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文予翻译工作室18283895755WWW.MSSOY.ORG.June 20156GENERAL AGRICULTURAL SCIENCE TERMINOLOGYArticles posted on this website contain terms and phrases that are specific to agriculture or agricultural enterprises and activities. The below definitions (listed alphabetically) should aid in the understanding of the content of these articles and articles that are linked in them.Abiotic. Environmental factors such as drought, wind, hail, or excess moisture that impact the growth of living organisms. Usually used as “abiotic stresses”.Adsorb, adsorption. In soil terms, the adhesion of ions (i.e., K+, Ca+) or molecules to the surface of soil particles. This process differs from absorption where a materialthe absorbateis dissolved in the soil solution.Alluvial Soil. Soil that is deposited by water flowing over flood plains, river valleys, and creek bottoms; may be coarse- to fine-textured, depending on proximity to water deposition source. Usually the product of erosion from an uphill or upstream source; thus the term“Lower Mississippi River Valley alluvium”.Aquifer. Porous, underground deposit of permeable rock or sediment such as sand or gravel that contains water that can be used to supply wells. Pores in the deposits are interconnected so that water flows through them over a large area. Aquifers may be shallow (the Delta aquifer) or deep.Available soil water holding capacity. The amount of soil water that is available for plant use, or the amount of water volume between field capacity and permanent wilting point.Available water ranges from an average 0.7 in/ft of soil in coarse sand to an average 2.25in/ft of soil in very fine sandy loam and silt loam.Banded. Fertilizer placed below and to the side of seed at planting, or herbicides applied to a defined width that includes the planted row.Biennial rotation. Practice of growing two different crops in alternating years. Examples corn and soybeans, rice and soybeans.Biological control. Pest management that protects, augments, or releases organisms that are natural enemies of a pest. Biological control agents are important in Integrated Pest Management systems.Biomassenergy definition. Plant matter expressed on a dry weight basis (after removal of all water) that can be converted to an energy or fuel source by either direct or indirect methods. In todays agriculture, the most popular indirect method is conversion to ethanol.Biotic. Biological factors such as insects, disease pathogens, nematodes, and weeds that affect other living organisms.Breakeven price. Per-unit revenue (or income) required to provide an economically sustainable enterprise; calculated by dividing a cost (e.g., dollars/acre) by a production quantity (e.g., bushels/acre).Broadcast. Fertilizer spread on the soil surface, or herbicides applied across the entire width of a cropped or planted area.C factor. Cover management factor used in the Revised Universal Soil Loss Equation that文予翻译工作室18283895755reflects the effect of cropping and management practices on erosion rates.Cation exchange capacity (CEC). Refers to the quantity of negative charges that exist on the surfaces of clay particles and organic matter in soil. These negative charges attract positively charged ions or cations such as potassium (K+), calcium (Ca+), magnesium (Mg+), and ammonium (NH4+), which are major plant nutrients. Hydrogen (H+), sodium (Na+), and aluminum (Al+) are the otherpredominant cations occupying the CEC in soils. High percentages of clay particles will impart a higher CEC, while a high percentage of sand particles will impart a low CEC. Smallincreases in organic matter will greatly increase soil CEC. The CEC of a soil is important because it implies the size of the reservoir of nutrients that is available to replenish the nutrients removed by plant uptake. Also, the CEC of a soil can be an indicator of how much leaching of nitrogen and potassium fertilizers will occur; i.e., higher CEC soils will experience less leaching of cationic elements.Cellulosic ethanol. Biofuel that is produced from lignocellulose, the structural material that comprises the mass of most plants. Corn stover, switchgrass, and wheat straw are common agricultural sources of lignocellulose that are being/can be used in cellulosic ethanol production.Conservation tillage. Limited mechanical operations with implements that result in the soil surface being covered with >30% plant residue.Conventional tillage system. Combination of mechanical operations with implements thatresult in a seedbed that is essentially free of weeds and plant residue cover. This is the antithesis of conservation tillage.Cover crop. Crop grown to provide soil cover during seasons when an annual grain crop is absent.Crop rotation. Practice of growing two or more annual crops in a given field in a planned pattern or sequence in successive crop years.Cultural control