Irrigation Research

Sprinkler head being adjusted

NEW: U.S. Consumer Water and Irrigation Usage 2014

Contact: Hayk Khachatryan

Summary: The results of the U.S. consumer water and irrigation usage study provide insights into homeowners' water use and conservation strategies. The information within this report serves to assist turf, landscape, and irrigation specialists as they strive to sustainably serve their customers. Results provide an overview of household water usage, current irrigation practices, smart irrigation perceptions, and consumers' likelihood of purchasing smart irrigation technologies in the near future. Recommendations are provided based on the results.

Characterization of Organic Compounds in Nursery Reclaimed Water

Principal investigator: Gurpal Toor
Other investigator: Geoff Denny

The overall goal of this study is to obtain information about organic compounds in reclaimed water that would help develop scientifically sound solutions to manage reclaimed water and will enhance the environmental and economical sustainability of nurseries.

Water reuse is a growing practice and Florida leads the nation in using reclaimed water. But Florida’s growing population, and the accompanying increased demand for freshwater, mean that the state’s commercial and agricultural industries will need to rely increasingly on reclaimed water.

Reclaimed water is known to contain nutrients and soluble salts, and may also contain other organic compounds, such as plant growth regulators. The presence of excess amounts of organics in water may have phytotoxic effects on plant growth, making it necessary for reclaimed water to be treated prior to use. Therefore, we need to know if reclaimed water contains organics in excessive amounts, and if so, what mitigation approaches are needed to remove these compounds from the water.

For this project, the investigators will collect reclaimed water samples from four to six nurseries in the Tampa Bay area that represent different plant species and management practices. The samples will then be analyzed for organic compounds. If organics are present in significant amounts, the investigators will test the scope of chemical amendments to remove the compounds in a laboratory study.

Determination of Landscape Irrigation Water Use in Southwest Florida

Principal Investigator: Michael Dukes

It is important to have an accurate baseline of existing water use to track impact of future conservation efforts. Currently, only scattered and isolated data of irrigation water use on residential homes in southwest Florida exist. It is difficult to assess the current efficiency of irrigation water use and to benchmark conservation efforts without measuring representative irrigation water use data in the DISTRICT. Then, it is important to measure the effectiveness of FFL’s practices.

This PROJECT will use Automatic Meter Recording (AMR) devices on subsets of utility customer bases throughout the DISTRICT to monitor utility meters at a high frequency (i.e. every 5 or 10 minutes). This frequency of monitoring will allow the separation of relatively low volumetric uses inside the house compared to the higher irrigation water use. Thus, the irrigation water use can be determined from select customers without solicitation of the customers.

Determination of Maximum Acceptable Irrigation Deficit on Turfgrass for Water Conservation

Principal Investigator: Michael Dukes

Urban landscape irrigation is one of the largest growing water use sectors in Florida. The state's Water Management Districts (WMD) have been working collectively to find ways to assist urban users to irrigate more efficiency. In May 2008, UF-IFAS hosted a Best Management Practice (BMP) workshop in Apopka with the goal of identifying current knowledge base of BMPs in horticultural crops including turfgrass and landscape plants. During the workshop, it was clear that water use and potential conservation in landscapes (turfgrass and ornamentals) was a high priority for many of the stakeholders. The Southwest Florida Water Management District is funding a five year study "Investigation and Development Methods to Determine Urban Landscape Irrigation for Planning and Permitting in Central Florida (P424). It is expected that P424 will identify appropriate coefficients for permitting water use in the irrigation of landscapes. However, as water supplies become strained there may be a future need to permit based on less than well-watered conditions, or to restrict uses during periods of water shortage. While P424 will determine, as a starting point, water needs for optimal landscape aesthetics, this project will determine the absolute minimum irrigation needed to ensure landscape survival.

Determining Water Needs of Shrubs During Establishment

Principal Investigator: Ed Gilman
Other Investigator: Amy Shober

Research has shown that shrubs and trees can take up to a year before they are established. However, current water restrictions allow for establishment watering of shrubs for only 30 - 60 days. This study is designed to determine how much irrigation is actually needed to establish shrubs in the landscape. Hibiscus and Sweet Viburnum are being used as the plant materials. Study locations include Ft. Lauderdale Research and Education Center (REC), Gulf Coast REC, Mid-Florida REC, and Citra Tree and Landscape Unit.

EPA SWAT Test Update

Principal Investigator: Michael Dukes

Since the completion of the official EPA SWAT test for Climatologically Based Controller Draft 8 Protocol, data has continued to be collected and recorded from the SWAT controllers. It is desired to further analyze this data and update the SWAT analysis. The following task is associated with this effort.

