Effects of Seasonal Variation on some Soil Chemical Properties under Different Land Use in Santa Barbara, Bayelsa State-Nigeria

A study was carried out to examine the effect of seasonal variation on some soil chemical properties under different land-use in Nembe, Bayelsa State-Nigeria. The objective was to evaluate changes in soil nutrient contents in both wet and dry seasons. A total of eighteen soil samples were collected at 0-30 cm depths in August, 2017 (Wet Season) and March, 2018 (dry season) in natural forest, oil palm plantation and arable land-use and analyzed for pH, soil organic carbon (SOC), total nitrogen (N), available phosphorus (P), exchangeable cations (Ca, Na, K and Mg), and cation exchange capacity (CEC) using standard analytical methods. Results showed that soil pH was highest (4.2) under oil palm plantation in the wet season, while high content of N 0.52 mg/kg was recorded during the wet season in all the thee-land use. Organic carbon was highest 1.69 mg/kg in natural forest, followed by 1.39 and 1.04 mg/kg for oil palm plantation and arable land use. Maximum value of P 0.22 mg/kg was observed under natural forest during the dry season, and the minimum was recorded under arable land use during the wet season. The concentration of exchangeable Ca was highest 0.3 mg/kg in the oil palm plantation, while Na was highest 2.19 mg/kg for natural forest, 1.26 and 1.06 mg/kg for oil palm plantation and arable land use. The CEC values of the soils in the natural forest were moderately high, followed by oil palm plantation and arable land use in the wet season; whereas low CEC values were observed across the three-land use in the dry season. The study concluded that soil nutrients were more available during the wet season than in the dry season in the various land use, probably due to adequate soil moisture availability in the wet season that facilitates soil nutrient release, this implies that chemical properties of soils were influenced by seasonal changes which could in turn affect agricultural production. It is recommended that crop production is encouraged in the wet season than in the dry season so as to utilize more availability of soil nutrients.