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- Author or Editor: Gabriel T. LaHue x
Irrigation water productivity is a priority for sustainable orchard management as water resources become more limiting. This study evaluated reduced irrigation (RI) as a management strategy for cider apple (Malus domestica Borkh.) production in 2019 and 2020 in northwestern Washington, which has a Mediterranean climate and averages 14.1 cm of precipitation from June to September. RI was evaluated on three cider apple cultivars, Dabinett, Porter’s Perfection, and Golden Russet, in their third and fourth leaf. Stem water potential (stem ψ) was measured weekly throughout the growing season to monitor water stress and implement the RI treatment: irrigation would be applied when stem ψ values dropped below −1.5 MPa, a threshold indicative of moderate water stress in apples. Soil water potential was monitored throughout the season, vegetative growth was assessed by measuring shoot length and non-destructive imaging of the plant canopy using lateral photography, and yield, fruit quality, and juice quality were measured at harvest. Moderate water stress as indicated by stem ψ did not occur either year, thus irrigation was never applied to the RI treatment plots. There was a negative relationship between average stem ψ and both yield and air temperature (P < 0.0001 for each); as yield increased by 5.9 kg per tree or temperature increased by 3.3 °C, stem ψ decreased by 0.1 MPa. The juice quality attributes of the three cultivars in this study were similar to their historic measures at this site and there were no differences due to irrigation treatment, likely because trees did not reach the threshold to induce physiological stress. Both years, trees in the RI treatment did not differ from the control treatment in vegetative growth, fruit yield, juice yield, or any juice quality attribute, but weight per fruit decreased by 7 g, and fruit firmness (measured only in 2020) increased by 2 N. Results from this study indicate that fruit yield and quality in an establishing orchard can be maintained when irrigation is reduced relative to crop water requirements that are estimated from a calculated water balance or relative to conventional grower practices for this region. This finding highlights the benefits of using plant water status to schedule irrigation.
Mechanical hedging was evaluated at Washington State University Northwestern Washington Research and Extension Center, Mount Vernon, WA, in 2019 and 2020 on eight cider apple (Malus ×domestica) cultivars with four bearing habits: tip—Golden Russet, Harrison; spur—Brown Snout, Cap of Liberty; semispur—Tom Putt, Campfield; and crab—Puget Spice, Hewe’s Virginia Crab. Trees were planted on ‘Geneva 935’ (Malus hybrid) rootstock in one replicate block in 2014 and the second replicate block in 2016 and the central leader of all trees was headed in 2017 to equalize tree size and stage of development. Summer hedging was carried out on all cultivars on 16 July in 2019 and 7 July in 2020. The response of different cultivars was evaluated both years by measuring canopy area removed, shoot biomass removed, and fruit removed, and the amount of time to hedge was measured. Additionally, fruit diameter and fruit yield per tree were measured at harvest both years, and fruit weight was measured at harvest only in 2020. The hedger traveled at an average speed of 1.32 mph; it took 6 seconds on average to hedge both sides of one tree when in-row spacing was 6 ft and took 1.25 minutes to maneuver around the end of a row. The estimated time to hedge 1 acre was 1.45 hours when the hedger traveled at 116 ft/min and the orchard had 10 rows spaced 12 ft apart. Biomass removed on an area and weight basis was less in 2020 than in 2019, whereas yield per tree was 2.6 times greater in 2020 than 2019, and cultivars within a bearing habit differed in these responses to hedging both years. Fruit damaged by the hedger was assessed but observed to be negligible for all cultivars. Yield per tree was negatively correlated with fruit diameter (P < 0.001) and positively correlated with the number of fruit removed per tree (P < 0.025). Further research is needed to assess the long-term effects of hedging on biomass removal, yield, and biennialism to determine whether summer mechanical hedging is a cost-effective and suitable method for managing cider apple orchards.