Soil Organic Carbon Sequestration As Influenced By Tillage, Organic Manuring and Cropping Systems in an Ultisol, Southeastern Nigeria.

SOIL ORGANIC CARBON SEQUESTRATION AS INFLUENCED BY TILLAGE, ORGANIC MANURING AND CROPPING SYSTEMS IN AN ULTISOL SOUTHEASTERN NIGERIA

IGWE, C.A^1* AND ONUNWA, A.O²

¹Department of Soil Science & Land Resources Management, University of Nigeria Nsukka, Nigeria.

²Department of Soil Science & Land Resources Management, Nnamdi Azikiwe University, Awka, Nigeria.

 

*Corresponding Author

 

ABSTRACT

Climate change has been a global issue in the recent years. The study of soil organic carbon sequestration under the local farmer’s real situation is of importance due to the alarming increase in the atmospheric concentration of carbon dioxide (CO₂) and other greenhouse gases (GHGs) resulting from land use changes, fossil fuel combustion for the production of energy and other human activities (industrial revolution) over the years leading to measurable global warming. An understanding of the dynamics of soil organic carbon (SOC) as affected by farming practices is imperative for maintaining soil fertility, productivity and mitigating (GHGs emissions) global warming hence the objective of this study was to investigate the influence of some organic amendments, cropping systems and tillage on SOC sequestration in a sandy loam ultisol, southeastern Nigeria. Experimental plot of 1124.5 m² was planted to cowpea (sole), maize (sole) and maize-cowpea intercrop under tillage and minimum tillage and amended with poultry manure, pig waste, cassava peels at the rates of 20t/ha, 90t/ha, 100t/ha respectively with a control using split-split plot in a Randomized Complete Block Design (RCBD) for two planting years and the third year as the residual. Result indicated cropping system had no significant effect on all the soil chemical properties measured in the first and second year of planting but for H⁺ (P < 0.05) in the second year of planting. Tillage did not have any significant effect on all chemical properties measured in both years except for exchangeable K⁺ (P < 0.05) in the first year. The SOC and the soil chemical properties measured were significantly affected by organic amendments (P < 0.05) except sodium and potassium in the second year. During the third year, cropping system significantly affected pH, exchangeable K⁺, and H⁺ concentration while tillage had a significant effect on SOC, and total nitrogen (TN). Organic amendments significantly affected all the chemical properties measured with the exception of exchangeable Na⁺. Comparatively, in the three years, pig waste exerted a marked influence on the SOC, organic matter, available phosphorus and TN. Maize –cowpea intercrop also helped in influencing these parameters whereas tillage influence on these parameters was dependent on the organic amendment used. The SOC sequestration however, related significantly with tillage, soil amendment and soil aggregate stability indices.

 

Keywords: soil carbon sequestration, farming practices, organic amendments, tillage, soil aggregate stability