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141 Cards in this Set
- Front
- Back
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why do plants need nitrogen?
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to make proteins (enzymes, chlorophyll,etc.)
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is N mobile once inside plant tissues?
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YES
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is N a micro or macro nutrient?
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Macro
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what are the major sources globally and locally of N?
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internal cycling (plant>soil>plant...)
biological N fixation human activities (synthetic fert. auto combustion N2 fixation in lightning |
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what are the main causes of N output from the land
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denitrification
river flow dust and NOx from land |
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does N go thorough both chemical and biological transformations?
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YES
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define ammonification
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biological conversion from organic nitrogen to inorganic nitrogen-ammonium. many soil microorganisms perform this biological conversion, rate is dependent on SOM decomposition rate
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define assimilation
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inorganic nitrogen is converted into organic nitrogen forms. happens only within living cells
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denitrification
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a process only occurring under anaerobic conditions usu. by denitrifying bacteria. is the conversion of NO3 ions to gaseous N2
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Nitrification.
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ammonium > nitrite > nitrate (oxidation conversion).
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why is nitrate in groundwater a serious problem? (3 reasons)
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1. nitrate + amino compounds = nitrosamines (highly carcenogenic)
2. blue baby syndrome 3. nitrate reduction in animal rumen causing disease |
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N2 fixation
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converting N2 to ammonium or nitrate
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three major forms of N2 fixation
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lightning
artificial haber bosch process biological |
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biological N fixation is performed by these two categories of biota
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symbiotic (mutualistic) and free-living
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what are three environmental issues related to the nitrogen cycle?
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eutrophication
acid rain food production and world population growth |
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why do plants need sulfur?
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to create proteins
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is S mobile once inside plant tissues?
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YES
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what is the relative quantity that plants need S (macro, secondary, micro)?
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secondary
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where does the element S come from globally and locally?
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mostly in sedimentary rock and other rock types. oceans in the form of SO4. very little organic S in soils or biomass
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how does S cycle through time and space?
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rock cycle, weathering, leaching, transformation
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sulfur mineralization
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the transformation of organic sulfur into inorganic sulfur by biological processes
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sulfur immobilization
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conversion of sulfur from organic to inorganic form within plant or microorganism tissues
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at what pH range does sulfur oxidation occur and why?
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sulfur oxidation occurs under a wide range of pH values because the different types of bacteria associated with oxidation each have a different range of operating pH levels. some are low and some are high
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define sulfur oxidation
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sulfur gains oxygen atom changing from sulfide to sulfate
can be either chemical or biological, producing sulfur acids |
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define sulfur reduction
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sulfur looses oxygen atom changing from sulfate to sulfide
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why do plants need phosphorous?
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formation of cell membranes and nucleic acids
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is P mobile once inside plant tissues?
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yes
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what is the relative quantity of P a plant needs (macro, secondary, micro)
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MACRO
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where does P come from globally and locally
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rock weathering, locally it is in insoluble phosphates
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how does P cycle through time and space
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rock cycles and leaching, slowly, no gaseous form, imperfect cycle
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does P go through chemical and or biological transformations
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yes, the famous mycorrhizae mobilize chemically fixed P organically and acids transform P into soluble compounds, P is easily transformed chemically
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is P pH dependent, why or why not?
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yes, depending on the form of P ions the pH can be very high or very low, highly variable
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list the P ions in order of most acidic to most basic
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H3PO4 is most acidic
H2PO4 acidic HPO4 basic PO4 most basic |
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what processes influence or control the availability of P to plants?
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chemical fixation (pH & oxisols)
microbial mobilization |
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what happens to plants under P deficiency (limitation)?
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produces purple coloration (chlorosis) and small vegetative growth
or change in leaf shape |
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what is P banding
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cutting P fertilizer into a plot row
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what is better, banding or broadcast application of P for availability?
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banding because the predominant problem with P availability is chemical fixation. banding increases contacting area between P and soil (incr. availability)
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what affect does liming or other form of pH change have on P availability?
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adding lime will increase P availability but also increases Ca which lowers P availability
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what does over fertilization of P do to aquatic ecosystems?
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eutrophication of waterways
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major inputs of P into the soil
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commercial fertilizers and soil organic matter
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major outputs of P from the soil
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fixation or plant removal
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why do plants need K?
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essential metal ion for +60 enzymes
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is K mobile once within plant tissues
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yes, it only exists in mobile form
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what is the relative quantity of plant need of K (macro, secondary, micro)
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MACRO
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where does K come from globally and locally
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rocks, rock weathering, clay minerals
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how does K cycle through time and space?
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rock cycle, weathering, leaching
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does K go through chemical and or biological transformations
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NO always stays as K+
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what factors influence the availability of K
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K fixation
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why do plants need Ca?
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a cementing agent for dividing cells and cell membrane division
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why do plants need Mg?
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is the most critical metal ion for chlorophyll and many other enzymes need it
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is Ca mobile once inside plant tissues?
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NO, it is fixed once being utilized by tissues
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is Mg moble once inside plant tissues?
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YES, acts like K+
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what is the relative quantity of plant need for Mg and Ca? (macro, secondary, micro)
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both are secondary ions
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where do Ca and Mg come from globally and locally?
