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
desertification
conversion of productive land to desert, threatens 1/3 of earth’s surface and over 1 billion people
intensive farming practices are responsible for…
row crops leave soil exposed, weed free-fields, removal of windbreaks, no crop-rotation or resting periods for fields, continued monoculture cropping can increase soil loss tenfold
rangelands and pastures are highly susceptible to…
overgrazing and soil degration
africa and china are of particular concern
rapid population growth and poverty create unsustainable pressures, removal of trees for fodder and firewood triggers climate change that spreads desertification
low cost of water encourages…
overuse of water through waterlogging and salinization (mineral salts accumulate in soils; lethal to plants)
limits plant growth
lack of nitrogen, potassium, and phosphorus
alternative way to replenish soil
manure and nitrogen-fixing bacteria
the US food system consumes ___ of total energy
16%, eating locally grown foods have less environmental impact
biological pests
organisms such as insects or fungi that compete with humans to consume agricultural crops
pesticides
chemicals that kill biological pests
biocides
pesticide that kills a wide variety of living organisms
herbicides
pesticide that kills plants
insecticides
pesticide that kill insects
fungicides
pesticide that kill fungi
synthetically produced pesticides
most common method of controlling pests in modern agricultural production
DDT
inexpensive, stable, easily applied, highly effective, synthetic organic pesticide, almost killed off the bald eagle by thinning the shell of the egg leading to an inability to reproduce, banned in the US
conventional pestides
roughly 80% applied in the US are used in agriculture or food storage and shipping
organophosphates
most abundantly used synthetic pesticides, used as insecticides and inhibit cholinesterase, an enzyme necessary for nervous system function, quickly degrade, dangerous to workers, can be lethal
roundup
most commonly used organophosphate herbicide, genetically modified roundup resistant crops have been produced
chlorinated hydrocarbons
type of pesticide, fast acting and highly toxic to sensitive organisms, persistent and concentrate in food chains, atrazine, mothballs, and DDT
fumigants
small molecules which are delivered as a gas to penetrate soil or other materials, used in fungus control on strawberries or to prevent insect/rodent damage to stored grains, extremely dangerous to workers, restricted/banned in areas
inorganic pesticides
compounds of toxic elements such as mercury or arsenic, highly toxic, indestructible, persistent, generally act as nerve toxins
natural organic pesticides
generally extracted from plants and include such pesticides as nicotine or pyrethrums, toxic to insects and may prevent wood decay
microbial agents and biological controls
type of pesticide, living organisms or toxins derived from them that are used in place of pesticides.
non-target species
broadly sprayed pesticides might not reach intended target and instead kill beneficial organisms
pest resurgence
few resistant pests survive the pesticide and repopulate the area with more resistant pests, require finding new pesticides
persistent organic pollutants
chlorinated hydrocarbons that are stable, soluble in fats and toxic, travel far from the point of dispersal, stored in far and tend to bioaccumulate, high levels detected in upper level animals, evaporate from warm regions and condense in cold
human health problems due to pesticides
25 million have poisoning, 20,000 die each year. 2/3 result from occupational hazards. 73% of conventionally grown foods in the US contain residue of at least 1 pesticide
organic agriculture
eco-friendly, leaves soil healthier, less than 1% of american farmland but market growing, must be produced without use of hormones, antibiotics, pesticides, synthetic fertilizers or genetic modification, animals must be raised on organic feed, given access to outdoors, no steroids, and only given antibiotics when sick
behavioral changes to reduce pests
crop rotation, mechanical cultivation, flooding fields, habitat diversification, adjusting planting times,plant mixed polycultures, tillage at the right time
biological controls
predators or pathogens, insects that eat weeds, plants like neem tree that make their owrn pesticides, bio-engineering, hormones that disrupt the development or attract instects to traps
integrated pest management
flexible, ecologically bases strategy that is applied at specific times against specific pests, some use of pesticides takes place, time, type and method are controlled
trap crops
IPM, small areas are planted before the main crop, these plants mature first and attract insects, the trap crop is destroyed along with pests
contour plowing
plowing across slope to slow flow of water
strip farming
planting different crops in alternating strips along land contours
terracing
shaping land to create level shelves of earth to hold water and soil
highest rates of erosion
annual row crops because they leave soil bare for much of the year
method of providing ground cover
plant cover crops (clover) after harvest, interplant two different crops in the same field; harvest one the other is left to hold the soil, mulch
minimum till
less frequent plowing and cultivating
conservation-till
uses a disc called a coulter to open a furrow just wide enough for seed placement, have to depend on pesticides heavily
no till
drilling holes in the ground for seed through mulch and ground cover
vegetarian diet
reduce environmental impact concerning energy input
organic diet
reduce environmental impact concerning pesticide use
locavore
person who only eats locally grown, seasonal food
