practice of raising crops and livestock for human use and consumption
the land used to raise plants for human use; it produces most of our food and fiber. (76% of our food from 12% of land)
the land used for grazing livestock. (16% of our food from 26% of land)
Began 10,000 years ago
Our ancestors began intentionally planting seeds from plants whose produce was most desirable, called selective breeding.
People followed the same process of selective breeding with animals, creating livestock from wild species.
Once our ancestors learned to cultivate crops and raise animals, they began to settle in more permanent camps and villages.
Traditional agriculture usually relies on a variety of crops (polyculture), requires only human and animal muscle power, hand tools, and simple machines.
high input and high yield
reliance on fossil fuels
commercial fertilizers and pesticides
growing a single crop (often a single genetic variety) usually on a large area of land
improves efficiency and yield
Disadvantages: All the plants are susceptible to the same things. If one plant is vulnerable to a particular disease, it is likely that the rest of the plants in the field (and all your neighbors’ fields) are going to die too. Allows pest species to have higher population sizes
applied technology to boost crop yields in developing nations.
Responsible for most (88%) of increase in food production since 1950
Involves shift from traditional to industrialized agriculture
Development and planting of monocultures high-yield crops (key crops have been rice, wheat and corn)
Increased yield with application of large amounts of fertilizer, pesticides, and water.
Grow multiple crops per year on the same piece of land
a complex system of disintegrated rock, organic matter, water, gases, nutrients, and microorganisms
an ecosystem in its own right
1st step in formation of soil
the physical, chemical, and/or biological process that converts large rock particles into smaller particles.
climate - forms faster in warm, wet climates
organisms - plants and decomposers add organic matter over time
topography - hills and valleys affect exposure to sun, wind and water
time - can take decades to millennia
parent material - the base geological material in a location
one type of parent material
the continuous mass of solid rock that makes up Earth's crust
the cross-section as a whole, from surface to bedrock
layers of soil due to the input of water and organics from the surface and minerals from weathering below
mostly organic matter in various states of decay
first true layer; "topsoil"
most roots, decay processes, and nutrient recycling
food comes from this level
vital for Agriculture
contains materials leached from upper levels, although these materials mostly accumulate in the next horizon down
the process whereby solid particles suspended or dissolved in liquid are transported to another location. (E = lEaching)
B-Horizon or subsoil
lower organic content and higher concentration of minerals
partially weathered parent rock
determined by size of particles; texture influences soil moisture
divided into size ranges:
Clay: particles less than 0.002 mm in diameter
Silt: 0.002–0.05 mm
Sand: 0.05–2 mm.
Particle size influences infiltration rate
Large particles = porous – water passes through easily
Fine particles = smaller pore spaces – water binds to particles more tightly
Soil with an even mixture of the three particle sizes is known as loam – good for plant growth
in general, plants don't tolerate soils that are too acidic or alkaline
plants gain nutrients through this process
Cation exchange capacity
expresses a soil’s ability to hold cations (preventing them from leaching and thus making them available to plants) and is a useful measure of soil fertility
a general deterioration of land that diminishes its productivity and biodiversity, impairs the functioning of its ecosystems, and reduces the ecosystem services that the land offers.
Productive soil is a renewable resource
Productive soils are not evenly distributed
In general, temperate soils have a larger store of nutrients than tropical soils due to the speed of decomposition (warm moist=fast).
This influences the kind of agriculture that can be successfully practiced.
soils have deteriorated in quality and declined in productivity due to drier conditions
the removal of material from one place and its transport toward another via wind or water
natural process that redistributes weathered materials
Common types: wind, water, splash (raindrop impact), sheet (water flowing over a gently sloping area that removes a thin uniform layer), rill (little rivulets of running water gather together and cut small channels in the soil, gully (occurs when rill erosion develops larger channels not easily dealt with by tilling)
3 Practices that increase erosion vulnerability
a loss of more than 10% productivity due to soil erosion, soil compaction, forest removal, overgrazing, drought, salinization, climate change, depletion of water sources, etc.
Can increase desert size or create new deserts.
Often involves positive feedback cycles, leading to a local state shift
measures to slow soil degradation
Conservation districts within each county promoted soil-conservation practices
renamed Natural Resources Conservation Service in 1994; responsibilities expanded to include water quality protection and pollution control
alternating the kind of crop grown in a particular field from one season or year to the next
returns nutrients to the soil
breaks cycles of disease and pests
growing multiple crops on one field minimizes the amount of time the field is left bare
protects the soil
Leaving crop residue (dead vegetation) on the soil is the easiest way to provide cover
Cover crops can also be used (such as rye, clover, or alfalfa)
Can be plowed under for mulch
protective groundcover that protects the soil, saves water, and prevents weed growth