Late-season plastic covering delays the occurrence of severe water stress and improves intrinsic water use efficiency and fruit quality in kiwifruit vines

Kiwifruit is widely recognized as a fruit crop sensitive to water stress due to low stomatal regulation. Unfortunately, many of the most important kiwifruit producing areas have been affected by increasing water scarcity due to climate change. Protected cultivation may be used in kiwifruit vines not only to mitigate water stress and potential reductions in fruit quality but also to increase intrinsic water use efficiency. At the beginning of fruit maturation, two environmental conditions (uncovered and covered with a transparent plastic covering) were assessed in mature kiwifruit plants (Actinidia deliciosa Chev. cv. Hayward) subjected to conventional and deficit irrigation regimes in San Nicolás, Chile, for two consecutive seasons. The results showed that covered plants under deficit irrigation required twice the time to exhibit severe water stress levels (~−1.3 MPa) than plants under open-field conditions. Despite changes in solar radiation quantity and quality due to the transparent plastic covering, differences in rates of water stress occurrence between cover treatments in deficit-irrigated vines were not explained by differences in soil desiccation or stomatal conductance. The delay in severe water stress onset led to considerable water savings and caused no reductions in either yield or fruit quality, which increased water productivity between 21% and 71%. Fruit from covered plants subjected to deficit irrigation exhibited higher firmness at greater maturity (>7.0 Brix). The increase in water productivity in severely water-stressed kiwifruit vines, when using late-season plastic canopy cover, confirms that protected cultivation can be an excellent tool to reduce the impact of limited irrigation in many kiwifruit producing areas affected by water scarcity.