Introductory Lecture for Landscape Horticulture on Water: Plant and Soil Relationships

1. LH1 WaterPlant and Soil Water Relationships

3. Water keeps cells rigid so that they don’t collapse

5. Areas of High Water Potential include very wet or moist soils or where the molecules of water are greater than molecules of dissolved minerals

7. Roots and other plant parts contain high concentrations of solutes: molecules dissolved in water necessary for all biochemical reactions.

8. Water moves into roots from an area of high water potential to low water potential in an attempt to equalize the contents of the plant cellsOsmosisThe process which water enters the Root System

9. Water Travels Upwards in Plants through the Xylem Through Cohesion and Adhesion Cohesion is the attraction water molecules have for other water molecules. Adhesion is the attraction between water molecules on mineral particles

10. Xylem is formed by sections of long ultrathin segments known as vessel elements or tracheids

14. Temperatures are high

15. Under warm and windy conditions

17. Needle-like Leaves Reduce Surface Area Loss of Water

18. Summer Dormancy in Mediterranean Climates Babianacorms grow during wet winters and … Are dormant in the summer

19. Water Movement in Soil Gravitational Water: water that moves down through the soil due to the effect of gravity Capillary Water: Water that is held on soil particles and aggregates which can be used by plants Hydroscopic Water: Water that is bound tightly to soil particles and not available to plants

20. A Totally Saturated SoilOccurs During a Rainstorm

22. This water is held against the pull of gravity by the forces of adhesion, the attraction of water molecules to other particles

23. This water is known as Capillary water. It is the available water in the soil which plants can suck off of soil particles

24. Capillary forces can move water laterally or upward through the small soil pores through the cohesion of water molecules from areas of high water potential to low water potentialField CapacityA measure of the amount of water a soil retains after gravitational water drains

27. Adding organic matter to sandy soils can significantly increase its field capacity

28. Clay soils hold more capillary water and also hydroscopic water

29. At the point where plants cannot obtain water from a soil they will wilt

30. If they are not quickly watered they may reach their PWP (Permanent Wilting Percentage) and die! Soils differ in their ability to retain water, both capillary and hydroscopic water

32. More water must be applied to a clay soil to reach the same depth as sandy or loamy soil

34. Movement of Water into Soil is known as Infiltration *When the application of water is higher than infiltration then run-off will occur *Infiltrometer gauges how fast water will penetrate soil. Will give you an idea of soil texture.

35. How to Determine the Water Content of the Soil? Tensiometer is an airtight, hollow tube filled with water with a porous end inserted into the soil A vacuum gauge at the other end measures the pull exerted by the soil on the water. The greater the pressure the drier the soil

36. Hand-Feel Test

37. Practical Hand-Feel Test

38. Water Quality

39. Misc. Water Quality Parameters

40. Hard vs. Soft Water Hard Water is due to high levels of dissolved minerals, commonly calcium and magnesium Causes spots on dishes, scale on shower heads, and can clog drip irrigation emmiters Hard Water is worse in S. California Soft Water has

41. Guidelines for Using Grey Water in the Garden Mix washwater with rinse-cycle water before using on plants Some plants are more sensitive, eg. Azaleas and strawberries Do not use wash water for potted plants with restricted root zones Do not pour directly onto base of plants which may cause crown rot Use of black water not allowed by law

42. Chlorine in Bleach will damage plants, let water stand overnight before using to let chlorine dissipate Boron will burn leaf edges. Fabric softeners contain either boron or metaphosphates containing sodium. Use natural detergents. Phosphates will generally not hurt plants, usually acts as a fertilizer, but can cause algae blooms in lakes and streams.

43. Watering and Irrigation

44. Hunter Sprayers used for some Large Landscape Installations but wasteful

45. Underground Watering Systems(E.g. Netafim)

46. Micro-Sprayers

47. Microsprayer Set-up

49. Filter

51. Many Different Types of Sprayers are Available

53. Swale Gardens

54. How Deep to Water? LEAFY VEGETABLES AND ANNUALS 6 inches – 1 foot SMALL SHRUBS, COOL SEASON TURFGRASS, CORN, TOMATOES 1 feet – 2 feet LARGE SHRUBS, TREES, WARM-SEASON TURFGRASS 1.5 feet – 5 feet

55. Soil Auger to test how deep you are actually watering

56. How Much Water Do Plants Require? Water is loss from plants through TRANSPIRATION Water is also lost from the soil surface through EVAPORATION Total water loss from plants and soil is known as EVAPOTRANSPIRATION WATER LOSS THROUGH EVAPOTRANSPIRATION MUST BE REPLACED FOR HEALTHY PLANTS

58. Coastal Areas have lower evapo-transpiration rate

60. Type of plant and root depth

61. Evapotranspiration Coefficient,

62. Wind, heat, rainfall

63. Topography: slopes usually require more water, also Southern exposures

65. Turn on irrigation system for 20 min., measure inches of water & multiply by 3 to determine inches of water per hour

66. If the amounts vary by more than 15-20% your irrigation system needs adjusting

67. Run normal irrigation time or until run-off starts. Check to see how deep the water has penetrated

69. Plants begin using water as soon as sunrise

71. Low water pressure

73. Disease and rots