Effect of the method and volume of irrigation on yield and fruit quality of yellow fleshed kiwifruit in northern Italy

The aim of the study was to evaluate the effect of type of irrigation and of amount of water supplied on vine growth, yield and fruit quality at harvest and after 2 and 4 months of cold storage. The study was carried out in 2019, in northern Italy, on kiwifruit Gold 3®(A. chinensis var. chinensis) grafted onto micro-propagated 'Hayward' (A. chinensis var. deliciosa) rootstocks in 2012, planted at a distance of 4.5×2 m apart. The investigated irrigation systems included: 1) control (T0); 2) drip irrigation with a single line (T1); 3) drip irrigation with double lines (T2); 4) sprinkler (T3); 5) drip irrigation with double lines + sprinkler (T2+T3). Water management in the control treatment was carried out with drip irrigation with a single pipeline according to the advisory service, based on daily evapotranspiration only. In T1, T2, T3, and T2+T3 water was applied according to the soil water content measured by potentiometric probes, located at two depths: 0.20 and 0.60 m, and two distances from the line of the trees: 0.20 and 1 m. Irrigation started when soil water content got down below the field capacity (-0.03 MPa) and returned the same amount of water lost the day before and measured by a PAN evaporimeter. Compared to the control, T1 reduced the volume of water applied by 34%, T2 by 3%, while T3 increased the irrigation volume by 14% and T2+T3 by 17%. Sprinkler application induced an excess of water in the inter row, where soil structure was impaired by the frequent passes of machines, reducing soil permeability. No effect of treatments on vine yield was observed, however, fruit soluble solid concentration and fruit dry matter at harvest was increased by T2 compared to the other treatments. A similar response was also found after 2 months of cold storage, but disappeared after 4 months. The incidence of storage break down (SBD) was higher in fruits of the control and T3 (22 and 40% of the fruits, respectively), while T2 and T2+T3 irrigation strategies showed the lowest percentage (5-8%, respectively). Finally, the incidence of SBD was negatively correlated with the fruit dry matter (r=-0.88; P≤0.05).