledonous plants or dicots. A grouping of flowering plants whose seed typically has two embryonic or first leaves of a seedling plant.

Dinitroanilines. A mode of action for certain herbicides. Dinitroaniline herbicides are considered selective preemergence herbicides.

Double crop. Two different crops grown on the same space in the span of one growing season.

Draft force. A measure of the amount of force required to move tillage implements through a field.

Drainage. Movement of water out of the soil profile.

Dry matter. The portion of feed remaining after the removal of water.

E horizon. A mineral horizon in the soil profile in which the main feature is loss of silicate clay, iron, aluminum or some combination of these, leaving a concentration of sand and silt particles, and in which all or much of the original rock structure has been obliterated. See also Horizonation.

E85. Ethanol-gasoline blends containing a high level of ethanol, from 51–83 percent ethanol. E85 can be used in flexible fuel vehicles.

Economic threshold. The density of a pest population at which a control treatment is necessary to provide an economic return.

Ecosystem services. The benefits people obtain from ecosystems, including provisioning services such as food and water; regulating services such as flood and disease control; cultural services such as spiritual, recreational and cultural benefits; and supporting services such as nutrient cycling.

Ecotype. A genetically distinct geographic variety, population or race within a species, which is genotypically adapted to specific environmental conditions.

Eluviated. The removal of soil material in suspension (or in solution) from a layer or layers of a soil. Usually, the loss of material in solution is described by the term “leaching.” See also Leaching.

Enterprise budget. Used to record the revenue, expenses and returns for a single crop or livestock enterprise on a per unit basis.

Evapotranspiration. The sum of evaporation and transpiration.

Fragipan. Dense subsurface layers that severely restrict water flow and root penetration.

Generalist pests. Attack a wide range of plant species. Examples include wireworms, seed corn maggots and aster leafhoppers.

Giant cells. Feeding sites created by plant-parasitic nematodes on the roots of plants. The plant loses nutrients at these sites.

Glomalin. A coating found on the hyphae (hair-like projections) of arbuscular mycorrhizal fungi (AMF). AMF are microorganisms that evolved with plants to aid in acquiring nutrients, especially immobile nutrients like phosphorus. Glomalin keeps water and nutrients from getting lost on the way to and from the plant.

Glycoprotein. A complex protein containing a carbohydrate combined with a simple protein.

Green manure. A crop grown for the main purpose of building up or maintaining soil organic matter. It is sometimes called a cover crop.

Hairpinning. The process by which residue is trapped in the seed furrow due to the dragging of fresh, wet residue by implements following termination. Hairpinning reduces seed-to-soil contact, resulting in poor seed germination.

Herbicide-resistant weed. Weeds that resist herbicide application at doses that usually give effective control of the species. Resistant weeds are a consequence of evolutionary processes.

Herbicide-resistant variety. Inherited ability of a plant to survive and reproduce following exposure to a dose of an herbicide normally lethal to the wild type. In a plant, resistance may be naturally occurring or induced by such techniques as genetic engineering or selection of variants produced by tissue culture or mutagenesis.

HG types. Subspecies groups of the soybean cyst nematodes that are morphologically identical but may infect and reproduce on different soybean varieties in different ways.

High-residue cover crop. A cover crop that produces at least 4,000 dry matter pounds per acre.

Hipper. A common-use term for a piece of equipment used to make raised beds.

Horizonation. Soil profiles are made up of discrete layers, called horizons, with distinct characteristics. They are typically parallel with the ground surface.

Humus. The very well decomposed part of the soil organic matter. It has high cation-exchange capacity.

Hydraulic conductivity. A quantitative measure of a saturated soil’s ability to transmit water when subject to a hydraulic gradient. It can be thought of as the ease with which pores of a saturated soil permit water movement.

Immobilization. Process by which microorganisms and plants store nutrients in their bodies.

Inoculum. The pathogen or part of the pathogen that causes infections. Inoculum for plant-parasitic nematodes consists of eggs and vermiform life stages of the nematode.

Input costs. The costs of crop establishment and production (e.g., seed or fuel costs).

In-row subsoiling. The soil surface and residue are left undisturbed except for strips up to one-third of the row width. Within these strips, soil below the surface is disturbed or loosened using deep-tillage implements. Other names for in-row subsoiling include strip-till, row-till and slot-till. Depending on the type of tillage shank used, names for this practice may also include paratill or terra-till.

Integrated pest management (IPM). An ecosystem-based strategy that uses a variety of biological and cultural practices to limit pest damage. Pesticides are used only when monitoring indicates they are needed to avoid an economic loss.

Internal drainage. The continuing process in a soil that results in water removal under natural conditions.

Interseeding. The general practice of sowing a crop into another standing, growing crop late in the season, usually to enhance biomass production or erosion control, or to increase soil organic matter. This practice is also known as overseeding.

Inversion tillage. Tillage that flips over a layer of soil, burying surface residues in the process.

Invisible seeding. Furrowing with minimum soil movement.

Leaching. The downward movement of dissolved nutrients in the soil profile with percolating water.

