Ergonomic design of fertilizer application equipment to enhance the health and safety of Thai coffee farmers

Abstract

Introduction: Thai coffee farmers are prone to musculoskeletal disorders (MSDs) due to repetitive tasks, heavy lifting, and awkward postures. This study evaluated the impact of prototype fertilizing equipment on reducing ergonomic risks among farmers.

Methods: A quasi-experimental pre–post study assessed ergonomic risks in six body regions using the Rapid Entire Body Assessment (REBA) method. Data were collected during actual fertilizer application, both before and after one month of equipment use. The “worst” postures were captured via photos and videos over the course of this one month. Basic demographic information was recorded for 30 purposively selected coffee farmers aged 25–50 years in Ban Nam Ki, Nan Province.

Results: The results revealed a significant reduction in ergonomic risks, with total REBA scores dropping from 8.83 (SD = 1.14) before equipment use to 3.63 (SD = 0.47) after use (p < 0.001). Significant improvements occurred in the neck, trunk, legs, and upper arms (all p < 0.001), while the lower arm showed little change and the wrist slightly worsened. These changes may relate to equipment design or specific tasks. Overall, the proportion of high-risk postures decreased to 13.3% from 86.7% of low-risk postures, indicating substantial ergonomic safety gains.

Conclusion: The prototype fertilizing equipment proved effective in reducing overall ergonomic risks, as evidenced by improvements in REBA scores and a more even distribution of risk levels. Although wrist strain increased slightly, the overall reduction in risk highlights the positive impact on farmer health and safety. Future improvements to equipment design should focus on addressing wrist strain to further enhance ergonomic benefits.