Soil Test Crop Response Based Phosphorus Calibration Study on Bread Wheat (<i>Triticum</i><i> </i><i>Aestivum L</i>.) in Adami Tulu Jido Kombolcha District, East Show

Agricultural production and land productivity have been declining due to various factors, with unbalanced fertilizer application identified as a major cause. To address this issue, soil test-based crop response fertilizer recommendations offer an effective solution. An on-farm experiment was conducted in Adami Tulu Jido Kombolcha district over three consecutive cropping seasons (2022-2024) to determine the optimum nitrogen (N) level, phosphorous critical level (Pc), and phosphorus requirement factor (Pf) for bread wheat production. In the first year, fifteen factorial treatments combining five nitrogen levels (0, 23, 46, 69, and 92 kg/ha) and four phosphorus levels (0, 23, 46, and 92 kg/ha) were tested using a randomized complete block design with three replications on 9m² plots. Bread wheat variety Kingbird was used as the test crop. In the subsequent two years, the optimum nitrogen rate (46 kg/ha) identified in the first year was uniformly applied, while five phosphorus levels (0, 10, 20, 30, and 40 kg/ha) were evaluated to determine phosphorus critical level and requirement factor. Grain yield data were analyzed using SAS statistical software with mean comparisons by LSD at p<0.05, and partial budget analysis was conducted using CIMMYT guidelines. Results showed significant differences among treatments, with the highest grain yield of 3296.5 kg/ha obtained from the combined application of 46 kg/ha N and 69 kg/ha P, while the control plot yielded 2330.2 kg/ha. The economically optimum nitrogen rate was 46 kg/ha, with phosphorus critical level and phosphorus requirement factor determined as 19.92 ppm and 2.38, respectively. These findings provide essential parameters for soil test-based fertilizer recommendations to enhance bread wheat productivity in Adami Tulu Jido Kombolcha district.