Unleash the strength of precision irrigation with Portable L-band microwave and cosmic ray neutron sensors

By 2050, the demand for food must increase by 50% to satisfy the needs of the expected 9 billion people. Precision agriculture, primarily driven by technology, aims to produce more with less input (i.e., water) by managing in-field soil and plant variability. Point measurement with traditional soil moisture sensors calls for a large number of sensors, thus increasing costs. The low spatial resolution and the limited measurement depth of the space-borne microwave sensors are not pertinent to field-scale and agricultural applications. Cosmic Ray Neutron Sensors (CRNS) emerge as an alternative technology for large-scale measurements of moisture (SM) content and biomass water equivalent (BWE). However, a lot of uncertainties are still in assessing the measurement footprint in space and depth. This work will explore the potential of combining high-resolution microwave L-band measurements using a UAV platform with CRNS to evaluate the spatial and temporal moisture content distribution. An experimental setup of one eddy covariance station and 2 Finapp CRNS (with and without Gadolinium) was installed on an alfalfa field  (Davis, California). TDR measurements were taken before and after irrigation at two different depths to calibrate both CRNS and Microwave L-band measurements. An on-site multispectral sensor (Arable) was used to monitor canopy development and to validate CRNS’ BWE and the microwave’s vegetation optical depth (VOD). The calibrated values were also compared with satellite measurements. Both CRNS and high-resolution microwave measurements showed promising results, especially when used in conjunction. However, research is still needed before unlocking the full commercial potential and mass adoption in the agricultural sector.