Eco-physiological response, water productivity and fruit quality of sweet cherry trees under high tunnels

It is known that high tunnels modify sweet cherry physiological and agronomical response; however, horticultural practices such as irrigation have usually not been adapted to this cultivation system because there is no information about the effects of sweet cherry growing under this controlled environment on fruit tree water relations, water productivity and the possibility of saving water. The present work aims to assess the positive and negative impacts of irrigation regime and protective cultivation on tree water status, agronomical and physiological responses of the sweet cherry tree combination 'Santina'/'Colt' in Mediterranean dry weather conditions of Central Valley of Chile. Two treatments were imposed, plastic covered trees under multi-bay high tunnels and uncovered trees under open field conditions. Within each environment, two irrigation treatments were assayed, a conventional treatment, which followed growers' normal irrigation practices in the region, and a reduced irrigation treatment, which was irrigated the 75 % of the conventional treatment. High tunnel increased maximum air temperature, relative humidity and altered light radiation in relation to the environmental conditions in the open. Overall, trees under high tunnel showed higher values of soil matric potential, midday stem water potential (-0.8 MPa) and stomatal conductance (250 mmol m(-2) s(-1)). In the open, trees under reduced irrigation showed soil matric potential values below -150 kPa. Thus, soil water deficit affected tree water status, decreased vegetative growth and fruit size. Covered trees blossomed 7 d earlier than those in the open and were harvested 10 d earlier. Total tree yield did not show significant differences among treatments (11.9 kg tree(-1)); however, when the tree was divided into bottom and top canopy layers, it was found that the top layer of covered trees resulted in significantly lower yield. The cherries from the covered trees were significantly larger (10.4 g) and less firm (75 Durofel units) than those from uncovered trees (8.4 g and 82 Durofel units). The reduced irrigation strategy did not negatively affect tree yield or fruit quality of covered trees and increased water productivity compared with those irrigated with the conventional irrigation. The results obtained highlighted the possibility of decreasing the irrigated water applied to sweet cherry trees under high tunnels by 25 % compared to conventional irrigation.