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IRRIGATION MONITORING & SCHEDULING
October 2017 Karen vd Westhuizen
Pr.Sci.Nat (Soil Science)
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SOIL PROPERTIES
Dry PWP
50%
Saturated STOP irrigation START irrigation Field Capacity
Total Available Water
40% 60%
IRRIGATION MONITORING & SCHEDULING October 2017 Karen vd - - PowerPoint PPT Presentation
IRRIGATION MONITORING & SCHEDULING October 2017 Karen vd - - PowerPoint PPT Presentation
IRRIGATION MONITORING & SCHEDULING October 2017 Karen vd Westhuizen Pr.Sci.Nat (Soil Science) 1 SOIL PROPERTIES Total Available Water START irrigation 50% STOP 40% irrigation 60% Field Capacity PWP Saturated Dry Irrigation is
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- The effective soil depth
(limiting layers)
- Effective rooting depth
(70-80% of roots)
- Volume of soil to irrigate
length height width
SOIL PROPERTIES
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SOIL MOISTURE CAPACITANCE PROBES
- Continuous data logging for temporal variation in soil moisture
- Sensors at multiple depths
- Data collected using: radio, hand logger, GPRS, Wi-Fi
2 sensors
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SOIL MOISTURE PROBES
Soil differences Sand Clay
- Probe placement is crucial
- Ensure emitter is functioning
- Representative position within block
- Representative plant
- In root zone to see water extraction
- In wetted zone to see when irrigation water applied
Sand Clay
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INTERPRETING PROBE GRAPHS
Buffer zone Cooler Period (3 days) Root zone 0-40cm Hotter period (1 day) Buffer zone 40-80cm Depth graphs
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SETTING GRAPH LINES ON SUM GRAPH
- Step 1: Set root zone depth
– Do a field observation – Look at depth graphs 40cm root zone 30cm root zone
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SETTING GRAPH LINES ON SUM GRAPH
- Step 2: Setting upper line
– Find drainage spike at EACH depth within the root zone – Field capacity Set upper line
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SETTING GRAPH LINES ON SUM GRAPH
- Step 3: Setting lower line
– Find stress point at EACH depth within the root zone – 50% of total available water Set lower line
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SETTING GRAPH LINES ON SUM GRAPH
- Step 4: Setting cultivar line
– Set manually depending on the phenological dates & strategies followed Wine Grapes: 40%
Bud break Flowering & set Veraison harvest Leaf drop
Root activity begins Dormancy Cell enlargement Berry ripening
70-80% 70 – 80% 50% 70 - 80%
Shoot growth
Pea size
Cell division
40-50%
Post harvest
50% 70%
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Irrigation duration
- Soil textures vary with deep drainage & runoff
- Select the correct emitter delivery
HOW LONG TO IRRIGATE?
Rapid Infiltration deep drainage may result Slow Infiltration runoff may result
Sandy Loam Clay Loam
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Irrigation frequency
- Soil textures hold & supply varying amounts of water
- Need for irrigation breaks
- Check field observations & probes
- Weather & crop dependant
WHEN TO IRRIGATE?
Sand Loam More frequently in smaller quantities Less frequently in larger quantities
3x 3x x x x
Irrigation = ETo x CF x 10
x x 3x
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Dry Permanent wilting point Refill Saturated Field Capacity 50% 40% 0% 100%
Field Capacity (0%) Cultivar line (40%) Refill point (50%)
1 2 3 4 5
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Dry Permanent wilting point Refill Saturated Field Capacity 50% 40% 0% 100%
Field Capacity (0%) Cultivar line (40%) Refill point (50%)
1 2 3 4 5
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Dry Permanent wilting point Stress starts Saturated Field Capacity 50% 40% 0% 100%
Field Capacity (0%) Cultivar line (40%) Refill point (50%)
1 2 3 4 5
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Dry Permanent wilting point Saturated Field Capacity 50% 40% 0% 100%
Field Capacity (0%) Cultivar line (40%) Refill point (50%)
Refill Point
Stress starts
1 2 3 4 5
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Dry Permanent wilting point Saturated Field Capacity 50% 40% 0% 100%
Field Capacity (0%) Cultivar line (40%) Refill point (50%)
Stress starts
1 2 3 4 5
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Dry Permanent wilting point Saturated Field Capacity 50% 40% 0% 100%
Field Capacity (0%) Cultivar line (40%) Refill point (50%)
Stress starts
1 2 3 4 5
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