CONFERENCE BROCHURE

March 19-21, 2007- Waikiki

Honolulu - Hawaii

Hawai'i Soil Moisture Sensing Technology Conference: Current and future research directions in soil moisture sensing

Conference Theme and Objectives 

Theme        

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This  conference  is focusing  on   current  and  future  research  directions  in  soil  moisture  in‐situ  sensing  technology  with  special  emphasis on sensor reliability and  measurement scale   dependency.     

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Objectives  •

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Discuss  techniques  for  new  generation  soil  moisture  and  thermal  probes  to  ensure  reliable  data  with  adequate  measurement  volume  Provide  background  theory  as  needed  on  complex  permittivity,  thermal  properties,  and  sensor/  soil interaction 

Describe  effects  of  electrical  conductivity, bulk density, clay type  and  amount,  organic  matter,  water  repellency, and soil structure.  Describe  measurement  volume  as  related to sensor size, configuration  and method of operation.    Discuss  techniques  for  on‐site  calibration of sensors.  Conference Venue: Ocean Resort Hotel Waikiki 175 Paoakalani Avenue Honolulu, HI 96815. Phone: (808) 922-3861 www.oceanresort.com      

 

     

PROGRAM

Monday March 19 2007 7:00-8:00 AM Registration Opening Session: Capacitive Water Sensors: Current Status and Theoretical Advances Conference Opening Remarks and over view Ali Fares, Chair of of the program Organizing Committee Welcome from the University of Hawaii Andy Hashimoto Dean College of Tropical Agriculture and Human and Director of CTAHR 8:00 - 8:20 Resources Welcome from the USDA – Natural Mr. Kent Matsutani, Resources & Conservation Services Hawaii Assistant State Office Conservationist Technical Session I: Capacitive Water Sensors: Current Status and Theoretical Advances Moderator Daniel Jenkins, Secretary Alan Mair Plenary Lecture: Advances in Capacitive 8:20 – 9:10 Ali Fares*. Univ. Hawaii Water Sensors: A Review Mike Schwank & Timothy Green*. ETH, Laboratory and Theoretical Investigations of 9:10 – 9: 30 Zürich, Switzerland & a Ring-capacitor Sensor. USDA-ARS, Fort Collins. Lin, C-P*, Chung, C-C., Apparent Dielectric Constants from TDR Tang. S-H., National 9:30- 9: 50 Waveforms: Influencing Factors and Chiao Tung University, Comparison. Taiwan

9:50 – 10:10

Activation Energies and Temperature Effects from Electrical Spectra of Soil

Sally Logsdon*. USDAARS-NSTL. Ames, IA

10:10 – 10:40

Break Visit Exhibit Area Vendors and Displays Technical Session II: Calibration, accuracy and Precision Moderator Peter Van Oevelen, Secretary Ted Radovich Temperature-Dependent Scaled Reading to A. Fares, Hamdhani, M. Mitigate Temperature Effects on Selected Safeeq and D. M. 10: 40 – 11: 00 Capacitance Sensors. Jenkins*, Univ. of Hawaii D. Goorahoo*, D. Adhikari, D. Zoldoske, F. Assessment of Standardized Testing Protocol 11:00 – 11:20 Cassel and E. Norum for Soil Moisture Sensors. California State University-Fresno. Intra-sensor Variability of Three Capacitance M. Safeeq* A. Fares 11:20 – 11: 40 Sensors. University of Hawaii 11:40-12:00 Discussion 12:00 – 1:30 Lunch on Own Technical Session III: Calibration, accuracy and Precision Moderator Sally Logsdon, Secretary Farhat Abbas 1:30 – 2:20 2:20 – 2:40

2:40 – 3:00

3:00 – 3:20

Plenary lecture: An Overview of Soil Water Sensing Technology and Problems Matric potential response characterization and temperature sensitivity of heat dissipation sensors for soil matric potential Field and laboratory Calibration of a Multisensor Capacitance System in Tropical Soil. Calibration and Characterization of an Improved Low-Cost Water Content Sensor

Steven Evett*. USDAARS.Lubbock, TX. Jim Bilskie*, Campbell Scientific, Inc. V Polyakov, A Fares and M Ryder*. University of Hawaii Colin Campbell. Decagon Devices, Inc.  Pullman, WA

3:20-3:50 Break Visit Exhibit Area Vendors and Displays Technical Session IV: Irrigation Scheduling and Nutrient Management Moderator T J Jackson, Secretary M Safeeq B McMichael*, R Soil Water Sensor Needs for the Evaluation Lascano, and D. Gitz 3:50 – 4:10 of Hydraulic Lift in Crop Plants USDA-ARS Lubbock, TX. Weather and Soil Moisture Based Landscape P Sunde* and M Spears 4:10 – 4:30 Irrigation Scheduling. Bureau of Reclamation. Denver, CO.

4:30 – 4:50 4:50 – 5:00

Soil Moisture Variability Under Six Broccoli Cultivars Grown With and Without Weed Pressure. Discussion Session IV Adjourn

T Radovich*, G. Ortega and A. Fares. University of Hawaii

Evening Program 6:00 – 9:00

Reception and dinner at Casablanca Restaurant, Kailua. Transportation will be provided: 5:45 Departure from Ocean Resort Hotel, Waikiki. Tuesday March 20 2007, Second Day of the Conference

Technical Session V: Challenging Media and Environmental Conditions Moderator Tim Green, Secretary Farhat Abbas Plenary Lecture: Soil Moisture Sensors for Sally Logsdon*. USDA8:00 – 8:50 Problem Soils. ARS-NSTL Ames, IA Y Yamakawa*, K. Combined penetrometer-moisture probe for Kosugi, N. Masaoka, and 8:50 – 9: 10 measuring water content distribution in T. Mizuyama. Univ. hillslope. Japan. 1 B. K. Bellingham*, 2M. Seasonal Wetting Front Characteristics Of A Russel, 2F. Mukome, 2J. Typic Fragixeralf Base On Measurements Randan, 2S. Burns, 9:10- 9: 30 1 Using The Stevens Hydra Probe Sensor. Stevens Water Monitoring Systems, Inc. 2 Portland State Univ. Samira Fares, Amjad Ahmed*, Ali Fares, Spatio-Temporal Variability of Water Flow Micah Ryder and Farhat 9:30 – 9:50 and Solute Transport Under Different Abbas Vegetative Filters In a Hawaiian Watershed. University of HawaiiManoa 9:50 – 10: 20 Break Visit Exhibit Area Vendors and Displays Technical Session VI: Remote Access, Telemetry and New Technologies Moderator Steven R Evett, Secretary Dean Meason T. J. Jackson*, USDAARS Beltsville, MD. P. J. Global Soil Moisture Networks. 10:20 – 10:40 van Oevelen, European Space Agency, Netherlands P Buss*, Sentek Pty Ltd. Integrated Precision Viticulture – A strategic South Australia alliance between Multispectral Imaging and G Dridan, Manager 10:40 – 11:00 Soil water Sensing. Director, Integrated Precision Viticulture / Agriculture Pty Ltd

11:00 – 11:20

11:20 – 11:40

11:40 – 12:00 12:00 – 1:30

Soil water measurements and wireless technology: many choices. Determining the Effects of Site-Specific Calibration of Capacitance Sensors on Estimating Groundwater Recharge. Evaluation and calibration of a new wireless sensor. Lunch on Own Technical Session VII: Divers applications Moderator Ali Fares, Secretary Alan Mair A coil-type TDR probe for monitoring rainwater dynamics within weathered granitic bedrock

Jim Bilskie*. Campbell Scientific, Inc. Alan Mair* and Ali Fares, University of Hawaii Ty Barrick* and M Barrick. New Mexico State University

