Seasonal variations of some soil nutrients in a natural and an agricultural olive grove in Adana, Turkey

The bioavailability and cycling of nutrients in soil are two of the most important factors for healthy plant growth and development in natural and agricultural ecosystems. Seasonal variations of some soil macronutrient (phosphorus and potassium) and micronutrient (copper, manganese, and zinc) contents were investigated in a natural olive (Olea europaea L.) grove (NO) and an agricultural olive gene garden (OGG) located in Adana, Turkey. Soils were sampled at 0–10 cm and at 10–20 cm depth in the months of November, February, May, and August between 2013 and 2015. Soil phosphorus, potassium, copper, manganese, and zinc contents were in the range between 0.37 and 8.65 mg kg−1, 181.81 and 1030.67 mg kg−1, 1.41 and 2.74 mg kg−1, 13.88 and 51.06 mg kg−1, and 0.39 and 2.27 mg kg−1, respectively. All soil nutrients significantly decreased as soil depth increased in all sampling times (P < 0.05). In general, significant seasonal effects were observed in all soil nutrients at 0–10 cm depth that was more variable than at 10–20 cm depth. Soil phosphorus negatively and positively correlated with soil potassium in NO and in OGG at 0–10 cm depth, respectively (P < 0.05). Soil zinc was negatively and positively correlated with soil phosphorus in NO and in OGG at 10–20 cm depth, respectively (P < 0.05). In conclusion, soil depth might be a more important factor than seasonality on the vertical distribution of soil nutrients in olive groves. In addition, correlations between soil nutrients in this study should be taken into consideration for the optimum management of agricultural practices in biological olive groves.