Soil organic matter and F1 hybrid cultivar influence Coffea arabica yields in south‐central Guatemala

Smallholders produce 60% of global coffee ( Coffea arabica ) supply but lack recommendations on nutrient management. We tested hypothesized N‐ and K‐driven yield gaps using on‐farm omission trials established across 21 fields in Guatemala. The effects of a single and combined application of N (285 kg ha −1 ) and K (350 kg ha −1 ) were evaluated for coffee cherry yield; N and K concentrations of soil; leaf and coffee cherries; and yield‐based export of N, P, and K. Despite low soil‐extractable N and K, yields were similar among fertilization treatments, consistent with similar N and K concentrations in leaves and soil‐extractable pools over three intraseasonal timepoints. Yields were twofold greater in fields with high (4.1%–5.0%) versus low (2.5%–3.0%) soil organic matter (SOM), and 1.8‐fold greater for the F1 hybrid than traditional American varieties. Relatively constant cherry N, P, and K concentrations entailed scaling of macronutrient removal with yield. Because yields and N and K harvest export were unaffected by fertilization, nitrogen use efficiency and potassium use efficiency values were near‐zero or negative. Our results indicate that a single, high‐rate application of N and K fertilizers in smallholder coffee production on coarse‐textured soils in this region is neither agronomically nor economically sensible. Coffee smallholders may be able to increase yields by building SOM and employing hybrid varieties. While our multisite evaluation provided insight into coffee yield relationships with SOM and by coffee cultivar, intra‐seasonal variability may limit the applicability and reproducibility of coffee yield response to N and K fertilization due to single season evaluation.