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Subsurface Drip Irrigation

Engineering Feature

United States Department of Agriculture
Natural Resources Conservation Service
1221 College Park Drive, Suite 100
Dover, Delaware 19904
For More Information:

Larry Tennity, 302-678-4190
Dastina Wallace, 302-678-4179


Partnership Explores Subsurface Drip Irrigation

As is typical with the introduction of a technology new to a region, questions start to surface about its purpose, cost, and effectiveness.  This is exactly what happened when Subsurface Drip Irrigation (SDI) was introduced to Delaware in recent years.  SDI is a system of plastic irrigation tapes or drip lines, that are installed 10-16 inches below ground to continuously “drip” water to plants above ground through tiny slits spaced evenly apart. 

As interest continued to grow, so did the complexity of questions.  Questions surfaced about drip tape spacing, determining crop water needs, moisture sensor placement and more.   Unfortunately for Delawareans, those answers weren’t already documented in a technical paper or scientific journal.  In fact, while decades of research on subsurface drip irrigation had been done in the Middle East and West, there had been little done on the sandy loam/loamy sand soils of the mid-Atlantic region.

 There have been approximately 500 acres of SDI installed in Delaware, and several times that amount is in the planning stage.  In an effort to help guide Delaware farmers on SDI management systems,  James Adkins, Irrigation Engineer with the University of Delaware’s (UD) Carvel  Research and Education Center, is piloting the first SDI research farm in the Delmarva region.  With funding from the USDA Natural Resources Conservation Service (NRCS), the Delaware Department of Agriculture, and Vincent Farms, Adkins hopes to have science-based answers for Delaware’s growers.   The project’s goal is to increase grower profitability, improve water quality, and provide efficient management of water resources through SDI.

Research is being conducted on 20 acres of UD’s Warrington Irrigation Research farm in Harbeson, DE.  As of early March 2012, Adkins and his team had more than 120 drip tape lines installed using Real Time Kinematic technology, which tracks the exact location of the buried drip tape.  Adkins has the SDI system set up in 42 zones to have the flexibility to compare various irrigation scenarios.  In some of the zones corn, will be conventionally planted on either side of the drip tape-- one drip line for every two crop rows.  In other zones, soybeans, lima beans, and small grains will be planted to learn how these crops respond to various configurations of the SDI system and irrigation scenarios.  He will measure crop yields during harvest to help determine which scenario produces the best yields, uptakes most nutrients, uses water efficiently, and more. 

 Each drip tape is connected to a water supply line, which is controlled by valves through a computer.  For a drip irrigation system to work, a clean water source must be available.  Soil moisture sensors placed throughout the field at varying depths will determine if soil is wet or dry and water will be automatically dispersed as needed.  The system will be flushed every two to four weeks to prevent sediment build up and damage.  Insecticide and fertilizer can be applied through the system to prevent insects from preying on the tape while nourishing the crops. 

 Proper irrigation water management not only uses water more efficiently, it can also increase crop yields, which take up more nutrients from the ground.  This prevents excess nutrients from running off into local waterways, while increasing grower profitability.

 SDI could prove useful for fields that are oddly shaped that wouldn’t benefit from the center pivot irrigation systems as well as smaller fields.  The average cost of SDI is $1500-3000/acre. 

 Producers interested in subsurface drip irrigation should contact their local USDA Service Center for information regarding financial assistance.  Currently, NRCS is offering a payment rate of $1170/acre for SDI through the Environmental Quality Incentives Program (EQIP) to those who meet program criteria.


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