Soil carbon and nitrogen changes under a long period of sugarcane monoculture in the semi-arid East African Rift Valley, Ethiopia

Sugarcane cultivation has been practiced over decades in a semi-arid area of the Ethiopian Rift Valley. This study evaluated the effect of sugarcane cultivation on soil C and N storages. We measured the differences in soil C and N along chronosequence fields. We estimated soil C and N losses associated with land conversion and the rate of changes over time. Results indicated that the soil C accumulation was lower under sugarcane field but slowly approached to never tilled (NT) condition. Land conversion resulted in soil C initial losses predicted to 37 Mg C ha(-1) or 58%, which recovered with a net change of 0.35 Mg C ha(-1) yr(-1) or 0.29% yr(-1). Under the current management practices, the loss in soil C is projected to require a century to reach the sugarcane pre-establishment levels. Land conversion induced soil total nitrogen (TN) initial losses estimated to be 113 kg N ha(-1). However, the predicted net change in soil TN as a function of time appeared to be insignificant. Sugarcane as a direct replacement of native vegetation triggered losses in soil C levels. Yet, sugarcane cultivation as land use option established on marginal lands can have a great potential for soil carbon sequestration. (C) 2016 Elsevier Ltd. All rights reserved.