An integrated multi-sensor system for the continuous monitoring of water dynamics in rice fields under different irrigation regimes

Paddy areas located in Northern Italy provide around half of the European rice production and represent a characteristic agro-environment due to the continuous flooding of paddy fields from April to September. However, the increasing competition among water users is pushing towards the adoption of different irrigation regimes, which improve water use efficiency, but substantially alter the typical landscape of the area. In this context, a two-year experiment funded by the Lombardia Regional Authority (BIOGESTECA Project) was performed at the National Rice Research Centre (Ente Nazionale Risi, ENR) located in Castello d’Agogna (PV, Italy), with the objective of comparing the effects of different irrigation regimes on the productivity and environmental impacts of rice, and on the water and matter fluxes. The experiment was laid out in six plots of about 20 m x 80 m each, with two replicates for each of the following water regimes: i) continuous flooding with wet-seeded rice (FLD), ii) continuous flooding from around the 3-leaf stage with dry-seeded rice (DRY), and iii) surface irrigation every 7-10 days with dry-seeded rice (IRR). During the agricultural seasons 2012 and 2013 one replicate plot for each regime was instrumented with different devices and sensors, with the main purposes of developing and testing an integrated system for the continuous monitoring of water fluxes and storages in rice agro-ecosystem and of comparing the water balance terms, the water use efficiencies and the water productivity of the different regimes. In particular, water inflow and outflow meters, pressure transducers to measure ponded water depth, piezometers, tensiometers and multi-sensor moisture probes were installed in the three plots. Additionally, an eddy covariance station was mounted on the levee between FLD and IRR treatments. Data recorded at a sub-hourly time step were sent by a wireless connection to a remote PC, where a custom Java interface allowed the real time control of the data acquisition. Moreover, periodic measurements of crop biometric parameters (LAI, crop height and rooting depth) were performed in both 2012 and 2013 (11 and 14 campaigns respectively). The experiment was quite successful and, in spite of some limitations in capturing the soil water fluxes, it provided almost complete sub-hourly time series of the most relevant water balance components, that allowed a thorough comparison of the performances of the three irrigation regimes.