Wheat Yield Responses to NPK Fertilizers and Nutrient Omissions for QUEFTS Model Validation in Tigray, North Ethiopia

Improving crop productivity largely depends on understanding soil fertility constraints and the effects of nutrient management on yield performance. Accurate determination of existing soil nutrient status and targeted application of limiting nutrients are essential for enhancing wheat (Triticum spp.) productivity. However, the specific effects of omitting one of the macronutrients such as nitrogen (N), phosphorus (P), or potassium (K) on wheat yield have not been investigated in the target area. This study employed the Quantitative Evaluation of the Fertility of Tropical Soils (QUEFTS) model to estimate the N, P, and K fertilizer requirements needed to achieve a predefined wheat yield target. The objectives were to: (i) evaluate yield responses to complete versus nutrient omission (N, P, or K) fertilization treatments, and (ii) analyze corresponding nutrient uptake and use efficiency dynamics. The experimental treatments included: (1) full NPK fertilization, (2) NP only (K omitted), (3) NK only (P omitted), (4) PK only (N omitted), and (5) an unfertilized control. Topsoil samples were analyzed and used as inputs for the QUEFTS model. Yield and agronomic data, as well as nutrient uptake and use efficiency, were measured. Model performance was validated using standard statistical metrics. Results showed that full NPK application significantly (p < 0.05) improved yield, yield components, and nutrient uptake compared to omission treatments and the control. The strong agreement between QUEFTS-predicted and observed yields highlights the model’s potential as a reliable, cost-effective decision-support tool for optimizing site-specific fertilizer recommendations. These findings demonstrate that balanced NPK fertilization markedly boosts wheat yield and nutrient uptake, while the QUEFTS model provides a powerful, reliable tool for tailoring fertilizer management to local soil conditions.