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rocks, weathering, minerals
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how does Ca and Mg cycle through time and space
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rocks, rock weathering, and leaching
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does Ca and Mg go through chemical and or biological transformations
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YESSSSS
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what are the four types of Ca and Mg chemical/biological forms and which forms are available to plants?
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soluble ions in soil solution (available to plants)
adsorbed onto cation exchange sites (available to plants) insoluble salts (not available to plants) organic form in biomass (not available to plants) |
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why do organic forms of Ca and Mg exist in very small quantities in the soil
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they get leached out quickly during the initial stage of litter decomposition
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what factors control the availability of Ca and Mg in the soil
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pH
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name the five micronutrients
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Boron (B), Iron (Fe), Manganese (Mn), Zinc (Zn), Copper (Cu), Chlorine (Cl) and Molybdenum (Mo)
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define chelates and their role in plant nutrient uptake
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chelates are a type of organo-metallic complex. they act to free certain metals to plant roots and tissues more so than un-chelated forms.
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define siderophores
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are small, high-affinity iron chelating compounds secreted by microorganisms such as bacteria, fungi and grasses.
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define leibig's law of the minimum
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the nutrient at minimum supply (limiting factor) determines the rate of growth or maximum performance of a given system
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why do we manage soil fertility?
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yield, costs, product quality, limit environmental pollution, etc.
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what is the coding on commercial fertilizers? %_,%_,%_
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%N,%P,%K
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briefly define and discuss utilization efficiency vs. economic efficiency
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utilization efficiency is the percentage of added fertilizer that is actually used by plants. economic efficiency is often measured by the change of economic return after fertilization. the two do not necessarily equal each other.
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briefly touch on some guidelines for achieving high utilization efficiency
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law of the minimum, understand the concept of factor interactions, maximize recycling, budget input with output, timing and system dynamics
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ammonia volatilization is primarily driven by what characteristic and why?
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pH - basic pH because OH ions drive the reaction of NH4 ions into NH3 gas
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biological N fixation is controlled by what enzyme?
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nitrogenase
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what is raindrop splash in terms of soil erosion
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raindrop splash transports soil particles, can be highly transformative
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define sheet erosion
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splashed soil is removed more or less uniformly. except where pebbles intercept the raindrops
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define rill erosion
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when water concentrates in channels as it runs off the soil creating small valleys. can be erased by cultivation
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define gully erosion
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when water concentrates in channels like in rill erosion, but is more pronounced, creating deep valleys that cannot be erased by cultivation
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what is the formula for the universal soil loss equation (USLE)?
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A=RKLSCP
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what does the USLE define?
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predicts the amount of soil loss by water sheet and rill erosion for a given year and location
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define the variables in the USLE
A=RKLSCP |
A= predicted soil loss
R= rainfall erosivity K= soil erodibility L= slope length (run) S= slope steepness (rise) C= cover and management P= erosion-control practices |
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explain R = erosivity
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the driving force of sheet and rill erosion. takes into account the total annual rainfall and rain intensity
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explain K = erodibility
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a soil's inherent susceptibility to erosion based on infiltration capacity and structural stability
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explain LS = topographic factor
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the influence that length (run) and steepness (rise) of a slope has on its erodibility
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explain C = cover and management
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as C increases to 1.0 there is no cover as C decreases to 0 there is absolute cover
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explain P = erosion-control practices
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as P increases to 1.0 there are no control practices
as P decreases to 0 there are absolute control practices |
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define accelerated erosion
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accelerated erosion is human caused and can be up to 1000 times faster than natural erosion
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define natural erosion
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caused by geologic systems
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what are the three processes of both water and wind erosion?
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detachment, transportation, and deposition
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define saltation
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[small particle movement/bouncing]
the movement of soil by a series of short bounces along the ground surface |
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define soil creep
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[large particle movement/rolling]
the rolling and sliding of saltation particles strike along the surface of the larger particles, causing larger particle movement |
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define suspension
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[very small particle movement/high up into atmosphere]
particles are moved upward from a few meters to as high as kilometers into the atmosphere |
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two factors that influence wind erosion
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soil moisture and wind velocity/turbulence
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what is the formula for wind erosion prediction?
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E = f(ICKLV)
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what are the variables associated with the wind erosion equation E=f(ICKLV)?
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E= predicted wind erosion
I= soil erodibility factor C= climate factor K= soil-ridge-roughness factor L= width of field factor V= vegetative cover factor |
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4 beneficial impacts of earthworms
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maintain healthy soil structure
speed up litter decomposition free up nutrients to support plant growth increase soil biodiversity |
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4 detrimental impacts of earthworms
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change water and nutrient retention
disperse weed seeds transmit pathogens soil erosion and compaction |
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3 main classifications of earthworms
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epigeic
endogeic anecic |
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define epigeic
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SURFACE FEEDER
feeds on litter at the soil surface |
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define endogeic
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SUB-SURFACE FEEDER
feeds on SOM in the soil (1-2m deep) |
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define anecic
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DUAL FEEDER
litter and SOM feeder, burrows deep in the soil and feeds on the surface primarily |
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what are five ways that invasive earthworms were introduced to the US
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agricultural application
ornamental plant import waste management land bioremediation (toxic spill clean-up) fish baits |
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where are invasive earthworms heavily prevalent in the US and why
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Wisconsin glaciation because the history of permafrost created a earthworm barrier until recently
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what is forest decline syndrome and how does it tie into invasive earthworm research?
