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Soil Conservation

Soil Conservation. Erosion. Two billion tons of U.S. soil lost annually Improved from Five billion tons in 1982 Conservation programs and voluntary conservation tillage practices Tolerable losses (rule of thumb) at most – One to five tons/acre annually Missouri 5.6 tons/acre (1997 data).

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Soil Conservation

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  1. Soil Conservation

  2. Erosion • Two billion tons of U.S. soil lost annually • Improved from Five billion tons in 1982 • Conservation programs and voluntary conservation tillage practices • Tolerable losses (rule of thumb) at most – • One to five tons/acre annually • Missouri 5.6 tons/acre (1997 data)

  3. Erosion • Damage may be On-site or Off-site • On-site damage includes: • Topsoil losses • O.M. and nutrients • Decreased root zone • Decreased Plant Available Water • Gullies - make equipment operation difficult

  4. Erosion • Off-site damage includes: • Pollution of lakes and streams (nutrients and pesticides carried with eroded soil) • Sediment filling in lakes and reservoirs

  5. Erosion • Cost of Erosion • Two separate costs • Costs to the farmer and consumer (production loss) • Costs to the public (pollution and sedimentation)

  6. How Water Erosion Occurs • Three steps: • 1) raindrop impact shatters aggregates • Loosened particles seal soil voids limiting infiltration • Moving water also removes particles • 2) detached grains move in flowing water • 3) soil is deposited when water slows down

  7. How Water Erosion Occurs • Erosion (a form of work) takes energy • Energy comes from falling raindrops or moving water • Energy relates to size of drop and velocity • High energy can remove more and larger particles affecting amount carried off field • Deposition occurs when energy of running water decreases

  8. Four Erosion Factors • Texture and Structure • Slope • Soil cover • Roughness of soil surface

  9. Four Erosion Factors • Texture and Structure • Texture has two effects • Influences infiltration rate • Particle size affects ease of detachment • Silt particles are most easily detached • Structure also influences infiltration • Granules reduce runoff • Strong peds resist impact of raindrops • O.M. content aids in good structure formation

  10. Four Erosion Factors • Slope: • Two components • Length • Grade • Long, gentle slopes can have the same erosive potential as short, steep slopes • see figure 18-6, p. 300

  11. Four Erosion Factors • Surface Roughness • Rough surface slows velocity • Depends on tillage practices • Conventional tillage – smooth • Chisel plowing - rough

  12. Four Erosion Factors • Soil cover • Reduces energy available to cause erosion • Mulch • Cover of crop • e.g. turf or hay reduces energy plus plant roots hold soil • Row crops or nursery have varying effects depending on planting distances and stage of growth (canopy increases with growth)

  13. Types of Water Erosion Listing by Increasing Severity • Splash erosion • Sheet erosion • Rill erosion • Ephemeral gullies • Gully erosion • Severity limits workability; e.g. gullies can’t be crossed by equipment

  14. Predicting Soil Loss:The USLE and RUSLE • Universal Soil Loss Equation • Main tool for estimating erosion rates • Predicts only sheet and rill erosion

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