%0 Conference Paper
%A Brogi, Cosimo
%A Nieberding, Felix
%A Köhli, Markus
%A Pisinaras, Vassilios
%A Dombrowski, Olga
%A Huisman, Johan Alexander
%A Panagopoulos, Andreas
%A Hendricks-Franssen, Harrie-Jan
%A Bogena, Heye
%T Fostering the understanding of sub-footprint heterogeneity in Cosmic-Ray Neutron Sensing – challenges of irrigation monitoring
%M FZJ-2024-00462
%D 2023
%X Cosmic-ray neutron sensors (CRNS) can measure soil moisture (SM) at the field scale due to their large sensing volume of tens of ha. Recently, lower instrument costs and improved data processing make CRNS increasingly attractive for agricultural applications. However, soil moisture in complex environments, such as small fields that are irrigated or cultivated differently or large fields with heterogeneous soils, is still challenging to monitor with CRNS. In this work, we show results from two studies that investigate the effects of sub-footprint heterogeneity in Greece and Germany.In Greece, we selected two ~1.2 ha apple orchards in the Pinios Hydrologic Observatory that are irrigated with micro sprinklers. In 2020, each orchard was equipped with an Atmos41 all-in-one climate station, four water meters, and 12 wireless nodes (SoilNet) that monitored SM at 5, 20 and 50 cm depth. A CRNS with a 25 mm HDPE (high density polyethylene) moderator and a gadolinium-based thermal shielding was installed at the centre of each field. In Germany, we selected a 14 ha potato field near Kogenbroich. Based on an electromagnetic induction (EMI) soil mapping campaign, in 2023, one CRNS with two detector tubes was installed in the middle of the field and two CRNS with a single tube were installed in the SW and NE areas, covering different soil types and soil depths. These CRNS had a 25 mm HDPE moderator. The potato field in Germany receives strip irrigation, which is conducted from SW to NE. One irrigation cycle lasts three to four days, resulting in a strong SM heterogeneity.  At each CRNS location, two soil moisture profile probes were installed, measuring soil moisture and soil temperature at six different depths. Additionally, an Atmos41 all-in-one climate station, as well as a novel evapotranspiration sensor based on the Eddy Covariance (EC) method were installed at the central site. As the EC sensing volume is of similar size as the CRNS footprint, the ability of both methods to estimate irrigation deficits in a heterogeneous landscape may be investigated.Results from the Greek experiment show that CNRS could offer reliable SM estimations only during non-irrigated periods (RMSE < 0.020 cm3 cm-3) while soil moisture content was underestimated in both fields during the irrigation season (RMSE of 0.058 cm3 cm-3) due to the small field dimensions. We developed and tested a novel correction approach based on neutron transport simulations and an additional single SM sensor located outside the irrigated area. We found that soil moisture estimates can be greatly improved (RMSE of 0.031 cm3 cm-3) through this approach. In addition, we will present first results from the experiment in Germany, which provide important insights on sub-footprint heterogeneity and ways to improve the use of CRNS in complex agricultural environments.
%B 2nd TERENO-OZCAR Conference 2023
%C 25 Sep 2023 - 28 Sep 2023, Bonn (Germany)
Y2 25 Sep 2023 - 28 Sep 2023
M2 Bonn, Germany
%F PUB:(DE-HGF)24
%9 Poster
%U https://juser.fz-juelich.de/record/1021002