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forest decline syndrome is the removal of the forest floor layer which causes plant death, removal of leaf layer is caused by invasive epigeic and anecic worms
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define biological oxygen demand
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how much oxygen is consumed by a water body's biological organisms
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define and explain the importance of riparian buffer zones
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zone where hydrophilic plants exist as a intermediary from land to aquatic systems.
slows down the water runoff from the land to the water channel giving microbial processes in the soil time to utilize nutrients in the runoff. |
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define pedon
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the smallest sampling unit of a particular soil, demonstrating that particular soil's properties
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define polypedon
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a soil individual, a grouping of pedons (like soil types)
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define epipedons
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diagnostic horizons that occur at the soil surface
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mollic epipedon
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-surface horizon
-dark color associated with high OM -soft even when dry -high base saturation (>50%) -typical for soils under grasslands |
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umbric epipedon
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similar to mollic except:
-base saturation is lower than mollic -somewhat higher rainfall than mollic where parent material has lower Ca and Mg content |
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ochric epipedon
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similar to mollic/umbric except:
-its horizon is either too thin, too light in color, or too low in OM to be mollic or umbric |
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melanic epidedon
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black, OM rich mineral horizon characteristic of soils developed from volcanic ash
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histic epipedon
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-a layer of black to dark brown peat or muck with very low density
-formed in wet areas -all organic soil material which sits on top of mineral soils |
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argillic horizon
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accumulation of silicate clays that have moved downward from upper horizons or have formed in place. identified by clay skins (aka argillans) coating pore walls
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natric horizon
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similar to argillic except clay is made up of more than 15% exchangeable sodium. mostly in arid/semiarid areas
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kandic horizon
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accumulation of Fe and Al oxides as well as low activity silicate clays (kaolinite) not necessarily with clay skins (argillans)
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oxic horizon
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highly weathered
high in Fe and Al oxides low activity silicate clays (kaolinite) mostly in humid, subtropical areas generally physically crumbly, not sticky |
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spodic horizon
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illuvial horizon characterized by the accumulation of collodial OM and Al oxide
found in highly leached forest soils cool humid climates |
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sombric horizon
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illuvial horizon
dark in color high OM low base saturation found in cool moist soils of high plateaus and mountains in tropical and subtropical areas |
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albic horizon
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eluvial horizon
light color low in clay and oxides of Fe and Al |
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calcic horizon
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accumulation of carbonates CaCO3
white chalk-like nodules arid/semiarid regions |
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gypsic horizon
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accumulation of gypsum CaSO4
arid/semiarid regions |
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salic horizon
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accumulation of soluble salts
arid/semiarid regions |
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duripan, fragipan, placic soils
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cemented or densely packed subsurface materials
relatively impermeable to water and or roots |
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duripan
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not slaky in water after dried
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fragipan
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very hard and dense, but brittle (no cementing)
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placic
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extremely hard horizon, cemented
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Aquic
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a SMR where:
-soil is saturated with water for sufficient periods of time as to cause poor aeration -almost free of gaseous oxygen -evidence of poor aeration (gleying and mottling) |
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udic
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a SMR where:
-soil moisture is high year-round in most years. -common for soils in humid climatic regions (1/3 of worldwide soil types) |
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perudic
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a SMR where:
-similar to udic except is extremely moist causing leaching throughout the year |
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ustic
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a SMR where:
-moisture is intermediate (read between udic and aridic) |
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aridic
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a SMR where:
-soil is dry for at least half of the growing season -characteristic of arid regions |
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xeric
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a SMR where:
-Mediterranean type climates -cool moist winter -warm dry summer -drought can occur |
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gelisols
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soils with permafrost and or cryoturbation
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histosols
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soils with organic materials without andic (low density, glass, pumice, etc.) properties
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spodosols
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soils with a spodic horizon (accumulation of colloidal organic matter and Al oxides occuring in highly leached areas) without andic (low density, glass, pumice, etc.) properties
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andisols
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soils with andic (low density, glass, pumice, etc.) properties
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oxisols
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soils with an oxic horizon
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vertisols
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soils with 30% or more clay that has shrinking/swelling properties
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aridisols
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soils with an aridic (arid regions) soil moisture regime. some B-level horizon development
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ultisols
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soils with an argillic or kandic horizon or fragipan and low base saturation
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mollisols
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soils with a mollic epipedon and high base saturation
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alfisols
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soils with an argillic, kandic, or natric horizon of a fragipan with clay skins
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inceptisols
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soils with a cambric, sulfuric, calcic, gypsic, petrocalcic, or petrogypsic horizon or with a mollic, umbric, or histic epipedon, or with an exchangable sodium percentage (ESP) >15%, or a fragipan
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entisols
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all other soils
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