Farm management in mixed crop-livestock systems in the Northern Highlands of Ethiopia

Key Words: nutrient dynamics, fertility management, feed availability and quality and livestock production, Northern Highlands of Ethiopia In the Northern Highlands of Ethiopiaone of the least-favored areas in East Africa , f arming systems are characterized by the integrated management of crop and livestock components, in which resources, such as nutrients and energy are cycled within the system. The overall objective of this study was to increase insight in the functioning of these farming systems, with special attention for the heterogeneity among farm households and farm fields, and the influence of farm management regimes on soil nutrient dynamics and livestock production, 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. Crop production is limited by indigenous soil nutrient supply and water availability, as concluded from the results of an on-farm field study on barley on three soils classified as Cambisol, Luvisol-1 and Luvisol-2. Results of this study were also used to calibrate the QUEFTS model that can serve as a tool to quantify indigenous soil nutrient supply as a basis for determination of the best fertilizer combinations for targeted (barley) yields in the Northern Highlands of Ethiopia To quantify the possibilities for animal production, knowledge of on-farm available feed resources and their quality is fundamental. Our results show that crop residues comprise the major source of animal feed, in addition to roughage from natural pastures. Availability and quality of forage and hence live weight dynamics of the animals show a distinct seasonal pattern. In the late wet season, September to November, cattle graze natural pasture, and the high availability and quality of this feed resource is reflected in high rates of live weight increase. Starting December, cattle graze aftermath in crop fields, and the lower feed availability (in both quantity and quality), results in lower live weight gains. From April onwards, animals loose live weight, with the maximum loss observed in August. Observed live weight gains (LWG) were close to the potential for well-endowed farm households, implying favorable nutritional conditions, whereas for medium and poor farm households they were significantly lower, associated with low quality feed. The relationships between feed availability (quantity and quality) and feed intake on the one hand and animal performance, in terms of live weight and milk production, manure production and draught power, on the other, indicate that currently manure and draught power are the major production targets, attained by maximizing herd size (HS). Our results suggest that maximum live weight production and milk production would be associated with selective use of the better feeds at strongly reduced HS. Partial balances of the macronutrients, nitrogen (N), phosphorus (P) and potassium (K) were studied at farm level, and the results indicate that soil nutrient depletion proceeds at an alarming rate at both 'farm field' and plot 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, 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 to maintain current levels of soil N, organic carbon and P, external inputs in the form of inorganic fertilizers and/or animal feed (concentrates) are indispensable. In this study, attention focuses on the bio-physical aspects of sustainability in terms of soil qualities, with special attention for nutrient elements. Adoption of more sustainable farm management practices however, is constrained by the (socio-) economic environment.