Modelling the Effects of Soil Conditions on Olive Productivity in Mediterranean Hilly Areas
The majority of olive production in Mediterranean environments is characterized by low external inputs and is practiced in hilly areaswith shallowsoils.This study aimed to study the nutritional status for olive trees innorthwesternSyria anddetermine themost yield-affecting soil and land factors. Our methodology relied on establishing correlations between soil and land factors and fruit yield from 50 rainfed olive (Olea europaea L. cv. Zeiti) orchards under fairly similar climatic and management conditions, but with different soil and land conditions. Land and soil fertility parameters (field slope, soil depth, and soil nutrients) and concentrations of leaf minerals were determined. As olive roots can go deep in the soil profile to extract nutrients, the total available nutrients per tree (over the whole profile) were estimated. Multiple regression analyses were performed to determine the model that best accounts for yield variability. Total available soil potassium amount (R2 = 0.68), soil total N amount (R2 = 0.59), and soil depth (R2 = 0.56) had the highest correlations with olive fruit yields. Available soil potassium amount and soil depth explained together 77% of the yield variability observed. In addition to these two factors, adding leaf B and Fe concentrations to the model increased the variability explained to 83%.