Beyond soil moisture probes: improving field scale soil moisture mapping

This research questions the value of data from a single-point soil moisture probe sited in a dryland farmer’s field. The reliance on single-point soil moisture probe data to provide quantitative information on the spatial heterogeneity of soil moisture within a field is imprecise. The soil moisture data can be supplemented and enhanced to improve farm management decisions on a dryland farm. High resolution maps are produced with archived Quantitative Precipitation Estimate (QPE) merged radar-rainfall data of the accumulated rainfall between any two dates for a single field, with a grid resolution of 500 m × 500 m. This data provides a temporal area-based measurement of rainfall facilitating the use of hydrological models to provide near real-time estimates of soil water at the field level. Delineation of soil moisture-based management zones are created based on the antecedent spatio-temporal distribution of soil water content at the within-field scale. A decision support tool is applied to assess the current risk levels with appropriate management actions determined from the available water content levels in the delineated zones. Merged radar-rainfall data is used as an area based measure of rainfall in conjunction with a water balance model such as SoilWat from the Agricultural Production Systems sIMulator (APSIM). This model can determine the spatial distribution of soil moisture within a field at a grid resolution of 500× 500 m, incorporating the surface soil layer not measured by soil moisture probes.