2018 ASHS Annual Conference

Variability in autumn climate resulting in warmer and drier conditions can delay leaf senescence in deciduous fruit trees. As leaves remain for an extended season, trees may allow additional nutrient mobilization to the reserves (stem and roots), which can impact nutrient uptake in the following spring. In this study, we evaluated the nutritional responses of two-year-old peach trees to fall temperatures and soil moisture on two cultivars (‘Scarletprince’ and ‘Autumnprince’ both on Guardian^TM rootstock). We applied four treatments to the two cultivars: 1) well-watered trees (100% ET_c needs) grown under ambient outdoor temperatures; 2) water deficient trees (50% ET_c needs) grown under ambient outdoor temperatures; 3) well-watered trees grown in a greenhouse; and 4) water deficient trees in a greenhouse. Average temperature in the greenhouse was 5 °C warmer than ambient outdoor temperature. Trees inside the greenhouse had delayed senescence and there were no significant differences in total leaf number or leaf area between the trees in the greenhouse and outdoor environments prior to senescence. We measured nutrient concentrations in leaves during the fall and in the reserve tissues (new shoots, one-year old shoots, stem above and below the graft union, lignified roots, and fibrous roots) during the winter to assess mobilization. Across fall sampling, leaf nitrogen and phosphorus concentrations were significantly lower inside the greenhouse while potassium was significantly higher in trees outside. Across all tissue locations during winter, nitrogen and potassium concentrations were significantly higher in greenhouse trees than in trees outside, while both nitrogen and phosphorus were significantly higher in water deficient trees than in well-watered trees. Significantly higher levels of potassium were also found in ‘Autumnprince’ compared to ‘Scarletprince’ across tissue locations during the winter. Provided consistent differences between treatments regarding remobilized nutrients, this study could provide a model for the larger climate change discussion within deciduous fruit tree cultivation and provide a platform for further research to optimize management practices encouraging environmental and orchard sustainability.