Enhancing Soil Health and Fruit Quality in Calafate Orchards Through Sustainable Amendments

Calafate (Berberis microphylla G. Forst.) produces fruits with a high antioxidant activity. There is limited information on the effect of compost application on the soil properties and physicochemical parameters of fruits. A 2-year compost fertilization experiment was conducted in a calafate orchard established in 2017. The effects of compost fertilization (0, 5, 10, and 15 t ha⁻¹ of compost) on soil, plant, and fruit were evaluated. The treatments with 5 and 10 t ha⁻¹ compost, without significant differences between them, significantly improved soil fluorescein diacetate activity (FDA) by 18% and basal respiration by 43% compared to the control. The 10 t ha⁻¹ treatment resulted in a 42% increase in leaf area index and a 68% increase in chlorophyll compared to the other treatments including the control. Likewise, the 10 t ha⁻¹ treatment also had a 200% higher fruit yield than the control and achieved a fruit oxygen radical absorbance antioxidant capacity (ORAC) of 3029 μmol TE 100 g⁻¹ FW. The 15 t ha⁻¹ treatment had the highest fruit production 3.8 t ha⁻¹, but it decreased soluble solid concentration by 28% and ORAC to 2526 μmol TE 100 g⁻¹ FW. Multivariate analysis revealed a positive correlation between FDAse activity and fruit antioxidant activity (r = 0.61). Compost application at varying doses enhances FDAse activity and basal soil respiration. Notably, a dose of 10 t ha⁻¹ is recommended to boost FDAse activity and basal soil respiration. This, in turn, results in a substantial increase in the antioxidant activity of the calafate fruit after a 2-year application period.