Grain yield productivity, nutrient uptake and use efficiency and profitability of oat (Avena sativa L.) as influenced by variety and levels of nitrogen and phosphorus fertilizers in the central highlands of Ethiopia

Fodder crops are generally cultivated using the blanket recommended fertilizer rate in Ethiopia. However, use of optimum and economically feasible fertilizer rate based on the requirement of species and factors of climate, soil, and management conditions is very important to improve the grain yield performance of oat varieties. Thus, the study aimed to evaluate the effect of fertilizer levels on the performances of agro-morphological traits, nutrient uptake and use efficiency, and relative profitability of oat (Avena sativa L.) varieties at Holetta, Ethiopia. The experiment was laid out in a randomized complete block design in a factorial arrangement with three replications. The study consists of twenty-four treatment combinations comprised of three oat varieties (CI-8251, SRCPX80Ab2291, and Sorataf) and eight fertilizer levels (0, 25, 50, 75, 100, 125, 150, and 175%). The results revealed that fertilizer level, variety, and year had significant effect on grain yield (GY), grain nutrient uptake (GNU), partial factor productivity (PFP), and agronomic efficiency (AE). The highest GY (6.5 t/ha) and GNU (141.7 kg/ha) were recorded for 150% fertilizer level while unfertilized treatment produced the least. Among oat varieties, Sorataf produced the highest GY (5.7 t/ha) and GNU (129.3 kg/ha). On the other hand, the highest PFP (346.6 kg/kg) and AE (164.8 kg/kg) were observed for 25% fertilizer level while the lowest PFP (59.4 kg/kg) and AE (33.4 kg/kg) were recorded for 175% fertilizer level. Sorataf variety exhibited the highest PFP (143.3 kg/kg) and AE (74.9 kg/kg). Moreover, the 2021 cropping season had 5.8, 10.4, 12.0, and 17.3% advantages over the 2020 cropping season in GY, GNU, PFP, and AE, respectively. The Pearson correlation analysis indicated that the nutrient concentration and uptake had positive association with fertilizer level and GY while nutrient harvest index and nutrient use efficiency had inverse correlation with fertilizer level and GY. The combined partial budget analysis for oat varieties showed that application of 150% fertilizer produced the highest net benefit. Therefore, the blanket recommended fertilizer dose of 150% (61.5 kg N + 30 kg P/ha) could increase the grain yield performance of oat varieties and farm profitability in the study area.