Irrigation for the Greenhouse

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  • Most common cause of plant stress in the greenhouse environment; Under-watering can be a problem; Over-watering can be a problem; Once stressed plants may be morphologically and physiologically different. Wilting Leaf loss Premature flowering Flower abortion Necrotic lesions on stems an leaves (secondary pathogen attack) only in severest cases.

Transcript

  • 1. Greenhouse Irrigation Practices The most important and often undervalued practice in controlled environment production.
  • 2. Source: www.ualr.edu/~botany/ transpiration.jpg
  • 3. UNDER-watering
    • Plants can wilt
    • Plants can look OK, but stomates are closed more than normal
    • Fruit cracking
    • Leaf abscission
    • Increase of disease and pest damage
  • 4. Source: weather.nmsu.edu/.../ stress_function.htm
  • 5. Source: weather.nmsu.edu/.../ stress_function.htm
  • 6. OVER-watering
    • Lush foliage, soft and susceptible to damage
    • Poor root aeration – increase in root rots
    • Increase run-off more waste
    • Less efficient use of nutrients
    • Over time even moderate amounts of over-watering can result in stunted plants
  • 7. Water Quality Parameters
    • Soluble Salts (EC)
    • Alkalinity
    • Hardness
    • Specific Elements
  • 8. Soluble Salts (EC)
    • Measured by determining electrical conductivity
    • For seedlings the maximum tolerance is 0.75 dS/m
    • For mature plants max tolerance is 1.5 dS/m
    • Salts are transferred to the substrate during watering – in addition to salts that build up from fertilization
  • 9. Soluble Salts (EC)
    • When salt increases in the substrate it makes water uptake more difficult for the plants. Why?
    • When salt levels in the solution are the same as solute levels in the roots – the plant can’t take up water – drought stress will occur even if the media is moist
    • Salt build up can be a particularly difficult issue in some bottom irrigation systems
  • 10. Source: http://ss.jircas.affrc.go.jp
  • 11. Source: weather.nmsu.edu/.../ stress_function.htm
  • 12. Source: www.ces.ncsu.edu/.../ fig_water1.html
  • 13. Source: www.liv.ac.uk/ ~sd21/stress/salt.htm
  • 14. Alkalinity
    • Alkalinity is a separate term from pH
    • Measure of the facility of water to raise the pH –Carbonate –Bi-carbonate
    • Very similar to applying limestone
    • me=milliequivalents of calcium carbonate
  • 15. “ Hard” Water Issues
    • High alkalinity – should test for hardness
    • Measure of calcium and magnesium in water (me of calcium carbonate)
    • For each part Mg there should be 3 to 5 parts Ca
    • If there is more calcium this can block plant uptake of Mg
    • Opposite problem and Ca uptake can be inhibited
  • 16.  
  • 17. Types of Irrigation Systems
    • Hand watering
    • Drip Tube
    • Overhead Sprinklers
    • Boom Watering
    • Mat Watering
    • Ebb-and-Flood Systems
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  • 25. Source: http://www.bizave.com/vme/boom2.jpg
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  • 28. Image Source - http://www.igcusa.com
  • 29. Source: www.microgrow.com/ irrigation-controls.html Source: www.agrisupportonline.com/.../ soft_prod.htm