Task 1: Update the SWAT analysis for all existing data collected to date.

  1. Data collected from March 2009 through May 2010 will be analyzed for a range of conditions to include rainy/dry as well as high/low ET periods. A minimum of four 60 day periods will be selected for analysis.
  2. Add in the check for 3 d maximum missing and 2 d consecutive maximum missing weather data, and the 3 minute minimum run time assessment.
  3. Revise the analysis spreadsheet for website posting as necessary.
  4. Develop a final report that shows the update of the SWAT analysis.

Evaluation of Minimal Required Number of Soil Moisture Sensors for Uniform Agricultural and Turfgrass Irrigation Control

Principal Investigator: Michael Dukes

Agricultural water use is the largest single category of water use in Florida. According to USDA, there are 3.7 million acres of crop land in Florida and, in 2003, 49% of this land was irrigated and 62% of harvested crop land was irrigated in the same year. Frequent occurrence of drought conditions associated to the large use of water by municipal, agricultural and industrial purposes has been increased the needs of implementation of more efficient irrigation systems.

Recently, SWFWMD and FDACS have funded multi-year projects to investigate the potential use of soil moisture based irrigation for vegetable production and landscape applications. The use of soil moisture sensors has shown strong potential for saving of irrigation water in experimental plots. This type of control system has been successfully used on sweet corn, green bell pepper, zucchini, tomato, turfgrass and is currently being used with promising results on golf course fairway irrigation control.

The expansion of the use of soil moisture sensor technology to control and monitor irrigation in large areas requires a more detailed study of soil moisture in the upper soil layer. The variance of soil moisture spatial patterns is expected to be dominated by soil type, topography and vegetation. In addition, the characterization of soil moisture variability can be related to the topographical attributes such as slope, elevation, and distance from the drainage channel. This information is crucial to a successfully implementation of soil moisture sensor system especially for areas susceptible to flooding or with high water infiltration rates. The number of soil moisture sensors needed to effectively control irrigation or monitor soil in cropped areas is still unknown. This project will investigate the spatial variability of soil moisture in irrigated agricultural with potential for use of soil moisture sensor irrigation in relation to topography and soil properties and will also address the issue concerning the minimum spot measurements or/points for soil moisture sensor location number to estimate the representative water content in a given field area.

Evaluation of Soil Moisture Based On-Demand Irrigation Controllers Using Reclaimed Wastewater Irrigation (Phase III)

Principal Investigator: Michael Dukes

In many areas of the state where water supplies are limited, reclaimed wastewater is being increasingly used for irrigation purposes. Often, reclaimed wastewater contains high levels of salts as a result of the treatment process. Salts can interfere with the operation of some types of soil moisture sensors. Thus, commercially available soil moisture sensor irrigation control devices need to be tested for functionality under reclaimed wastewater irritation. Similar steps taken in previous phases of this project will be incorporated into this phase. Several commercially available on-demand soil moisture based control systems will be will be evaluated under a number of test conditions, and the one showing the most promise will be selected for installation on cooperating homes in Pinellas County. Four treatment scenarios shown below will be evaluated and results presented.

  1. Soil moisture sensor irrigation control (one sensor brand) only.
  2. Time based irrigation control (homeowner) with a rain sensor.
  3. Time based irrigation control (homeowner) without a rain sensor.
  4. Time based irrigation control (homeowner) where the homeowner is given educational materials with instructions on programming irrigation time seasonally with a rain sensor.

Investigation and Development Methods to Determine Urban Landscape Irrigation for Planning and Permitting in Central Florida

Principal Investigator: Michael Dukes

Florida’s urban landscape water use is expected to grow considerably over the next few decades. With the development of a more precise approach to the allocation of water for landscape irrigation, more water could become available for other demands. This project addresses five main objectives to aid in establishing acceptable landscape aesthetic quality while reducing water demand. The objectives are:

  1. Determine the crop coefficient for species of turfgrass used in Florida landscapes.
  2. Determine turfgrass rooting characteristics to allow an accurate determination of irrigation allocation.
  3. Determine the crop coefficient for several ornamental species under reduced water conditions commonly encountered in residential landscapes.
  4. Determine landscape coefficient of mixed species landscapes under varying percentages of planted area and well-watered conditions.
  5. Determine landscape coefficient of mixed species landscapes with a fixed ratio of turfgrass to ornamentals and three levels of ET replacement (i.e. variable irrigation levels).

