Soil nutrient balances under diverse agro-ecological settings in Ethiopia

Soil fertility is one of the main constraints to agricultural intensification in Ethiopia. Like in many East African countries, nutrient depletion rates are exacerbated in Ethiopia by high erosion rates, biomass and animal manure removal from farm plots and limited application of mineral and organic fertilizers. In this paper, soil nutrient balances at plot level were calculated for 350 farms spread across the high potential highlands of Ethiopia. The nutrient input flows and output flows were monitored over a period of 3 years (2012-2014) using the monitoring for quality improvement toolbox. Average nitrogen (N), phosphorus (P) and potassium (K) balances were -23 +/- 73, 9 +/- 29 and -7 +/- 64 kg ha(-1), respectively. The situation was most severe for N, where average depletion rate was 0.2 % of the soil total N stock per year, which equals about 4.2 % of the available soil N pool. Depletion rates were highest in the relative intensive farming systems in mountainous areas located in the central and southern parts of Ethiopia. Nutrient depletion rates increased in time with 13, 3 and 10 kg ha(-1) year(-1), respectively for N, P and K during the monitoring period. The Ethiopian government responds to the on-going, and worsening, soil nutrient depletion by stimulating the use of mineral fertilizers. We conclude that the current efforts on increased inputs of mineral fertilizers are a step in the good direction, but to really halt and reverse soil fertility decline, organic fertilizer application and soil and water conservation should be an integral part of the intervention strategy.