Ken’ichirou Kosugi*, Shin’ya Katsura, and 1 :30 – 1 :50 Takahisa Mizuyama. Kyoto University, Japan. Meason*, D.1, NazarioThe strengths and weaknesses of Decagon Leary, C.1, Idol, T.1, ® Devices ECH2O soil moisture probes in two Friday, J.B.1, and 1:50 – 2:10 different forest environments in Hawaii Scowcroft, P.2 1 University of Hawaii 2 USDA Forest Service,. A. Fares1, A. Dogan2, L. R. Parsons3, T. A. Obreza3 & K.T Morgan*3 Water Balance Components in a Mature 1 2:10 – 2:30 University of Hawaii, Citrus Orchard. 2 Suleyman Demirel University, Turkey, 3 University of Florida Technical Session VIII: Soil water sensor improvements – Panel Discussion with Audience Participation Moderator Steven Evett, Secretary M Safeeq Panel: Jim Bilskie, Peter Buss, Colin Campbell, Ali Fares, Tim Green and Sally Logsdon. • Permittivity, Interferences (salinity, clay type and content). • Sensed volume size and shape. • Communication: Wireless and Remote Access • Sensor integration: Water content, Matric potential, Heat and Solute monitoring • New sensor designs – Where do we go? 2:30 – 4:55 o Sense bulk permittivity, bulk EC, and frequency. o Include frequency and bulk EC in the calibration equation – correct the permittivity. o Ensure even integration over the sensed volume Increase sensed volume (will this take care of unevenness of integration?)

*Name of the presenter 4:55 – 5:00

Closing statement: Ali Fares. Wednesday March 21 2007, Third Day of the Conference Field Trip to The College of Tropical Agriculture and Human Resources, Waimanalo. Demonstration of Different Soil Water Monitoring Equipments. 8:30AM Departure time for field trip to Waimanalo 9:15 AM Arrival time Welcome by Dr. Raymond S Uchida Oahu County Administrator

9:15-9:45 AM

9:45:11:00 AM

11:00 AM -2:00 PM

Tour of the station by Mr. Roger Corrales, Manager CTAHR Experiment Station at Waimanalo

On site demonstration by Dr. Ted Radovich And Dr. James Bilskie, Campbell Scientific, Inc. Mr. Michael van Bavel, Dynamax, Inc. Tour of the Island (Snacks will be provided)

Exhibitors    Dynamax, Inc. Houston, Texas Web: http://www.dynamax.com Contact: Michael van Bavel E-mail: [email protected]

Stevens Water Monitoring Systems, Inc. Beaverton, OR Web: http://www.stevenswater.com Contact: Keith Bellingham E-mail: [email protected]

Sentek Pty Ltd Stepney, South Australia Web: http://www.sentek.com.au Contact: Peter Buss Email: [email protected]

Field demonstration  Campbell Scientific, Inc. Logan Utah, USA Web: http://www.campbellsci.com Contact: James Bilskie E-mail: [email protected]

Dynamax, Inc. Houston, Texas Web: http://www.dynamax.com Contact: Michael van Bavel E-mail: [email protected]

Organizing Committee Dr. Ali Fares, Associate Professor of Hydrology Nat. Res. & Environmental Management Dept. University of Hawai’i- Manoa Associate Editor, SSSAJ Phone: (808) 956-6361(d)-7530(Sec), Fax: (808) 956-6539 Email: [email protected] Website: http://www.ctahr.hawaii.edu/faresa/

Dr. Sally D. Logsdon National Soil Tillage Laboratory Soil Science Society of America Editor-in-Chief, 2150 Pammel Drive Ames, IA, 50011-3120 Phone: (515) 294-8265, Fax: (515) 294-8125 Email: [email protected]

Industrial Committee

Dr. Steven R. Evett

Research Soil Scientist USDA-ARS Conservation & Production Research Laboratory P.O. Drawer 10, Bushland, TX 79012 Phone: (806) 356-5775, Fax: 806-356-5750, Email: [email protected]

Dr. Daniel Jenkins Assistant Professor Molecular Biosciences and Bioengineering University of Hawai’i- Manoa 1955 East West Rd., Room 218 Honolulu, HI 96822 Phone: (808) 956-6069, Fax: (808) 956-3542 Email: [email protected]

Local Committee

Dr. Colin S Campbell Environmental Biophysicist,      Decagon Devices, Inc. Pullman, WA    Email: [email protected]      

     

Mr. Peter Buss

Manager, Agronomic R&D, Sentek Pty Ltd 77 Magill Road, Stepney, South Australia 5069 Australia Email: [email protected]

Mr. M Safeeq Mr. Alan Mair   Dr. F Abbas   Hydrology Laboratory Nat. Res. & Environmental Management Dept. University of Hawai’i- Manoa Phone: (808) 956-2807, Fax: (808) 956-6539 Dr. T Radovich Department of TPSS, CTAHR, University of Hawai'i-Manoa

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Abstracts

1. Advances in Capacitive Water Sensors: A Review Ali Fares* Natural Resources & Environmental Management Dep., Univ. of Hawaii-Manoa, 1910 East West Rd., Honolulu, HI. Demands on water resources worldwide are increasing as the world population keeps growing and quality of living keeps improving in many countries. Several water management techniques have been developed, tested and used with different levels of success. Capacitance sensors have been used to measure soil water content in a wide range of physical and weather conditions, various land use/covers and for different natural resource managements. This presentation will be presenting a synthesis of the current and previous research work of the author and other colleagues in the use of capacitance soil water monitoring sensor. Special topics will be discussed are as follows: i) theory and operations of capacitance sensors, ii) calibration, iii) determining soil physical properties, iv) irrigation scheduling, v)temperature and salinity effects, and future research directions. Research results demonstrated that considerable improvement to efficient water use can be made by collecting high resolution soil water content data in the soil, around the crop in real or near real time. Field trials incorporating this style of technology to understand soil water processes provide a comprehensive way of studying crop water response. Combining capacitance sensors with other sensors and software, researchers were able to determine different soil hydraulic properties, i.e. soil water release curves, hydraulic conductivities, porosity, field capacity and effective rainfall. Some of the challenges that have been facing capacitance sensors are: 1) correlating the real-time components of water balance in the soil–plant–atmosphere system over large areas to enhance our understanding and predictive capability of water and chemicals in agricultural systems; 2) eliminating or at least considerably reducing the effects of soil temperature and salinity that are limiting their performance and their spread; 3) establishment of a user friendly and cost effective telemetry to help expanding the use of these sensors in conducting different spatial and temporal analysis of natural resources. Improved capacitance sensors have the potential to help meet these needs.

2. Laboratory and theoretical investigations of a ring-capacitor sensor Mike Schwank(1) and Timothy R. Green*(2) (1) ETH, Institute of Terrestrial Ecosystems, Zürich, Switzerland, [email protected]. (2) USDA-ARS, Agricultural Systems Research Unit, Fort Collins, Colorado, USA, [email protected]

Ring-capacitor sensors are used widely for real-time estimation of volumetric soil water content θ from measured resonant frequency fr which is affected by the complex bulk soil permittivity ε = ε’ + iε’’. However, the relationship fr(ε) requires improved investigation in terms of the dependence of fr on the real and the imaginary parts ε’ and ε’’. Electrical losses relevant in saline soils have high values of ε’’, and soil moisture is correlated with both ε’ and ε’’. Laboratory experiments under nearly lossless conditions were performed to characterize the response fr(ε’) of a Sentek EnviroSCANTM capacitance sensor over a full range of ε’ values from air to water and over a range of temperatures. The responses fr(ε’) were recorded while encompassing the sensor with water-dioxane mixtures at different mixing ratios. This led to a new empirical relationship N(ε’) between normalized readings and real permittivity ε’. Furthermore, total capacitances Ctot were measured using a vector network analyzer. The readings were sensitive to changes in the dielectric properties within given annular distances. Additional sensitivities of the sensor readings with respect to ε’’ via liquid salinity S and soil temperature T were investigated theoretically. The new model is based on an electrical circuit analogue approach in conjunction with a dielectric mixing model and a finite element model of the steady Maxwell’s equation to compute electrical field distributions E. The mixing approach estimates ε = ε’ + iε’’ of solidwater-air mixture representing moist soil. Different values of ε’ were used in simulations for computing E, from which the capacitive circuit analogue components were computed. Circuit resistances representing the electrical conductivity losses were calculated from ε’’ and E. The circuit analogue was used to model fr(ε’, ε’’) in an iterative manner to account for the frequencydependent values of the circuit analogue components. Modeled sensor readings fr and N display sensitivities to both T and S, and the temperature gradients can go from negative to positive values. Finally, the results from the theoretical sensitivity study were combined with the empirical relationship N(ε’) to quantify the temperature effect on the permittivity values at different salinity and moisture levels. Temperature variations in the range 0 < T < 40 oC caused deviations in measured permittivities within a range of about ± 10 %. Although the investigation has been done with a specific sensor, the combined experimental and simulation results improved our generic understanding of processes affecting instrumental sensitivities of capacitance sensors. The results are crucial for scientific applications of these sensor types used in natural soils, and the work provides a foundation for further inference of soil water content under field conditions.

3. Apparent Dielectric Constants from TDR Waveforms: Influencing Factors and Comparison Lin, C-P*, Chung, C-C., Tang. S-H Dept. of Civil Engineering, National Chiao Tung University, Taiwan

Abstract Several methods were proposed for determining the apparent dielectric constant (Ka) from a TDR waveform. Their influencing factors have not been extensively investigated and results obtained from different methods have not been critically compared. Effects of electrical conductivity, dielectric dispersion, and cable length were numerically studied, while the influence of boundary condition was experimentally demonstrated. The electrical conductivity and dielectric dispersion seem to be interrelated as they affect Ka measurements. For materials with relaxations outside the TDR frequency bandwidth, the apparent dielectric constant is not affected by electrical conductivity. But the apparent dielectric increases with electrical conductivity in dispersive materials. Dielectric dispersion also plays an important role on the cable length effect. In a non-dispersive material, the cable length effect may be corrected by calibrating the first reflection time and electrical length of the probe. If the material is dispersive within the TDR frequency bandwidth, apparent dielectric constant increases with cable length even though the probe has been calibrated for each cable length. The fringing effect is experimentally demonstrated for an open-ended probe, while short-ended probe seems free from fringing effect. A unique electrical length may not exit for a TDR probe since the fringing effect depends on the dielectric constant. Short-ended probes are probably more desirable than conventional open-ended probes. The penetration problem may be circumvented by adopting a penetrometer-type probe construction. Three methods of determining Ka were compared, including double tangent line, single tangent line, and apex of derivative. Double tangent line method gives an Ka with the highest effective frequency. It is also least sensitive to the influencing factors. This is advantageous to consistent water content measurements but it suffers from automation difficulty. The apex of derivative method has the lowest effective frequency and it is sensitive to electrical conductivity and cable length for dispersive dielectric materials. It may yield unreasonable results in very conductive materials or when long cables are used. Single tangent line method gives results similar to double tangent line method except that it is more sensitive to electrical conductivity. And it does not apply to shorted-end probes. Besides the dependency on those influencing factors, the effective frequency of Ka can not be appropriately estimated in practice. Future study is suggested to emphasize on the spectral analysis of TDR waveform.

4. Activation Energies and Temperature Effects from Electrical Spectra of Soil Sally Logsdon* USDA-ARS-NSTL. Ames, IA. Apparent permittivity often has soil-specific temperature responses as well as soil water responses. Variations of permittivity as a function of frequency and temperature can be used to calculate activation energies. The purpose of this study was to examine permittivity-temperature responses for six soils, and variation in calculated activation energies. Each of the six soils were packed into a truncated coaxial cell, and the permittivity spectra was determined for a range of water contents and temperartures. Then activations energies were calculated due to ion migration or due to rotation. The rotational activation energy was not correlated with temperature, did not vary across frequencies, and was not significantly affected by soil differences. Ion migration activation energy was significantly less for Cecil (kaolinite and quartz dominant mineralogy) than for Weld or Okoboji (smectites dominant mineralogy). There were significant positive temperature correlation for the dc electrical conductivity and for the real permittivity at low frequencies, but not at higher frequencies. Fraction of sorbed water had a significant correlation with electrical conductivity and real permittivity at a range of frequencies. Delineation of these tmperature and activation energy responses is necessary for describing how various soils respond to electromagnetic measurements.

5. Temperature-Dependent Scaled Reading to Mitigate Temperature Effects on Selected Capacitance Sensors A. Fares1, Hamdhani1, M. Safeeq1 and D. M. Jenkins*2 Natural Resources & Environmental Management Dep., Univ. of Hawaii-Manoa, 1910 East West Rd., Honolulu, HI; and 2 Molecular Bioscience and Bioengineering Dep., Univ. of Hawaii at Manoa, 1955 East West Rd., Honolulu, HI. 1

Several newly developed capacitance sensors have simplified real-time determination of soil water content. Previous work has shown considerable effect of salinity and temperature on their performance. The objectives of this study were to: i) quantify the effect of media temperature on the apparent water content measurement of three capacitance sensors, two single sensor (SCS1 and SCS2) and one multisensor (MCP) probes, and 2) evaluate the effectiveness of a new temperature-dependent scaled reading (frequency and voltage) algorithm to correct for the temperature effect on the performance of MCPs. Sensors and thermocouples were placed in the middle of plastic columns filled with air, deionized water, or quartz sand at different water contents (0.0, 0.02, 0.04, 0.06, 0.08, 0.12 and 0.38 m3 m-3). These columns were placed in a water bath with temperature varying between 5 and 45°C. Scaled frequency (SF) and Scaled voltage (SV) readings in saturated sand (0.38 m3 m-3) were negatively correlated with temperature. However, positive correlations were observed between isothermal SF and SV readings and media temperature for air and unsaturated quartz sand. Temperature effects in the unsaturated sand decreased with increasing water content; observed SF (MCP) for quartz sand at 0.0 and 0.12 m3 m3 water contents increased 58 and 4%, respectively, when temperature increased from 5 to 45°C. Hysteretic temperature effects were observed in all tested media and for all the three sensors. Our newly developed temperature-dependent SF and SV calibration methodology mitigated the increase in apparent water content caused by the use of the isothermal SF and SV calibration equations. Our experimental data indicate that quartz sand temperature effects on apparent volumetric water content measured with the tested capacitance sensors can be mitigated using this new temperature-dependent scaled reading ( SF and SV) methodology. Future work is needed with soils having different clay and silt contents, i.e., tropic soils.

6. Assessment of Standardized Testing Protocol for Soil Moisture Sensors Dave Goorahoo*1,2, Diganta D. Adhikari1, David Zoldoske1, Florence Cassel S1 and Ed Norum1. 1.Center for Irrigation Technology, 2. Dept. of Plant Science, California State UniversityFresno. 5370 N Chestnut Avenue, MS OF18. Fresno. CA. 93740. U.S.A *email for presenting author: [email protected] The development of Smart Water Application Technologies™ or SWAT™ was initiated by the water purveyors who wanted to improve residential irrigation water scheduling. SWAT™ is a national initiative designed to achieve exceptional landscape water use efficiency through the use of irrigation technology. SWAT™ identifies, researches, and promotes technological innovations and related management practices that advance the principles of efficient water use. It is estimated that typical residential landscapes apply 30 to 40% more water than is required by the plants. Hopefully, the widespread adoption of “smart” controllers and soil moisture sensors would conserve a significant portion of the excess water applied. Over the past three years, the Center for Irrigation Technology (CIT) has been working closely with water purveyors statewide and the Irrigation Association (IA) as part of SWAT™ to develop standardized testing protocols for evaluating the reliability, accuracy and repeatability of commercially available soil moisture sensors. These sensors can provide closed-loop feedback to time-based system controllers, thereby allowing the controllers to recognize soil moisture levels and terminate irrigation events when soil moisture reaches predetermined levels. In this presentation, we discuss the testing protocol adopted by the IA for evaluating the sensors under laboratory conditions of varying levels of moisture, soil type, and salinity. We will also evaluate the data obtained from two different sensors operating on the principles of time domain transmissivity (TDT) and amplitude domain reflectometry (ADR), respectively. Preliminary findings indicate that for the tests conducted at -5, 20, 25 and 30 °C temperatures with the application of increasing salt solutions of 0, 1.5 and 3.0 dS/M on a sandy loam soil and coarse textured soil, there was excellent correlation (r2 ranging from 0.89 to 0.99) between the volumetric water contents measured with the sensors and the calculated values. Calibration requirements, repeatability, accuracy over the range of test conditions, along with what level of information should be reported to the everyday user, will also be discussed. We conclude the presentation with an outline of phase 2 of the testing protocol, which will focus on conducting similar tests outdoor on turf plots.

7. Intra-sensor Variability of Three Capacitance Sensors M. Safeeq1* A. Fares1 1 Natural Resources & Environmental Management Dep., Univ. of Hawaii-Manoa, 1910 East West Rd., Honolulu, HI. Several reports have been published on calibration of capacitance soil water content measuring sensors. Most of the calibration equations correlate raw sensor readings to actual water content. Little work, if any, has been conducted to determine the error that might be introduced due to variability between sensors of the same type. Thus, the objectives of this study were to i) quantify individual sensor variability on three different capacitance sensors (EasyAG, Theta ML2x, and ECH2O probe; these sensors will be referred to as MCP, SCS1 and SCS2 in the rest of the text); and ii) to estimate the error introduced by such variables on the accuracy of these sensors. Two MCP, two SCS1, and three SCS2 probes were used. Sensors and thermocouples were placed in the middle of plastic columns filled with air, deionized water, and quartz sand at different water contents (0.0, 0.05, 0.10, 0.38 cm3 cm-3). The columns were placed in a water bath with temperature varying between 5 and 45 °C. Sensor readings were logged every 1 minute using manufacturer’s data loggers. An ANOVA analysis was conducted to determine the significance of the variability due to sensors and compare to that due to temperature. There were mixed results as differences between readings of identical MCP and SCS2 sensors under the same conditions were statistically significant (α=0.05); however, those of SCS1 sensors were not. Differences in readings of all three sensors as a result of media temperature were statistically significant. Our experimental data indicated that sensor reading variability either due to sensors or external effects, i.e. soil temperature are influencing the accuracy of the tested sensors.

8. An Overview of Soil Water Sensing Technologies and Problems Steven R. Evett* USDA-ARS.Lubbock, TX. ABSTRACT During a period of five years, a group of soil water instrumentation experts from five nations and three continents were contracted by the International Atomic Energy Agency of the United Nations to carry out a range of comparative trials of soil water sensing methods under laboratory and field conditions. The detailed results of those trials are in press (Field Estimation of Soil Water Content: A Practical Guide to Methods, Instrumentation and Sensor Technology, IAEA). Most of the devices examined worked well some of the time, but most also performed poorly in some circumstances. The expert group reached several important conclusions. First, the field calibrated neutron moisture meter (NMM) remains the most accurate and precise method for soil profile water content determination in the field, and is the only indirect method capable of providing accurate soil water balance data for studies of crop water use, water use efficiency, irrigation efficiency, and irrigation water use efficiency with a minimal number of access tubes. Second, those electromagnetic sensors known as capacitance sensors exhibit much more variability in the field than either the NMM or direct soil water measurements; and they are not recommended for soil water balance studies for this reason (impractically large numbers of access tubes and sensors required) and because they are rendered inaccurate by changes in soil bulk electrical conductivity (including temperature effects) that often occur in irrigated soils, particularly those containing appreciable amounts of clays with high ion exchange capacities, even when using soil-specific calibrations. Third, all sensors must be field calibrated (factory calibrations were inaccurate in most soils studied) in order to obtain reasonable accuracy. Fourth, the one exception to conclusion three is conventional time domain reflectometry (TDR, with waveform capture and graphical analysis), which is accurate to ±0.02 m3 m-3 in most soils when using a calibration in travel time, effective frequency and bulk electrical conductivity. Fifth, with the possible exception of tensiometers and the granular matrix resistance sensors, none of the sensors studied is practical for on-farm irrigation scheduling; they are either too inaccurate (capacitance sensors) or too costly and difficult to use (TDR and NMM). Sixth, for research studies, only the NMM, conventional TDR and direct measurements have acceptable accuracy. In light of the intense commercial introduction of electromagnetic (EM) soil water sensors in the 1990s and to date, these conclusions are somewhat disappointing. However, the joint work of the IAEA Expert Group on Water Sensing Technologies has resulted in numerous scientific publications detailing the problems with EM sensors, including the theoretical underpinnings of these problems, and sparked a special issue of the Vadose Zone Journal summarizing much of the fundamental work done by others to date. The presentation will highlight some of these results. Now that the problems are well understood, research and development of new sensor systems to overcome these problems can, and we expect will, proceed to a satisfactory conclusion for both scientific studies and on-farm irrigation management.

9. Matric Potential Response Characterization and Temperature Sensitivity of Heat Dissipation Sensors for Soil Matric Potential Jim Bilskie* Campbell Scientific, Inc., Logan, Utah Heat dissipation methods are commonly used for indirect measurements of soil water matric potential. While currently providing crucial information in many applications, these methods have inherent sensitivities which can be sources of error. Recognizing these limitations, the sensors and measurement methods are continually being improved. This work builds on previous work since the heat equation solution for infinite line source was applied to this measurement and most recently on work of simplified calibration methods. The objective of this work is to (1) consider calibration requirements and provide calibration improvements for matric potential sensors, (2) study the temperature dependence of the measurement and provide a empirical temperature correction that works very well with currently available ceramic sensors. Careful and repeated laboratory measurements provided accurate water retention characterization of the ceramic used for heat dissipation sensors and calibration data to define the relationship between matric potential and temperature increase during sensor heating. Pressure plate extractor, tensiometry and chilled mirror psychrometry methods were used to independently measure matric potential. The difference between water content when saturating the ceramic with free water and with water under vacuum of approximately 90 kPa is about 0.10 m3 m-3. Upon desorption of the ceramic after vacuum saturation, the 0.10 m3 m-3 is released when matric potential reached about -8 kPa. In field and typical laboratory applications the water content of the ceramic never exceeds the water content at -8 kPa therefore sensor response at -8 kPa should be used instead of when vacuum saturated. The sensor response while capillary saturated is paired with -8 kPa for one of two calibration points. The response data for matric potential less than -8 kPa is not needed which allows use of an exponential function, simplifying calibration. The temperature sensitivity was characterized with sensors in soil of independently measured matric potential under controlled temperature over the range 5 °C to 50 °C.

10. Field and laboratory Calibration of a Multisensor Capacitance System in Tropical Soil Viktor Polyakov, Ali Fares and Micah Ryder* Univ. Hawaii-Manoa A field/laboratory calibration study of a multisensor capacitance (MCP) system (EasyAg, Sentek, South Australia) was conducted for Ewa silty clay loam and silica sand. The objectives of this research were to (i) conduct field and laboratory calibration of a new MCP in silica sand and soil, (ii) evaluate the performance of MCP for a shrinking–swelling tropical soil, and (iii) evaluate the effect of medium temperature on the MCP reading at constant water content. Field calibration was performed on rangeland and cultivated sites. The effect of soil temperature on capacitance sensors was examined. A wide range of soil water content (0.01 – 0.55 m3 m-3) was used in the study. The depth of the soil profile had significant effect on soil bulk density in both rangeland and cultivated sites. In addition, soil bulk density on the cultivated site showed greater coefficient of variations (20%) comparing with those on the rangeland (8%), indicating greater shrink-swell potential of undisturbed soil. Three-parameter power model described the relationship between the soil water content and the SF as measured by the MCP. The default calibration fitted the field data well only in the higher water content range (0.35 – 0.45 m3m-3). This equation performed poorly in the lower range, severely underestimating the actual water contents. The precision of the site specific calibration equation in the field condition was ±0.08 m3 m-3 at α = 0.05. The soil column calibration for both soil and sand had larger correlation coefficients (R2 = 96% and 97%, respectively) than the rangeland (R2 = 73%) and cultivated site (R2 = 74%). The laboratory calibration data from the sand and soil were less scattered and had smaller root mean square error than that from the field. The differences between the default calibration curve and the curve proposed for sand were small over most of the θv range (0 - 0.3 m3 m-3); however, the default manufacturer calibration equation underestimated the θv in the sand in the upper range (0.3 - 0.5 m3 m-3). These differences were attributed to the presence of bound water on the clay surfaces, which affected and corresponding bulk permittivity, and shrinking and swelling of soil that might have affected the contact between MCP probe and the media. The temperature of the media resulted in 15% overestimation of the actual water content for Ewa silty clay loam and 10% for silica sand over 45oC interval. This study demonstrated that site-specific calibration improved the accuracy of water content measurement by MCP as compared to the default equation. In addition, we quantified the effect of temperature on MCP reading and demonstrated the need to account for temperature variations by integrating capacitance and temperature sensors.

11. Calibration and Characterization of an Improved Low-Cost Water Content Sensor Colin S. Campbell*, Environmental Biophysicist, Decagon Devices, Inc. Pullman, WA With the increasing emphasis of field and catchment scale hydrologic monitoring comes a need for reliable, spatially distributed soil moisture measurements. While several high-quality sensors are available, often users are left with a choice between cost and number of installation sites. Further, some low cost sensors can require soil specific calibration and may have considerable sensitivity to soil electrical conductivity (EC). The objective of this study was to calibrate and characterize a new, low cost sensor to determine how it performed in soil with varying water content and EC and to provide dielectric calibrations for the sensors. No differences were found between probe calibration curves for the sand, sandy loam, silt loam, and clay soils that were tested. Changing soil salinity in each of the same soils (solution EC from 0.1 to 8 dS/m) did not appear to have an effect on the probe output either. Additional tests to characterize a standard production probe showed good agreement between measured and actual water content. Additional work to increase probe measurement volume by increasing the length of the probe show considerable promise.

12. Soil Water Sensor Needs for1 the Evaluation of Hydraulic Lift1 in Crop Plants 2 B.1 L. McMichael* , Robert Lascano and Dennis Gitz USDA-ARS, Cropping System Research Laboratory, 2 Texas Agricultural Experiment Station, Lubbock, Texas Hydraulic lift (HL) in plants is defined as the process by which water is redistributed from wet soil zones to drier soil zones through the plant root system in response to gradients in water potential. Water is released into the dry soil when plant transpiration is low (night) and reabsorbed by the plant when higher transpiration rates are resumed (daylight). The crops in our area, consisting mainly of cotton, are increasingly being produced under dryland and limited irrigation conditions due to a decreasing water supply. Rainfalls during the growing season in the area generally come in the form of high intensity short duration events and are frequently less that 10mm per event. In many cases, the plant is unable to take advantage of these rainfall events due to runoff and/or high evaporation since there may be an absence of viable roots in the upper (0-10 cm) soil profile. We have hypothesized that since HL would probably not be of a sufficient magnitude to meet total transpirational demand, there may be sufficient water transferred to maintain roots in the dry soil zone in a viable condition to absorb water in case of a rainfall event. Preliminary results with cotton using a split root system for growing roots of the same plant in both wet and dry soil have shown that HL did in fact occur. The amount of water transferred was very small (on the order of 0.006 m3/m3 difference in water content) but amounted to approximately 11-32 % of daily evapotranspiration rates of from 2-6 mm/day. Subsequent preliminary results using stable isotope (deuterium) as a tracer have also confirmed the occurrence of HL. We have also documented genetic variability for HL on a limited basis in cotton. One particular difficulty we have encountered is to be able to document the small changes in soil water content accurately and consistently. Also, new techniques for water content measurement needed to evaluate HL on a large scale must be devised in order to determine genetic variability for the trait. These and other issues concerning the measurement of HL will be discussed further.

13. Weather and Soil Moisture Based Landscape Irrigation Scheduling Paula Sunde* and Mark Spears Bureau of Reclamation, Denver, CO

This presentation discusses the preparation and contents of the Bureau of Reclamation’s September 2006 Weather and Soil Moisture Based Landscape Irrigation Scheduling Technical Review Report, focusing on the soil moisture based scheduling portion of the report and associated research. The report was prepared by Reclamation’s Southern California Area Office under the Water Conservation Field Services Program, with the assistance of Reclamation’s Technical Service Center. It documents the current status of weather and soil moisture based residential and commercial irrigation scheduling products by 25 different manufacturers. The report is targeted for water agencies to assist in their efforts to promote this technology as a means of conserving water and reducing irrigation runoff induced pollution. The research performed during 2005-06 will be presented, as well as the following report topics: Technology Overview, Control System Principles, Product Features and Comparison Criteria, and Product descriptions.

14. Soil Moisture Variability Under Six Broccoli Cultivars Grown With and Without Weed Pressure T. Radovich*, G. Ortega, A Fares. College of Tropical Agriculture and Human Resources, University of Hawaii, Honolulu Hawaii 96822. Crop varieties differ in their ability to utilize water and other resources. These differences may be exploited to minimize yield loss under adverse environmental conditions. Six broccoli cultivars selected for tolerance to weeds using morpho-physiological markers such water use efficiency, leaf temperature and canopy development were planted at Waimanalo Experiment Station in a silty clay loam Mollisol of the Waialua series. Cultivars were managed in both weed-free and weedy plots. Drip irrigation was supplied every 3-5 d to exceed evapotransipration. Soil moisture at 15 cm was monitored prior to and following irrigation events with a hand held TDR unit in all plots. Real-time soil moisture was logged at 30 min intervals in select plots using multiple sensor capacitance probes. Temperature, solar radiation, wind speed, relative humidity, and rainfall were also logged on a sub-hourly basis. The influence of crop physiological characteristics and weed pressure on soil moisture variability will be discussed.

15. Soil Moisture Sensors for Problem Soils. Sally Logsdon* USDA-ARS-NSTL. Ames, IA. Soil dielectric sensors are based on the assumption that all soil water has the permttivity of free water (~76 to 80 depending on temperature and salt load) at all relevent frequencies (< 1.5 GHz); however, this assumption is not valid when there is appreciable amounts of water sorbed to high charge clays or organic matter. The purpose of this review is show where this assumption is in error, and what the consequences are for soil moisture sensing. Soils containing high-charged clays usually have high measured electrical conductivity that is not due to salinity. The charges develop in the water sorbed to the clays. The high electrical conductivity gives these soils a positive temperature response for the apparent permttivity because of the incorporation of the imaginary component that includes electrical conductivity. Sensors based on the real permittivity have less temperature sensitivity for these soils. The high charge clays attenuate the electrical signal, resulting in a small sampling volume. This small volume is even smaller for coated probes or for sensors that are placed inside a plastic access tube. In spite of these limitations, successful measurements can be made with some soil dielectric probes on these soils, using sitespecific calibration.

16. Combined penetrometer-moisture probe for measuring water content distribution in hillslope Yosuke Yamakawa*, Ken’ichirou Kosugi, Naoya Masaoka, and Takahisa Mizuyama Graduate School of Agriculture, Kyoto University Objectives Numerical simulation models have been frequently used to predict shallow landslides on steep landscapes. However, these models cannot reproduce actual slope failures sufficiently, which is partly attributed to the fact that the structure of soil mantle is heterogeneously distributed on a hillslope. It is hard to get adequate and precise information on the soil mantle, including soil depth, soil structure, and soil water movement. Especially, information on soil water flowing paths is important since perched groundwater formation in the soil mantle has a dominant effect on slope instability induced by rainwater infiltration. In this study, a combined penetrometermoisture probe (CPMP) was developed for measuring vertical profiles of soil penetration resistance and water content simultaneously, providing essential information for detecting vulnerable points for shallow landslides on steep landscapes. Methods CPMP consists of a moisture probe attached to Hasegawa-type cone penetrometer with a 60º bit, a cone diameter of 20 mm, a weight of 2 kg, and a fall distance of 50 cm. The moisture probe uses the time domain reflectometry (TDR) technique to determine soil water content. The TDR moisture sensor consists of two parallel stainless wires, each 0.55 mm in diameter, coiled around an acrylic column along grooves on the surface of the column. Measurements using a prototype moisture prove showed that CPMP tended to underestimate actual water content probably because of inadequate contact between soil and the moisture probe. Actually, many cracks were found on the soil surface in contact with the moisture probe affected by penetrations of the sensor rod, which was detected to be a main reason for the measurement error. Therefore, we examined most appropriate structure of the moisture probe for minimizing the error. Nine probes having diameter between 19 and 21 mm and coiling width between 2 and 5 mm were tested. Subsequently, filed experiments were conducted at a forested watershed underlain by weathered granitic bedrock, for measuring profiles of penetration resistance and water content simultaneously by using CPMP. For evaluating the accuracies of CPMP, we also conducted water content measurements by the traditional gravimetric method and penetration tests using the ordinary Hasegawa-type cone penetrometer. Then, CPMP was applied for measuring soil mantle structure along a main hollow of the watershed. That is, CPMP was applied to measure profiles of water content and penetration resistance at 17 points along a 50 m line situated in the main hollow of the watershed. Results

It was found that the moisture probe 20 mm in diameter and 3 or 4 mm in coiling width was the best for reducing the water content underestimation by CPMP. By using the best type moisture prove, CPMP generally succeeded in reproducing vertical distributions of soil water content measured by the gravimetric method for many soil profiles in the field. Moreover, penetration resistances measured with CPMP and ordinary Hasegawa-type cone penetrometer were about the same. Thus, CPMP is an effective tool for accurate and prompt measurements of distributions of soil water content and penetration resistance in a soil mantle on a hillslope. Along the main hollow of the watershed, average soil water content within a soil profile was roughly correlated with the catchment area for each point determined based on microscale topography. However, soil water content was also influenced by local distribution of fine soil particles and preferential flow pathways. We found that CPMP can be effectively used to detect such microstructure distributions within a soil mantle which affect soil water flow. Thus, CPMP has a large potential as a tool for detecting vulnerable points for shallow landslides on steep landscapes.

17. SEASONAL WETTING FRONT CHARACTERISTICS OF A TYPIC FRAGIXERALF BASE ON MEASUREMENTS USING THE STEVENS HYDRA PROBE SENSOR. 1 B. K. Bellingham*, 2 M. Russel, 2 F. Mukome, 2 J. Randan, 2 S. Burns, 1 Stevens Water Monitoring Systems, Inc. 5465 SW Western Ave. Suite F Beaverton, OR 97005, 2 Department of Geology, Portland State University P.O. Box 751 Portland, Oregon 97207. *Corresponding author ([email protected]) ABSTRACT The seasonal variations in soil moisture along with diurnal fluctuations in temperature were measured using the Stevens Hydra Probe Soil Sensor placed at six depths on a catena. Six Stevens Hydra Probe Soil Sensor calibrated to measure soil moisture based on the complex dielectric permittivity measurements, were in installed in each horizon and two sensors were installed in the horizon above the fragipan. The soil was identified as a typic fragixeralf and had five distinguishable horizons, A1, A2, B1, B2, and Bgx. The wetting front from the beginning of the water year was recorded and the velocities were found to be a function of bulk density. The depths of the sensors in cm were 6, 22, 43, 54, 81, and 104 and the wetting front arrival time in days was 1, 2, 19, 20, 21, and 22 respectively. The porosity values found in the literature from the bulk density data, were in good agreement with the measure soil moisture at saturation. The porosity of the Bgx was 0.42 and the water content at saturation was 0.40 m3 m-3. The amplitude of diurnal temperature fluctuations were more pronounced near the surface and decreased with depth respectively. The Bgx horizon diurnal temperature fluctuations were 1 to 2 degrees Fahrenheit and the A1 diurnal temperature fluctuations were within 1 to 2 degrees Fahrenheit of ambient air. This study helps assess root zone frost hazards and irrigation management.

18. Spatio-Temporal Variability of Water Flow and Solute Transport Under Different Vegetative Filters In a Hawaiian Watershed Samira Fares, Amjad Ahmad*, Ali Fares and Micah Ryder University of Hawaii-Manoa A study was conducted to determine the effects of three land covers (Sunn HempCrotalaria juncea, Sudex, a sorghum-sudangrass hybrid- Sorghum bicolor x S. bicolor var. sudanese, common oats- Avena sativa)) planted as vegetative filter strips on the reduction of sediment, nutrient loadings and water and solute movement in the subsurface within the Kaika-Waialua watershed on the island of Oahu, Hawaii. The current presentation is focusing on the soil water and nutrient dynamics as influence by these different land covers. A Six-probe multisensor capacitance system (EasyAg, Sentek Ltd, South Australia) was used to monitor the soil water content at 10, 20, 30 and 50 cm below the soil surface, every 15 minutes at each of these locations. Two MCP probes were used for each of the Sunn Hemp and Oat treatments. However, one probe was installed at the fallow and Sudex treatments. Rainfall and basic weather parameters were also monitored. Suction cups were installed in each of the 12 plots at 31 cm below the soil surface. Soil solutions were collected following several rainfall events. Results showed that land cover reduced the concentration of nitrogen several folds in the soil solution compared with the fallow treatment. Nitrate was the dominate form of nitrogen collected. The phosphorus did not show any substantial subsurface movement as compared to nitrogen. Sunn hemp, a nitrogen fixer, showed the second highest nitrogen concentration after the fallow treatment. Spatial variability was detected between plots of individual cover crops located at the top, middle, and bottom of the slope. These results were highly influenced by extremely low soil hydraulic conductivities (.0001-7 cm day-1 at the soil surface, 15 cm, and 30 cm below the soil surface. Sunn hemp, a nitrogen fixer, showed the second highest nitrogen concentration after the fallow treatment. Thus, this crop is better suited for cover crop to enhance N levels in cropped areas but should be avoided in vegetative buffer areas, and in areas with high water tables or near surface water bodies.

19. Global Soil Moisture Networks Thomas J. Jackson* and Peter J. van Oevelen [email protected], [email protected] USDA-ARS Hydrology and Remote Sensing Lab, Bg. 007 BARC-West 10300 Baltimore Avenue, Beltsville, MD 20705-2350 United States European Space Agency, POBox 299, Noordwijk, ZH 2200 AG Netherlands Abstract There has been growing recognition of soil moisture as an observational input in large scale water cycle and climate studies. Traditionally these have been model based analyses. With the arrival of satellite based sensors (the current Advanced Microwave Scanning Radiometer, AMSR) and the upcoming Soil Moisture Ocean Salinity Mission, SMOS), attempts are being made to integrate these observations into models and analyses. However, satellite observations have limited depth capabilities and mostly undefined accuracies. This has brought about increase interest in ground based networks of sensors that can be used to characterize these missing elements. Although there are a number of existing ground based networks, the techniques and protocols are highly variable. Currently there is no global network of linked in-situ soil moisture measurements and soil moisture is only routinely measured in certain basins and areas in the world. A review of some of these networks and an ongoing effort to coordinate these activities through international programs will be described.

20. Integrated Precision Viticulture – A strategic alliance between Multispectral Imaging and Soil water Sensing 1 2 Peter Buss * and George Dridan 1 Manager, Agronomic R&D, Sentek Pty Ltd; 2Manager Director, Integrated Precision Viticulture / Agriculture Pty Ltd

Site selection for soil water sensors is a very important task in management of commercial irrigated agriculture. How many are required and where are they to be placed? Vineyard managers in the premium wine industry are concerned with soil water storage and crop water use as they are affected by different soil types, aspect and topography and the impact on vine vigour and vineyard consistency. This contribution describes the outcome of a 2 year trial to create irrigation precision management zones of representative soil water monitoring sites to improve vine vigour and vineyard consistency. Site selection was based on a plant cell density map derived from Digital Multispectral Imaging (DMSI) during flowering and veraison and the overlay of other information layers such as topography, aspect, slope, soil type and irrigation system information. Plant cell density (PCD) maps allowed the exact sizing and location of areas either high or low in vine vigour. Multi-sensor profiling soil water probes were installed into these defined zones within the vineyard to give near continuous soil water trends which were then used to derive irrigation management strategies specific to irrigation zones. The success of applied irrigation and cultural management strategies and its impact on vine vigour and consistency were reviewed on an annual basis by DMSI and field data. Measured review criteria were vine vigour expressed as a mean of PCD, coefficient of variation CV% of PCD reflecting overall vineyard consistency, vine yield and fruit quality data. This new approach of zoning irrigation management areas and have them represented by soil water probes generated soil water data trends specific to these irrigation management zones. This allowed site specific prescription of cultural and irrigation management strategies to be implemented, which have not only resulted in significant commercial gains for the grower, but have highlighted the importance of well chosen site representation of soil water monitoring probes.

21. Soil Water Measurements and Wireless Technology: Many Choices Jim Bilskie* Campbell Scientific, Inc., Logan, Utah Cables connected to sensors impose numerous limitations such as restricting the maximum distance from sensor to datalogger, interference with tillage and irrigation, and cables are a source of sensor failure particularly from rodent and machinery damage. Recent developments in radios and batteries have brought a variety of wireless and semi-wireless options though wireless soil water sensors are not yet common. The first generation of soil water sensors is just coming to the sensor market, and there will be many wireless configurations available within a couple of years. Semi-wireless systems (cables from local datalogger to sensors and radio frequency (RF) link from datalogger to a base station) are currently available and allow soil water monitoring on the watershed scale. Motes, miniature wireless transceivers combined with sensors, are receiving increasing attention because of size, low power consumption, repeater functionality and flexible operating systems. Transceivers that are directly linked to sensors can be used to move data other than what comes the sensor. The objective of this talk is (1) to present information about currently available wireless soil sensors, (2) discuss configurations such as completely integrated sensor/radio with lifetime of 1 or 2 years or buried sensor and radio with external antenna and power supply (3) present results of field studies with buried antennae and address radio signal propagagation through soil.

22. Determining the Effects of Site-Specific Calibration of Capacitance Sensors on Estimating Groundwater Recharge Alan Mair* and Ali Fares University of Hawaii-Manoa. Automated measurements of soil water content using commercial capacitance sensors have been used to estimate groundwater recharge rates in field applications. Commercial sensors are equipped with default calibrations that are not accurate for every soil type; therefore, a sitespecific calibration is needed to improve the accuracy of soil water content measurement. The objectives of this study were to i) establish site-specific calibration equations for three commercial capacitance sensors, ii) determine the effect of site-specific calibration on recharge estimates under field conditions. Twelve ECH2O soil moisture sensors EC-20 (Decagon Devices, Inc., Pullman, WA) were installed at depths of 20 cm and 80 cm at six (6) locations across a 5.5 km2 study area in the upper Makaha valley, Oahu, Hawaii. Soils from these locations are stony clay loam (Pulehu series) and silty clay (Tropohumult-Dystrandepts association). Disturbed and undisturbed soil samples were collected from each EC-20 sensor location. A Watermark soil matric potential sensor, 6450WD (Spectrum Technologies, Inc., Plainfield, IL) was co-located with each EC-20 sensor at four locations across the watershed. All sensors were logged using electronic dataloggers at 60-minute intervals beginning in 2005 and 2006. Undisturbed soil samples were used to determine total porosity, bulk density, and particle density. Disturbed soil samples were initially sieved and then oven dried. Starting with an air dried soil an incremental amount of water was added and the soil was carefully mixed. The soil was placed into plastic columns, where the EC-20 sensors were inserted in the middle, and compacted to the field bulk density. To insure uniform bulk density throughout the soil column, the soil was added and compacted in small increments. The same procedure was used to calibrate the EC-10 (Decagon Devices, Inc.) and the ThetaProbe soil moisture sensor ML2x (Delta-T Devices, Cambridge, UK). The unsaturated hydraulic conductivities were estimated using the field soil water release curve. Groundwater recharge rates were then calculated using the manufacturers’ default equation and the site specific laboratory calibrations that we determined.

23. Turfgrass Irrigation Scheduling with Soil Moisture Sensors. M. Ty Barrick* Science Specialist Cooperative Extension Service Department of Extension Plant Sciences MSC 3AE New Mexico State University. Water conservation is of utmost importance in the arid south west of the United States. Turfgrass irrigation is therefore scrutinized and must be extremely efficient to avoid accusations of squandering a critical resource. Soil moisture sensors are an accurate way of scheduling irrigation only when soil moisture is below a threshold that would affect turfgrass quality. A study was conducted at New Mexico State University to investigate the accuracy of a wireless Frequency Domain Reflectometry (FDR) soil moisture sensor at several salinity levels in a USGA-type sand. The sensor has a wireless configuration which allows for a range of up to 2 miles between sensor and data processing. This provides both researchers and turf managers with a valuable and versatile tool to monitor soil temperature, moisture and conductivity. Sensor temperature and moisture readings correlated highly (r2>0.94) with actual values and were not affected by salinity levels between 1 and 4 dS/m.

24. A coil-type TDR probe for monitoring rainwater dynamics within weathered granitic bedrock Ken’ichirou Kosugi*, Shin’ya Katsura, and Takahisa Mizuyama Department of Forest Science, Graduate School of Agriculture, Kyoto University, Kyoto, Japan Recent studies in hillslope hydrology indicate that rainwater can infiltrate into bedrock, which had been conventionally treated as an impermeable layer, and that bedrock groundwater can influence both the water budget and material balance in headwater catchments. However, few studies have directly measured water flow processes in bedrock. As a first step toward describing physical water movement within bedrock, we made a coil-type TDR probe capable of determining the volumetric water content in weathered bedrock at multiple depths. The coil-type TDR probe can measure water content at three depths. Three coaxial cables, the ends of which were individually connected with two stainless wires (0.3 mm in diameter), were inserted inside a 149-mm-long PVC column (19 mm in external diameter and 13 mm in internal diameter). These coaxial cables were individually connected to a time domain reflectometer (TDR100; Campbell Scientific, Logan, UT, USA) that generates an electromagnetic wave with a short rise time and analyzes a reflected electromagnetic waveform. The wires connected to the cables were taken from the PVC column via small holes drilled into the PVC column, and individually coiled 40 mm apart around the surface of the PVC column. These coiled wires act as waveguides and sensors detecting the water content. The top and bottom of the PVC column were closed completely with silicone sealant (Cemedine 8060; Cemedine, Tokyo, Japan) to prevent water from leaking into the PVC column. Finally the probe was entirely coated by a thick PVC sheet to protect the wires. Compared to conventional TDR probes, a coil-type TDR probe has two major advantages derived from the coiled waveguides, which are markedly longer than the probe itself; i.e., they provide high resolution and small volume of influence. In this study, the larger diameter of the coil-type probe (19 mm) than that of conventional probe rods (5-8 mm) had another advantage; it is far easier to drill one guide hole of a large diameter to fit the coil-type probe than to drill two or three smaller, accurately spaced guide holes to fit conventional probe rods into highly weathered bedrock. The calibration results for the individual sensors suggest that the values measured by the coil-type TDR probe are strongly dependent on water content in the surrounding

medium. The calibrated probe, together with commercially available profile soil moisture sensors, was installed in the bedrock and soil at a point in a granitic headwater catchment, and was used to monitor the water content profile for 1 year. Even rainfall events with relatively small cumulative rainfall of 15 mm increased both the soil and bedrock water contents, and the increment in the water content in the bedrock was comparable to, or even larger than, that in the soil. After the end of each rainfall event, the bedrock water content dropped more sharply than that in the soil, and then varied little during the period of no rainfall. As a result, bedrock water content was concentrated in a very narrow range throughout the year. The water storage, calculated as the total water volume held within the soil and shallow bedrock layer, showed similar tendencies; the water storage in the bedrock rose in response to rainfall events, and decreased more abruptly and varied less than that in the soil after these events. All these observation results suggest that the bedrock water content, and therefore water movement processes in the bedrock in the study site, are controlled by clearly distinguished macropores and micropores contained in the bedrock. The sharp increase and decrease in the bedrock water content and water storage can be attributed to rainwater infiltration into and drainage from macropores in the bedrock. In this study, we successfully measured the bedrock water content using the coil-type TDR probe. It can be concluded that the coil-type TDR probe is an effective and powerful tool to measure water content in weathered bedrock. This study revealed that bedrock, conventionally defined using the results of cone penetration tests and treated as an impermeable layer, does conduct and hold substantial amounts of water, and therefore contributes effectively to hydrological processes in headwater catchments.

25. The strengths and weaknesses of Decagon Devices ECH2O® soil moisture probes in two different forest environments in Hawaii Meason*, D.F.1,2, Nazario-Leary, C.2, Idol, T.2, Friday, J.B.2, and Scowcroft, P.3. 1, 2. Univ. Hawaii-Manoa, 3. Inst. Pacific Islands Forestry, USDA Forest Service, Hilo, HI. Decagon Devices (Pullman, WA) ECH2O® Dielectric Aquameter’s has been widely used in agriculture for a number of crops. However, their use in forest ecosystems to measure volumetric water content are limited. The problems faced in using these devices in forests are different from agricultural situations. These include the unmanaged nature of the soils, the presence of rocks and debris, the depth and location of tree roots, steepness of the terrain, and forest soils heterogeneity. Two studies in Hawaii highlight some of the strengths and weaknesses of the devices method in measuring soil premittivity in tropical forest soils. The first study examined the effect of removing invasive grass from underneath crop trees of the endemic tree species Acacia koa (Gray) on volumetric soil water content of 3,000 – 5,000 year old Hapludands. The second study examined the effect of invasive tree species on volumetric soil water content located on slopes greater than 60 % with Hapludands over 100,000 year old. Data to be presented includes the sensitivity of the device under a forest canopy to precipitation events, its sensitivity during dry periods, issues arising from calibration curves, its ability to measure treatment effects, and spatial variability of the data.

26. Water Balance Components in a Mature Citrus Orchard A. Fares1, A. Dogan2, L. R. Parsons3, T. A. Obreza3 and K.T. Morgan3*. 1 University of Hawaii-Manoa Email: [email protected]. 2 Suleyman Demirel University, Isparta, Turkey 3 University of Florida, The low water holding capacity of Florida’s sandy soil, together with spatial and temporal variations of rainfall, requires Florida citrus trees to be irrigated for optimal production. Citrus tree root systems are exposed to various hydrologic conditions as a result of soil temperature and water gradients due to tree canopy shading and under-tree micro irrigation. The main goal of this study was to evaluate water balance components in a mature citrus orchard grown on central Florida ridge soils with special interest in quantifying rainfall interception by a citrus canopy and its effect on effective rainfall (ER) estimation. Soil water content was monitored every 30 min at 10, 20, 40, and 80 cm depths, using two multisensor capacitance systems (EnviroScan of Sentek, South Australia), in three-dimensional under and outside of citrus tree canopies. Basic weather data were also monitored under and outside same citrus canopies. Under-tree micro irrigation, rainfall and weather data were used to calculate effective rainfall, plant water uptake, and deep drainage. We found that tree canopy intercepted 35% and 50% of the incoming high (≥ 5 mm) and low (< 5 mm) intensity rainfalls, respectively. Effective rainfall calculated without accounting for the canopy interception effect was overestimated by about 30 and 5% for the dry and wet periods of the study, respectively. Citrus crop ET (plant water uptake) was higher under tree canopy (irrigated area) than outside tree canopy (non-irrigated area) during the dry season because of supplemental irrigation.

27. CARTOGRAPHY OF INTRINSEQUE VULNERABILITY OF GROUND WATER AGAINST POLLUTION USING THE P.R.K. METHOD AND INFORMATION SYSTEM GEOGRAPHIQUE (GIS) APPLICATION TO THE SOUSS GROUNDWATER AT THE SOUTH FIELDWELL (GRAND AGADIR - SOUTH OF MOROCCO) H. CHERKAOUI DEKKAKI(1), H. SAHBI (2), A. LAMRHARY(3), H. DAKKAK(4), M. BAQQALI (4), A. LARABI(1) (1) Department of the Mineral Genius - Mohammadia School of Engineers - University Mohammed V, Reduction - Morocco. Email: [email protected] Or [email protected]; (2): Geological laboratory of Engineering - University Moulay Ismail - Faculty of Science - Meknès - Morocco. Email: [email protected]; (3): Direction of the cleansing and the environment - O.N.E.P. - Reduction; (4): National institute of the Agronomic research. Regional center of the Agronomic research of Reduction. UR Environnement and Conservation of the Natural resources. Laboratory SIG and Remote sensing. The cartography of the vulnerability of ground water to pollution is a fundamental step for the regional planning. It makes it possible to the decision maker to better manage and analyze information necessary for the delimitation and/or the identification of the zones for the lower part of which the groundwater are vulnerable to pollution. Considering the strategic role of the ground water of Souss in the socio-economic development of the South region, the National office of Drinking water (O.N.E.P.) in collaboration with the Mohammadia School of Engineers, carried out the development of the chart of vulnerability of this tablecloth particularly on the level of the two principal field well : South and Ahmar Boudhar, established respectively in the part downstream and median of the Souss. For this end, a multicriterion approach of acronym P.R.K., based on three principal parameters considered to be most relevant for the evaluation of the vulnerability of ground water to pollution, was developed. These three parameters are: the topographic slope (P), the ratio (R), combining the variation of the amplitude of the fluctuations of the piezometric level compared to the thickness of the unsaturated zone and the permeability of the aquiferous formation (K), from where generic term P.R.K., taking again these initial. This method, based on the principle of the parametric methods with system of class, has as a principal objective to design on the scale of the fieldwell, an indicielle map relating to the intrinsic vulnerability of the hydrogeologic system by gathering the total indices by classes. Within the framework of this communication, we present the results related to the application of this multicriterion method thus adopted at the South fieldwell, using the Geographical Information system (G.I.S.). This tool allowed the multiplicative combination of the layers of information relative to each criterion retained by superposition space set of themes. The total indices obtained vary between 14 and 160. They are distributed in six classes corresponding to the degrees of vulnerability fluctuating of "little" to "the extreme". However, the dominant class is "very little vulnerable". It covers up to 74 % of the total surface of the studied zone. For the present communication, we present the results related to the application of this multicriterion method thus adopted at the South fieldwell, using the Geographical Information system (G.I.S.).