Abstract

So far, application of fertilizer to mitigate problems of nutrient-limited yields in farmers’ fields in the Highlands of Ethiopia has been based on conventional blanket fertilizer recommendations, without taking into account indigenous soil nutrient supply. In this study an attempt was made to take into account indigenous soil nutrient supply, internal nutrient use efficiency at maximum nutrient accumulation and dilution, and actual uptake and recovery fractions of applied fertilizers in order to parameterize the nutrient requirement of barley in the Northern Highlands of Ethiopia. For parameterization of fertilizer requirements, factorial field experiments have been carried out with different application rates, in soils identified as Cambisol, Luvisol-1 and Luvisol-2, characterized by different soil nutrient contents, in three replicates in four fields. Coefficients for estimation of potential supply of N, P and K, respectively, Nq = 6.0, Pr = 0.55, and Ks = 166, were estimated by using transfer functions calibrated for barley in the Northern Highlands of Ethiopia on the basis of soil OC content, exchangeable K, and P-Olsen. Yields at maximum accumulation and dilution, internal nutrient use efficiency and agronomic efficiency have been estimated for barley. The results show that different rates of fertilizer application are required for different soils with different indigenous soil nutrient supplies for different objectives, that is, either to attain maximum agronomic efficiency of a given nutrient or maximum yield. The coefficients used to quantify indigenous soil nutrient supply and parameterization of nutrient requirements of barley would help to consider different NPK combinations for different soils with different values of indigenous soil nutrient supply for targeted barley yields in the Northern Highlands of Ethiopia in stead of applying blanket fertilizer recommen-dation.

Key words: Agronomic efficiency, internal nutrient use efficiency, maximum accumulation, maximum dilution, nutrient-limited yield.