Soil Physical Properties: Static & Dynamic, Key Properties, Color, Consistency, Quizzes of Agricultural engineering

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TERM 1 Static Soil Physical Properties DEFINITION 1 Do not change on short time scales under natural conditions TERM 2 Dynamic Soil Physical Properties DEFINITION 2 Readily changed on short time scales under natural conditions TERM 3 Key soil physical properties DEFINITION 3 Color Texture Structure Consistence Density TERM 4 Soil Color DEFINITION 4 Most obvious and easily determined soil physical property TERM 5 Organic matter content DEFINITION 5 Darkens the soil, typically associated with surface layers, mask all other coloring agents TERM 6 Soil coloring agents DEFINITION 6 manganese oxides Calcium carbonates and salts Organic matter (important) Iron oxides (important) TERM 7 Sand textures and size DEFINITION 7 Very coarse sand: 2.0 - 1.0 mm Coarse sand: 1.0 - 0.5 mm Medium Sand: 0.5 - 0.25mm Fine Sand: 0.25 - 0.10 mm Very Fine Sand: 0.10 - 0.05 mm TERM 8 Distinct physical size group of mineral particles DEFINITION 8 Sand: 2.0 - 0.05 mm Silt: 0.05 - 0.002 mm Clay: <0.002 mm TERM 9 Specific Surface Area DEFINITION 9 The amount of particle surface area exposed and available as sites for chemical and physical processes per unit mass or volume of soil. TERM 10 Specific Surface Area affects DEFINITION 10 Adsorption/ retention of water Adsorption of chemicals Area for chemical reactions Aggregation Microbial colonization TERM 21 Crusting DEFINITION 21 Results from raindrop and dispersion of surface. As a result, the dispersed clay particles accumulate at the surface and plug the poresDramatically decrease infiltration TERM 22 Grades DEFINITION 22 Structureless - particles are not arranged to aggregates of peds Weak - barely observable in place Moderate - not very distinct in undisturbed soils Strong - quite evident in undisturbed soils TERM 23 Particle Density DEFINITION 23 Dp Density of soil solids alone Determined by the mineralogy of the soil material Assumed to be 2.65 g/cm^3 TERM 24 Bulk Density DEFINITION 24 Db Density of bulk soil (volume of pores included in the computation Determined by mineralogy as well as packing and sorting of soil particles The higher bulk density, the more compact the soil TERM 25 Extensive Cultivation DEFINITION 25 Farm operation that may cause compaction TERM 26 Bulk Density increases DEFINITION 26 Soils become more compact Soil strength increases pore space decreases TERM 27 Compaction DEFINITION 27 Decrease in size and/or number of micropores TERM 28 Porosity DEFINITION 28 indicates how much of the bulk volume of the soil is occupied by pores. Normal range: 0.35 - 0.65 non-compacted, medium textures assumed 0.5 or 50% TERM 29 High porosity DEFINITION 29 Soil can accommodate a large volume of air and water Air and water movement may be effective Limited or no problem of root penetration Soil is relatively less prone to erosion TERM 30 Size of Pores DEFINITION 30 Macropores: >0.08 mm diameter, allowair and watermovement. Micropores: <0.08 mm diameter, holds water and less air movement TERM 31 Consistence DEFINITION 31 Soil Science term Refers to degree of Plasticity and Stickiness Affected by the and amount of clay in the soil Zones may restrict root growth and seedling emergence Whether soils are likely to develop compacted zone; ruts, crusts, hardpans, etc. TERM 32 Description of Consistence DEFINITION 32 Wet: Stickiness (non-sticky, slightly sticky, sticky, very sticky) Plasticity (non-plastic, slightly plastic, plastic, very plastic) Moist: very Friable, friable, firm, very firm Dry: Loose, soft, slightly hard, hard, very hard, extremely hard TERM 33 Consistency DEFINITION 33 Engineers term describe how soil resists penetration of blunt end of pencil TERM 34 Physical Properties relevant to engineering uses DEFINITION 34 Soil consistence and consistency Soil strength Soil expansion TERM 35 Soil Bearing Strength DEFINITION 35 Defined by engineers Capacity of a soil mass to withstand stress without rupturing or becoming deformed Failure can result in buildings, dams, levees giving way to the pressure of impounded water TERM 46 Plant Available water DEFINITION 46 PAW Often referred to as Total Available Water Max PAW = FC - PWP Current PAW = current water - PW TERM 47 Quantitative Water content DEFINITION 47 Gravimetric Water Content (0g) - common unit: g/g Volumetric Water Content (0v) - common unit: cm^3 / cm^3 Thickness of water (l) - common unit: cm, mm, or in TERM 48 Reasons to know water content DEFINITION 48 Possible soil biochemical reactions that may occur Whether we need to apply water and how much without TERM 49 Pressure DEFINITION 49 Matrix Potential: attractive forces (adhesion/cohesion)between water and soil matrix, under saturated conditions Pressure Potential: weight of water (hydrostatic pressure) on the point of interest TERM 50 Total Water Potential DEFINITION 50 Sum of pressure and gravity acting upon water Lowest location of water movement TERM 51 Flux DEFINITION 51 V Flow of water in the soil Governed by Darcy's law V=k(delta H/L) Delta H - difference between sum of forces acting on inlet and outlet L - length of soil being considered TERM 52 Hydraulic Conductivity DEFINITION 52 k Ability of