H.D. Adams1,2, L.M. Benton2, M.L. Cavanaugh2, J.R. Martin2, A.L. Neal3, S. Rajagopal3, R. Rosolem3, A.P. Tyler1, J.C. Villegas2
1Dept. of Ecology and Evolutionary Biology, 2School of Natural Resources, 3Dept. of Hydrology and Water Resources
The University of Arizona, Tucson, AZ
IntroductionLawns, golf courses, sport fields and other
areas planted in turfgrass are common, important components of urban systems
Effective and efficient irrigation management is:important economically and ecologicallyrequired for turfgrass function, particularly in
water-limited areas
IntroductionArizona: ~18,200 hectares of
golf courses (Schmidt 2006)
Many, many more hectares of turfgrass in urban areas being irrigated
Are these facilities and residences making an effort to maximize water use efficiency of their lawns?
turfgrass.unl.edu
IntroductionWhy Bermudagrass?
Grass of choice in southern USTolerates high sunlight and
high air temperaturesAble to grow in shallow soil
conditions and withstand trampling
Can tolerate salty water, salty soil conditions
Needs little water once established
www.answers.com
IntroductionBermudagrass requires:
508 mm of precipitation inputs needed for survival762 mm for acceptable color 1016 mm for adequate color and growth
Oracle, AZ received less than
500 mm, so irrigation
is necessary
www.lawnsprinklers.us
ObjectivesTo establish the pre-response conditions of turfgrass
under early-season, pre-watering conditionsTo measure and consider influence of environmental
variables on turfgrass phenology, including measurements of:carbon, water and energy flux via eddy covariancedistributed soil moisture and soil salinitythe distribution of applied water from the sprinkler irrigation
system on-siteProvide suggestions for efficient irrigation
management at Biosphere 2
Why Care?Better irrigation efficiency at Biosphere 2
lawn makes sense economically and environmentally
Reduces chance of high soil salinity from over-watering
Potential to guide irrigation regimes in other turfgrass areas of similar climate
Brides like nice grass (Biosphere weddings!)
www.redflagdeals.com
Jeffrey, isn’t it lovely to have efficiently irrigated grass at
our Biosphere wedding?
Doesn’t she mean Biodome?
Field SiteBiosphere 2, Oracle, AZ
~56.3 km North of TucsonElevation: 1378 m
Average Annual TemperatureMaximum: 23.55oCMinimum: 9.94oCFebruary to April - Max: 18.83oC, Min: 4.94oC
Average Annual Precipitation: 492.8mmFebruary to April: 109.2mm
Soil: loam and fill
Be sure to visit the Chalet Village
www.pbase.com
Field SiteLocated on north side of
Biosphere 2Lawn area ~1.24 acresSurrounded:
South and East sides by buildings
North and west sides by large berm
Field SiteSouth Tower
Daytime predominant
wind direction
Field Site
South Tower
North Tower
Sprinklers
Methods Tower Instrumentation and Variables Measured
3-D sonic anemometer (wind direction and speed)
Infrared gas analyzer (fCO2, fH2O)
Net radiometer (Rnet)
CR5000 Datalogger collected data
MethodsOther Site Instrumentation – Automated
Ground heat flux plates (G)TDR soil water content probes (automated θ)Tipping bucket (P)
Point MeasurementsRain gauges placed at equal intervals across field
Spatial irrigation inputs measured every 2 weeks
EM38 (relative soil salinity) Measured at each grid point every 2 weeks
Hydrosense (manual θ) Measured at each grid point every 2 weeks
Methods – Tower Comparison
Latent Heat
SensibleHeat
Carbon Flux
Methods – Energy Balance Closure
Half Hourly Daily
Methods – 2D Schmid Footprint
P=0.5 source area for westerly winds (+/- 30°)
Rule of thumb (1:100) would need 175 m in direction of mean wind (total source area). Gash (1986) model says 240 m in direction of mean wind. We have 80-100m of lawn, large berm, desert flora.
Full source area 4/17/08
Results – Soil Moisture
Initial Dry Down – Irrigation Period – Intense (2 hours / station) Irrigation Period
Results – Diurnal Energy
Pre-Irrigation Data looks reasonable, Wide range of “morning” LE
Sensible Heat
Latent Heat
Ground Heat Flux Net Radiation
Irrigation results in higher LE – driven by water or available energy?
Results – Diurnal Energy
Sensible Heat
Latent Heat
Ground Heat Flux
Net Radiation
Results – Diurnal CO2
CO2 flux doesn’t change much – perhaps increase in LE is just E at this point.
mg/
m2 s
Results - Grid Soil Moisture
Soil moisture for day 1, before irrigation
Eddy Tower
Results – ET time series
ET near ETcrop during initial watering, above ETcrop (near ETo) during intensive watering
Results - Salinity
No real salty spots!Found out where the Tubing is!
Results - Sprinkler Irrigation
Irrigation as measured by precipitation gage grid
Units Check!
Results - Grid Soil Moisture
Soil moisture for day 3, after irrigation
Results - Grid Soil Moisture
Irregularity in soil moisture due to irregular sprinkler irrigation
Discussion Point – Irrigation Efficiency IndexTwo Indices were developed
IUE 0 IUE > 0, overwatering
IUErel1
IUErel >1, overwatering
I
ETIIUE crop
tower
croprel ETI
ETIIUE
Show plot here
Discussion Point – Irrigation Efficiency Index
Wet spots based on grid data are at “30, 25”, are we catching this at the south tower?? Maybe if we just used north tower…
Discussion Point – Positioning is important.
Wet spot Wet spot
ConclusionsTowers can be used on lawn at Biosphere 2Salinity effect many not be evident due to use of well
waterIrrigation efficiency can be improved
Early irrigation schedule is near idealLate schedule (double-watering) is overwatering
Spatial coverage of sprinklers is poorHighly variable soil moisture across lawnPoor drainage in some locations near edge of lawnSprinkler operation may be defective!
Proposed Future of TowersLook for green-up in CO2 signal
Plants may not be fully active during irrigation studySoil respiration may offset signal in early spring
Comparison of records between towersError analysis using co-located measurementsDistribution of soil moisture, footprints
Irrigation during summer monthsWill the towers be there?
RecommendationsIrrigate during nighttime
Reduce ET lossesPromote increase in soil moisture
Irrigate with less waterConsider timing of operation of each sprinkler headSpatial distribution of water and resultant soil moisture
Improve drainage Prevent water-logging
Consider use of reclaimed waterWhat about salinity associated with this?
AcknowledgmentsWe would like to thank:
• Shirley Kurc, Jim Shuttleworth, and Travis Huxman for their guidance on this project
• John Adams, and the many Biosphere 2 staff members who assisted us throughout the semester
• Greg Barron-Gafford at the University of Arizona for his help in providing instruments
• James B. Callegary at the USGS for use of his EM38
• Dave Breshears at the University of Arizona for use of his soil moisture and eddy covariance equipment
Henry
Juan