Forage and Grasslands Program Texas Tech University

1. Forage and Grasslands Program Texas Tech University Calibration of ALMANAC for warm-season pasture production Chuck West1 chuck.west@ttu.edu Philip Brown2 philip.brown@ttu.edu 1Professor, 2Senior Research Associate Plant and Soil Science Department

2. Forage and Grasslands Program Texas Tech University Preview of OAP funded research project Objective 2.1: Improve irrigation strategies and scheduling to improve water use efficiency in crop production systems. Product 4: Crop models to predict yield and water use with stress Objectives: Develop growth and senescence curves and ground-cover trends of ‘WW-B.Dahl’ Old World bluestem. Calibrate and validate ALMANAC model for growth.

3. Forage and Grasslands Program Texas Tech University • Justification • Why forages? • Integrating perennial forages for beef cattle into cropping systems • reduces overall water extraction • provides competitive economic returns • conserves soil and rebuilds organic matter • Why WW-B.Dahl? • Shows good yield with modest irrigation (8-10”) • Delayed flowering slows the decline in forage quality • Opportunity for seed harvest in fall diversifies income

4. Forage and Grasslands Program Texas Tech University

5. Forage and Grasslands Program Texas Tech University Information is lacking: Yield:water-use relationships for irrigation schedulingunder grazing Crop coefficients as affected by management and environment

6. Forage and Grasslands Program Texas Tech University • ALMANAC model grew from EPIC model, refined by Kiniryet al. (2005, Biomass Bioenergy 29:419) • USDA-ARS, Southern Plains Area, Temple, TX • Grassland Soil and Water Research Laboratory • http://ars.usda.gov/Main/docs.htm?docid=16601 • Applied to switchgrass for bioenergy production. • Has default input values for many forage/range grasses, • but not validated. • Soil-water output is not validated.

7. Forage and Grasslands Program Texas Tech University Y = -1.12 - 17.36 (-0.5*(ln(x)^2)/x) R2= 0.79 Modeling switchgrass using ALMANAC

8. Forage and Grasslands Program Texas Tech University • Procedures • Measurements from May - October • Leaf area index • Light interception • Yield of live and dead mass • Growth stage • Volumetric soil water content • Weather data • Calculate and input radiation use efficiency (RUE) • Run ALMANAC • Re-calibrate on RUE and soil water parameters • Validate on yield data from other field trials

9. Forage and Grasslands Program Texas Tech University Innovation from Turfgrass Research Measure canopy ground cover with digital image analysis Calibrate canopy images to leaf area development and light interception

10. Forage and Grasslands Program Texas Tech University Digital Image Analysis Take overhead photos of canopy from 5 ft. height Use ImageJ software to define live, senesced, and background Calculate proportion of pixels of each component

11. Forage and Grasslands Program Texas Tech University http://imagej.nih.gov/ij/

12. Forage and Grasslands Program Texas Tech University

13. Forage and Grasslands Program Texas Tech University Area of 239220/307200 = 77% Green

14. Forage and Grasslands Program Texas Tech University Applications Ground-truth remote sensing of crop water status for data input for irrigation scheduling tool www.TAWCsolutions.org

15. Forage and Grasslands Program Texas Tech University Applications Ground-truth remote sensing of crop water status for data input for irrigation scheduling tool www.TAWCsolutions.org Grazing management, decision support, marketing options

16. Forage and Grasslands Program Texas Tech University THANK YOU. QUESTION??