Deficit Irrigation Study

Pomona, CA—Merit Award, Research


Alan Moss
Water Concern, LTD
Rancho Santa Margarita, CA



Deficit irrigation of bermudagrass to conserve water while maintaining plant health was performed at the Center for Turf, Irrigation, and Landscape Technology (CTILT), at California Polytechnic University, Pomona California.  The study was started on June 6, 2014 and continued until September 25, 2014.

The purpose of the study was to provide research-based information to demonstrate satisfactory levels of turf quality, while still saving water through deficit irrigation on bermudagrass.  As irrigators are using less water on turf due to the continuing drought, there is an increased need for defined irrigation requirements for a range of acceptable turf qualities.  The practice of deficit irrigation on turfgrass can also be a valuable tool in providing monetary savings in water and maintenance budgets.

The continuation of deficit irrigation research is pertinent to the sustainability of water resources and the standard of living that many have come to expect.  As more research is conducted in this field, the tools necessary to conserve water will be better understood and more readily available.



The Irrigation Consultant performed all necessary research activities including management of irrigation and turf systems, as well as collection of data for the duration of the study.

The study was conducted on 12 3x3m well-established GN-1 hybrid bermudagrass plots.  Three irrigation treatments were arranged by distribution uniformity with four replications.  The irrigation treatments were approximately 40%, 60%, and 80% of calculated CIMIS ETo.  The amount of water applied was adjusted on a weekly basis and calculated to deliver 50%, 75%, and 100% of the calculated ETcrop.  A scheduling multiplier for each plot was used which compensates for the lack of perfect irrigation distribution uniformity (DU).  Routine measurements included; dried clipping yields, percent gravimetric soil water content, and visual turfgrass quality and color ratings.  Of the three irrigation treatments of 100%, 75% and 50%, it is no surprise that the 100% treatment, being the control, produced the highest quality and color ratings, but the lower treatment levels also produced surprising results with the 75% treatment maintaining acceptable turf color and quality, as well as the 50% treatment maintaining a minimally acceptable turf color and quality.  These results show while loss in overall quality will occur with deficit irrigation, bermudagrass has the potential to maintain acceptable levels of overall turf quality.



  • Weekly runtimes were calculated
  • Irrigation checks were performed on a biweekly basis
  • Prior to the start of the study catch can tests were performed to determine the rate of water applied to each individual plot in inches per hour, the distribution uniformity of the irrigation system (DULQ). Twenty-four plastic catch cans were used to conduct the test
  • Turf on plots were maintained at a height of 1.9cm and mowed two times per week on Tuesday and Friday morning beginning on June 6, 2014
  • Three weeks prior to the initiation of the study, 48.8 kg / ha of actual nitrogen using Turf Supreme 16-6-8 was applied
  • At the initiation of the study plots were put on a biweekly fertilizer program of turf supreme 16-6-8 at a rate of 14.6 kg/ha of actual nitrogen
  • Visual ratings of color and quality were taken biweekly
  • Clipping yields were taken to monitor the physiological response of the turf to deficit irrigation
  • Gravimetric water content was taken
  • Gravimetric soil samples were taken every three weeks
  • Soil samples were taken at the beginning and end of the study and sent to a lab for a detailed soil analysis



To view project images, click HERE