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 4.1 tons/acre (2003 data)

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

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

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

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

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

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

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

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

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

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)

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

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