Micrometeorological test of microsprinklers for frost protection of fruit orchards in Northern Italy

Microclimate modification induced by intermittent water sprinkling at ground level has proven to be suitable to enhance protection against spring hoarfrosts in orchards. This research investigates about the efficiency of different sprinkler types and water volumes in enhancing air temperature in the canopy layer and to optimise the amount and the cycling of the water applied. Tests have been done over three consecutive years in purpose-built boxes delimited by polyethylene film where different sprinklers and sprayers tested were positioned along two pipes. Microsprinklers and microsprayers with different characteristics and outflow capacity were compared to evaluate whether the size of the drops can induce modification of energy balance at the surface. The impact of below tree water sprinkling on the temperature profile appeared to be evident independently on the irrigation device and of the outflow tested. While no substantial differences between sprinklers and sprayers did not arise when the temperatures kept above 3 °C, when temperatures fell below 3 °C (even down to 7/−8 °C), a better performance of the microsprinklers with respect to microsprayers was observed. Differences tend to fade out with height. In the same temperature conditions, a better performance of the microsprinklers with higher outflow (65 l/h) with respect to the same model characterised by a lower outflow (45 l/h) clearly emerged.