Does Providing Free Trial Packs With Demonstration Plots Increase the Adoption of Agricultural Technologies? Cost Effectiveness Evidence From Tanzania

ABSTRACT This study evaluates the effectiveness of the common practice of providing free trial packs alongside demonstration plots managed by local extension agents to promote learning‐by‐doing and increase technology adoption among bean farmers in Tanzania. The experiment randomly assigned some villages to forgo trial packs containing seeds and a seed treatment for 1 year. Adoption data were collected 1 and 4 years after the intervention. Our findings show that trial packs raised program costs by 37.5 times, but did not lead to a significant or cost‐justified increase in adoption. The adoption of improved bean varieties increased from 11% pre‐intervention to 28% 4 years post‐intervention, with no significant difference between villages with and without trial packs. Although trial packs showed potential for specific groups—such as female, more educated farmers, households in farmer groups, and those living closer to demonstration plots or in smaller villages—their overall impact was limited. These results suggest that demonstration plots, a lower‐cost intervention, are more cost‐effective. Trial packs may still hold value when targeted, but their widespread use does not justify the additional costs. This study offers key insights for policymakers and development practitioners seeking to implement scalable, efficient agricultural interventions.