Introduction ➢ Quantifying surface and root-zone soil moisture spatial variability remains decisive in agriculture, hydrology, ecology, and climatology. ➢ There is a gap between traditional point-level sensors and remote sensing soil moisture products. ➢ A roving Cosmic-ray Soil Moisture Observing System (COSMOS) has great potential to monitor soil moisture at the hectometer scale and to bridge the gap between existing technologies. ➢ COSMOS a non-invasive soil moisture sensing technology based on background epithermal neutrons (EN). ➢ EN are moderated mainly by hydrogen atoms, thus a direct relationship can be established with soil water content. ➢ The are under study had a spatial domain of 77 km 2 and was located near Gypsum, KS. ➢ The COSMOS rover was used to conduct bi-weekly transects of 160 km of soil and gravel county roads. Objetive: calibrate the roving COSMOS probe and analyze the sensitivity of the instrument to different soil moisture conditions Figure 2: Aerial image of the study area. Orange dots show the rover transect, blue dots indicate calibration sites, and yellow dot indicates the Kansas Mesonet station. (Photo by GoogleEarth). ➢ Three calibration sites were selected. Radial volumetric soil sampling (0 to 15cm depth) was used to calibrate the sensor. ➢ Neutron counts were corrected and calibrated to estimate volumetric water content. Figure 1: COSMOS rover mounted on the truck while conducting a field calibration field (A), taking measures next to the Mesonet station at Gypsum, KS (B), taking volumetric soil samples(C) . Conclusions Sensitivity Calibration Spatial analysis Figure 4: Calibrated curve for corrected neutrons curve to volumetric water content. ➢ COSMOS rover was able to capture soil moisture spatial patterns across the studied landscape, resolution 30x30 meters. ➢ COSMOS rover was capable of detecting soil moisture spatial patterns at the landscape scale, which can be used to i) validate coarse-resolution remote sensing soil moisture products; ii) inform hydrological and crop models; and iii) upscale in situ soil moisture monitoring stations. ➢ Future work will be focused on better understanding the factors controlling soil moisture spatial variability at the landscape scale. Figure 5: Volumetric soil water content estimated from Cosmos. Black dots denote the rover transect. Date 08/02/17. Figure 6: Volumetric soil water content estimated from Cosmos. Black dots denote rover transect. Date 10/17/17. Acknowledgement: Kansas Soybean Commission / Farmer: Justin Knopf & Garrett Kennedy Results Materials and Methods ➢ Neutron counts ranged from 215 cpm to 409 cpm, indicating high sensitivity to changes in soil moisture conditions. Landscape-scale Soil Moisture Monitoring Using Cosmic-ray Neutrons Pedro Rossini 1 , Samuel Long 1 , Vibhavi Jayasinghe 1 , Andres Patrignani 1 1 Department of Agronomy, Kansas State University, 2004 Throckmorton Hall, Manhattan, KS, 66506 [email protected] Φ 0 = neutron count dry soil, W =water lattice, W SOC = water in the Organic matter, = bulk density Φ 0 = 550 cpm RMSE= 0.015 Figure 3: Distribution of corrected neutron counts through different water conditions. Before rainfall event After rainfall event A B C