Monitoring and modelling evapotranspiration in flooded and aerobic rice field

Italy is the Europe's leading rice producer, with over half of total production. The high water requirement of rice (flooded throughout its growth period) encouraged the introduction of new and more efficient irrigation practices. From spring 2012 an intense monitoring activity on three experimental fields located in the Padana plain (northern Italy) and characterized by different irrigation managements (traditional flood irrigation, flood irrigation after sowing in dry soil, intermittent irrigation) is being conducted, with the aim of carrying out a detailed comparison of the water balance for the three treatments. An eddy covariance station was installed between the traditional flood and the intermittent irrigation treatments to monitor the evapotranspiration flux (ET). A detailed footprint analysis was conducted to determine the position and the size of the footprint area at each time step. Results of the elaboration are two discontinuous datasets of half-hourly ET values, each one concerning one of the two treatments. Since, in order to compute the water balance for each field, ET must be continuously available throughout the agricultural season, Penman-Monteith (PM) type models have been applied to estimate the complete hourly ET data series for the three irrigation treatments. Results show comparable values of total ET over the agricultural season for the irrigation treatments based on flooding (traditional and after sowing in dry soil), while lower values are found in the case of intermittent irrigation. Estimated ET values are in good agreement with the available eddy measurements.