Characterization of microclimate and turbulent fluxes at a Mediterranean kiwi orchard covered with hail-protection net

Screens and covers are increasingly used to protect crops from pests and extreme meteorological events. Their use affects plant microclimate and physiological responses as well, but this is only partly understood, particularly when considering the interaction among the cover and the training system. This study focuses on the microclimatic effects of the use of a hail protection net and an horizontal (pergola) kiwifruit canopy. The system splits the orchard environment in three distinct layers, determining a shaded understory, a space comprised between the canopy and the net, and the atmosphere above the net. To accent the effects, we considered a high-water demanding crop-kiwifruit, in an environment characterized by high evaporative demand (Bernalda, southern Italy).Three full eddy covariance and radiative balance equipment were used to assess fluxes (carbon dioxide, water vapor, and sensible heat) in the three layers and monitor meteorological variables (air temperature and relative humidity, wind, upward and downward short and long wave radiation, carbon dioxide and water vapor concentrations). Data from a typical clear-sky summer day are considered in this paper.While the net strongly reduced wind speed, it had a modest impact on all other variables. Conversely, the tick canopy layer had a major impact on all variables, determining a highly shaded, cooler and more humid understory, with very light wind. Nevertheless, the combination of high relative humidity and presence of the net was able to reduce the net loss of longwave radiation from the canopy during night, mitigating its cooling under these conditions.The reduction in wind speed and the increase in incoming longwave radiation around the crop, observed at night time, indicate potential valuable mechanisms that may be exploited to decrease water needs and prevent late frosts in the context of climate change, where extreme climatic events are more frequent and crop water requirements continue to increase.