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A1258690742rGWKX

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... moisture depletion at each stage of plant growth ... The amount of water available to the plant is a function of root depth and ... plant growth. For ... – PowerPoint PPT presentation

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Title: A1258690742rGWKX


1
Irrigation Scheduling
2
New Legislation
  • Act 148 Water use reporting, mapping of
    groundwater information, consider need for
    addition legislation
  • Act 177 Water use conflict resolution
  • Governor - Water Legacy Act
  • http//www.michiganlegislature.org/

3
Irrigation Scheduling
  • Know available soil water for each unit
  • Known depth of rooting for each crop
  • Know allowable soil moisture depletion at each
    stage of plant growth
  • Use evapotranspiration data to estimate crop
    water use
  • Measure rainfall in each field
  • Use container capacity for nursery crops

4
Why Schedule
  • Prevent stress health of plant - yield loss
    appearance
  • Maximize water use efficiency beneficial use
    of resource
  • Minimize leaching of nitrates or pesticides

5
Irrigation amount
  • The amount of water available to the plant is a
    function of root depth and soil available water
  • For example plant with a rooting depth of 2 ft
    on Coarse-textured loamy sand has .08 in/in X 2
    ft X 12 in/ft 1.98 in
  • For an allowable depletion of 50 - a 1 in
    application would replenish available water

6
Reference Evapotranspiration
  • ETo or potential evapotanspiration represents a
    well watered, fully developed plant such as grass
  • Reference evapotranspiration is multiplied by a
    crop coefficient to obtain the ET rate for a
    specific crop
  • The crop coefficient varies throughout the
    growing season
  • For Example Corn at 20 0.67 at 501

7
Estimates of ET
  • Max and min temperatures
  • Relative humidly
  • Wind
  • Net radiation
  • Modified Penman to estimate ETo
  • U of Wisconsin web site
  • http//www.soils.wisc.edu/wimnext/et/miet.html

8
ET Measurements
  • Weighing Lysimeters
  • Uniformity of soil important
  • Representative plant growth

9
For Annual Crops
  • Depth of root zone increases during the growing
    season
  • Allowable soil moisture depletion varies with
    each stage of plant growth

10
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11
Methods to Estimate Soil Moisture
  • Feel and Appearance
  • Electrical resistance electrodes on blocks in
    soil
  • Tensiometers measures soil moisture tension
  • Must be measured at a range of depths in root
    zone

12
                                                  
                                
                                  
13
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14
Irrigation Scheduling Methods
  • All methods require keeping sufficient records
  • Appearance and feel of soil must look at a
    range of depths in the root zone
  • Checkbook method inputs are rainfall and
    irrigation output ET Automated spreadsheet
    will be available by Jan 15
  • http//www.extension.umn.edu/distribution/cropsyst
    ems/DC1322.html
  • SCS-Microcomputer Irrigation Scheduling Package
    1992
  • Computer simulations

15
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