Assessment of of high-resolution L-band radiometry application in precision irrigation

Spaceborne microwave radiometers are historically used to estimate and analyze global soil moisture and ocean salinity. Despite providing valuable inputs to global hydrological models, the use of satellite-based L-band radiometry in agriculture was limited by the coarse spatial resolution not pertinent to field level observations or by the cost and size of the ground-based system.  TerraRad has recently developed a portable dual polarization passive L-band radiometer (PoLRa) for meter-scale retrievals of soil moisture (SM) and vegetation optical depth (VOD) suitable for field level application. PoLRa is designed to be mounted on UAV, fitted on ATV’s, or fixed on a tripod for continuous measurement. To examine the potential of L-band microwave radiometry in precision irrigation, the retrieved VOD and SM from PoLRa were compared against high resolution vegetation indices (i.e NDVI), plant parameters (i.e. LAI), surface soil moisture and  soil apparent electrical conductivity (ECa) from multi-frequency EMI soil scanner. We will summarize the findings from measurements conducted over bare soil, alfalfa, tomatoes, almonds and olive fields in California. We will also discuss the performance of the L-band radiometer in detecting spatial soil variability, surface soil moisture content, plant water status and vigor. We will also identify research gaps and limitations for L-band use for precision irrigation.