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62 Cards in this Set
- Front
- Back
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Name three types of soil degradation |
Surface soil, physical degradation, and chemical degradation |
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Define soil erosion |
Detachment and transportation of soil or rock by wind, water, ice, or gravity |
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What is accelerated erosion? |
When people disturb soil or vegetation |
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What is sheet erosion? |
Removal of uniform layers of soil |
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What is rill erosion? |
Numerous small channels removed in depth |
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Some impacts of soil erosion? |
Loss of productivity, nutrient and organic matter losses Sedimentation of water reservoirs and rivers |
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What does USLE mean? |
Universal Soil Loss Equation |
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How can erosion be controlled? |
Vegetative cover, organic matter, grassed waterways, terraces, windbreak |
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What does A = RKLSCP mean? |
A = predicted soil loss R = Climatic erosivity K = Soil erodibility L = Slope length S = Slope steepness C = Cover and management P = Erosion control practice |
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What is soil pollution? |
Inorganic chemicals resulting from industrial, domestic, and agricultural products bound by soil minerals Limit to soil's capacity to deal with these chemicals |
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Name some results of leaving organic chemicals in soil |
Vaporize without chemical change, absorbed by soil, leaching and runoff, groundwater contamination, broken down by soil organisms, taken up by plants and soil animals, |
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How long do chemicals last in soil? |
2 days to 20 years reduces soil flora and fauna But most recover naturally |
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What are two methods to remove soil pollutants? |
Ex situ - excavate soil to treatment bins or incinerated or push/pulling water through soil In situ - contaminants removed or bound up in soil matrix or by water flushing, leaching |
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What is phytoremediation? |
Higher plant roots take up pollutant in soil and are then harvested, plant metabolizes contaminant into harmless by-product |
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How do we ingest toxic substances? |
Soil into plants into animals into humans |
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What are some reactions of inorganic contaminants in soil? |
Small amount is held in soluble or exchangeable forms available to plants, bound by organic matter, |
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What are some methods to prevent contamination? |
Reduce soil application, industrial waste inputs, keep chemicals in soils and not plants, drain wet soil |
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What is a landfill? |
A designated area to dump municipal waste Most materials buried in earth |
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What are some soil requirements for natural attenuation landfills include |
1.5m of soil between bottom of landfill and groundwater Moderately permeable soil Sufficient CEC End of day, cover with impermeable soil |
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What does CEC mean? |
Cation exchange capacity Sum of exchangeable cations a soil can adsorb Expressed in amount (moles) of negative charge adsorbed per unit mass of soil |
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What are some traits of containment landfills? |
Complex and expensive,
Contains all leachates 1 or more impermeable liners around sides/bottom |
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Environmental impacts of landfills? |
Water pollution from leachates Organic part loses volume and landfill settles Undesirable liquid + gaseous products Lack of oxygen leads to methane and an explosion hazard |
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What is a soil colloid? |
Organic and inorganic matter with very small particle size |
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General properties of soil colloids? |
Positive or negative charges, but most have negative charges |
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Why are soil colloids so important? |
Influence most chemical, physical, and biological properties of soils, the exchange of ions between soil and plant roots is vital Cation (+) and anion (-) exchanges take place on colloid surfaces |
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Types of soil colloids? |
Silicate clays - each particle made up of a series of layers Organic soil colloids - highly charged humus colloids surrounded by cations |
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Types of colloid charges? |
Permanent charge - at the time minerals form pH dependent - higher charge with higher pH |
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Types of silicate clay colloids? |
Kaolinite - does not shrink/swell, not sticky, large size, hard to adsorb cations Montmorillonite - shrink/swells, small, easy to adsorb cations |
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Which soils have a high CEC? |
Clay and humus |
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What does pH mean? |
Pouvoir hydrogene or concentration oh H+ ions |
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What are three types of acidity? |
Active acidity - due to H+ and Al3+ ions in soil solution Exchangeable acidity - exchangeable H+ and Al3+ ions on exchange sites Residual acidity - H+ and Al3+ ions bound on soil particles |
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What are some acid-forming factors? |
