Sustainability and economic efficiency of agroforestry systems in Embu District, Kenya: An application of environmental modelling

The steep slopes, high rainfall and intensive cultivation have led to soil erosion in the coffee-based, land use areas of Embu District, Kenya. The farmers face shortages of fodder for livestock, lack of fuelwood, and limited incomes. These problems could be resolved by introducing napier grass strips, or agroforestry in the form of alley cropping with calliandra hedges. The objective of the study is therefore to compare the sustainability and profitability of napier grass strips, calliandra hedges, and soil-and-nutrient replacement, against the traditional agriculture. Biophysical simulation, to assess the sustainability of the four farming systems, was undertaken using the Soil Changes Under Agroforestry (SCUAF) model. The economic efficiency and risk of the four systems was assessed with the @Risk model. The calliandra system proved the most sustainable and the traditional system the least, although the calliandra system is not truly sustainable. But it is the most profitable and so it seems the most appropriate system to meet the farmersʹ expectations of increased and sustained production.