Substrate water status and evapotranspiration irrigation schedulingin heterogenous container nursery crops

A study was conducted to determine the effects of implementing different irrigation scheduling meth-ods on heterogeneous container hardy ornamental nursery stocks. Four ornamental shrub specieswere grown in the same irrigation sector during the summer of four consecutive years (2007–2010):Forsythia × intermedia, Photinia × fraseri, Prunus laurocerasus L. and Viburnum tinus L. Automated dripirrigation based on either substrate water status (SW) or calculated crop evapotranspiration (ET; MODEL)was compared with “typical” timer-controlled irrigation (TIMER). In TIMER treatment, containers wereirrigated based on grower management. In SW treatment, irrigation was controlled either by a water-filled tensiometer (2007) or by a dielectric soil moisture sensor (2008–2010) placed in one pot with aPrunus plant, the species with intermediate water need as found in preliminary work. In MODEL treat-ment, irrigation was controlled on the basis of the species with the greatest ET. Crop ET was calculatedmultiplying reference ET (ET0) by a species-specific crop coefficient (KC), which in turn was estimated fromplant height. In all treatments, pre-irrigation substrate water deficit was lower than the plant availablewater in the container. Compared with TIMER treatment, SW and MODEL irrigation scheduling reducedconsiderably both water use (-21% to -40%) and nutrient emission (-39% to -74%) with no significanteffect on plant growth and quality. Water saving resulted from a reduction of irrigation frequency andleaching fraction (water leached/water applied). Wireless sensor network technology and near/remotemonitoring techniques can facilitate the application of plant-driven irrigation scheduling in commercialnurseries, where generally hundreds of plant taxa are cultivated in many independent irrigation sectors.