Projected Changes in Soil Organic Carbon Stocks over a 50-Year Period under Different Grazing Management Systems in Semi-Arid Grasslands of Kenya

Rangeland cover approximately 85% of Kenya’s land mass and is a major resource for livestock farming with a considerable potential to mitigate climate change, yet these lands are stressed differently by various management. Our study aimed at predicting the long-term changes in Soil Organic Carbon (SOC) in grazing lands of Kenya under different grazing management systems (rotational, continuous and ungrazed), for a 50-year period using RothC 26.3. This research was conducted on a commercial grazing ranch which practices the two grazing management systems. Soil samples were collected at the depths of 0-10, 10-20 and 20-30 cm for the determination of soil organic carbon concentrations and bulk densities, results were later used for running the RothC model. The predicted results showed that the rate of SOC stock [t/ha] was higher under rotational grazing system in comparison to ungrazed and continual grazing system for the modelling period of 2015-2064. In the absence of grazing, the system was predicted to accumulate 19.22 Mg C ha-1 of SOC at the rate of 0.369 Mg C ha-1yr-1, whereas rotational grazing system was predicted to accumulate 30.46 Mg C ha-1 at the rate of 0.61 Mg C ha-1yr-1. The continual grazing management system resulted in the accrual of 18.49 Mg C ha-1 at the rate of 0.37 Mg C ha-1 yr-1 over 50 years. Thus, rotationally grazing management system have the potential of accumulating soil organic carbon in semi-arid grasslands.