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Irrigation Management of Strawberry

Irrigation Management of Strawberry. Dr. John R. Duval Asst. Professor of Horticulture University of Florida http://strawberry.ifas.ufl.edu. Importance of proper Irrigation. Optimization of resources Minimization of inputs Social issues. Irrigation (The Basics).

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Irrigation Management of Strawberry

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  1. Irrigation Management of Strawberry Dr. John R. Duval Asst. Professor of Horticulture University of Florida http://strawberry.ifas.ufl.edu

  2. Importance of proper Irrigation • Optimization of resources • Minimization of inputs • Social issues

  3. Irrigation (The Basics) • When is irrigation needed? • How much water should be applied at each irrigation?

  4. Things to know • Pumping capacity • Irrigation efficiency • Soil characteristics

  5. Pumping Capacity / Irrigation Efficiency • How much water can be applied with available irrigation equipment? • How much water is lost in the system? • Typically 10-30% loss in drip system with an average of 15% • 20-30% loss with solid set overhead with an average of 25%

  6. Water balance of a FieldFrom Basic irrigation scheduling in Florida by Smajstrla et al

  7. Soil Texture Inches of Water per 12" of Soil Sands very coarse 0.4 to 0.8 Sands coarse 0.8 to 1.7 Fine sandy loams moderately coarse 1.2 to 1.8 Loams, silt loams medium 1.7 to 2.3 Sandy clay loams moderately fine 2.0 to 2.5 Clay, silty clay fine 2.0 to 3.0 Peats and mucks 2.0 to 3.0 Typical soil water holding capacities

  8. Determining Plant Water Needs • Gravimetric • Tensiometers • Resistive Sensors • TDR • Crop water balance models • Other

  9. Gravimetric Techniques • Oven drying of soil • Measures absolute water content • Used to calibrate other soil moisture determination techniques • Very accurate

  10. Tensiometers • Measures soil water tension

  11. Advantages Inexpensive Works well in saturated range Easy to install and maintain Can operate for extended periods Can be used in an automated system Disadvantages Difficult to translate data into water volume content Requires regular maintenance Subject to breakage Automated system costly Limited range Tensiometers

  12. Resistive Sensors(Gypsum block, Watermark) • Measures soil water tension

  13. Advantages Inexpensive High level of precision when ion concentration in soil constant Function over entire range of soil moisture Disadvantages Needs calibration Limited life of sensor Calibration changes over time (Gypsum blocks) Resistive Sensors

  14. Water Tension Measurements • General recommendations on when to water: Soil Type Tension (cbars) Sand 20-30 Silt 30-50 Clay 50-60 60 cbars limit of readily available water.

  15. Water Tension Measurements • Need to be calibrated • Need to know field capacity of the soil and the amount water needed to bring soil back to field capacity from a given tension

  16. Time Domain Reflectometer(TDR) • Measures volumetric water content

  17. Advantages Independent of soil texture, temperature and ion content Useful for long term measurements Can be automated Responds quickly to change Disadvantages Costly Time Domain Reflectometer (TDR)

  18. Other Sensors • Capacitive Sensors -Measures soil water content, measures at any depth, high precision -Costly, stability questionable • Neutron Probes -Measures soil water content non- destructive, can make real time measurements -Costly, dangerous, dependent on soil characteristics

  19. Advantages Doesn’t rely on soil moisture readings Inexpensive Takes into account climatic conditions Disadvantages Time consuming Crop water balance models(check book method)

  20. Crop Water Balance • Class A pan evaporation is used to estimate crop Evapotranspiration • Basic equation taking into account stage of plant growth Example DWU = R + I – (CF X ETo) – (D + RO) CF=0.15 + 0.018DAT + 0.0001DAT2

  21. Crop co-efficient curves

  22. Water Balance Assume a sandy loam with a soil water holding capacity of 1.5 inches of water Water use estimate Day 1 0.28 in. Day 2 0.37 in. Day 3 0.15 in. Day 4 0.30 in. Total 1.00 in. (2/3 Soil water) So irrigate to replace 1 inch of water on the 5th day

  23. So how much water do we put out? Example: Plasticulture system 4 ft bed spacing (10,890 linear bed feet) 2 ft bed top Emitter rate of 0.38 GPH Emitter spacing of 18 in (1.5ft)

  24. Example (Continued) So determine total number of emitters and multiply by discharge rate (10,890 ft / 1.5 ft) X 0.38GPH = 2759 GPH 1 acre inch of water = 27,154 Gallons So: 27,154 Gal / 2759GPH = 9hrs 50 min

  25. But Wait! We only want to water the bed. Which is only 2 ft wide. So: 2 ft bed / 4ft bed spacing = 0.5 And therefore we water for: 9hrs 50 min X 0.5 =4hrs 55 min

  26. Overhead Irrigation Flow rate Acre-In. water GPM/Acre applied in 1hr. 100 0.22 300 0.66 500 1.10

  27. To determine run time Assume flow rate of 300 GPM/A 1 inch of water needed divided by the Acre inches of water put out in a hour by the system 0.66 and multiply by 1 + the % loss in the system (25%) So: (1 A/in / 0.66 A/in/hr) X 1.25 = 1hr 54 min

  28. Irrigation Scheduling for Strawberry • When is irrigation needed? • How much water should be applied at each irrigation?

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