GEOG 3000 Resource Management 9' Soil Conservation

1
GEOG 3000 Resource Management9. Soil
Conservation

• M.D. Lee CSU Hayward Fall 2002

2
Soil Conservation Approaches

• Soil conservation can be achieved through
  effective crop management and through the use of
  physical structures.
• The USDA encourages farmers to practice a series
  of best management practices. To see these, check
  out
• http//www.ctic.purdue.edu/Core4/CT/Choices/Choice
  s.html

3
How to Conserve Soils

• A critical element in most soil erosion controls
  is the prevention of the uncontrolled movement of
  water across a sloping soil surface.
• Similarly, efforts against wind erosion are
  designed to reduce wind velocity and surface
  shear above a soil surface.
• Controls also seek to boost soil cohesiveness and
  increase surface friction coefficients.

4
Predicting Soil Loss

• Soil scientists have had great success with the
  RUSLE (see p 147 CRO).
• A RKLSCP
• Where A soil loss, R rainfall erosivity, K
  erodibility of soil, L length of slope, S
  steepness of slope, C cover-type and P
  conservation BMP.
• R, K, L and S are fixed factors for a farmers
  land but C and P can be greatly modified by
  changing land management practices.
• Look at box 7.2 for the impacts of typical
  changes.

5
Some key conservation measures

• Minimal or no-till farming - doesnt destroy soil
  structure or remove residues, drills in seeds
  w/out furrows.
• Contour farming - plants rows at right angles to
  water flow
• Strip cropping and crop rotation - pairs mutually
  beneficial crops avoids leaving bare soil
• Alley cropping/agroforestry - grows trees and
  crops together, provides shade, leaf litter,
  nitrogen fixing, etc.
• Terracing - breaks slopes into shallow steps
• Gully control/reclamation - gullies can quickly
  swallow up topsoil and must be stopped by walls,
  plugs, etc.
• Windbreaks/shelterbelts - slow down winds and
  wind shear.

6
Best Management Practices

• Over the years, US farmers and the USDA have
  perfected many effective soil conservation
  practices.
• The USDA encourages farmers to practice total
  resource management to trap water and sediment
  within the farmers land and anchor the soil to
  the land surface.
• The following slides highlight some of the BMPs
  featured in the online version of the USDA guide
  called Conservation Choices
• http//www.ctic.purdue.edu/Core4/CT/Choices/Choice
  s.html.

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Crop Residue Management
Leaving last year's crop residue on the surface
before and during planting operations provides
cover for the soil at a critical time of the
year. The residue is left on the surface by
reducing tillage operations and turning the soil
less. Pieces of crop residue shield soil
particles from rain and wind until plants can
produce a protective canopy.
8
Crop Rotation
Crops are changed year by year in a planned
sequence. Crop rotation is a common practice on
sloping soils because of its potential for soil
saving. Rotation also reduces fertilizer needs,
because alfalfa and other legumes replace some of
the nitrogen corn and other grain crops remove.
9
Cover Crops
Crops including cereal rye, oats, clover, hairy
vetch, and winter wheat are planted to
temporarily protect the ground from wind and
water erosion during times when cropland isn't
adequately protected against soil erosion.
10
Contour Farming
Crop row ridges built by tilling and/or planting
on the contour create hundreds of small dams.
These ridges or dams slow water flow and increase
infiltration which reduces erosion.
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Terraces
Terraces break long slopes into shorter ones.
They usually follow the contour. As water makes
its way down a hill, terraces serve as small dams
to intercept water and guide it to an outlet or
help it infiltrate safely.
12
Grassed Waterways To Prevent Gullys
A natural drainage way is graded and shaped to
form a smooth, bowl-shaped channel. This area is
seeded to sod-forming grasses. Runoff water that
flows down the drainage way flows across the
grass rather than tearing away soil and forming a
larger gully.
13
Using soil conservation

• All of the example conservation approaches
  depicted in the previous slides are suitable for
  US farmers to adopt.
• The steeper the slope being farmed and the more
  erosive the rainfall, the more important it is
  that farmers use physical barriers rather than
  more simple surface treatments.
• In developing countries, similar BMP techniques
  have been developed, even for peasant farmers
  working on very steep hillsides.
• Terracing of slopes for soil stability is an
  ancient art going back to the earliest
  agricultural civilizations.

14
Land capabilities and limitations

• Years of experience and tools such as RUSLE allow
  us to predict pretty well how different land
  types will react to farming.
• Conservation districts bring farmers and
  extension workers together to carry out soil
  surveys, make land capability classifications,
  and coordinate soil conservation actions.
• Clearly in every landscape, uphill and downhill
  land uses must be in balance to prevent
  uncontrolled drainage or unchecked erosion
  affecting fields up or down slope.