MANASOTA & PEACE RIVER BBDs Meeting Notebook 10-21-09.docx

B228
Evaluation and Demonstration of Soil Moisture Based On-demand
Irrigation Controllers for Vegetable P
Project Type Basin Initiatives
AOR(s)
Water Supply, Water Quality
Basin(s) Manasota
Cooperator(s)
University of Florida
Project Manager COHEN, RON
Task Manager(s)
Status Ongoing
Description
Agricultural water use is the largest single permitted category of water use in Florida. As population pressure continues
to grow and water availability becomes more limited, agricultural irrigation water users will be forced to become more
efficient. This problem is exacerbated in areas such as the Southern Water Use Caution Area where water demand
continues to increase where supply is limited. One potential method to increase irrigation water availability is to
improve irrigation scheduling. Knowing when and how much to irrigate is the key to irrigation scheduling and water
conservation. Soil moisture sensors can play an important role in irrigation scheduling. This four budget year project
will identify and test a commercially available on-demand soil moisture based control system in a vegetable production
system.
Benefits
Water use information from this project will be used by growers to save water and reduce pollutant loading. The
amount of water saved will be a function of the number of acres planted and their water use, which will change
annually based on market and climatic conditions. Assuming that results from this project will help reduce, at a
minimum, 5% of the permitted water, the savings would be about 17 Mgd of the permitted amount. Using the most
recent published water use estimates and assuming a 10% savings, this project could reduce water agricultural water
use in the Basin by about 10 Mgd.
Costs
This project will cost $142,900 and will be budgeted over four fiscal years. The Manasota Basin Board will budget
$35,725 in FY2006, FY2007, FY2008 and FY2009.
Additional Information
The project sites will be representative of a typical crop grown in the District, such as green bell pepper or tomato. The
production system will consist of raised beds, drip irrigation and plastic mulch according to typical practices in the
region. Horticultural guidelines published by the Institute of Food and Agricultural Sciences (IFAS) at the University of
Florida will be followed. Results from the project will help the growers reduce water use and potential runoff with
possible water quality problems. The soil moisture sensor control system will be configured as an interrupt to a timer
that is set to irrigate the vegetable production system in 4-5 irrigation windows per day. The irrigation timer will be set
to provide the maximum crop water requirement. The soil moisture sensor will be set at or slightly above field capacity
for the field soil such that under low water use conditions (e.g. immediately after transplanting) the soil moisture
sensor will bypass scheduled irrigation events, thus conserving water. The amount of water saved will be documented
and presented to growers as another method for them to conserve water. Although soil moisture based control has
been investigated in the past, the systems tested required either too much maintenance (e.g. tensiometers) or were
too expensive to be practical for farmers. The technology being tested in this project will consist of commercially
available controllers that have been marketed for irrigation control but have not been tested under Florida conditions
for vegetable crops. It is anticipated that results from this project will help expedite the growers acceptance of this
water conserving technology. The project's statistical design will be a randomized complete block design with four
replicates. Treatments will consist of three soil moisture sensor control treatments with irrigation thresholds 2-3%
volumetric water content (VWC) below field capacity, at field capacity, and 2-3% above field capacity. One timer based
treatment will be established to represent typical farmer irrigation practices where irrigation is scheduled 1-2 times
each day. The field trial will be conducted for the first two years. Based on field trial results, in year three a
demonstration trial will be conducted in a vegetable field within the District using one soil moisture sensor control
treatment (i.e. one moisture threshold).
021 - Manasota Basin 141