CARBON STOCK AND FLUX UNDER THE INFLUENCE OF VARIOUS AGRICULTURAL PRACTICES IN TROPICAL SOILS OF SOUTHEASTERN NIGERIA

Abstract

This study investigated carbon stock under different agricultural practices in tropical soils of Southeastern Nigeria in two distinct seasons. Six agricultural practices {Natural undisturbed forest land (NUFL); Afforestation (AFP); Continuous cultivated land (CCL); Cattle transit (CT); Grassland (GRL) and Uncultivated land (UCL)} were identified. Carbon stock and flux were investigated at three distinct depths (0-30, 30-60 and 60-90 cm). Experimental design adopted was randomized complete block design. Results showed that under NUFL practices, highest concentrations of carbon were obtained from soil aggregates (macro-aggregates: 1.86 and 1.93 g kg-1; micro-aggregates: 4.48 and 4.64 g kg-1) in both raining and dry seasons. Carbon concentrations in the studied sites diminished with depth. Highest soil organic carbon stock (SOCs) contents of 85.77 and 99.86 kg C ha-1 were obtained from site under NUFL practices. Carbon stocks in the study soils declined with depths 99.86 to 27.31 kg C ha-1; 89.49 to 48.13 kg C ha-1 in raining and dry seasons. High values of CO2 (4.96 and 7.77%) were obtained from soil under intensive cultivation (CCL) in both seasons. Maximum Net carbon fluxes (-22.35 and -23.31) were recorded in soils under CCL practices in raining season and dry season. Net carbon flux was consistently negative and significantly lower in soils under NUFL (-84.68 and -97.88) in both seasons. Conclusively, NUFL and AFP practices enhanced vegetation cover which reduced carbon emissions, improved storage of carbon as well as other soil properties with lower risk of soil degradation when compared to soil under other farming practices.