Evaluation of phosphorus fertilizer sources and nitrogen optimization for wheat and tef in Ethiopia’s central highlands

Abstract

The application of appropriate fertilizer sources and the optimization of nitrogen management are key strategies for increasing crop yield and nutrient use efficiency. An on-farm experiment was conducted in five districts of the North Shewa Zone, Amhara Region, Ethiopia, to evaluate three phosphorus sources (NPS, DAP, and TSP) and nitrogen application times (100% and 75% of the recommended rate, with split applications) for wheat and tef production. The experiments for bread wheat were conducted on contrasting soil types (Cambisols, heavy Vertisols, and light Vertisols), whereas the experiments for tef were conducted on heavy Vertisols. A randomized complete block design was used, with a farm considered a replication (only a single replication with all treatments was planted at a farm). Data on growth and yield were analyzed using R software version 4.3. All phosphorus sources significantly increased yields compared to the control, with wheat yields increasing from 1,898 to 4,640-5,360 kg ha-1 and tef from 1,376 to 2,382-2,591 kg ha-1. Notably, the 75% N rate with split application improved the agronomic efficiency of nitrogen (AEN) by 38.8% and the nitrogen use efficiency (NUE) by 19.5% compared with the previously recommended two-split applications, suggesting a cost-effective and efficient N management approach. Farmer preferences, assessed via Likert scales, aligned with the observed biological yield trends. These findings suggest that NPS, DAP, and TSP perform similarly from an agronomic perspective, and fertilizer choice can be guided by local availability and cost. Reduced, split nitrogen applications offer a cost-effective way to improve wheat and tef productivity and nutrient use efficiency, supporting sustainable fertilizer management.