Investigation of the effects of different fertilizer applications on the microbial diversity of Pistacia vera L. orchard soils and fruit quality

Pistachio shell residues are generated in large quantities during pistachio processing, yet their potential as a sustainable soil amendment has received limited attention under field conditions. This study evaluated the effects of pistachio shell compost on soil physical properties, leaf nutrient status, fruit quality, and culturable soil bacterial communities in a semi-arid pistachio orchard in Gaziantep, Türkiye. A field experiment was conducted during the 2022–2023 growing season using a randomized complete block design with five fertilization treatments: unfertilized control, mineral fertilizer, vermicompost plus mineral fertilizer, farmyard manure plus mineral fertilizer, and pistachio shell compost plus mineral fertilizer. Soil physical properties, leaf macro- and micronutrient concentrations, fruit quality characteristics, and culturable bacterial populations identified by MALDI-TOF MS were evaluated. Pistachio shell compost significantly improved soil water-related physical properties, including field capacity, infiltration rate, and water-holding capacity, compared with mineral fertilization alone. Compost application also increased leaf nutrient concentrations and improved fruit quality traits, while culture-dependent analyses indicated greater abundance and diversity of dominant culturable bacterial taxa in compost-amended soils. These findings demonstrate that recycling pistachio shell residues as compost improves soil functionality, plant nutritional status, and orchard performance while promoting beneficial soil microorganisms. Pistachio shell compost therefore represents a promising organic amendment for sustainable nutrient management and circular agricultural practices in semi-arid pistachio production systems.