Soils Soils are the result of weathering F Mechanical F Chemical l Critical resources for food, timber, textiles... l Waste filters l Understanding soils is important for land-use planning, and engineering
Idealized soil profile from a humid climate at middle latitudes Zone of Leaching
Horizon Development and Climate
Soil textural classes
Topsoil ecosystem in a temperate climate
Porosity and Permeability Water saturation and air space Nutrients to plant roots
The Water Table The level below which the soil is saturated with water (no air space)
Soil water Representative water budgets Deficiencies can be remedied by storage and irrigation
Effect of climate on soil development
The Principal Soil Types
Effect of climate on soil types tundra soils Precipitation Temperature cold hot cool lowhigh50 cm/yr pedalferspedocals laterites tundra soils
Principal soil types in the USA
Effect of climate on soil types A typical pedocal with white caliche (CaCO 3 ) deposits in a shallow B horizon
Effect of climate on soils Making laterite bricks Temple at Angkor Wat Cambodia (700 yrs old) Laterite Tundra soil
A Newer Classification of Soil Types Pf Pc Pf Pf, Pc L Pf, L
Rates of soil formation: Central USA: ~ 1 cm/100 years in very porous and permeable rock Humid N. Carolina: ~ 1 cm/5 years“ Granite may require over 1000 years for a cm
Universal Soil Loss Equation A = RKLSCP l A = long-term average annual soil loss for site l R = long-term rainfall runoff erosion factor l K = soil erodibility index l L = hill slope/length factor l S = hill slope gradient (slope) factor l C = soil cover factor P = erosion-control practice factor
Both Ends of the Erosion Problem Serious soil erosion and gully formation related to diversion of water runoff over a few months in central California Sediment pollution following heavy rains in North Carolina
Soil Degradation l Erosion l Deforestation l Agricultural depletion l Contamination - Pollution F Salinization F Pesticides F Chemical additions and spills l Urbanization l Desertification l Overgrazing
Raindrop impact: millions in a single shower hit at ~ 30 mph Soil Erosion
Rill-wash and gullying in loose and poorly-consolidated soils Soil Erosion
Number of dust storms during the month of March, 1936 Soil Erosion
Effects of logging in Madagasgar
Soil Erosion Figure 3.12:(a) a natural forested slope (b) the same slope following a clearcut
Soil Erosion Figure 3.12:(c) the same slope after conversion to farmland (b) the same slope following urbanization
Soil Erosion
1968 motorcycles first come to Deer Creek near Bakersfield, CA 1972 after only 4 years of ORV use little vegetation or topsoil remains
Soil Erosion ORV users increased from 21 to 38 million between 1982 and 1992 ATVs rip through a marsh in West Virginia Great Grizzly Hike, Montana
Soil Erosion 1985 photo of bulldozer and jeep tracks in Alaskan tundra made in 1946
Soil Erosion
Salt accumulation due to irrigation in an arid climate: San Fernando Valley
Worldwide Distribution of Salt-affected Soils
Chemical Contamination of Soils
Grain production levels off while population continues to grow
Cleaning Up Chemical Contamination
Combating Soil Degradation
Strip-croppingand Contour plowing Combating Soil Degradation
Rice terraces in Asia Combating Soil Degradation
No-tillFarming
Soil Surveys and Adequate Planning