Plant Available Water Monitoring with the Oklahoma Mesonet

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1 Plant Available Water Monitoring with the Oklahoma Mesonet 2013 No Till Oklahoma Conference, Norman, OK, Feb , 2013 Tyson Ochsner Plant and Soil Sciences, Oklahoma State University Funding provided by the Oklahoma Water Resources Research Institute, the Oklahoma Water Resources Board, and the Oklahoma Agricultural Experiment Station.

2 Drought classifications Severe impacts begin during agro ecological drought Meteorological Precipitation deficits Precipitation measurements Agro ecological drought often foreshadows hydrologic drought Agro ecological drought is defined by soil moisture Agro ecological Hydrological Soil moisture deficits Soil moisture measurements Surface water and groundwater deficits Surface and groundwater measurements Pocasset, OK, Aug. 22, 2012 (Sue Ogrocki) Texas Co., OK, Aug (Mark Mabry) Luther, OK, Aug. 4, (Jim Beckel) Kay Co., OK, Oct. 18, (AP)

3 Large Scale Soil Moisture Monitoring Automated monitoring networks first emerged in late 1990 s Oklahoma Mesonet NRCS SCAN " " " " " " " " " " " " " " " " " " " " " " " " " " " Legend USDA SCAN NOAA CRN COSMOS Illinois Water Survey ARM SGP Sites OK Mesonet " NC EcoNET West Texas Mesonet NE High Plains Climate Center Georgia WeatherNet USDA ARS Watersheds Today there is a large and growing system of networks around the world Transformative approaches are emerging, e.g.: Cosmic rays GPS receivers Station locations (>700) for some of the in situ soil moisture monitoring networks currently operational in the US. (Mike Cosh) Soil moisture stations currently contained in the ISMN. Green dots show the stations that are still measuring soil moisture, red dots the stations that were imported from the Global Soil Moisture Data Bank. (Wouter Dorigo)

4 Large Scale Soil Moisture Monitoring Soil Moisture and Ocean Salinity mission (ESA) Launched 2009 Surface soil moisture, 25 mile resolution Soil Moisture Active Passive mission (NASA) Artist s rendition of the ESA Soil Moisture and Ocean Salinity (SMOS) satellite (courtesy of Yann Kerr). Schedule launch 2014 Surface soil moisture, 6 mile resolution Problem 1: In situ soil moisture measurements have not been used in any operational drought monitoring system Artist s rendition of the NASA Soil Moisture Active Passive (SMAP) satellite (courtesy of Eni Njoku).

5 Plant Available Water (PAW) Problem 2: Soil moisture alone does not indicate the water available for plant uptake Soil moisture (% by vol.) Plant available water is the amount of water stored in the soil and available for plant uptake. Soil depth (in) Plant available water (3.2 in) 28 We developed an operational, PAW based drought monitoring system for Oklahoma. 32 Wilting point Actual soil moisture

6 The Oklahoma Mesonet the gold standard for statewide mesoscale surface networks (National Research Council, 2009)

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10 The 16 inch Plant Available Water map is based on the 24 hour averaged plant available water for the top 16 inches (40 cm) of soil under the existing vegetation at each Mesonet site for the previous day. Plant available water under other vegetation types may differ. Plant available water is the amount of water in the soil that is potentially available for plant uptake. Technically, it is calculated as the amount of soil water at matric potentials above 1500 kpa. The maximum possible plant available water varies between sites due to soil differences. Most plants experience water stress when less than 50% of the maximum plant available water remains in the active root zone. This map is updated once each day between 7 and 8 AM

11 How can we use this information? Soil moisture (and related variables) are key indicators of agroecological drought. Availability of soil moisture measurements is rapidly increasing.? Problem 3: The science required to use these measurements within the context of drought is not well developed. Pocasset, OK, Aug. 22, 2012 (Sue Ogrocki) Texas Co., OK, Aug (Mark Mabry) Luther, OK, Aug. 4, (Jim Beckel) Kay Co., OK, Oct. 18, (AP)

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16 2008 wheat crop (the good) 167 million bushels 37 bushels/ac

17 2006 wheat crop (the bad) 82 million bushels 24 bushels/ac

18 2011 wheat crop (the ugly) 70 million bushels 22 bushels/ac

19 2013 wheat crop (the?) 69% poor or very poor 22% of wheat grazed 36% is 5 yr average

20 Summary Soil moisture is a key drought indicator that has not been used for systematic drought monitoring. We are just beginning to develop the science needed to make use of these data within the context of drought. Departure from average tools can help you interpret Mesonet plant available water. tyson.ochsner@okstate.edu