Model-based assessment of soil organic carbon dynamics and potentials for carbon sequestration under integrated soil fertility management and conservation agriculture in Western Kenya.
A key message of the 2015 International Year of Soils was that 'soils help to combat and adapt to climate change by playing a key role in the carbon cycle'. With 1 417 000 Mt C in the 1st meter, soils store more carbon (C) than found in the atmosphere and aboveground biomass combined. Expectations are high that little positive changes in soil organic carbon (SOC), i.e. a sequestration of C in soils, if implemented worldwide, could offset a significant share, if not all, of the anthropogenic carbon emissions into the atmosphere, and hence mitigate climate change. However, it is known that unsustainable management practices of soils indeed cause the exact opposite, a loss of SOC. 'With approximately 33% of the world's soils being degraded, large losses of soil organic matter (SOM) (and hence SOC) have occurred with soils from various global agroecosystems (i.e. croplands, grazing lands, rangelands, peatlands, etc.) having lost 25-75% of their original SOC pool.'. The Soil Protection and Rehabilitation for Food Security global program, commissioned by the German Federal Ministry for Economic Cooperation and Development (BMZ) and implemented by GIZ and partners in Benin, Burkina Faso, Ethiopia, India and Kenya, addresses the issue of soil degradation and loss of productivity and its impact on smallholder livelihoods. The primary goal, as the program title implies, is to support and promote the immediate function that protected, fertile soils play in terms of providing and sustaining food security. In addition, taking up the aforementioned idea of SOC sequestration in soils, improved agricultural management practices may have a role to play in terms of climate change mitigation. Besides increased productivity and climate change resilience, mitigation is the third pillar of climate smart agriculture (CSA). To assess the climate smartness of selected GIZ-supported soil protection and rehabilitation measures in the five countries, GIZ engaged CIAT scientists in the project Climate-smart soil protection and rehabilitation in Benin, Burkina Faso, Ethiopia, India and Kenya, which builds on CIAT's expertise in both soil science and CSA. As part of this project, this brief report summarizes a study that investigated to what extent Integrated Soil Fertility Management and Conservation Agriculture can contribute to climate change mitigation by SOC sequestration. These are two of a range of improved management practices which have been endorsed by some GIZ Soil program country initiatives as promising ways to protect and rehabilitate soils. Given CIAT's long-standing presence in Kenya and the fact that CIAT maintains two long-term trials in which these two improved agricultural management practices are tested for their impact on crop productivity long term, Western Kenya was selected as the focus region for this case study. The study complements five rapid climate smartness assessments of GIZ soil protection and rehabilitation technologies carried out by CIAT scientist in Benin, Burkina Faso, Ethiopia, Kenya and India, and published individually as well summarized together in one document.