aggregates
groups of tightly bound soil particles
cation exchange capacity
the maximum quantity of cations a soil is capable of holding
chemical weathering
a process by which rocks are broken down by chemical forces such as acids
clay
an impermeable type of soil with very small particles (less than 0.002 mm in diameter)
compost
a mass of humus produced from decomposition of organic waste
conservation district
a county-based entity established by the Soil Conservation Service
Conservation Reserve Program
a program that pays farmers to stop cultivating highly erodible cropland
conventional irrigation
a method of irrigation that involves spraying water broadly on fields
contour farming
a method of farming that involves planting crops in horizontal contours to create natural erosion-preventing dams
cropland
any land used for production of crops
crop rotation
a method of farming that involves varying which crops, if any, are planted in any given field
dead zone
a body of water characterized by a lack of marine life due to eutrophication
deposition
the arrival and accumulation of eroded material at its new location
desertification
the phenomenon by which already arid land loses its remaining water, vegetation, and wildlife
drip irrigation
a method of irrigation that targets specific plants instead of spraying the entire field
Dust Bowl
an event in the 1930s United States where unsustainable farming led to destructive dust storms
erosion
the removal of material from one place and its transport toward another by the action of wind or water
eutrophication
the sudden influx of excess nutrients that promote algal blooms, endangering wildlife
Fertile Crescent
the region in the Middle East whence agriculture originated
fertilizer
a substance added to soil to facilitate crop growth
genome
the complete genetic code of an organism or species
gravel
a type of soil whose particles are very large (greater than 2 mm in diameter)
green manure
the use of already dead and uprooted plants as fertilizer
groundwater
water stored inside an aquifer
guano
a rich fertilizer derived from bat feces
Haber-Bosch process
the process by which atmospheric nitrogen can be artificially converted to ammonia
humus
organic material that cannot be further broken down
hypoxia
a condition resulting from a lack of sufficient oxygen
industrialized farming
a type of agriculture that requires planting of monocultures
infiltration
the process by which surface water enters the soil
inorganic fertilizer
a type of fertilizer produced synthetically or obtained from mining
intercropping
a method of farming that involves planting different types of crops adjacent to each other
irrigation
the allocation of water to cropland
leaching
the loss of water-soluble minerals from soil
leaf litter
dead plant material on the ground suitable for decomposition
legume
a family of plants whose root nodules contain nitrogen-fixing bacteria; includes lentils, peanuts, and soybeans
loam
a mixture of soil consisting of relatively even parts sand, silt, and clay
macronutrient
a nutrient required in large quantities for an organism's survival
micronutrient
a nutrient required only in trace amounts for an organism's survival
monoculture
a field in which only one variety of crop is planted
mycorrhizae
a symbiotic relationship between a fungus and a plant; important for primary succession
Natural Resources Conservation Service
a division of the USDA that assists in sustainable farming practices; formerly the Soil Conservation Services
nitrate
a polyatomic ion and macronutrient that is often the limiting factor for growth in saltwater environments
nitrification
the process by which ammonia is converted to nitrates and, further, to nitrites
nitrogen fixation
the process by which atmospheric nitrogen is converted into ammonia, by lightning, specialized bacteria, or the Haber-Bosch process
no-till agriculture
a method of farming in which fields are not tilled before planting to reduce soil disturbances
nutrient
a chemical compound necessary for the survival of an organism
organic fertilizer
a type of fertilizer that consists of natural materials
parent material
the rock from which a given sample of soil was formed
pasture
Land that is plowed, planted, and harvested in order to provide forage for animals.
permeability
the capacity of a soil to allow liquids to pass through it
pH
the logarithmic ratio of hydrogen ions to hydroxide ions; a measure of acidity or basicity
physical weathering
a process by which rocks are broken down by physical forces such as wind and rain
polyculture
a field in which more than one variety of crop is planted
porosity
the size and density of empty spaces in a soil; the percent of volume in a soil that is unoccupied
rangeland
any land used to raise or graze livestock
reduced tillage
a method of farming in which fields are tilled less than in conventional agriculture
retention
the holding of water by a soil
rock cycle
the dynamic transitions that describe the formation, breakdown, and reformation of rock
root nodule
a raised bump on a plant's root that houses symbiotic nitrogen-fixing bacteria
runoff
the flow of water resulting from oversaturated soil
salinization
the process by which dissolved salt accumulates in water
sand
a type of soil whose particles are fairly large (0.05 mm to 2 mm)
sediment
rock material derived from weathering and erosion and settling in an area
shelterbelts
the planting of tall, perennial plants to obstruct wind flow and reduce erosion
silt
a type of soil whose particles are of medium size (0.002 mm to 0.05 mm)
soil compaction
the process by which soil is pressurized and becomes denser as pore space is reduced
soil horizon
one of six distinct layers of soil
soil profile
a vertical column of soil representing the larger distribution
soil structure
the composition and clumping of soil granules
soil texture
the relative abundances of sand, silt, and clay in a soil
soil texture triangle
a diagram that can be used to classify a soil given percentages of sand, silt, and clay
symbiont
an organism that has a symbiotic relationship with another organism
symbiosis
a mutualistic relationship between two organisms in close physical contact
tillage
the practice of overturning soil to mix in organic matter and break up weeds
traditional agriculture
the practice of agriculture without powered machines or artifical supplements
transpiration
the process of water moving throughout a plant and evaporating into the air
USDA
the United States agency that oversees food, agriculture, natural resources, rural development, nutrition
waterlogged soil
a soil that is completely saturated with water
water table
the boundary in an aquifer between partially filled pores and fully filled pores
watershed
the area whose groundwater stems from a given river
weathering
the process by which rocks are degraded by physical or chemical forces
subsistence agriculture
Agriculture designed primarily to provide food for direct consumption by the farmer and the farmer's family