Influence of Soil Phosphorus Dynamics on Soil Carbon Sequestration in Four Land Use Types in Abakaliki, Ebonyi State, South Eastern Nigeria

Abstract

Information on soil phosphorus dynamics and its influence on soil carbon sequestration in different land use types is scanty. A research was conducted to determine the influence of soil phosphorus on soil organic carbon sequestration in four land use types in Abakaliki, south eastern Nigeria. The four land use types selected include managed forest plantation, fallow land, grass land and continuously cultivated soil. Soil samples were randomly collected from each of the land use types seasonally; two times in rainy season and two times in dry season annually at three months interval respectively for two years (2022 and 2023). Undisturbed and auger soil samples were collected at three soil depths (0 – 20 cm, 20 – 40 cm and 40 – 60 cm) in the selected land use types and replicated five times for bulk density determination and chemical analysis such as soil organic carbon and available phosphorus using standard methods. On the average, soil bulk density values obtained were lowest (1.54 gcm3) in the fallow land and highest (1.71 gcm3) in the continuously cultivated soil for both seasons and for the two years. On the average, managed Gmelina plantation (MP) recorded the highest soil organic carbon (SOC) (15.45 and 23.70 gkg-1 for dry and rainy seasons respectively) and mean available phosphorus (AP) (8.03 and 12.37 mgkg-1 for dry and rainy season respectively) while continuously cultivated soil (CCS) had the lowest values (9.03 and 8.88 gkg-1 for dry and rainy seasons respectively) and (0.93 and 0.95 gkg-1 for dry and rainy season respectively) for the soil nutrients in both seasons. The result on total organic C storage showed that continuously cultivated soil (CCS) had highest value (160.17 Mg C ha-1) and lowest(116.84 Mg C ha-1) in grass land (GL) in dry season year 1 while in rainy season year 1 managed Gmelina plantation recorded the highest (365.51 Mg C ha-1) and GL recorded the lowest (135.63 Mg C ha-1).Similarly, MP recorded the highest value (340.67 and 372.06 Mg C ha-1) while CCS recorded the lowest value (151.49 and 220.42 Mg C ha-1) for dry and rainy seasons respectively in second year. The results also showed that the soil physical and chemical properties were significantly different (P < 0.05) among the four land use types and depths. It is therefore recommended that continuous cultivation without organic amendments which exposes the soil should be discouraged. Also, management practices and land use types like managed forest plantation, fallow land and grass land that increase soil carbon content should be encouraged. This is because soil phosphorus encourages carbon sequestration that helps to mitigate the effect of climate change.