Yield-limiting Nutrients for Wheat (Triticum aestivum L.) Production in Farta to Lay Gayint Districts of the Amhara Region in Northwest Ethiopia

Abebe Getu Asfaw^*Getachew YilmaWubayehu Gebremedhin WoldieTessema Minale Getahun

• Ethiopian Institute of Agricultural Research (EIAR), Dessie, Ethiopia

Wheat (Triticum aestivum L.) is the third most important crop in Ethiopia yet its productivity in the country remains significantly below experimental yields and water-limited yield potential due to soil fertility variability and the absence of site-specific fertilizer recommendations. To identify yield-limiting nutrients and support the development of a precision fertilizer recommendation tool, a nutrient omission study was conducted in the 2021 main cropping season across eight sites in the South Gondar Zone of Northwestern Ethiopia. Results indicated that nitrogen (N) omission significantly reduced wheat yield and yield-related traits across all sites, while phosphorus (P) limitation was significant in 50% of the locations. The average yield response to N application was 2071.9 kg ha⁻¹ (ranging from 847.2 to 2873.6 kg ha⁻¹), followed by P, with a mean response of 499.1 kg ha⁻¹ (16.6-850.8 kg ha⁻¹). Soil indigenous nutrient supply (SINS) assessments revealed that N was only 45.0% sufficient, whereas P sufficiency was higher (87.0%). Potassium (K), sulfur (S), zinc (Zn), and boron (B) were found to be non-limiting, with soil supplies exceeding 90%. Yield gaps due to N and P omission averaged 53.9% and 11.9%, respectively, while omissions of K, S, Zn, and B had negligible effects. Agronomic efficiency was highest for P (22.2 kg kg⁻¹), followed by N (13.1 kg kg⁻¹) and K (5.2 kg kg⁻¹). These findings demonstrate that N is the primary yield-limiting nutrient in the study area, with P being secondary in half of the evaluated farms. To enhance wheat productivity and minimize yield gaps, site-specific fertilizer recommendations emphasizing optimized N and P application are critical.The study was conducted for one season, and hence multi-year experiments to address season varation on the effect of the nutrient omission treatments is recommended. The single-season design may not fully capture weather-mediated changes in soil nutrient mineralization dynamics, suggesting the need for interannual studies to assess temporal stability of SINS values.