RESUMEN
Soil acidity is the major soil chemical constraint that limits agricultural productivity in the highlands of Ethiopia receiving high rainfall. This study was conducted to evaluate the effect of different lime rates determined through different lime rate determination methods on selected soil chemical properties and yield of maize (Zea mays L.) on acidic Nitisols of Mecha district, Amhara Region, Ethiopia. The experiment had 10 treatments (0, 0.06, 0.12, 0.18, 1, 2, 3.5, 4, 7 and 14 tons ha-1 lime) that were calculated by three lime rate determination methods and applied through three lime application methods (spot, drill and broadcast). The experiment was arranged in randomized complete block design (RCBD) with four replications. N at the rate of 180 kg ha-1 and P at the rate of138 P2O5 kg ha-1 were applied to all plots. A full dose of P and lime as a treatment were applied at planting; whereas N was applied in split, 1/2 at planting and 1/2 at knee height stage. One composite soil sample before planting from experimental site and again one composite sample from each experimental unit were taken after harvest to analyze soil chemical parameters following appropriate laboratory procedure. Liming showed a positive significant difference on pH-H2O, pH-buffer, cation exchange capacity (CEC) and exchangeable bases but it had an inverse and significant effect on exchangeable acidity (EA). However, it didn't show any significant difference on soil C and N. Grain and above-ground biomass of maize yields had significant differences among treatments. The highest grain and biomass yields (7719 and 18180.6 kg ha-1, respectively) were obtained from application of broad cast method while the lowest (6479 and 15004.6 kg ha-1, respectively) were obtained from control treatment. Drill lime application method provided better efficiency with over 200% cost reduction advantage compared to the broadcast method to ameliorate the same level of acidity. Application of 3.5 tons ha-1 lime in the drilling method is recommendable to ameliorate soil acidity. However, from an economic point of view, application of 0.12 tons ha-1 lime applied in the micro-dosing method is more profitable due to low variable cost.
RESUMEN
Ethiopia has a huge potential to increase the production and productivity of potato (Solanum tuberosum L.) mainly in north-western regions where current potato yields are less than 10 t ha-1. Soil fertility and disease are the major yield-limiting factors of potato in this part of the country. Three-year's on-farm research was conducted to get the optimum economic levels of nitrogen (N) and phosphorus (P) nutrients for the major potato-growing areas of north-western Ethiopia. A factorial experiment with four levels of N (46, 92, 138, and 194 kg ha-1), three levels of P2O5 (46, 69, and 92 kg ha-1), and one pilot treatment with no NP nutrient inputs was used. A randomised complete block design with three replications was used. The findings of the research showed that more than 40 t ha-1of potato could be attained (about four times the current productivity) in the study areas through NP nutrient management. The yield was increased significantly with an increased rate of N at all sites (p < 0.01). The yield difference was nonsignificant (p > 0.05) between P levels for most of the sites and years. The financial analysis of the findings for Yilmana Densa district indicated that applying 138 N and 46 P2O5 kg ha-1, together, gave a marginal return of (Birr/Birr) 70.9, whereas 138 N and 69 P2O5 kg ha-1 resulted in 10.7. For the South Gondar, 138 N and 46 P2O5 kg ha-1 gave a marginal return of 24.3 (Birr/Birr). Therefore, based on the farm gate price of potato and the cost of fertilizer, 138 N, combined with 69 P2O5 kg ha-1, is recommended for the Yilmana Densa. For the South Gondar, 138 N, combined with 46 P2O5 kg ha-1, is recommended.