Lignocelluloses. Any of several closely related substances consisting of cellulose intimately associated with lignin and constituting the essential woody cell walls of plants.

Macropores. Large pores responsible for preferential flow and rapid, far-reaching transport.

Major land resource area. Geographic area characterized by a particular pattern of soils, climate, water resources, land uses and types of farming.

Microbial biomass. The living component of soil organic matter. Microbial biomass consists mostly of bacteria and fungi, which decompose crop residues and organic matter in soil. This process releases nutrients, such as nitrogen, into the soil that are available for plant uptake.

Microbial degradation of pesticides. The process by which the pesticide compound is broken down by living organisms, usually bacteria.

Microflora. The constellation of living microorganisms, such as bacteria and fungi, that are found on or in a particular location, such as the soil environment.

Mineralization. Process by which soil organisms change organic elements into the “mineral” or inorganic form as they decompose organic matter (e.g., organic forms of nitrogen are converted to nitrate).

Mode of action. The way in which a pesticide destroys or controls the target pest (e.g., affecting an insect’s nerves or molting).

Mortality factor. A factor of, or contributor to, insect mortality that brings about population regulation.

Natural enemy. A species that preys on another species for food.

Nitrification. The conversion of ammonium to nitrate by bacteria.

Nitrogen fixation. The conversion of atmospheric nitrogen by bacteria to a form that plants can use. A small number of bacteria, which include the rhizobia living in the roots of legumes, are able to make this conversion.

Nodulation. A symbiotic event between a host plant and a bacterium. The plant gains a steady supply of nitrogen, and the bacterium gains a steady supply of carbon.

Non-inversion tillage. Also known as conservation tillage. Includes systems of tillage that involve fewer passes than conventional tillage but that incorporate crop residue into the surface soil layers, while leaving at least 30 percent of crop residue on the soil surface. Also includes direct drilling, which leaves the soil completely undisturbed from harvest until seeding and all crop residues remain on the surface. With direct drilling, seed placement is achieved by discs, coulters or chisels opening a narrow slot where the seed is delivered.

Nonpoint source pollution. Pollution that cannot be traced to a single point source such as a pipe or smokestack. Nonpoint source pollution comes from many diffuse sources, generally from land runoff, precipitation, atmospheric deposition, drainage, seepage or hydrologic modification. It may be caused by rainfall or snowmelt moving over and through the ground.

Non-selective herbicide. Herbicides that tend to kill all plant species they are exposed to rather than being designed to kill particular types of weeds such as grasses and broadleaves.

No-till. Soil is undisturbed by tillage during the entire year. Crop residues left on the soil surface may be disturbed in strips up to one-third of the row width for planting or drilling seed. Other common terms for no-till include direct seeding, slot planting and zero-till.

Nutrient cycling. The process of storing, moderating the release of, and cycling nutrients and other elements by soil. During this process, nutrients can be transformed into plant-available forms, held in the soil or lost to air or water.

Opportunity cost. When presented with multiple potential uses of a resource, this cost represents the lost value associated with those potential uses that are not pursued.

Organoarsenicals. These chemicals have been used in pesticides and insecticides, as well as in additives in animal feeding operations.

Overseeding. See Interseeding.

Paraplow. A slant-shank chisel plow that fractures and loosens soil to a working depth of 12–16 inches. The soil surface is left smooth with little disturbance of the standing stubble.

Parasitoid. Insects that spend a portion of their lives in a pest host, ultimately killing the host.

Paratill. See also In-row subsoiling.

Partial budgeting. Used to analyze the effects of proposed changes in cropping systems or farm systems. Partial budgets only consider changes in revenue and expenses due to a management change or the adoption of a new technology. Partial budgeting is used to determine if the proposed change will have a net positive or net negative effect on farm profits.

Pegging (peg). A stage in the life cycle of the peanut plant. After pollination, when the plant’s petals begin to wither and fall, a stalk called the peg forms and begins to grow toward the ground.

Penetrometer. An instrument in the form of a cylindrical rod with a cone-shaped tip designed for penetrating soil and for measuring the end-bearing component of penetration resistance. The resistance to penetration developed by the cone equals the vertical force applied to the cone divided by its horizontally projected area.

Percolation. The movement of water within the soil. Percolation rate controls the infiltration rate and is controlled by grain size.

Photosystem II inhibitors. A mode of action that interferes with the electron transfer chain of Photosystem II, which is essential for the production of photosynthetic energy.

Physiological races. Subspecies groups of plant-parasitic nematodes that are morphologically identical but may infect and reproduce on a given set of plant host varieties differently.

Planting flat. Not using a raised bed.

Post-emergent (POST) herbicides. Herbicides applied after the crop has germinated and must be used when the plant is actively growing.

Precision ditch. Technique using contour intervals of less than 2 inches to show where to put drainage ditches so they will channel water off of the field.

Precision grade grassed waterway. Constructed graded channels that are seeded to grass or other suitable vegetation. The vegetation slows the water and the grassed waterway conveys the water to a stable outlet at a non-erosive velocity.

