Optimization of irrigation on walnut through the IRRIFRAME water balance model

Abstract

In recent years, reduced summer precipitation frequencies related to climate change have raised the probability of water scarcity, even in the Po Valley of Italy, thus requiring an optimization of the irrigation management for walnut cultivation which has become very present in the area. The aim of the present study was to evaluate, during four consecutive seasons (2018–2021), the physiological (stem water potential Ψ w , leaf photosynthesis A and stomatal conductance g s ), yield (nut weight, shelled yield, kernel colour) and water use efficiency (WUE) responses of walnut trees to different irrigation levels (100% ET c , 75% ET c , and 50% ET c ) in order to obtain an improved water balance model, fit for walnut production under Emilia Romagna conditions. Water supply in 100% ET c (CTRL) was managed according to the IRRIFRAME water balance model. CTRL trees generally showed higher stem Ψ w at midday, than those irrigated at 75% (DI75) and 50% ET c (DI50). Less sensitivity was found for g s and A, than for Ψ w, to the different water regimes: in fact, differences among treatments occurred only in the first two years, when yield was reduced by 50% ET c irrigation, compared to 100% and 75% ET c . No differences were registered for shelled yield and kernel colour during the experimental period. On the contrary, irrigation treatments affected WUE in all the seasons, with CTRL being the less efficient treatment, followed by DI75 and DI50.

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