This document discusses best practices for greenhouse irrigation. It notes that both under-watering and over-watering can harm plants, and that the optimal practice is to water properly based on plant needs. It also discusses factors like water quality, including measuring electrical conductivity and salt levels to avoid drought stress, as well as alkalinity, hardness, and the proper calcium to magnesium ratio. Finally, it briefly outlines different types of irrigation systems used in greenhouses.

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

17. Types of Irrigation Systems Hand watering Drip Tube Overhead Sprinklers Boom Watering Mat Watering Ebb-and-Flood Systems

25. Source: http://www.bizave.com/vme/boom2.jpg

28. Image Source - http://www.igcusa.com

29. Source: www.microgrow.com/ irrigation-controls.html Source: www.agrisupportonline.com/.../ soft_prod.htm