Current fertilization recommendations for mature peach orchards rely on spring soil sampling and postharvest leaf analysis. Soil sampling assesses nutrient status at the soil level, while standard leaf analysis is mainly useful for the next crop cycle, limiting major in-season adjustments. The objective of this study was to understand how macro and micro elements change over time using leaf sap nutrient analyses. This study was conducted in a nine-year-old peach orchard using a split-plot randomized complete block design with three replicates, where irrigation systems, drip vs micro-sprinkler, served as whole-plots and foliar treatments as split plots. Foliar treatments included water (control), nanocellulose crystals (CNC 3%), Calcium (Ca 6%), Potassium Silicate (K2SiO3), CNC plus Ca, and CNC plus K2SiO3. Trees did not receive any soil-based fertilization and water was managed based on the Peach Smart Irrigation App recommendations (https://smartirrigationapps.org/peach-app/). Foliar applications were carried out three or four days prior to leaf sampling. Leaf samples, including petioles, were collected between 8 am and 11 am at 40, 72, 86, and 100 days after full bloom (DAFB) for sap analysis. Leaf sap analysis showed that N, primarily as NH₄, and Mg, were within sufficiency ranges. P and K were excessive; and Ca, S, and all micronutrients were deficient. Elevated P likely limited Zn and Fe uptake. B deficiency may have impaired sugar, N, and P loading and transport to sink tissues. Mo (
