SCHEDULING IRRIGATION IN HETEROGENEOUS CONTAINER NURSERY CROPS

Abstract

One of the major production areas in Europe for Hardy Ornamental Nursery Stocks (HONS) is located around Pistoia (Tuscany, Italy). In this area, pot ornamental crops show low water use efficiency (WUE). Main reasons of poor irrigation efficiency are both the inaccurate irrigation scheduling, which is normally based on grower’s personal experience, and the choice to group different plant species together in the same irrigation plot in order to simplify irrigation and to reduce growing costs. An efficiency-oriented approach for the management of HONS requires the use of soil/substrate moisture sensors (SMS) and/or crop evapotranspiration (ET) model to regulate irrigation frequency. In order to compare different methods for irrigation scheduling in container beds hosting four different HONS species, two experiments were carried out in the spring-summer season of 2009 and 2010 at ‘Centro Speri-mentale per il Vivaismo’ (CESPEVI), Pistoia. In particular, we tested two irrigation control methods based on SMS or ET model as compared to conventional timer scheduling. The WET sensor was used for SMS control while the ET model consisted of a composite regression model of crop ET (as function of plant height and potential evapotranspiration) along with a specific algorithm implemented in the software of an irrigation controller prototype. Scheduling irrigation by means of the WET sensor (irrigation was activated when the matric potential of substrate was less than -5.0 kPa) or applying ET model reduced seasonal water use respectively by 40% and 45%, and water runoff by 74% and 81% in comparison with timer control strategy, without significant effects on plant ET, growth, and commercial value at the end of growing season. Both new irrigation scheduling are useful for growers, but for a large use of RZS method, a low cost RZS sensor is required. The use ET-model is less expensive, but it requires the knowledge of the Kc for the hundred of different species grown in the nurseries.