RESUMEN
Nitrogen has becoming the most limiting nutrient in the northern highlands of Ethiopia due to continuous cropping with application of limited external inputs. To improve soil nutrient availability, farmers have been using legumes in crop rotation. However, the roles of various legumes on subsequent wheat (Triticum aestivum) crop are unknown in northern Ethiopia. The objective of this study was to investigate impacts of legumes on yield and N uptake of subsequent wheat crop. Experiment was conducted at farmer's field with faba bean (Vicia faba L.), 'dekeko' field pea (Pisum sativum var. abyssinicum), field pea (Pisum sativum), lentil (Lens culinaris) and wheat (Triticum spp.) in the first season and all plots were rotated by wheat in the second season. Yield of subsequent wheat crop was recorded and N uptake was analyzed. The result revealed that grain yield and dry biomass yields of subsequent wheat crop were significantly (p < 0.05) higher in the legume-wheat rotations than in the wheat-wheat rotation. The wheat yield is increased by 2196, 1616, 1254 and 1065 kg ha-1 and the N uptake is increased by 71.4%, 51.0%, 49.2% and 29.8% in the faba bean-wheat, 'dekeko'-wheat, field pea-wheat and lentil-wheat rotation plots compared to the wheat continuous cropping, respectively. The findings indicated that legumes improved yield and N uptake of the subsequent wheat crop. Thus, soil fertility management policy need to consider legume crop rotations as nutrient management option to improve sustainable soil fertility and yield.
RESUMEN
Establishing model based balanced nutrient requirements for barley (Hordeum spp.) in the northern Ethiopia can solve the fertilizer recommendation problems and enhance crop yield. The Quantitative Evaluation of Fertility of Tropical Soils (QUEFTS) model was used to estimate balanced nitrogen (N), phosphorus (P) and potassium (K) requirements for barley production in Alaje, northern Ethiopia. The objectives were to (i) quantify soil N, P and K supply and recommend fertilizers using QUEFTS model; (ii) investigate response of QUEFTS fertilizer application on yield and nutrient uptake and (iii) validate QUEFTS model performance. The experiment had four treatments: (T1) model based fertilization; (T2) blended fertilization; (T3) farmers' fertilization practices and (T4) control/no fertilizer. Soil information of the experimental plots were analyzed and used as model input to estimate soil nutrient supplies and recommend fertilizer. Yield and agronomic data were recorded and nutrient uptake and use efficiencies were analyzed. Model performance and accuracy were also checked using root mean square error, coefficient of determination, index of agreement and percent bias. The result revealed that the N, P and K soil supply ratio in the field experimental plots were 9:1:6. The higher grain yield of 4747 kg ha-1 was recorded in the QUEFTS based fertilization plots. Validation results indicated that there is a good correlation between the QUEFTS predicted and observed grain yields implying that the QUEFTS model can be a base for development of simple and cost-effective decision support tools for nutrient management and fertilizer recommendations. Thus, the model performance and prediction accuracy is promising and can help farmers to adjust fertilizer application rates based on crop requirements.