Soils Flashcards
What is the definition of soil?
a dynamic natural body composed of mineral and organic solids, gases, liquids and living organisms which can serve as a medium for plant growth
What are the 4 soil forming processes?
additions - to the surface
losses - from the surface or to deeper in the profile
translocations - movement within the profile, but not away from the location
transformations - weathering (chemical change)
What are the soil forming factors?
parent materials climate biota topography time
What are parent materials?
organic, mineral or a combo formed in place or transported by water, wind, ice or gravity
How does climate effect soil formation?
soil development tends to increase when soil moisture and soil temperature increase
How does topography effect soil formation?
landscape position influences susceptibility to erosion, particle decomposition, and microclimate (slope vulnerability)
What role to biota play in soil formation?
deposition of organic matter, mining of nutrients, decomposition of organic materials by heterotrophs
What are the general soil horizons?
O - organic matter A - mix of organic and mineral soil E - zone leached of clays B - accumulation of clays C - undifferentiated parent material (weathered) R - bedrock
What is the soil profile?
all the horizons in an area
What are the 12 soil orders?
alfisols, andisols, aridisols, entisols, gelisols, histosols, inceptisols, mollisols, oxisols, spodisols, ultisols, vertisols
What are alfisols?
moderately leached, lower elevations, good for agriculture
What are andisols?
volcanic ash, can be fertile, but constrained by mineral content
What are aridisols?
long dry periods, hard to see horizons, minimal O layer
What are entisols?
no horizon development, can be very young and turbulent, may or may not be good for ag
ex) sand dunes
What are gelisols?
cold, permafrost within 2 meters
What are histosols?
muck, almost entirely organic, usually wetlands
can be drained for ag, but often have micronutrient deficiencies
What are inceptisols?
weak horizon development, young or cool soils, often higher elevations, not the best for ag, but are frequently used
What are mollisols?
grassland soils, organic rich surface, very rich ag soils
What are oxisols?
intensely weathered, tend to be nutrient poor, tropics
What are spodosols?
sandy acid forest soils, distinct E layer, not great for ag
What are ultisols?
highly leached, nutrients lost quickly, SE US
What are vertisols?
shrink swell clays, cracks allow for redistribution, some used for ag
What are major soil properties?
texture, water holding capacity, pH, slope, drainage, cation exchange capacity
How is texture determined?
a combo of sandy, silt and clay
What is water holding capacity?
ability to absorb and hold water against gravity, often the most limiting factor
available vs unavailable water
Why is proper drainage important?
air is needed for proper root growth
What is cation exchange capacity?
ability of soil to adsorb and supply ions, concentration in solution so they are available for plant uptake (nutrients are obtained in the form of dissolved ions)
What is the regolith?
layer between the soil surface and soil bedrock
How can soil be transported?
gravity - colluvium
water - alluvium
glaciers - glacial
wind - Eolian
What is humus?
organic matter left in soil as a result of decomposition and mineralization
What are the components of prime farmland?
adequate and dependable water supply favorable temp and growing season acceptable acidity and alkalinity acceptable salt and sodium content few or no rocks permeable to water and air not excessively erodible not saturated w/water for long periods of time doesn't flood frequently OR protected from flooding
Why is tillage done?
prepare soil for planting incorporate crop residue (manage disease) destruction of weed and weed seed warm soil dry out soil stimulates decomposition
What is the spectrum of tillage?
*leaves different amounts of residue on the surface
conventional - multiple passes; plow, disk, harrow
no till
reduced - minimal passes, ridge, strip
What are the challenges of no-till organic?
weed management
organic is generally dependent on tillage
special roller-crimper machine to smash and break cover crop
What are the impacts of conservation tillage?
very effective at reducing erosion, runoff
decreases nutrient and agrichemical flows
less clear impact on soil C sequestration
What is the soil condition index?
SCI = OM + FO + ER
organic matter, field operations, erosion
What are the types of water erosion?
runoff - water moving laterally
sheet - uniform removal of soil
rill - irregular dispersion, small channels
gully - large channels, disrupts tillage
What are the first components to move with water?
soluble nutrients, clay, organic matter
What is RUSLE?
Revised Universal Soil Loss Equation A = RKLSCP R = rainfall intensity and distribution K = soil (texture, SOM, stability, infiltration) L = length of slope S = steepness of slope C = crop (sequence, cover, etc.) P = practice (reduce velocity)
What happens when you plant to close to water bodies?
the waterway is unprotected and moves pollutants quickly
What are some options to mitigate erosion?
contouring, terraces, field borders, catchment, sod, grassed waterways, filter strips, shelter belts (windbreaks)
What are the functions of soil microbes?
decomposition of organic matter mineralization and recycling of nutrients fixation of nitrogen detoxification of pollutants maintenance of soil structure biological suppression of plant pests parasitism and damage to plants
What are the characteristics of healthy soil?
good soil tilth, sufficient depth, sufficient but not excessive supply of nutrients, small population of plant pathogens and insect pests, good soil drainage, large population of beneficial organisms, low weed pressure, free of chemicals and toxins, resistant to degradation, resilient in unfavorable conditions
What is soil health?
capacity of soil to function, to sustain productivity, maintain/enhance water and air quality, promote plant/animal health
What are common soil constraints?
compaction, poor aggregation and crusting, weed pressure, high population of pathogens and root diseases, low water and nutrient retention
What soil properties change slowly?
texture, slope, mineralogy
What soil properties change quickly?
temperature, water content, available N
What soil properties change intermediately?
organic matter, pH, drainage
What are the properties of the Cornell soil health test?
physical - aggregation, available water capacity, surface hardness, sub-surface hardness
biological - organic matter, active carbon, potentially mineralizable N, root health
chemical - pH, extractable P, extractable K, minor elements
How can soil health be improved?
reduce tillage intensity
crop rotation - disrupts disease cycle
cover crops - protection, added SOM, added N, weed suppression
organic amendments - manure and compost (turn waste into a resource)
chemical amendments
