The impact of foliar NPK fertilization on fruit characteristics and oil quality of the Moroccan olive cultivar ‘Menara’

Abstract In Morocco, olive yields and oil quality are still low compared to the potential of the crop because olive is usually produced in poor soil and most groves are under rainfed conditions. Most of olive orchards suffer from major macronutrients NPK (nitrogen, potassium, and phosphorus) deficiency. The aim of this study is to evaluate the impact of foliar fertilization of N, P and K nutrients and harvest stage on olive fruit yield, fruit characteristics and olive oil composition. The fertilization treatments are a combination of nutrients N, P and k applied as a foliar spray: T1(N), T2(P), T3(K), T4(N+P), T5(N+K), T6(P+K), T7(N+P+K) compared to control T0 (without NPK). A total of six foliar sprays were applied, one per month, from February to July. Olive samples were harvested in 2 dates (S1: September, S2: October). Results showed that fruit maturity index increased with harvesting period. The foliar fertilization with N, P and K separately increase the olive fruit yield significantly to 16.7 Kg/tree, 16.3 Kg/tree and 15 Kg/tree respectively, compared to control 11.7 Kg/tree. The combination of these 3 nutrients (NPK) significantly maximize the olive fruit yield 26.7 Kg/tree. Except oil acidity, we noted significant changes in olive oil phenols content, oil fatty acids composition. Nevertheless, values obtained for all quality parameters studied were conform to IOC International Olive Council (IOC) norms. Suggesting that any single deficient nutrient limit olive yield potential and oil quality. Nutrient synergy is more critical to enhance high olive yield and oil quality.