Influence of Land Use on Carbon Sequestration and Carbon Dioxide Emission under a Humid Agroecosystem
The study determined the emission of CO2 from four agricultural land use types; namely, cultivated, fallow, secondary forest and control sites and the flux in CO2 emission with the alteration in land use practice. This was with a view to estimate the effects of management of C sequestration The study was carried out between July to December, 2004 at the Soil Science Unit of the Obafemi Awolowo University Teaching and Research Farm, Ile-Ife. A static chamber method was used to measure CO2 flux. The soil moisture content, pH, temperature and the organic matter contents at each point of sampling were also determined. This was repeated at 2-weekly interva1s. The data were analysed using descriptive and inferential statistics. The results show that the average CO2 emission was highest on cultivated land (60 mg C m-2h-1 ) followed by fallow (40 mg C m-2h-1) lastly by forest (32 mg C m-2h-1). This implied that the forest had the greatest capacity to sequestrate CO2. This is responsible for the highest content of soil organic matter under forest (1.88%) followed by fallow (1.21%) and then cultivated (0.44%). Temperature (r = 0.43, p < 0.05) and moisture content (r = 0.36, p < 0.05) were significantly positively correlated with CO2 evolution. Increase in both soil moisture and temperature were found to responsible for the increase CO2 emissions observed. Furthermore, increased soil bacteria population was found to be directly related to the increased CO2 emission obtained from the cultivated soil. Hence, forest and fallow soils were found to have the highest potential to serve as sinks for CO2, thus help reducing CO2 concentrations in the atmosphere. The soil pH apparently had no effect CO2 emission. In conclusion, the forest had the greatest capacity to sequester CO2 followed by fallow and lastly cultivated land While the conversion of fallow land to arable increased soil CO2 evolution.