Irrigation Literacy Evaluation, Phase II

Principal Investigator: Michael Dukes

This project has been developed as a Phase II of the Water-wise Irrigation Practices and Perceptions (WWIPP) survey. Phase I investigated outdoor water-use practices and perceptions of single-family homes, through a mail survey. The Phase I survey targeted lawn and garden practices, environmental skill, knowledge of ordinances, motives for conservation/use, and perception of community conservation/use of the typical household. Phase II will include an examination and review of various models based on social-psychological theories of behavior and change, (this is the study of how social conditions affect human actions). A model used with the collected data in Phase I can help to develop suggestions that can be incorporated to implement change in outdoor water use behavior for irrigation conservation. The model will be used to develop a scenario plan which can be used to weigh the options between impact and feasibility of an irrigation conservation campaign. From the Phase I survey conclusions, the ideal scenarios will be modeled to determine the most successful targeted water-wise irrigation education approach in Phase II. The application will include the development and implementation of campaigns to stress irrigation conservation practices.

Optimizing Water Use for Freeze Protection

Principal Investigator: Michael Dukes

Irrigation is the primary method used for fruit, vegetable and nursery cold protection. During cold events in recent years the Dover/Plant City region experienced several resource problems believed to be caused by irrigation used for crop protection. Although most agricultural producers follow best management practices for cold protection irrigation, there are opportunities to optimize this water use.

Current cold protection recommendations are based on 1960’s modeling for citrus nurseries and it’s not clear if these recommendations are for advective (i.e., windy) or radiation freeze events. In addition, the generally accepted recommendation of 0.25 inches/hr of sprinkler irrigation has not been thoroughly tested to determine if alternative rates may be effective at freeze protection. Lower sprinkler application rates may provide adequate cold protection and result in less pumpage required. Since this recommendation was developed, the irrigation and agricultural industries have gone through many changes. However, continued review of the recommendations has not been done. This project will investigate current irrigation cold protection practices with the intent to identify ways to enhance and optimize irrigation for crop cold protection. This will include current application rates and possible changes to system uniformity under varying events.

Organic Matter and Irrigation Frequency Effects during Shrub Establishment

Principal investigator: Kim Moore
Other investigators: Amy Shober; Michelle Scheiber, Environmental Horticulture Department

The overall goal of this study is to examine how the addition of organic matter to soil and watering frequency impact the establishment of woody ornamentals in the landscape. The addition of organic matter to Florida soils will be evaluated in relation to irrigation frequency to assess establishment of shrubs. This experiment will be conducted at the Fort Lauderdale Research and Education Center. The shrub species will be common ones used in the area. Growth indices, biomass, root to shoot ratios and plant quality will be used to evaluate physiological establishment in the landscape. Leaf transpiration rate and soil moisture will also be monitored, and soil samples will be collected to quantify soil organic matter.

Protocol for the Establishment of Shrubs in the Landscape

Principal Investigator: Dr. Amy Shober

Situation and Objectives: Florida has been one of the most rapidly urbanizing states in U.S, leading to increased competition for water between urban landscapes, agriculture, and natural systems. Unprecedented droughts have complicated the situation. Water management districts have responded by implemented irrigation restrictions to save water. Therefore, a study was conducted to determine how much water typical ornamental shrubs need during and after establishment.

Research methods: We first evaluated growth and quality of three shrub species using four irrigation frequencies at three locations. Subsequently, we evaluated twelve additional shrub species at each location (6 native and 6 non-native) using the optimum irrigation frequencies determined in the first phase.

Key findings: Three common shrub species could be established in the landscape with as little as 3 L of water applied every 8 days in north and central FL and every 4 d in south FL. This irrigation strategy was validated for 12 additional shrub species at each location.

Outputs and Impacts

  • The findings of this research have been made available to the science community (five peer-reviewed publications), and to homeowners and industry professionals (two EDIS publications plus a project website, Planting Shrubs and Conserving Water).
  • The Southwest Florida, South Florida and St. John’s River Water Management Districts are using the 3 L every 4- or 8-days for six months as the recommended protocol for irrigation of newly transplanted ornamental landscape plants.
  • Water use for shrub establishment can be reduced by about five gallons per shrub per watering event when high-pressure irrigation is replaced with low-volume microirrigation. This reduction would result in a potential savings of 50 gallons for a 500 ft² planting bed of newly installed shrubs in a single watering event. A homeowner with a newly installed 500 ft² landscape planting bed composed of primarily shrubs could potentially save 750 gallons of water in the first two months after installation by following our irrigation recommendations.
  • Water use policy based on these data can reduce plant death and replacement costs. This finding is significant considering the high expenditures required to replace shrubs, trees, and sod during the nursery and landscape guarantee period. For example, an Orange County landscape firm reported annual replacement costs of approximately $25,000 to $35,000 annually (equivalent to 1 to 1.5% of total income per job).

