Soil erosion 15

BY4215

Soil degradation

Part of global land degradation caused by overgrazing, deforestation, inappropriate agriculture, fuel wood overexploitation, urbanization, and other human activities

Land degradation spiral

Feedback loop between soil and vegetation leading to worsening conditions

Geological erosion

Natural soil transformation into sediment without human influence; forms landforms, occurs slowly, varies with rainfall and soil conditions

Water erosion in semiarid regions

Greatest damage where rainfall is enough to detach soil but insufficient to support dense vegetation

Sediment loads

Quantity of eroded soil transported by water

Human accelerated erosion

Moves twice as much soil as geological erosion; two-thirds unintentional; occurs when humans disturb soil

On-site effects of accelerated erosion

Loss of soil and deterioration of soil structure

Off-site effects of accelerated erosion

Sedimentation of lakes and rivers, windblown sand and dust

Soil susceptibility to erosion

Depends on texture (fine sand, silt, clay more vulnerable), structure (well-developed resists, poor structure susceptible), slope (steeper and longer slopes increase erosion)

Mechanics of water erosion

1. Detachment of soil particles 2. Transportation downhill by floating, rolling, dragging, splashing 3. Deposition at lower elevation

Raindrop splash

Detaches and disperses soil particles

Running water

Transports detached soil particles from higher to lower elevation

Sheet erosion

Uniform removal of thin soil layers over a wide area, often unnoticed, precursor to rill and gully erosion

Rill erosion

Small concentrated channels form due to overland flow, increasing detachment and transport of soil

Gully erosion

Deep channels (>30 cm) formed by concentrated surface water flow; severe, irreversible, destroys farmland, damages infrastructure, increases sediment in waterways

Deposition of eroded soil

Distance varies from meters to thousands of kilometers; delivery ratio

Contour cultivation

Planting along slope contours to slow water, reduce erosion, conserve moisture, improve water quality

Terraces

Level sections on slopes to slow runoff, prevent erosion, conserve water, improve productivity and stability

Conservation tillage

Minimizes soil disturbance, maintains ≥30% residue cover, includes no-till, strip-till, ridge-till, reduces erosion, improves soil health and sustainability

Maintain crop cover

Use cover crops to protect soil, maximize growth period, interseed before cash crop harvest

Vegetation barriers

Grass or shrub strips along slope contours to slow water, increase infiltration, trap sediment

Riparian zones

Vegetated areas along water bodies that stabilize banks, reduce runoff and soil erosion

Forest management for erosion control

Maintain ground cover, limit soil disturbance, design water management infrastructure, use continuous cover forestry, diverse species, restore cover crops or erosion control blankets

Vegetative cover importance

Protects soil from heavy rain, reduces sediment load, even light mulch significantly reduces interrill erosion

Windbreaks

Plant rows to reduce wind speed and protect soil from erosion