The Effects of Inorganic and Organic Fertilizers on An Olive Orchard Grown on A Sandy Soil

ِA FIELD experiment was conducted for two successive years in an olive orchard on sandy soil in the El-Tor area of South Sinai, Egypt. The goal was to investigate the effects of fertilization (inorganic or organic) and fertilizer application methods (surface application or mixing within the soil) on the soil physicochemical characteristics and the nutrient status of soils and plants. Two factors relating to the fertilizer source (F) and method of application (M) were as follows: (i) the fertilizer source (F) included two treatments, i.e., inorganic fertilizer (F1) (with each tree receiving 412 g N in the form of ammonium sulfate + 264 g P as calcium superphosphate) and olive compost (F2) (with each tree receiving 25 kg of compost containing 512 g N + 152 g P), and ii) the application method (M) included two treatments, i.e., surface application (in which fertilizers were added to the soil surface without subsequent plowing) (M1), and application by mixing the fertilizer and plowing it into the 15-cm soil surface layer (M2). The results showed that F1 surpassed F2 in increasing the N, P, K and Ca contents for olive plant parts relative to the non-fertilized treatment, with average increases of 26.8, 34.2, 32.8, 42.6 and 21.5% in leaf-N (N content in leaf), fruit-N, fruit-P, leaf-K, and fruit-Ca, respectively. Additionally, the F1 treatment resulted in average increases of 27.3 and 28.6% in available N and P, respectively, at the soil surface (0-20 cm); in the soil subsurface (20-40 cm) the respective increases were 12.3% and 13.6%. The F2 treatment positively affected soil physical properties. It increased the total porosity by an average of 13.5% and decreased hydraulic conductivity by an average of 32.6% and bulk density by an average of 6.5%. The M2 treatment was more effective than M1. M2 caused greater increases in the nutrient status than the non-fertilized treatment, producing average increases of 21.5, 31.0, 32.8, 38.0 and 19.5% in leaf-N, fruit-N, fruit-P, leaf-K, and leafCa, respectively. With respect to available nutrients in the soil, M1 surpassed M2 in its effects on soil surface nutrient status; it led to an average increase of 33.1 and 37.9% in available N and P, respectively, but had no effect on available K. In the soil subsurface, M2 surpassed M1, giving average increases of 36.4, 33.8 and 4.5% in available N, P and K, respectively