Experimental Design
Sampling
Our sample consists of smallholder farmers who either previously collaborated with the platform or became new clients in 2024, prior to the start of the trial. We included only those farmers who have cultivated soybeans in the past or plan to start cultivating soybeans in 2024. The platform selected 17 communities based on these eligibility criteria. Each community comprises between one and 14 farmer groups, and a random subset of farmers was selected from each group.
Due to the planting phase already commencing in five communities in the Northern region before the baseline survey could be conducted, these communities were replaced with five others in the North East region, ensuring an equivalent number of farmers per group. In total, 1,363 farmers were surveyed for the baseline.
Randomization procedure
The original 17 communities were divided into five strata based on the number of registered farmers in each community. The random assignment into the three treatment groups and the control group was then done within each stratum. Within each treatment group and the control group, the number of farmers to be interviewed was determined so that the number of farmers drawn per group was inversely proportional to the number of farmer groups in each treatment and control group.
The randomization had been done before the five communities had to be replaced. The random assignment was then transferred from the “old” to the “new communities” with only very minor adjustment to the number of sampled farmers per group. Overall, more farmers were sampled to prevent a loss in power in case of attrition.
Spillovers
Given the design of our study, we do not expect significant spillover effects. The treatment groups are geographically dispersed, which minimizes the likelihood of interaction between treated and untreated units. Furthermore, the treatment is highly specific and tailored to individual participants, further reducing the possibility of spillovers. These factors together suggest that any unintended influence of the treatment on control groups is likely to be minimal.
However, we cannot be certain to rule out spillover effects for communities that were assigned a different treatment status, but are located within the same region and geographically relatively close to one another. Therefore, we will test whether knowledge and demand for the use of soil tests and credit services is higher in the untreated communities in our sample that are closer in distance to the respective treatment groups. We can estimate this by incorporating the number of treated soybean farmers within a meaningful radius. This variable will be included both linearly and interacted with the treatment to examine whether spillover effects differ between treated and untreated farmers.
Another way of looking at spillovers is to check for impacts directly at the market level. In the case that the treatments lead to significant improvements in productivity for treated farmers, it could potentially affect local labor markets. Increased demand for labor to manage higher yields or expanded cultivation could drive up wages in treated areas. This effect might spill over into neighboring areas, particularly if there is labor mobility between treated and untreated regions. Similarly, if the treatment results in a substantial increase in soybean production among treated farmers, this could affect local soybean prices. An oversupply in treated regions might lead to a decrease in prices, which could spill over into adjacent markets, especially if these markets are closely linked. Conversely, if the treatment enhances the quality of soybeans, it could lead to price premiums that might influence market prices more broadly. While these impacts are plausible, their magnitude would depend on the scale of the treatment effects and the degree of market integration across regions. It is important to monitor these potential spillovers as they could have broader economic implications beyond the immediate scope of the study. In order to better understand any potential spillover effects, we will collect qualitative data via focus group discussions, interviewing famers, farmer group leaders and field agents in the control and treatment groups.