Irrigation automation with heterogeneous vegetation: the case of the Padova botanical garden

Abstract

An automated control system was set up in the Padova Botanical Garden integrating the information on the soil water status supplied by time domain transmissometry (TDT) sensors with the aid of an irrigation microcomputer. The automatic system consisted of four parts: (a) an irrigation network and electronic control unit (microcomputer); (b) a monitoring system of the soil moisture and water table depth; (c) a management software; and (d) a datalogger connecting sensors to the irrigation microcomputer. Sensors were chosen so that they could be remotely connected through cabling over more than 100 m, guaranteeing adequate accuracy and high reliability over time. To take into account the heterogeneity of plant cover, the site was divided into six irrigation macro-sectors managed separately by the automated system. These macro-sectors were selected by classifying the area on the basis of water requirements, cover type and evapotranspiration demand. The software allowed different irrigation criteria to be defined, considering the values supplied by the moisture sensors singly or on average. In the first year, the automation worked adequately, allowing the irrigation to be managed on the basis of defined thresholds. The irrigation criterion used in the first year for the automated management within macro-sectors, although allowing a favourable water potential to be maintained on average, does not appear to have adequately evaluated the variability of behaviour of the different plants.