Effects of Buffel Grass (Pennisetum Ciliare) and Guinea Grass (Megathyrsus Maximus) Ecotypes On Ground Cover and Select Soil Properties in Semi-Arid Kenya.

Background: Healthy soils are the key to the sustainability of dryland ecosystems. In semi-arid Kenya, indigenous rangeland grasses have been widely used to rehabilitate degraded lands with the aim of enhancing grass cover as well as enhancing soil quality and other ecosystem services. Objective: To assess the effects on ground or soil cover and soil physical and chemical properties of four indigenous grass ecotypes of two common rangeland grass species (Pennisetum. ciliare and Megathyrsus maximus) (Jacq.) B. K. Simon & S. W. L. Jacobs (Syn. Panicum maximum Jacq.), used for fodder and rangeland rehabilitation in semi-arid Kenya, four years after their establishment. Methodology: A field experiment was carried out in semi-arid southeastern Kenya comprising 4 grass ecotypes namely P. ciliare KLF, P. ciliare MGD, M. maximus ISY and M. maximus TVT). These were grown in a rhodic-ferralsol for determination of ground cover attributes and selected soil properties after 4 years. Soil samples were collected up to a depth of 30 cm in the established pastures and analyzed for bulk density, moisture content, pH, soil organic carbon (SOC), Total Nitrogen (TN) and elemental composition [Phosphorus (P), Potassium (K), Calcium (Ca) and Magnesium (Mg)]. Soil micronutrient status [Manganese (Mn), Copper (Cu), Iron (Fe), Zinc (Zn), Sodium (Na)] were also determined. Results: Inferences were made in comparison with conditions before the establishment of the grasses and comparison among the different grass ecotypes. Overall grass cover ranged between 52 and 85 % among the grass ecotypes, reflecting the importance of indigenous grasses in improving ground cover and rangeland rehabilitation. An improvement in SOC, N, K, Cu, Fe and Zn contents was observed. A decline was however observed in soil P, Mn and Na contents. Divergent responses were observed among the grass ecotypes in terms of soil attributes. Implications: The growing of indigenous grasses has the capacity and potential to improve soil conditions in the short term (< 5 years) and hence the productivity of semi-arid grasslands. Evidence is provided to guide decisions on the suitability of grasses for improving soil attributes in addition to enhancing forage productivity in semi-arid rangelands. Conclusion: The grass ecotypes enhanced the ground cover and improved certain soil properties over the 4-year period. In particular, there was an improvement in the soil organic contents, TN, Ca, Mg and K status of the soil.    

Keywords: Carbon; grassland; nitrogen; pasture; perennial grasses; range rehabilitation; restoration.