Examination of Radiocarbon Levels, Organic Matter, Phosphorus, and Potassium in Acidic Soils under Maize Cultivation in Akwa Ibom State, Nigeria

Abstract

This study examined the dynamics of radiocarbon (¹⁴C), organic matter, phosphorus, and potassium levels in acidic soils across three locations (Ntak Inyang Itam, Nto Ndanga, and Ikot Akpaden) under a maize cropping system in Akwa Ibom State, Nigeria. The control treatment exhibited a negative Δ¹⁴C value (-80‰), whereas compost and manure applications resulted in positive Δ¹⁴C values (50‰ and 30‰, respectively). When combined with NPK fertilizer, Δ¹⁴C values remained positive but slightly lower (40‰ for compost + NPK and 25‰ for manure + NPK). Organic matter content was highest in combined treatments (3.2% for compost + NPK and 3.5% for manure + NPK), followed by manure (3.0%), compost (2.8%), and NPK alone (1.8%), while the control had the lowest (1.5%). Phosphorus availability increased from 5.2 mg/kg in the control to 12.5 mg/kg with compost, 15.3 mg/kg with manure, and 20.4 mg/kg with NPK. The highest values occurred in combined treatments (25.8 mg/kg for compost + NPK and 28.1 mg/kg for manure + NPK). Potassium availability followed a similar trend, peaking at 0.55 cmol/kg (manure + NPK). Maize yields were lowest in the control (1.2 t/ha) and highest in combined treatments (4.2 t/ha for compost + NPK, 4.5 t/ha for manure + NPK). These findings advanced the understanding of carbon sequestration in acidic soils and highlighted the impact of organic and inorganic amendments on ¹⁴C dynamics and soil fertility.