Soil Test Based Crop Response Phosphorus Calibration Study on Bread Wheat in Degem District of North Shewa Zone, Oromia

摘要

Soil test based crop response phosphorous calibration study was conducted Degem district on bread Wheat crop during the main cropping season of 2017 -2019 with the objectives to determine Pc and Pf for bread wheat crop, to establish site-specific soil test based phosphorus fertilizer recommendation and to prepare guideline for bread Wheat fertilizer application. RCBD design was used with 3 replication using 4 rates of N (0, 46, 92 and 138 kg ha~(-1)) and 5 rates of P_(2)O_(5) (0, 23, 46, 69 and 92 Kg ha~(-1)) in a factorial combination to determine optimum level of N- rate for bread wheat crop production. And in the second and third year 6 levels of P_(2)O_(5) (0, 23, 46, 69, 92 and 115 Kg ha~(-1)) and 92 kg N ha~(1) of optimum nitrogen rate obtained were applied uniformly for all plots to determine P-critical value (Pc) and P-requirement factor (Pf) for bread Wheat. A total of experimental plot size 5m*4m (20 m~(2)) and Seeds were sown using a seed rate of 150 kg ha~(-1) in a plot size of 5 m x 4 m (20 m~(2)) by broadcasting. Fertilizers were applied based on the treatments. Grain yield of bread wheat was analyzed using R-Software. Composite Surface soil samples from 0-20 cm depth were collected from each experimental plot before planting for laboratory analysis of selected soil chemical properties. Similarly, after 21 days of planting, composite soil samples were taken at (0-20 cm depth) using auger for each treatment and replications separately and the sample were subjected to laboratory analysis using Olsen method to analyze available P content in the soils. The result of the study showed that low to extremely high available P ranged from 4 -55.06 ppm. The mean maximum grain yield (3665 kg/ha) was obtained from the application of 92 kg N /ha and 92 kg P_(2)O_(5) /ha where as the lowest (1260 kg /ha) was obtained from control (with out fertilizer). Fertilizer combination of 138 kg N/ha and 92 kg P /ha compared to 92 kg N /ha and 92 kg P / ha showed no significant difference on bread wheat grain yield. Therefore, 92 kg N /ha was selected as N fertilizer recommended for Degem district. From phosphorous calibration study, P-critical value (22 ppm) and P-requirement factor (5.85) was determined for phosphorus fertilizer recommendation for bread wheat crop production in the area. Therefore, the obtained result has to be verified and the economic benefit must be studied across farmers’ fields.