Influence of Compost Amendments on the Composition of Pistachio Nuts in Young Pistachio Trees (Pistacia vera L.)

New fertilization strategies in pistachio cultivation are necessary to reduce the environmental impact of mineral fertilization. The influence of organic fertilization strategies, compost and compost tea, on the growth, yield, and chemical composition of pistachio nuts (Pistacia vera L.) was investigated for two sequential seasons in Spain. Conventional synthetic fertilizers were compared with three organic treatments: compost (T1), compost with compost tea (T2), and compost tea combined with mineral fertilizers (T3). Organic fertilization, alone or combined with mineral fertilization, proved adequate for tree growth and production. The nut composition including mineral content, fatty acid profile, and amino acid composition, was comparable to that obtained with mineral fertilization. Linolenic acid content was higher in treatments that incorporated compost tea (T2 and T3). No changes were observed in mineral composition except for the Zn, which was higher in T3 during one season. Differences in pistachio nut composition between growing seasons were more pronounced than those associated with the fertilization treatments. This is probably a result of alternate bearing. In this trial, integrated organic–mineral fertilization of young pistachio trees reduced the need for mineral fertilization.