Wednesday, September 28, 2011

How much & when? A training in irrigation management!

This week I gave a presentation on irrigation management at the Miami-Dade County Extension Office.

Part of a seven-week course on horticulture, the training I conducted was entitled Irrigation Management for Nursery and Landscape Industry.

Plug and play: I = ETcrop - P

There were approximately 34 participants from diverse backgrounds that included landscapers, homeowners and stakeholders from the ornamental nursery industry.

My presentation emphasized the importance of good irrigation management in order to achieve the objectives for which specific irrigation systems are designed.

water balance = inputs - outputs

The participants were particularly delighted to learn of the online tools that they could use to guide their irrigation management decisions.

Isaya Kisekka

Monday, September 19, 2011

New WUEP research sites online! - Part 1 of 2

This summer’s work around the WUEP Irrigation Research Project has been somewhat different from that of previous years. The expansion of the study to include weather-based timers (or evapotranspiration (ET)-based) in addition to soil water sensors (SWS) resulted in a new approach to homeowner system retrofits (and new site initiation).

Because the ET timer factors irrigation zone details into system run time calculations (including sprinkler head type/application rate), this year zone redesign played a more critical role in the retrofit process. Poor zone design (such as head-type mixing, see image below) makes timer programming difficult can result in excessive water-use and inaccurate data. To eliminate this, new sites often required additional visits for zone redesign work before data collection could begin.

Rotor v. spray: there can be only one

Over the next several weeks, research sites initiated since July will be detailed and, since new site initiation has concluded, this summer’s efforts will be summarized.

Palmetto Bay

Out at the crack of dawn with the squirrels, we began this installation day at a homeowner property that has been a part of the irrigation study since last summer. Their soil water sensor system beset by all manner of malfunctions, the residents decided to continue with the study for an additional year only this time with an ET controller.

With the electric valves, backflow device, and water meters already in place from last summer, we were allowed to focus on installing the new timer and weather station.

We concluded the installation by removing all existing spray heads from the system. This permitted more accurate ET timer programming since all the remaining sprinkler heads (rotor or multi-stream spray) apply water at a more similar rate.

Our usual method for gathering data on a ET study site involves metering the system's mainline to tabulate total water use. Since this is a 2 zone system, both zones were metered last year for the SWS comparison study. Consequently, no additonal meter work was required.

Coral Gables

The day's next homeowner property featured a mechanical irrigation system on city water and required a complete retrofit.

We began with our favorite pastime: digging up and eliminating the indexing valve!

Due to wiring issues the mechanical timer was kept in place as housing for the power wire feeding the ET controller.

Other installation details included adding a backflow device to protect the potable water lines, electric valves for each of the two zones, a water meter on the mainline to collect water-use data, and mounting the on-site weather station that provides the ET controller with temperature and rain-depth information.

Much like the previous system, this one suffered from poor design: head-type mixing and excessive heads. Although we could not tackle the redesign work on this day, we made note of the changes required to improve the zones (eliminating heads and replacing all spray heads with multi-stream sprays) for subsequent visits.

Coral Gables, again

This day concluded with a homeowner property dying to work with us. A WUEP participant from the early days of the program, it was invited to participate in the research when its SWS burned out. So eager was the owner to take part in the research that she offered to have a power outlet installed so that the new ET timer could be accessible from outside the garage! It was an offer that could not be refused.

Beset by downpours and time constraints, our first day on the property was limited to installing the new ET-based timer.

Several weeks later we returned to advance on the work. We began by addressing the inefficient means of distribution and bid the indexing valve adieu.

We then installed a backflow device for potable line protection, electric valves for each of the two zones, a water meter on the mainline for data purposes, and mounted the on-site weather station.

A galvanizing lesson

Because this property dates back to the early days of the City Beautiful, all the underground water lines are galvanized steel. What we were not aware of during the retrofit is that these pipes also pack some serious pressure!

Fed by a turn-valve sub-meter, the pressure in the irrigation system was so excessive that a few days following our retrofit it fractured the new PVC pipe-work in three places around the water meter!

On our third visit to the property we replaced all the fractured fittings and tackled the redesign work. Since the large zones featured predominantley rotors, our objective was two completely rotor/multi-stream zones.

before redesign: spray heads

after redesign: multi-stream sprays

We set about removing some heads, replacing some sprays with multi-stream sprays and moving some rotors for better coverage. We also manually adjusted the water pressure at the sub-meter to avoid future fitting fractures.

See previous entires:

Friday, September 9, 2011

All images courtesy of: yours truly!

One aspect of what I do on a daily basis that offers some respite from the hard science and public education work that characterize my tasks with the Water Resource team and the Urban Conservation Unit (UCU) involves visual media – both still and video.

In August, I had the honor of having a collection of some of my UCU field pictures used as art for irrigation-related articles in two publications.

In early August, South Florida Water Management District issued their new Water Efficiency Improvement Guide for Commercial and Institutional Facility Managers. As its title suggests, this comprehensive manual offers a bevy of water-use efficiency information for property managers.

The outdoor irrigation and landscaping section begins on page 96, and is peppered with many UCU equipment and inefficient practice field shots! You can download the manual (and see my work) here.


The Florida Water Resources Journal is a publication that highlights topics of interest to Florida’s water and waste water professionals.

