Irrigating Efficiently: tools, tips & techniques. Steve Castagnoli, OSU Extension Service

Transcription

1 Irrigating Efficiently: tools, tips & techniques Steve Castagnoli, OSU Extension Service

2 Tonight s class: Why plants need water When plants need water How much water plants need Soil as a reservoir of water for plants Drip irrigation basics Hands-on exercise: design a drip system for

3 Climate & Weather Irrigating Efficiently Plants, Soil, Water, & Weather Plants Irrigation system Soil

4 Plants

5 Why do plants need water? Metabolic processes, e.g. photosynthesis Maintaining turgor water pressure inside plant cells provides support to stems, leaves, roots. Transpiration movement of water through plants from soil to atmosphere, mostly by evaporation from leaves.

6 When do plants need water? How much water do plants need?

7 We can accurately estimate how much water crop plants need, lawns* too, but landscapes are more complex and variable. Irrigation Needs (inches/month) April May June July Aug Sept Oct total apple cherry pears berry grapes corn onions peas grain pasture alfalfa *Lawns similar to pasture EM 8530

8 Precipitation (in) Seasonal Water Needs Evapotranspiration (in) Evapotranspiration (ET) Precipitation Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

9 ET (inches) Weather affects water needs. Daily ET Pear HOXO /15/02 4/29/02 5/13/02 5/27/02 6/10/02 6/24/02 7/8/02 7/22/02 8/5/02 8/19/02 9/2/02

10 Four AgriMet stations in Hood River Valley generate daily ET estimates.

11 Soil

12 What is soil? - a matrix or conglomeration of particles and spaces (pores) Particles can be mineral or organic. Pores can be filled with air or water. Soils have many properties relevant to irrigation management. Depth Texture Structure Porosity Water infiltration rate Field capacity Available water content

13 Soil and Water Loam soil: 50% porosity Add water - pores filled with water (saturation); 50% water content Pores drain by gravity (field capacity); 30% water content Water used by plant and lost to evaporation (permanent wilting point); 10% water content Available water content (AWC) = FC PWP (0.20 in/in) Max allowable depletion (MAD) = 50% AWC (0.10 in/in)

14 Soil and Water Runoff movement of water over the soil surface when rainfall or irrigation exceed the infiltration rate Deep percolation movement of water downward through the soil profile below root zone

15 Soil texture & structure Water infiltration rate Soil porosity Water holding capacity Available water content

16 Soil Texture & Plant Available Water soils are not created equally

17 What s my soil texture? Online Soil Survey and Mapper: Judging soil texture by feel: Jar test for soil texture:

18 Hood River Soils Orchards are planted on as many as 10 different soil types in the Hood River Valley, with AWC ranging from 0.11 to 0.28 (in H2O/in soil). The three most common are: Oak Grove loam 0.17 in/in Hood loam 0.20 in/in Parkdale loam 0.26 in/in Knowing your soil characteristics is important to efficient irrigation.

19 Irrigation Systems

20 Irrigation Methods Impact sprinkler ( Rainbird ) Basin or Flood High-volume / low frequency Drip Micro-sprinkler Low-volume / high frequency

21 Drip Irrigation Basics why drip? + minimizes water lost through evaporation (especially when combined with mulch!) + places water precisely + reduces weed growth & some plant diseases + very well suited to installation in zones, easy to expand for new plantings & maturation of landscapes - high silt content of water can be a significant challenge in Hood River area Filtration is usually necessary, especially when using irrigation water.

22 Drip Irrigation Basics - components 1. Connection to water source (backflow preventer for domestic water required) 2. Pressure regulator 3. Filter 4. Mainline 5. Lateral lines 6. Emitters 7. Timer/controller (optional, but highly recommended)

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24 Backflow preventers for connection to domestic water supply integrated hosebib Retro-fitted hosebib

25 Drip Irrigation Basics - maintenance flush filters periodically (depends on water source) check for clogged emitters (at least annually) flush mainline periodically (at least annually) add emitters/increase set times as plants grow larger (annually) winterize hard components (annually) (drain, blow out, or remove & put away)

26 Drip Irrigation Basics layout & operation How many emitters do I need per plant? What flow rate should I use? How long should I run my drip system? MANY CONSIDERATIONS: Plant species inherent water requirements Age/size of plant Time of year/weather conditions Soil water holding characteristics

27 We can accurately estimate how much water crop plants need, lawns too, but landscapes are more complex and variable. Irrigation Needs (inches/week) Hood River Apples, Cherries Apr May June July Aug Sep Oct Pears, Plums Lawn* *values for pasture EM 8530

28 inches/week?

29 inches/week? 2 inches

30 inches/week? 2 inches

31 Drip Irrigation Operation If we want to supply 2 inches of water, how long do we need to run the drip system? Gallons/week = inches/week x area (sq ft) x For a 6 foot diameter shrub: area = pi x (radius) x (3) 2 = 28.3 square feet (2 in) x (28.3 sq ft) x = 35.2 gallons/week for 28 square feet, we probably need more than 1 emitter Using 4 1-gallon/hour emitters (35.2 gallons/week) 4 = 8.8 gallons/week, and 8.8 hours per week or 1.3 hours per day

32 Drip Irrigation Operation If we want to supply 2 inches of water, how long do we need to run the drip system? Gallons/week = inches/week x area (sq ft) x For a 3 foot diameter shrub: area = pi x (radius) x (1.5) 2 = 7.1 square feet (2 in) x (7.1 sq ft) x = 8.8 gallons/week Using 2 1-gallon/hour emitters: (8.8 gallons/week) 2 = 4.4 hours/week, or 0.6 hours/day Using 2 1/2-gallon/hour emitters: (8.8 gallons/week) = 8.8 hours/week, or 1.3 hours/day

33 Drip Irrigation Basics layout & operation For diverse gardens or landscapes, vary the number and flow rate of emitters to match plant needs for water. Manage soil moisture in top 12 to 18 for annuals, vegis, herbaceous perennials, and lawns; top 24 to 30 for woody perennials. Adjust run time for time of year and for rain. Consider reducing the amount of water for well established woody perennials.

34 Mainline Pressure regulator Filter Battery operated timer Connection to water source

35 Timers/Controllers

36 Water-wise Gardening There are many conservation techniques you can employ in your landscape. Native Plants Ecolawns Bioswales & Rain Gardens Mulch

37 Water-wise Watering 1. Fix leaky hose, faucets, etc. 2. Adjust sprinklers to hit the target. 3. Avoid watering when windy. 4. Avoid watering during heat of day. 5. Mulch, mulch, mulch 6. Practice grass-cycling for lawns with mulching mower. 7. Use timers - adjust seasonally & for rain. 8. Use drip irrigation for non-turf landscapes. 9. Manage moisture in 12 to 18 for annuals, vegis, herbaceous perennials, and lawns; top 24 for woody perennials.

38 Assessing Rate & Uniformity of Water Application Photo: Tom Cook