Improving Drip Irrigation for Grape Vines Dr. Franklin Gaudi Irrigation Training and Research Center (ITRC) at Cal Poly 1
However. Before you can schedule irrigations, we need to make sure the system is performing well. Have you conducted a DU evaluation?
What is DU? Distribution Uniformity The measure of how evenly water is applied to the field Always expressed as a decimal value DU of 0.90 is achievable with PC emitters
DU POOR UNIFORMITY Depth of Water GOOD UNIFORMITY (NEVER PERFECT) Depth of Water
How is DU calculated? DU = Avg. depth of the low quarter Avg. depth infiltrated over the entire field Surface Loss 1 0 Portion of Area 25 50 75 100 Depth of Water Infiltrated 1 2 3 4 5 6 Contribution to Target = 2.75 avg. 2.25 = Avg. Low 1/4 Inf. 3 SMD Deep Perc. = 0.25 Avg. Underirrigation = 0.25 Avg. Avg. Applied = 3 Target = 3
Is DU Different than Efficiency? YES! Efficiency describes how much water was beneficially used compared to what was applied Always expressed as a percentage Efficiency can be high, especially if you underirrigate.
Efficiency Efficient Depth of Water Not Efficient Depth of Water
What are Beneficial Uses? Crop ET Leaching Cover crop Climate control Weed germination
Irrigation Managers prefer DU over Efficiency DU is repeatable It can be maintained Efficiency can only be determined after the event or the season It can be different each event depending on the duration and the initial soil moisture content
Water Destination Diagrams These are used to graphically show how well your system is performing and how efficient the event was. It also shows were the losses are and what is beneficially used
Water Destination Diagram: Under-Irrigation 0 0 Field Area (%) 100 Pre-Infiltration Losses Stored for Plant ET Depth of Water (inches) SMD D min Deficit D max Deep Percolation
Water Destination Diagram: Over-Irrigation Depth of Water (inches) 0 SMD D max 0 Field Area (%) Stored for Plant ET 100 D min Pre-Infiltration Losses Deep Percolation due to DU Deep Percolation due Poor Timing ITRC/BRAE
Basic Idea for Improvement #1 Achieve a high DU ITRC offers a week long training on Irrigation System Evaluation Next Class is June 18-22, 2018 at Cal Poly www.itrc.org for more details
Things to Check There are two basic ideas: #1. Ensure the pressures throughout the vineyard are as uniform as possible This means adjusting pressure regulators so that each manifold has the same inlet pressure Look for large pressure losses at the filters or along the manifolds Remove hose screen washers
Pressure Regulators
Things to Check There are two basic ideas: #2. Ensure that the flow from each of the emitters is uniform. Flush hose ends and manifolds at least monthly Ensure good filtration Don t just add emitters
Testing Emitters
Make sure your water goes to all plants uniformly Avg. DU = 0.86
Basic Idea for Improvement Keep Records #2
Can you look back 5 years and tell me what day you applied water in June? And tell me how much water you applied? Good records help you look back and see what worked and what didn t work.
Basic Idea for Improvement #3 Always use flow measurement Do you have a flow meter? How often do you record the volume of water applied? If you can t measure it, you can t manage it!
You need good flow rate measurements, to avoid driving without a speedometer.
Basic Idea for Improvement #4 Really learn about your crop.
In Paso, is there just one ET rate for wine grapes given one day and one age?
For Wine Grapes, a big factor influencing ET is * The % canopy cover, or % ground shading at noon
The cover crop ET is higher than the vine ET
Basic Idea for Improvement #5 Technology can be helpful But if you get too fancy, or if you believe in magic, it s probably not going to work for you.
Just a thought What does a soil moisture sensor such as a capacitance meter tell you, in a drip/micro irrigated orchard? And very specifically, how will you use the NUMBERS?
What a soil moisture sensor tells you with drip irrigated vines. When the water reaches a depth (assuming you have a real-time data logger on that sensor) The approximate moisture content or stress within about 2 of that sensor.
What a soil moisture sensor does NOT tell you with drip irrigated vines. The ET of the vines. The average soil moisture content The average soil moisture tension ***Instead, it is a POINT measurement. It is NOT a representative sample.
Never rely exclusively on one technique for irrigation scheduling. Use a combination of - ET based scheduling - Plant indicators - Soil moisture indicators
What about telemetry?!
You don t need exquisite hourly or daily values. Weekly values of ET are fine.
Keep in mind that digging backhoe pits, auger holes, and using soil moisture sensors are all helpful. Just don t start believing in magic!! Keep your hand on your wallet when talking to people selling all sorts of fabulous sensors.
Basic Idea for Improvement #6 Use technology to improve your yield.
Google and Satellite Remote Sensing now provide fantastic information.
Poor stand in a portion (Notice the lower ETc in that area)
Variability Do these areas have similar yields (quantity/quality)? Not Likely Should they?
Basic Idea for Improvement #7 Look at the big picture.
Single Irrigation Block If this system is a single block Where are tissues sampled? How do you manage deficits?
Could we Split the Irrigation Blocks Now we have more options Probably need a VFD Proper injection equipment Provides more uniform pressures Remember the idea of DU?
Targeted Nutrient Applications Now we have options: Ground based variable rate application Inject at main supply and operate blocks differently Inject at individual blocks (blocks operated at the same time)
Basic Idea for Improvement #8 Don t just add on to an existing block! That affects the hydraulics of the system It also affects the operation of the pump Together this greatly reduces the pressure available in the hoses Rather do the opposite if needed, add blocks.
Basic Hydraulics More flow in the mainline means more friction More friction means lower pressures at the manifolds Lower pressures at the manifolds means reduce flow rates PC emitters have helped limit this problem.
Pump Curve A larger flow requirement in the field means the pump needs to supply more flow More flow from the pump means the pump produces less pressure So you start with lower pressure and then you have more friction too! This means dismal pressures in the field
TDH (ft) Sample Pump Curve Pump Curve Pump Curve 200 180 160 140 120 100 80 60 40 20 0 0 500 1000 1500 2000 2500 3000 Flow Rate (GPM)
Microspray and Drip Pressure Differences - 44.9% Plugging, Wear, Manufacturing Variation - 51.5% Unequal Drainage - 1.1% Application Rate - 2.5%
Get a Resource ITRC wrote the book on drip/micro irrigation systems. It is available at www.itrc.org
Questions?