Comparative Analysis of Farmyard Manure and Blended N‐P‐S‐Zn‐B Fertilizer Equivalency and Optimal Application Ratios for Enhancing Crop Production in Smallholder Fields of Northwest Ethiopia

Crop‐yield decline is a chronic problem for smallholder farmers in Ethiopia and much of sub‐Saharan Africa. The main cause is the gradual depletion of soil nutrients when fields are continuously cultivated without adding sufficient external fertilizers. Most smallholders cannot afford inorganic fertilizers because they are costly and often unavailable at the right time. Although organic amendments such as farmyard manure (FYM) exist, farmers generally lack reliable guidance on how to use them effectively. To fill this knowledge gap, a 2‐year field trial was carried out in four Ethiopian villages: Koga, Bachima, Geray, and Jiga (Jabi Tehnan and Mecha districts). The experiment used a randomized complete block design with three replications and tested 20 treatment combinations: five rates of a blended N‐P‐S‐Zn‐B fertilizer (NPSZnB) (100,150, 200,250, and 300 kg ha −1 ) crossed with four FYM levels (0, 12, 16, and 20 t ha −1 ). A blanket recommendation of DAP + urea served as a satellite control. Across the two cropping seasons, both grain and above‐ground biomass yields responded significantly ( p  < 0.05) to the fertilizer, the manure, and their interaction. The highest biomass of maize (≈10,895.0 kg ha −1 at Jabi Tehnan and 10,787.9 kg ha −1 at Mecha) and grain yield (≈5524.6 kg ha −1 at Jabi Tehnan and 5487.652 kg ha −1 at Mecha) was obtained with the combined application of 250 kg ha −1 NPSZnB + 20 t ha −1  FYM. In contrast, the lowest yields occurred where only the blended fertilizer was applied (≈4600 kg ha −1 ). Equivalency calculations showed that to replace that inorganic blend entirely with FYM, farmers would need roughly 28 t ha −1  FYM for N, 6200 t ha −1 for P, 2030 t ha −1 for S, 25,000 t ha −1 for Zn, and 8350 t ha −1 for B, making the fertilizer indispensable.