Rain Sensor Protocol Testing

Principal Investigator: Michael Dukes

Rain sensors (RSs) appear to be a useful tool for water conservation at residential and commercial sites. However, little evidence related to RS performance and/or reliability exists. Testing of RSs against a standard procedure with respect to the rainfall depth before RSs switch to interrupt mode, and the accuracy, precision and variability of their set points will provide the needed data and evaluation to establish performance characteristics.

Testing of severarl sensors will be performed as specified in the Irrigation Association (IA) Smart Water Application Technologies specification

The units to be tested will be purchased from an irrigation dealer, and installed and set by University personnel. Every sensor will be placed in the same testing area at the testing facility. Each RS model test will require eight identical devices, which will be connected to a datalogger. Each time a rain sensor changes status (from allowing irrigation, to interrupt mode, or vice versa), the date and time will be automatically recorded. Each set point test will be repeated eight times to determine the variation inherent in individual sensors. Relative humidity, incoming solar radiation, and temperature data from a nearby weather station will also be collected. The standard test will use a rainfall simulator to allow faster data collection under controlled and uniform rain events.

Testing will begin June 2010 and continue through May 2011. It is anticipated that testing will be complete by the end of 2010 but the one year period will allow for any delays. At the end of the testing, a final report will be completed for each brand/model/set point. This will include weather conditions during the test, measured rain simulator application intensity for all tests, average depth of rainfall before shut off, accuracy, average and standard deviation, depth of rainfall precision, average coefficient of variation, rainfall events not detected, and shut off in absence of rainfall.

Smart Irrigation Controller Demonstration and Evaluation in Orange County

Principal Investigator: Michael Dukes

Orange County Utilities is interested in Smart Irrigation Controllers as a potential practice to reduce landscape irrigation water use. Since it is not certain what type of control system is best for a particular type of property or how best to implement the technology, this project aims to test SMS controllers, ET controllers, and to evaluate at least one Central Controlled irrigation system across a range of residential and commercial properties.

Recent research at the University of Florida and in other areas of the U.S. has shown that Smart Irrigation Controllers have the potential to conserve water by efficiently scheduling irrigation. However, most of the work in Florida has been on tightly controlled research plots. The plot work has been valuable to assess the performance potential of these controllers. However, these controllers are relatively complicated to set up and program correctly for efficient irrigation. Thus, it is not known how much feedback or interaction is needed by irrigation professionals to implement these devices to achieve their potential level of water conservation. This scope of work also proposes to have two levels of contractor training and follow-up on controller operation and performance. In addition, the study will target two areas of Orange County with distinct soil differences, sandy vs. flatwoods soils. Finally, if possible during recruitment of cooperators, there will be an attempt to recruit both residential and commercial customers.

Update of Net Irrigation Requirements for Turfgrass

Principal Investigator: Michael Dukes

Calculation of net irrigation requirements for turfgrass is essential for determining water allocation and irrigation scheduling. In the past, net turfgrass irrigation requirements were published in Bulletin 200 “Water Requirements of Florida Turfgrasses”. This document is no longer available via EDIS and needs to be updated with current ET estimation techniques and simulation of turfgrass water requirements.

Bulletin 200 used monthly values of ET determined by the McCloud method along with methods from TR-21 to determine effective rainfall. In the early 1980’s when this publication was developed these methods were state of the art. However, new methods to estimate ET have become available, including the ASCE-EWRI Standardized Evapotranspiration Equation. In addition, it is generally considered that a daily soil water balance is most accurate at determining plant water requirements.

The Southwest Florida Water Management District is funding a five year study to "Investigation and Development Methods to Determine Urban Landscape Irrigation for Planning and Permitting in Central Florida (P424). It is expected that P424 will identify appropriate landscape coefficients for permitting water use. Crop coefficient data are an essential input to the net irrigation requirement. It is anticipated that existing data on crop coefficients as well as data determined in P424 will be used in this proposed work.


  1. Gather and quality check climate data from cities around Florida to represent climate conditions from the panhandle down to south Florida.
  2. Calculate reference ET (ETo) via currently accepted scientific methods for each site with weather data.
  3. Perform a daily irrigation water requirements simulation with daily precipitation data, daily calculated ETo, and literature data for other input values.
  4. Create an internet web page with a summary of turfgrass and landscape water requirements information with links to detailed information.