Pre-emergent (PRE) herbicides. Herbicides applied at planting or within a few days before crop emergence. They are designed to prevent the germination of seeds by inhibiting a key enzyme.

Primary tillage. Also known as plowing, primary tillage is used to invert the top layer of soil, break up compaction, turn under residues and bury weed seeds. Precedes secondary tillage in conventional agricultural production.

Rainfed. Term used to describe farming practices that rely on rainfall for water.

Raised bed. A raised cultivated area between furrows or wheel tracks of tractors specially prepared, managed and/or irrigated to promote the production of a crop.

Residue mat. A layer of biomass that remains following the termination of a high-residue cover crop.

Residues. Plant material remaining after harvest, including leaves, stalks and roots.

Ridge till. Specialized planters and cultivators are used to form and retain permanent ridges on which cash crops are grown. Crops are planted on the top of the ridge after removing residue from the top of the ridge. Residue is left between ridges. Cultivation is used to form and maintain ridges and to manage weeds.

Ripping. Mechanical soil treatment aimed at improving infiltration rates in machine-compacted or water-repellent soils.

Risk management. Addressing concerns about weather, prices, yields, government policies, etc. that impact farming and can cause wide swings in farm income. Risk management involves choosing among alternatives that reduce the financial effects that can result from such uncertainties.

Roll. A broadcast, secondary tillage operation that crushes clods and compacts or firms and smooths the soil by the action of ground-driven, rotating cylinders.

Root exudates. Compounds exuded by plants into the soil. Root exudates maintain and support a highly specific diversity of microbes in the rhizosphere of a given plant species.

Salvage value. Estimated resale value of an asset at the end of its useful life.

Scavenging. The trapping of excess nutrients that would otherwise move out of the root zone.

Secondary tillage. Includes harrowing and/or disking the soil, resulting in smooth, clod-free seedbeds. Follows primary tillage in conventional agricultural production.

Selective herbicide. An herbicide that is designed to kill specific types of weed species.

Short-rotation woody crops. Woody tree species that have been bred and selected to have extremely high rates of growth, allowing them to be harvested after a short growing period.

Skip row. A pattern of planting in which a planted row or rows is followed by a row or rows that are not planted, or skipped rows.

Sod-based rotation. A rotation that alternates sod-forming grasses and legumes with row crops and cereal grains.

Soil fertility. The ability of the soil to supply essential plant nutrients and soil water in adequate amounts and proportions for plant growth and reproduction in the absence of toxic substances that may inhibit plant growth.

Soil health. See Soil quality.

Soil quality. The continued capacity of soil to function as a living ecosystem that is capable of sustaining plants, animals and humans while maintaining environmental quality. Also referred to as soil health.

Soil strength. A soil’s resistance to penetration and an increase in bulk density (an indicator of soil compaction). See also Bulk density.

Soil tilth. The physical condition of soil, especially in relation to its suitability for planting or growing a crop.

Spatial Plant Analysis Development (SPAD). Measures the relative greenness of leaves, which is proportional to the amount of chlorophyll present. This indicates the photosynthesis potential of the plant. The meter used in SPAD measures transmittance from the leaf at two wavelength ranges (600–700 nanometers and 499–500 nanometers)

Split applications. The division of fertilizer treatments into two or more applications.

Stale seedbed. Using cultivation to encourage weeds to germinate prior to sowing a crop. Each “flush” of weeds is destroyed by further cultivations or herbicide prior to sowing the crop. This should reduce the number of weed seeds left to germinate in the crop.

Strip cropping. Growing two or more crops in alternating strips, usually along the contour or perpendicular to the prevailing wind direction.

Strip tillage. See In-row subsoiling.

Stubble mulch. A blade plow or sweep plow cuts weeds at the roots and leaves most of the residue anchored at the surface with minimum disturbance of the soil surface.

Subsoiling. See In-row subsoiling.

Surface dribbled. Fertilizer placed on the soil surface rather than below the surface. This is likely to result in lower productivity but also in lower input costs.

Tennessee Biofuels Initiative. A research-business collaboration for biofuels development.

Terra-till. A method for in-row subsoiling that lifts and bends subsoil to remove hardpans.

Traffic pan. Compacted soil horizon created by the action of machinery, such as trucks or tractors, over the soil.

Transgenic crops. Contain a gene or genes that have been artificially inserted instead of the plant acquiring them through pollination. An example is Bt corn, which produces its own insecticide. Plants containing transgenes are often called genetically modified or GM crops.

Vegetative reproduction. The process by which some plants reproduce through vegetative parts such as roots, bulbs or stolons (runners) as opposed to reproducing through seeds. This is asexual reproduction, allowing a plant to propagate in isolation.

Volatilization. The process by which surface-applied fertilizers, such as nitrogen, are transformed into gas and lost to the atmosphere.

Volunteer plants. Plants found growing without having been planted, as by natural regeneration, and if undesired, are considered weeds.

Wash. A soil erosion effect caused by runoff of water.

Zone tillage. A reduced tillage method that limits soil disturbance to the area of the planting row and leaves the areas between the crop rows undisturbed.

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