Soil organic carbon, total nitrogen stocks and CO2 emissions in top- and subsoils with contrasting management regimes in semi-arid environments oleh Chukwuebuka C. Okolo, Girmay Gebresamuel, Amanuel Zenebe, Mitiku Haile, Jephter E. Orji, Chinyere B. Okebalama, Chinedu E. Eze, Emmanuel Eze, Peter N. Eze