chapter 10: Farming Flashcards
soil
renewable resource, develops gradually through weathering of rocks and the accumulation of organic material, accumulates 1mm/year, but severe erosion rates exceed 25mm/year
six components of soil
sand and gravel, silts and clay, dead organic material, soil fauna and flora, water, air
soil texture
amount of sand, silt and clay in the soil, is the most important characteristic of soils
loam soil
considered best for agriculture because they are a mixture of sand, silt, and clay
brazilian tropic soils
deeply weathered red clay with little organic material, hold few nutrients and water
black soil
rich in nutrients and organic material and contain a mixture of sand, silt, and clay to hold moisture well
soil bacteria
algae and fungi decompose leaf litter making recycled nutrients available to plants
mycorrihizal symbiosis
association between plant roots and certain fungi, plant feeds the fungus and the fungus provides water and inorganic nutrients to the plant enhancing growth
soil horizons
horizontal layers that soil are divided into
o horizon
organic layer, leaf litter, most soil organisms and partially decomposed organisms
a horizon
surface soil, mineral particles mixed with organic material
e horizon
washed out, depleted of soluble nutrients
b horizon
subsoil, often dense texture due to clays
c horizon
weathered rock fragments with little organic material
parent material
mineral material on which the soil is built, can be bedrock
identify soils based on..
thickness and composition of their upper layers
mollisols
dominant soil in the farm belt, thick, organic rich a-horizon, developed from deep, dense, roots when this land was covered with prairie grasslands
alfisols
type of soil important in farming, developed in deciduous forests and have a thinner a-horizon and less organic material
earth’s land currently in agricultural production
12.5%, four times as much could potentially be converted to farm land
ecological effects of converting land to farm land..
loss of biodiversity, clean water, other ecological services provided by these grasslands or forests
arable land
unevenly distributed around the world, best farming occurs in moderate climate with think fertile soil
gains in agricultural producation
come from increased fertilization, pesticides and irrigation rather than more land
hectare
2.41 acres
every year ___ of cropland worldwide are made unusable by _______ and another ____ are converted to non-agricultural uses
3 million hectares, erosion, 4 million hectares
sheet erosion
thin surface layer of soil removed
rill erosion
small rivulets (streams) of running water gather together and cut small channels
gully erosion
rills enlarge to form bigger channels too large to be removed by normal tillage
stream bank erosion
washing away of soil from banks of streams and rivers