Irrigation Management

Transcription

1 Irrigation Management Loren Oki UC Davis Irrigation Management Efficiency and Water Conservation in Nurseries November 17, 2014 Modesto, CA Technology and Soil Moisture Sensors Photo: L. Oki

2 Topics Soil moisture measurement Volumetric water content Matric potential Sensors Using soil moisture measurement to control irrigation 2

3 Soil moisture measurement Volumetric water content How much water is in the soil Proportion of the soil volume that is water Expressed as % 3

4 Soil moisture measurement Matric potential aka tension How tightly water is held by soil Expressed as kpa (kilopascal), MPa (megapascals), or cbar (centibar) 4

5 Water potential Potential energy components of water in substrates Matric potential - the energy required to remove water from the substrate Gravimetric potential the energy required to lift water Solute potential The energy required to dissolve things in it (salts, for example)

6 Water potential Potential energy components of water in substrates Matric potential - the energy required to remove water from the substrate Units of Measure: Kilopascals (kpa) Graphic: L. Oki Also: pounds per square inch (psi), bars or centibars (cbar)

7 Volumetric Water Content (%) Moisture Retention Curve describes the relationship between moisture content and moisture tension is different for every soil, but shape is similar for all potting soils Graphic adapted from J.H. Lieth Moisture Tension, kpa 7

8 Moisture Retention Curve Volumetric Water Content (%) Available Water Unavailable Water Graphic adapted from J.H. Lieth Moisture Tension, kpa 8

9 Moisture Retention Curve Volumetric Water Content (%) warning wet comfort sub-opt danger wilting Note how plants feel about different levels of moisture Graphic adapted from J.H. Lieth Moisture Tension, kpa 9

10 Moisture Retention Curve Volumetric Water Content (%) Irrigate based on Water content Available Water Unavailable Water Graphic adapted from J.H. Lieth Moisture Tension, kpa 10

11 Volumetric Water Content (%) Moisture Retention Curve warning wet comfort sub-opt Irrigate based on Water content Water potential Available Water Unavailable Water Graphic adapted from J.H. Lieth Moisture Tension, kpa 11

12 Moisture Retention Curve Volumetric Water Content (%) Wetting Drying Let tensions rise to 5 kpa Begin irrigating Stop irrigating when tensions fall to 1 kpa Graphic adapted from J.H. Lieth Moisture Tension, kpa 12

13 Moisture Retention Curve All soils have a characteristic curve Graphic: Brady & Weil, The Nature and Properties of Soils,

14 Soil moisture measurement Dielectric permittivity Time domain reflectometry TDR Photo: L. Oki 14

15 Soil moisture measurement Dielectric permittivity Capacitance Decagon EC-5 Decagon ECH 2 O-10, -20 Decagon 5TE Decagon GS3 Photo: L. Oki 15

16 Soil moisture measurement Watermark Granular matrix Photo: L. Oki 16

17 Soil moisture measurement Tensiometers Gauge Water loss Tube Ceramic cup Graphic: L. Oki 17

18 Soil moisture measurement Tensiometers Photo: L. Oki Photo: Soilmoisture Equipment 18

19 Irrigation based on soil moisture Tensiometer Analog-to-digital converter Transducer Emitter Valve Input channels Output channels 6V battery Water in Drain tile relay Graphic: L. Oki 19

20 Tension-based v. grower controlled irrigation Soil Moisture Tension, kpa Tension-based 906 sec 714 sec 687 sec Grower-controlled 5cm 24cm 40cm 0 09/16/94 09/19/94 09/22/94 09/25/94 09/28/94 Date

21 Tension-based v. grower controlled irrigation Soil Moisture Tension, kpa Tension-based 906 sec 714 sec 687 sec Grower-controlled 5cm 24cm 40cm 0 09/16/94 09/19/94 09/22/94 09/25/94 09/28/94 Date

22 Water use efficiency Rose Production Grower L/m 2 L/m 2 During test Test Difference during test -26%

23 Water use efficiency Rose Production Grower Test L/m 2 stems/m 2 L/m 2 stems/m 2 During test Difference during test -26% 67%

24 Water use efficiency Rose Production Grower Test L/m 2 stems/m 2 stems/l L/m 2 stems/m 2 stems/l During test Difference during test -26% 67% 122%

25 Water use efficiency Rose Production Grower Test L/m 2 stems/m 2 stems/l L/m 2 stems/m 2 stems/l During test After test Difference during test -26% 67% 122% Difference after test 1% 26% 18%

26 Length of rose stems harvested Stem length, cm Test Grower * Prob <0.05 * * * * * Test system removed Feb 6 Feb 13 May 3 May 10 May 17 May 25 Aug 4 Graphic: L. Oki Date

27 Sources of error Temperature variations Salinity Soil properties Texture Bulk density Organic matter content *Assuming the equipment is working properly 27

28 How to get started 1. Install your soil moisture monitoring system 2. Log data without irrigation control 3. Study the data a. Understand what it says b. Know your sensor 4. Turn on irrigation control 5. Repeat 3 and 3a above 28

29 Soil Moisture Tension Dry Night Day Wet Saturation 29

30 Soil Moisture Tension 30

31 Soil Moisture Tension 31

32 Some resources Soilmoisture Equipment Corp. P.O. Box Santa Barbara, CA USA Telephone: Website: Irrometer Company, Inc Palmyrita Ave. Riverside, CA Phone: Website: Decagon Devices 2365 NE Hopkins Court Pullman, WA Phone: Website: Vegetronix, Inc. P.O. Box 583 Riverton, UT Telephone: Website: Spectrum Technologies 3600 Thayer Court Aurora, IL Phone: Website: Delta-T Devices Ltd 130 Low Road Burwell Cambridge CB25 0EJ United Kingdom Website: Inclusion of a manufacturer on this page or presentation constitutes neither an endorsement nor recommendation. 32

33 Thank you Thank you Photo: L. Oki