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Potential Evapotranspiration/ Las Cruces

Water & Transpiration or Water, water everywhere and all the boards did shrink. Water, water everywhere and not a drop to drink. Potential Evapotranspiration/ Las Cruces. PET = evaporation + transpiration from a crop under non-stressed conditions Adjusted to a ‘reference crop’ (grass)

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Potential Evapotranspiration/ Las Cruces

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  1. Water & TranspirationorWater, water everywhere and all the boards did shrink. Water, water everywhere and not a drop to drink.

  2. Potential Evapotranspiration/ Las Cruces PET = evaporation + transpiration from a crop under non-stressed conditions • Adjusted to a ‘reference crop’ (grass) • Crop coefficient (kC) = ETC / ETO • Function of T, RH, season, leaf area, shading, crop species, soil moisture

  3. Las Cruces Potential Evapotranspiration Water (in/d)

  4. Warm Season Cool Season Trees and Water…Turfgrass Actual Water Use / Farmington NM/ D. Smeal

  5. ET (in/d) .25 Cool Season .15 Warm Season .05 Late, Warm Season Apr Jul Oct 200 300 100 Julian Days Trees and Water…Turfgrass Actual Water Use/ Farmington NM /D. Smeal

  6. Days without water (no.) Time since transplanting (d) Trees and Water…How often should new trees be watered?

  7. Irrigation Scheduling-nonstressed Fancy formula: • PAW = AWC x MAD x RZ • Sooo, Plant Available Water = soil Available Water Content x Maximum Allowable Depletion x Root Zone depth

  8. Irrigation .75 A B C .50 in/d .25 Budbreak Pecan Water Use/ Sammis et al.

  9. Water & TranspirationIrrigation & Water Management • Evapotranspiration: water loss through evaporation and transpiration • Yearly ET: ~ 200 cm • Yearly Ppt: ~ 20 cm • Deficit: ~ 180 cm • Daily ET (cm/d) Mar Apr May Jun Jul Aug Sep Oct 0.13 0.25 0.41 0.61 0.71 0.61 0.41 0.20

  10. Water & TranspirationIrrigation & Water Management • Goals of Irrigation: • Meet the needs of the plant • Minimize runoff • erosion • chemicals • Minimize evaporation • Manage leaching • salts • NO3

  11. Water & TranspirationIrrigation & Water Management • When to Irrigate? • Observe plants--too late! • Observe soil--’touchy-feeley’ • Measure soil or plant water stress • tensiometer * neutron probe • pressure bomb * electrical resistance • leaf temperature • Estimate water use • evapotranspiration

  12. Water & TranspirationIrrigation & Water Management • Reducing Water Use in the Landscape • Goal: Reduce evaporation • water at night or early morning • water deep to develop deep rooted plants • apply 5 cm organic mulch to cool soil • Goal: Put the water where you want it • directional sprinklers • berms or swales

  13. Water & TranspirationIrrigation & Water Management • Reducing Water Use in the Landscape • Goal: Use low water plants • xeriscaping • plant breeding • not ‘zeroscaping’ • Goal: Improve irrigation efficiency • drip irrigation • sub-irrigation

  14. Colligative properties Hydrologic cycle Irrigation Solvent Solute Field Capacity Permanent Wilting Point Water Use Efficiency Potential Evapotranspiration Transpiration Turgor Wilting MAD RH AWC Water Potential Xeriscaping Things to Know

  15. Water & TranspirationFactors Influencing Transpiration/ Musk mallow leaves Base of Plant Top of Plant

  16. Water & TranspirationHeat of Fusion/Frost protection in vineyard 495 L/min/ha 103 L/min/ha

  17. Water & TranspirationHeat of Vaporization/ Peach bud bloom delay

  18. Water & TranspirationFactors Influencing Transpiration/ Light, T, H2O Citrullus colocynthis Excised leaf Air T Intact leaf

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