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agriculture: a science, an art, and a business directed at the cultivation of crops and the raising of livestock for sustenance and for profit.

agrarian: referring to the culture of agricultural communities and the type of tenure system that determines access to land and the kind of cultivation practices employed there.

hunting and gathering: activities whereby people feed themselves through killing wild animals and fish and gathering fruits, roots, nuts, and other edible plants to sustain themselves. Sahara

pastoralism: subsistence activity that involves the breeding and herding of animals to satisfy the human needs of food, shelter, and clothing.

transhumance: movement of herds according to seasonal rhythms: warmer, lowland areas in the winter; cooler, highland areas in the summer.

subsistence agriculture: farming for direct consumption by the producers, not for sale.

shifting cultivation: a system in which farmers aim to maintain soil fertility by rotating the fields within which cultivation occurs.

swidden: land that is cleared through slash-and-burn and is ready for cultivation.

intertillage: practice of mixing different seeds and seedlings in the same swidden.

crop rotation: method of maintaining soil fertility where the fields under cultivation remain the same, but the crop being planted is changed.

Soils "A critical sustaining structure for plants, animals, and human life." (Elemental Geosystems)

Soil: combination of sediments and decayed organic matter (humus) and empty pore space.

Weathering: disintegration and decomposition of rock at or near the surface.

Formation processes of water: Water percolating down - moves and removes soluble material, leaching.Evaporation makes water soak upwards causing minerals to precipitate


salinization - Over irrigation in dry regions causes the water table to rise allowing ground water to soak upwards to the surface. Minerals and salts dissolved in the water are transported to the surface and concentrate there as the water evaporates away. This renders the soil dead and infertile.

Controls on Soil Formation:

water and energy:
Weathering rates are faster in a warm, moist climate.

Plants and Animals plants and animals are a source of organic matter (humus) organic acids enhance chemical weathering.

micro-organisms (bacteria, fungi) break down organic matter

Parent Material
Residual Soil - type of bedrock (granite? limestone? sandstone?)
Transported Soil - alluvial soils laid down by water, loess laid down by wind.
Volcanic Soils - parent material lands on top of the soil.

Slope and angle - soil poorly developed on steep slopes and piles up in cracks.
Angle determines sun exposure

soils generally take millennia to develop, but can be eroded away in a few years.

Elemental Geosystems (2nd ed.), by R.W. Christopherson, 1998