Organic matter decomposition creates acids Carbonic acid (Normal rain pH 5) Sulfuric and nitric acid causing acid rain |
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What are some base-forming factors? |
Processes that increase base-forming cations Conditions that keep cations in soil |
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What is the importance of soil pH? |
Affects availability of nutrients to plants Different soil microbes different tolerance to acidity and alkalinity Plants vary in different pH levels |
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What is percent base saturation? |
% of the CEC that is made up of base-forming cations % BS = base-forming cations (cmol/kg)/CEC (cmol/kg) * 100 |
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What does buffering capacity mean? |
Ability of a soil to resist changes in pH due to clay and other organic matter |
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What is the importance of soil organisms? |
Organic matter decomposition - releases organically held nutrients - incorporates organic matter into soil Makes nutrients available Converted by microbes to plant available form |
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What are the 6 classifications for soil organisms? |
Predators (animal eaters) Herbivores (live plant eaters) Detritivores (dead plant eaters) Parasites (live off other organisms) Bacterivores (bacteria eaters) Fungivores (fungi eaters) |
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What does mycorrhizae mean? |
A symbiotic association between fungi and plant roots Increases nutrient and water available to plant while fungi obtain food from plant and vice versa |
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Name some components of soil organic matter |
Living biomass (plant + animal tissue) Dead roots and plant residue Collodial mixture of complex organic substances no longer identifiable as tissue = humus |
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What are some sources of soil organic matter? |
Plant residue, animals, compost and manure, sewage sludge |
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Why is soil organic matter so important? |
Influences physical and chemical soil properties Accounts for 1/3 of CEC of surface soils Affects stability of peds Supplies energy for microorganisms |
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What is mineralization? |
Conversion of an element from organic to inorganic form by microbes Makes it available to plants |
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What is immobilization? |
Conversion of an element from inorganic to organic form Makes it unavailable to plants |
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What are some factors that affect decomposition and mineralization? |
pH level Soil moisture Aeration Temperature |
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What is the C/N ratio? |
A ratio of carbon to nitrogen Microbes require a ratio of 24:1 in their food If greater, microbes scavenge soil solution to obtain N |
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Display the C/N ratios for Microorganisms Young green leaves |
Forest soil = 30:1 Cultivated soil = 12:1 Microorganisms = 5:1 to 10:1 Young green leaves = 10:1 to 30:1 |
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What does soil fertility mean? |
The ability of soil to supply essential elements for plant growth |
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What do deficiency and toxicity mean in the context of plant growth? |
Deficiency - incorporation of more nutrient results in more growth Toxicity - incorporation of more nutrient results in less growth Luxury consumption - additional incorporation of nutrient has no effect on growth |
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What are some major soil nutrients? |
Macronutrients: required in large amounts for plant growth and includes carbon, hydrogen, oxygen Micronutrients: required in small amounts and includes Iron, Manganese, Zinc, Copperq |
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Why is nitrogen important? |
Plants require large amounts, soil N availability is low Essential for proteins, chlorophyll, root growth |
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What are the processes involved in the N cycle? |
Mineralization - converting organic N to inorganic Immobilization - converting inorganic to organic Nitrification - bacteria change NH4 to NO2 and NO3 Denitrification - reduction of NO3 or NO2 to gas N |
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What are the nine soil orders? |
Cryosolic Regosolic Organic Podzolic Gleysolic Solonetzic Chernozemic Luvisolic Brunisolic |
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Chernozem characteristics?
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Grassland soil on calcareous PM Ah, Bm, Ck |
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Solonetz characteristics? |
Grassland soils on salty PM Hard when dry, sticky when wet Ah, Bn, Ck |
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Luvisol characteristics? |
Deciduous forest on calcareous PM Clay accumulation LFH, Ah, Ae, Bt, C |
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Podzol characteristics? |
Coniferous forest on acidic PM Bf, Bhf, Bh |
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Brunisol characteristics? |
Under forest Little profile development LFH, Ah, Bm |
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Cryosol characteristics? |
Subarctic and arctic regions, permafrost Z horizons within 1-2m, Ah, Bm, Cz |
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Regosol characteristics? |
Weak profile development on young PM No B horizon Ah, C |
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Gleysol characteristics? |
Wet soils with light B horizons Ah, Bg, Cg |
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Organic soil characteristics? |
Saturated for most of the year Of, Om, Oh, Cg |
