Soil nutrient dynamics in integrated crop-livestock systems in the Northern Ethiopian Highlands

In the Northern Ethiopian Highlands, one of the least-favoured areas in East Africa, farming systems are characterized by the integrated management of crop and livestock components. The overall objective of this chapter was to increase insight into the functioning of these farming systems, with special attention to the influence of farm management regimes on soil nutrient dynamics, as a basis for formulation of recommendations for technological innovation leading to increased farm productivity, conservation of the natural resources and improved livelihoods for the farming population. Partial balances of the macronutrients - nitrogen (N), phosphorus (P) and potassium (K) - were studied at farm and field scales and soil organic carbon (C) balance at village scale, and the results indicate that soil nutrient balances were negative at all scales. Nutrient depletion rates differ significantly among farmer wealth groups, with the highest rates recorded for the rich farm group, followed by the medium and poor farm groups. Current levels of organic fertilizer input are much lower than required to maintain a dynamic equilibrium in soil organic matter content. Thus, limited availability of organic inputs is a crucial constraint for attaining sustainability in terms of nutrient elements. Results of a simulation study on long-term dynamics of soil C, N and P and the consequences of alternative farm management practices for crop-available N and P indicate that, in order to maintain current levels of soil N, organic carbon and P, external inputs in the form of inorganic fertilizers are indispensable. In this chapter, attention focuses on the biophysical aspects of sustainability in terms of soil qualities, with special attention to nutrient elements. Adoption of more sustainable farm management practices, however, is constrained by the (socio-)economic environment.Other chapters f