The August issue features an article by Dr. Kati Migliaccio and Extension Agent/UCU team leader Mary McCready that not only discusses the latest research in irrigation control technology, but also provides an excellent detailing of Miami-Dade County’s recent efforts to introduce the use of this technology in South Florida– an initiative that has birthed both the UCU and the research project I work on. Visuals for this article are provided by the UCU! You can find it on page 18-20, here.

The UCU collection

Michael in action: mirror in the back yard? Don't mind if I do!

Eager for additional field pictures? You can enjoy more of my still media work here.

Friday, September 2, 2011

Nicki’s Field Study, Phase III: the nuts & bolts!

Over the past 4 weeks the finishing touches have been applied to the field plot. These final flourishes have moved along on two fronts: wiring and lysimeters. The former included mounting and wiring all the irrigation related low-voltage electronics (3 timers, a rain sensor, an on-site ET weather station, 16 valves and 4 soil water sensors); the latter included assembling a lysimeter prototype, confirming its effectiveness in capturing leachate, and mass production and installation of the prototype. The following is a summary of the past month’s action.

The wire

With three irrigation timers and sixteen valves in place, the remaining step involved running wire to all the equipment so that each treatment is able to operate independent of the other and in accordance with its prescribed function.

To this end, Dr. Kati Migliaccio crafted a wiring map and drafted intrepid TREC electrician Jorge Vergel into the Water Resource Team to assist with the wiring work.

Jorge in action

The four treatments

The four irrigation treatments in the field plot are:
- control: irrigates on a set schedule whatever the circumstances.
- rain sensor: a simple rain sensor either allows or prevent the automated schedule.
- soil water sensor: a soil water sensor either allows or prevents automated irrigation based on a set soil water content threshold.
- weather-based: the timer uses temperature, rain depth, and landscaping specifics to calculate the duration of irrigation events within set parameters.

Grudge match: rain sensor v. on-site weather station

These four treatments are divided among three timers. How? Well, since an activated rain sensor effectively paralyzes all timer function, this treatment is assigned its own clock. Likewise for the weather-based treatment, as this timer is its own entity. This leaves one timer to pull double-duty as both the control and the soil water sensor treatments – 8 valves on two zones. What!? Enter the relay box!

A relay box allows a low-voltage digital irrigation timer to fire multiple solenoid valves at once without dissipation of the 24V electrical charge. In the interest of science, the relay box allows a specific treatment's reps to turn on at the same time; therefore each is subject to all the variables present at that specific moment. In the case of the control/soil water sensor treatment, each treatment wire moves into the relay box, then out from the box to the valve platforms, where it is broken 4 times, one for each rep valve.

Going underground!

A lysimeter can be loosely defined as a container used to capture water as it percolates, via gravity, down the soil column. In addition to volume, the captured water can also be analyzed for soluble constituents.

The lysimeter design of choice for the field plot is based on the size of the hole possible with available drilling equipment. Although irrigation events will be programmed to apply 0.5” of water, the lysimeter is designed to collect up to a 1.5” rainfall event, which is common in South Florida.

Once the lysimeter prototype proved effective in the field following an early August deluge, mass production was initiated.

Each lysimeter consists of the following materials:
· 23” of 1.5” PVC pipe
· 1.5” cap
· 2:1.5” reducer
· PVC drain with 2” opening (lysimeter top)
· ½” female-threaded coupling
· 3 elbows (1/2” male-threaded with 3/8” barb)
· 3/8” plastic tubing (clear and mesh-reinforced)
· ½” PVC
· Fiberglass screen
· Acid-washed sand
· PVC glue and primer
· Hot glue
· Weather-resistant sealant

The Baseline conundrum

Wiring the other irrigation treatments is logical enough, but how in the world are 4 soil water sensors wired to one timer and so that each of them produces a unique soil water content reading for its specific rep?

Especially when conventional installation of this sensor system requires connecting the buried component to a valve in the field and interrupting the “common” wire at the timer level. All the field plot’s valves rest on platforms away from the field and the “common” wire for the sensor treatment must power 4 valves, each with its own rep!

Case closed: Mike moves from theory to practice in the Hydrolab

The easy answer is that there is nothing conventional about the soil water sensor treatment’s wiring. Each Baseline is powered by its own 24V source; the “common” wire for this treatment is split into four (one for each Baseline to interrupt) before moving to the valves on the platforms; and the sensor-to-sensor-controller communication is achieved through direct wiring that bypasses the valves. Conclusion: 4 unique sensors with 4 unique water content readings on one timer!

Turf in a rep is prepared for sensor insertion

Four soil water sensors, four unique soil water content readings

Drill, baby, drill!

Nick & Tina on drill detail

Lysimeter installation was completed using the following methodology:

A top layer of soil and grass was removed with a shovel (approximately 1 foot in diameter was removed) and a hole was drilled in 12 of the 16 plots, approximately 30” deep.

Manuel finesses the tunneling bar

Then a tunneling bar was used to chip away the bedrock and soil was removed so that the top of the lysimeter could lay just below the rooting zone.

The lysimeter was placed in the hole and the top was filled about halfway with the acid-washed sand.

Nicki and Letty rock!

The rock and soil was then returned, covering the lysimeter, and the original piece of grass was put in place.

The next step

With several matters still left to resolve (such as fertilization and lysimeter sampling frequency, treatment uniformity tests, soil water sensor calibrations, etc.), the field plot remains a few weeks away from its formal inauguration. Stay tuned for further developments!

Previous field plot entries: