1. University of Nebraska Carbon Sequestration Program

2. Soil Moisture Monitoring and Modeling in the Nebraska Carbon Sequestration Project Kenneth G. Hubbard Todd T. Schimelfenig and Cynthia J. Hays University of Nebraska Carbon Sequestration Program

3. University of Nebraska Carbon Sequestration Program Objective To provide continuous measurements of rainfall, irrigation and root-zone soil water for the overall study on carbon sequestration and real-time data for use in irrigation management

4. University of Nebraska Agricultural Research Development Center Ithaca NE 1.Continuous irrigated maize 2.Irrigated maize/soybean rotation 3.Rain fed maize/soybean rotation

5. University of Nebraska Carbon Sequestration Program

6. University of Nebraska Carbon Sequestration Program SYSTEM COMPONENTS  Free Wave spread spectrum wireless data transceiver  Campbell Scientific datalogger  Theta-probe soil moisture sensor  Tipping bucket rain gauge

7. University of Nebraska Carbon Sequestration Program

8. University of Nebraska Carbon Sequestration Program

9. University of Nebraska Carbon Sequestration Program

10. University of Nebraska Carbon Sequestration Program www.hprcc.unl.edu/soilm/home.html

11. University of Nebraska Carbon Sequestration Program

12. University of Nebraska Carbon Sequestration Program

13. University of Nebraska Carbon Sequestration Program

14. University of Nebraska Carbon Sequestration Program

15. (Mahmood and Hubbard, 2003) University of Nebraska Carbon Sequestration Program  S/Δt = p + I - ET - R o - D r S = Σθ v Δz, the equivalent depth of water in the soil Δz = layer depth Θ v = volumetric water content t = time p = precipitation I = irrigation ET = evapotranspiration R o = runoff D r = drainage

16. University of Nebraska Carbon Sequestration Program

17. University of Nebraska Carbon Sequestration Program Conclusions  Theta probes should be calibrated for each soil type  It is important to include calibration set-points that are near the end of the range (wilting point & field capacity)  Clay soils present considerable challenge because of swelling, shrinking, and cracking  Quick disconnects and buried tubes ensure that sensors in agricultural fields are undisturbed from year-to-year

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19. University of Nebraska Carbon Sequestration Program