Postharvest deficit irrigation in ‘Conference’ pear: Effects on subsequent yield and fruit quality

The best time for applying deficit irrigation (DI) to pear is not yet known although it was the first fruit crop to be studied for regulated DI. We explored postharvest application. Over the growing seasons of 2007–2010, three irrigation treatments were applied to ‘Conference’ pear in an experimental orchard. They were full irrigation (control, C), withholding irrigation after harvest (DI-PHa+b), and full irrigation for two weeks after harvest followed by withholding irrigation (DI-PHb). According to our previous experience with ‘Conference’, the DI treatments were to be irrigated if midday stem water potential (Ψstem) became lower than −1.5 MPa. But it never did. The average annual irrigation water applied to C was 590 mm. This was reduced by 15% for DI-PHb and by 27% for DI-PHa+b. Fruit yield in DI-PHa+b was similar to C for each of the three years following DI. But a carry-over effect was observed after the dry season of 2008. In 2009 fruit set and crop load were therefore reduced for DI-PHa+b but fruit size was increased. For all years DI-PHb was similar to C in terms of fruit set, crop load, fruit size, and yield. Fruit soluble solids concentration (SSC), titratable acidity, and flesh firmness were measured in 2009 and 2010. They were the same in C and DI fruit except for 2009 when SSC was higher in DI-PHa+b fruit. ‘Conference’ adapted to DI in such a way that Ψstem could be maintained by higher water depletion at a greater soil depth as the experiment progressed. Postharvest DI is recommended for ‘Conference’ but to the extent that midday Ψstem does not become lower than −1.2 MPa.

► Pear irrigation continued (C), was stopped at harvest (T1), or at two weeks from harvest (T2).
► Compared to C, and over three years of study, T1 saved water by 27% and T2 by 15%.
► Soil water depletion by T1 trees increased in depth as the experiment progressed.
► Over three years fruit size was lowest for C while fruit yield and quality were similar for all treatments.