the soil to allow water to pass Under saturated conditions, known as Ksat or Saturated Hydraulic Conductivity Common units: cm/hr TERM 53 Hydraulic conductivity influences DEFINITION 53 Affected by soil properties that affects porosity and pore continuity Soil texture Soil structure Bulk density Soil mineralogy Water content TERM 54 Infiltration DEFINITION 54 Entry of water through the soil surface High infiltration rate prevents runoff which causes erosion Effective if soil surface structure is good and surface pores are not plugged TERM 55 Depth of Wetting DEFINITION 55 Zw = (Total water applied)/(0vf - 0vi) 0vf - final water content 0vi - initial water content TERM 56 Percolation DEFINITION 56 Downward movement of water through the soil profile Sat or nearly sat conditions when water is applied by rain or irrigation TERM 57 Leaching DEFINITION 57 Removal of material from the soil as percolating water moves through pores TERM 58 Importance in soil temperature DEFINITION 58 Affects agricultural decisions such as type of crops and when to plant and germinate Higher temp results in higher microbial activity, faster decomposition, shorter turn-over time of nutrients Influences dissolution of minerals Influences on soil moisture Affects soil formation/classification TERM 59 Affects soil temperature DEFINITION 59 Atmospheric conditions Land cover; vegetation, snow, structures, mulch Color of surface soil slope aspect Incidental sources of energy; rain or irrigation water, biological activity, warm air over cool soil TERM 60 Heat Capacity DEFINITION 60 Amount of heat energy it takes to hence temp by 1 degree C Water > soil solids Soil solids > Soil air Soil moisture content is major controlling factor in temp change meaning TERM 71 Actinomycetes DEFINITION 71 Prokaryotic and walls are like that of bacteria 2nd most abundant organism in the soil (over 1 million/gm) decompose resistant organic compounds (cellulose, lignin and chitin) Some fix Nitrogen Some produce Antibiotics such as Streptomycin and Chloramphenicol TERM 72 Fungi DEFINITION 72 Usually filamentous andmulticellular (molds, mushrooms)but may include unicellular organisms (yeast) No chlorophyll -- heterotrophic organisms (must eat carbs to generate energy) Fewer in numberthan bacteria but make up largest biomass Largely aerobic but can tolerate low oxygen concentrations Exists in a wide range pH -- Molds are widest range Decompose cellulose, lignin and complex organic compounds Plays a role in soil aggregate formation and stabilization Penicillin TERM 73 Mycorrhizae DEFINITION 73 "Fungus-Roots" Improves uptake of frequently limiting essential plant nutrients like phosphorus Most plant species including crops TERM 74 Lichen DEFINITION 74 "Fungus-Algae" Fungus proves growth factors (water, nutrients) to the algae Algae provides photosynthates to the fungi TERM 75 Algae DEFINITION 75 Contains Chlorophyll -- green color Photosynthetic -- produce their own food Autotrophic organisms Primary produces Live near soil surface bc they need light Found in moist to wet soils at or near neutral pH May live in leaves of aquatic fern TERM 76 Microbial Groups: size and number DEFINITION 76 Bacteria: 0.5 x 1.5 um, 10^8 - 10^9 organisms/g soil Actinomycetes: 0.5 - 2.0 um, 10^7 - 10^8 organism/g soil Fungi: 8.0 um, 10^5 - 10^6 organism/g soil Algae: 5 x 13 um, 10^3- 10^6 organism/g soil Protozoa: 15 x 50 um, 10^3 - 10^5 organism/g soil Nematodes: 1,000 um, 10^1- 10^2 organism/g soil Smaller the size, larger the population TERM 77 Distribution of Microorganisms in soil profile DEFINITION 77 Aerobic organisms >anaerobic organism: Aerobic is better atgenerating energy We don't see algae at deeper depths because it needs light TERM 78 Microorganisms environmental factors DEFINITION 78 Moisture content Adequate temperature range Adequate carbon Adequate soil pH Competing organisms Aeration TERM 79 Microorganism Moisture content DEFINITION 79 Best around Field Capacity Too wet or too dry inhibit microbial activity Directly affects soil aeration condition Microorganisms are about 90% moisture content TERM 80 Microorganism temp range DEFINITION 80 Microorganisms activity limited below 5 C Psychrophiles: -5 - 25 C Mesophiles: 15 - 40 C Thermophiles: 40 - 70 C Hyperthermophiles: about 60 C -- usually 80 - 100 C TERM 81 Microorganism carbon DEFINITION 81 Organic matter is primary food source for most microbes Different organisms prefer different types of organic matter TERM 82 Microorganism Soil pH DEFINITION 82 Microbial enzymes can be dentures due to pH change May affect solubility of other chemicals Microorganisms work in specific pH ranges Bacteria: near neutral and adversely affected by acidic cond. Fungi: more resistant to acidic conditions TERM 83 Microorganism competing organisms DEFINITION 83 Microbes must be able to compete or have favorable association with microbes around them TERM 84 Microorganism Aeration DEFINITION 84 Needs presents or absences of oxygen Aerobic - requires oxygen anaerobic - survives with absence of oxygen Facultative- undergo either aerobic or anaerobic TERM 85 Beneficial activities of soil organisms DEFINITION 85 Decomposition of organic matter Nutrient transformation Weather reactions/ Soil formation Treatment of wastes Improve soil physical properties