Development of a prototype fertilizer mixer to improve productivity and reduce ergonomic risks among small-scale farmers
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Abstract
This study aimed to develop a prototype fertilizer mixer for small-scale farmers and to evaluate its effectiveness in improving productivity and reducing ergonomic risks under actual operating conditions in Ban Dan Community, Ko Taeo Subdistrict, Mueang District, Songkhla Province, Thailand. The study involved 17 small-scale farming households, and manual fertilizer mixing was selected as the case study because the task required repetitive physical effort and caused worker fatigue during operation. The research process consisted of four stages: (1) pre-improvement ergonomic risk assessment using Rapid Upper Limb Assessment (RULA) and Rapid Entire Body Assessment (REBA); (2) the design and construction of a 200-L rotary drum fertilizer mixer powered by a 1-hp motor with an optional manual-crank mode; (3) performance testing of 15 kg fertilizer mixing under three conditions, namely manual mixing, manual-crank mixing, and motor-driven mixing, with five repetitions for each method; and (4) satisfaction evaluation involving six participants, including three experts and three actual users. The ergonomic assessment results showed that, prior to improvement, the manual fertilizer-mixing process involved a very high level of ergonomic risk, with RULA and REBA scores of 7 and 10, respectively. After the prototype had been developed, these scores decreased to 3 and 2, respectively. Regarding productivity, the average mixing time for 15 kg of fertilizer decreased from 5.12 ± 0.032 min in manual mixing to 1.17 ± 0.029 min in the manual-crank condition and 1.08 ± 0.029 min in the motor-driven condition. A one-way analysis of variance (ANOVA) indicated that the mean mixing times among the three methods differed significantly (p < 0.001). In addition, the overall satisfaction score was at the highest level, with a mean value of 4.51. The findings suggest that the developed prototype may help reduce fertilizer mixing time and physical workload under the field conditions examined in this study. However, further studies involving different fertilizer formulas, operating conditions, and larger groups of users are still required to confirm its broader applicability in community-based agricultural operations.
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