ESCI 2610 Lecture Notes - Lecture 12: Soil Retrogression And Degradation, Pedogenesis, Badlands
14 Jun 2018
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Lecture 12 – Soil Ecosystem
Factors of Soil Formation
State of soil system. Soil horizons.
Fundamental Equation s = f (cl, o, r, p, t) *factor of climate, organic matter, relief of
landscape, parent rock, time.
Polygenetic origin, steady-state conditions of the pathways of geologic cycle. Soils on
the basis of all that can come about in a variety of different ways – polygenetic origin.
Time required 102 to 104 years of a formation of a soil.
Global average value 178 years per centimeter for soil formation. Water has a major
role.
Enemy of all this is wind action and drought.
Influence of human activity
Ferricrete: strongly cemented deposits in tropical areas (presence of iron)
Calicrete: calcium carbonate
Silicrete: silica
Rainfalls of high intensity, localized occurrence, and short duration.
Soils and Human Activity
Degraded soil is related to human activity. Degradation makes the soil less rich in
organic matter. One of the main reasons are faulty cultivation (overplanting to more
than what the soil can handle) and doing it until the plant nutrients are exhausted and
leads to deforestation.
Pattern of events: you commonly see surface runoff, and the first thing to happen are
rills (small scale erosion forms, features parallel to the slope, metres long and
centimetres deep) and this is the start for bigger scale. Rills turn into gullies (steep sided
erosion forms, parallel to the slope, flat and narrow bottomed, made deeper and
longer by rainfall events). The product of multiple gullies is a series of steep sided
cazerns which are interconnected at badland topography, this is an early stage of
desert formation.
Communication systems are interrupted, roads are eroded, telephone poles,
Chemical degradation, clearing of vegetation in tropical regions, removal of nutrients
for fuelwood, over application of fertilizers is not a problem for LDCs cause they can’t
afford fertilizers, acidification, salination, chemical pollutants related to excessive
application of pesticides, herbicides and fertilizers
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