GNGTS 2017 - 36° Convegno Nazionale

GNGTS 2017 S essione 3.2 677 Evidence of RWU patterns from ERT data. The daily time-lapse images reproduce fairly complex patterns of ER (increasing and decreasing ER in % with respect to the background), caused by the effects of irrigation and SWC depletion by RWU processes (Cassiani et al. , 2015, 2016). Considering the results of the more frequent time-lapse measurements collected during the July and September irrigation experiments, Fig. 3a shows an example of time-lapse ER ratio images for q4 in T1, while Fig. 3b shows the hourly transpiration fluxes (mm h -1 ) of the irrigated tree in T1. By comparing the ER changes in T1 and T2, some key features are noted: i) the decrease in ER occurs in the soil volume while the irrigation front progresses; ii) the increase in ER corresponds in time with the higher rate of transpiration fluxes; iii) in T2, the higher ER increase occurs at the dried side of the plot; iv) the soil depth showing ER changes is 50% larger in T1 than in T2; v) in general, the finer time resolution of the single quarter acquisitions is very helpful at detecting processes linked to RWU that modify SWC on a hourly scale, while a comparison of patterns before and after irrigation alone is definitely more difficult to interpret. Conclusion. The study has proved the effectiveness of the 3-D ERT technique at a small scale of application in reproducing ER changes associated with soil water dynamics. Clear patterns of wetting and drying were evident in the investigated soil profiles at different experimental time resolutions (season and daily/hourly time steps). These patterns were clearly driven by the irrigation operations and plant transpiration due to RWU processes. The 3-D ERT results also identified the scale of the quarter plot (about 1.7 m 2 ) as the minimum for capturing the main processes at the soil-root interface in the experimental orange orchard. The complexity of the RWU processes by using soil electrical properties also emerges clearly from this study, together with the need of controlling several ancillary ground-based data. Due to the complexity and heterogeneity of the studied soil-root system, the integration of hydrological and geophysical modelling might be effective for improving the analysis of the recorded ER anomalies. Finally, ERT may be considered as a useful tool in precision irrigation strategies, in particular for identifying in which areas of the subsoil RWU occurs, thus allowing an optimisation of the irrigation procedure. Acknowledgements The authors acknowledge support in the frame of the collaborative international consortium IRIDA “Innovative remote and ground sensors, data and tools into a decision support system for agriculture water management” financed under the ERA-NET Cofund WaterWorks2014 Call and from the ERANET-MED project WASA “Water Saving in Agriculture: Technological developments for the sustainable management of limited water resources in the Mediterranean area”. References Amato M., Basso B., Celano G., Bitella G., Morelli G.,Rossi R. (2008). In situ detection of tree root distribution and biomass by multielectrode resistivity imaging. Tree Physiology, 28, 10:1441-1448 Binley, A., Ramirez, A., Daily, W., (1995). Regularised image reconstruction of noisy electrical resistance tomography data. In: Beck, M.S., Hoyle, B.S., Morris, M.A., Waterfall, R.C., Williams, R.A. (Eds.), Process Tomography - 1995. Proceedings of the 4th Workshop of the European Concerted Action on Process Tomography, Bergen, 6–8 April 1995, pp. 401–410 Binley, A., (2013). http://www.es.lancs.ac.uk/people/amb/Freeware/R3t/R3t.htm, R3t software version 1.8 March 2013 Cassiani, G., Boaga, J., Vanella, D., Perri, M.T., Consoli, S., (2015). Monitoring and modelling of soil-plant root zone interaction: the joint use of ERT, sap flow and Eddy Covariance data to define the volume of an orange tree root zone. Hydrology and Earth System Sciences, 19, 2213-2225, doi:10.5194/hess-19-2213-2015 Consoli, S., Stagno, F., Vanella, D., Boaga, J., Cassiani, G., & Roccuzzo, G. (2017). Partial root-zone drying irrigation in orange orchards: Effects on water use and crop production characteristics. European Journal of Agronomy, 82, 190-202. Friedman, S.P. (2005). Soil properties influencing apparent electrical conductivity: a review. Computers and Electronics in Agriculture 46, 45–70 Nijland, W., Van der Meijde, M., Addink, E. A., & De Jong, S. M. (2010). Detection of soil moisture and vegetation water abstraction in a Mediterranean natural area using electrical resistivity tomography. Catena, 81(3), 209-216