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Irrigation and Drainage

Irrigation and Drainage. http://ga-mac.uncc.edu/faculty/haas/geol3190/termpap/wilson,r/index.html. Topic 2071 Created by Torey Birchmeier. http://www.danbury.org/org/stillriver/zone1_install.htm. Water Water Everywhere!. 3/4 of the Earth’s surface is covered by water

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Irrigation and Drainage

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  1. Irrigation and Drainage http://ga-mac.uncc.edu/faculty/haas/geol3190/termpap/wilson,r/index.html Topic 2071 Created by Torey Birchmeier http://www.danbury.org/org/stillriver/zone1_install.htm

  2. Water Water Everywhere! • 3/4 of the Earth’s surface is covered by water • Less that 3% is fresh water • This fresh water is not always in the right place at the right time

  3. Irrigation verses Drainage • Irrigation is applying water to the soil, other than natural precipitation • Drainage is the removal of excess gravitational water from the soil by natural or artificial means http://ga-mac.uncc.edu/faculty/haas/geol3190/termpap/wilson,r/index.html

  4. Irrigation waters • Irrigation waters come from the following: • Normal precipitation • Surface water • Groundwaters

  5. Surface Waters • 75% of water used in the US is surface water • Using surface water is cheap and easy • The composition of surface water varies considerably • The composition is critical for the uses of the water

  6. Groundwater • 20% of irrigation water comes from groundwater • This water exists in underground reservoirs in deep soils • These reservoirs are called aquifers • Some aquifers will recharge in a few days, years or may take 3 to 4 years • In some areas water is not replaced and surface land sinks

  7. Managing water irrigation • Two factors need to be considered when managing water irrigation • Water holding capacity of the soil • Water infiltration rate of the soil

  8. Water Holding Capacity • Water holding capacity is directly related to the soil texture • Loam soil contains approximately 50% solid particles, 25% air and 25% water • This soil will be half solid and half pore space • Pore space is half air and half water

  9. Water Holding Capacity • One half of the water is available to the plant and one half is unavailable • Lighter or sandier soils, holding capacity decreases • Heavier soils increase holding capacity • Soil compaction and organic matter affect water holding capacity

  10. Water Holding Capacity Per Foot • Sandy Soil .5 to .75 inches /foot • Loam Soil .75 to 1.25 inches/foot • Clay Soil 1.25 to 2.0 inches/foot

  11. Water Infiltration Rates (IR) • Due to continuous pores in soil • IR is rapid in sandy soil, slow in silt and slowest in clay soils • Granular IR will increase infiltration rate • Greater amount of coarser organic matter, the faster water will enter soil

  12. Water Infiltration Rates • Hardpan, crust and other restricting layers will affect water IR • Wet soils do not have as high an IR as dry moist soils • Compaction slows IR • Warm soils absorb water faster than cool soils • Frozen soils may not absorb water

  13. Drainage • One third of the cropland in Canada and US is artificially drained http://www.afcap.com/ShiningHope/Hope/CampHope1.html

  14. Benefits of Drainage • Properly drained soils warm faster in spring • Entire field is more uniform in soil moisture • Increases aerobic microbial activity • Reduces the amount of toxic substances (salts, methane gas, sulfides)

  15. Still Even More Benefits of Drainage • Drained fields are adapted to a wider choice of crops • Drained soils adds to the volume of soil to the root zone-more available nutrients thus a greater crop yield • Drainage is essential for reclaiming alkaline soils

  16. Two Common Drainage Systems • Tiling • Ditches http://www.geo.ed.ac.uk/~belize/dept/boothriv/threats.htm

  17. Tiling • Requires much planning and experience • Can last for up to 100 years • Involves laying of clay, concrete or plastic pipe in continuous sections • Gravels is usually poured around tile to prevent soil from entering into the drain • Allows water to move away from a parcel of land

  18. Open Ditches • Surface system of drainage • Adapted to relatively flat acerages • Ditches are designed to conform to the lands topography, land use and soil characteristics • Ditches are usually parallel • Requires continuous maintenance of the open ditches (removal of soil and weeds)

  19. References • Water use of the World. [On-line]: • http://ga-mac.uncc.edu/faculty/haas/geol3190/termpap/wilson,r/index.html • AFCAP at Work. [On-line]: http://www.afcap.com/ShiningHope/Hope/CampHope1.html • Threats. [On-line]: http://www.geo.ed.ac.uk/~belize/dept/boothriv/threats.htm • Zone 1 Instalation. [On-line]: http://www.danbury.org/org/stillriver/zone1_install.htm

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