Regulation of nutrient content in peach fruits under different soil moisture regimes

Background: Peaches (Prunus persica) are known help improve metabolic health, as they contain bioactive compounds such as vitamins, flavonoids, and minerals. However, their biochemical composition changes significantly depending on environmental conditions, particularly soil moisture. These conditions can influence fruit development, nutrient accumulation, and overall quality. Objective: This study aimed to measure the impact of different pre-irrigation soil moisture levels (90%, 80%, 70%, and 60% of field capacity) on the growth of the "Narnji" peach variety. Fields such as yield, vegetative growth, and the biochemical composition of grown fruits were used to assess the optimal irrigation for maximizing nutritional value and functional food properties. Methods: From 2017 to 2019, experiments were conducted in the pre-mountainous zone of the Ararat Valley, Armenia, using 5–7-year-old "Narnji" peach trees. Trees were irrigated under four pre-irrigation soil moisture levels along with a control group based on standard farm practices. The gravimetric method monitored soil moisture on four horizons (0–80 cm). Morphological and biochemical measurements were performed using standard methodologies. Results: Soil moisture levels significantly influenced growth, fruit set, yield, and biochemical composition. The 80% field capacity (FC) regime produced the highest yield (16.04 tons/ha) and an effective fruit set rate of 11.8%, with a seasonal irrigation volume of 6630–7370 m³/ha. Total sugars (11.3–13.1%) peaked at 70% and 80% FC, organic acids (0.45–0.53%) were highest at 90% FC, and dry matter was greatest at 60% FC. The 80% FC regime best balanced productivity and bioactive compound accumulation. Novelty: The innovation of this study lies in its integrated assessment of irrigation levels on fruit yield, water use efficiency, and the concentration of key functional food. Unlike previous works that examined irrigation from a yield or growth perspective alone, this study combines plant physiology, soil-water dynamics, and functional food science to reveal how ecological management can optimize the health-promoting potential of fruits. The identification of 80% field capacity as the optimal irrigation level offers a scientifically grounded standard for maximizing both agricultural output and nutritional quality. Conclusion: Maintaining pre-irrigation soil moisture at 80% of field capacity is optimal for peach cultivation under Armenian conditions. It improves yield and nutritional quality, reinforcing the value of peaches as a functional food and supporting sustainable horticultural practices. Keywords: peach, fruit, variety, mid-season, Narnji, soil, pre-irrigation moisture, biochemical and bioactive compounds.