Abstract
In Egypt, the need for accurate information on soil organic carbon (SOC) content has increased due to the importance of SOC stocks for sustainable use of natural resources and to meet the requirements of the Kyoto Protocol. Thus, the objectives of the present study are: (1) to quantify the vertical distribution of the soil bulk density (SBD) and SOC content in the soil of north Nile Delta, Egypt under different types of land-use; (2) to provide estimates of the carbon sequestration rate (CSR) of those soils under different types of land-use; and (3) to establish a baseline data on SOC stocks for future studies on SOC dynamics. Ten sampling stations were selected to represent the north Nile Delta during May 2014. In each of the sampling station, 4 sampling sites were selected to represent the virgin lands, 4 to represent fish farms and 12 to represent crop lands (four cultivation histories: 5, 15, 30 and 50 years x three crop types: clover, Trifolium alexandrinum L., sugar beet, Beta vulgaris L., and rice, Oryza sativa L.). Effect of crop type was significant in relation to SBD, SOC content, and SOC stock. In general, SOC stock increases as the number of years of cultivation increases. The SOC stock under crop land and fish farm were 1.6 and 1.5 times as that of virgin land. Rice was the crop with lowest SBD and highest SOC stock. The average CSR of crop land was 352, 134, 88 and 62 g C m(-2) year(-1) for 5, 15, 30 and 50 years of cultivation, respectively. The highest CSR (545 g C m(-2) year(-1)) was observed in crop land cultivated for 5 years by rice, while the lowest (21 g C m(-2) year(-1)) was observed in crop land cultivated for 50 years by sugar beet. On the other hand, the average CSR of fish farm was 143 g C m(-2) year(-1). In conclusion, the conversion of virgin land into crop land or fish farm contributed to SOC sequestration.