Restoring degraded Kenyan grassland soils

Soils underpin food production in Africa, and they are under extreme pressure and while there has been considerable research into the management of African soils for crop production, far less research has been conducted into grasslands management. Poor grazing practices and the continuous removal of nutrients and organic matter negatively impacts on plant nutrition; soil erosion reduces soil depth lowering water storage and brings poorer subsoil to the surface and in extreme cases leads to the abandonment of livestock grazing altogether.

Estimates suggest 40 to 60% of soils in Africa are degraded, therefore there is clearly need to restore the soil productivity to sustain livelihoods.

Our GCRF-ODA funded Restoring Degraded African Landscapes (ReDeal) work in Kenya has begun to explore options for restoration. We have established three factorial experiments in contrasting pedological settings investigating the role of manures, seeding and tillage on soil biogeochemical processes. The long-term maintenance of these experiments has been guaranteed by our CASE partner ILRI.

In addition, we will establish in 2023 a large-scale experiment to study the influence of livestock grazing funded by ILRI and UKRI. These experiments will provide an unparalled resource for work into soil restoration strategies in tropical African grasslands.

This project aims to evaluate the impact of restoration strategies on grassland soil multifunctionality utilising the ReDeal experiments and new manipulation experiments to test how resilient the interventions are to future climate extremes including drought and flooding. This project will add mechanistic understanding to the ongoing programme delivering new knowledge on these understudied tropical grasslands.

Objectives:

1. Quantify the impact of restoration strategies on soil physical (aggregate stability, water holding capacity, water infiltration), biochemical (C, N and P stocks) and biological (nutrient cycling and microbial community) properties.

2. Examine whether differences in the soil response are influenced by the soil mineralogical characteristics and by grazing. 3. Determine the climate sensitivity and resilience of the soils following restoration interventions.