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Nudging Farmers to Use Fertilizer: Experimental Evidence from Kenya
Initial registration date
November 01, 2016
November 01, 2016 4:49 AM EDT
University of California, Santa Cruz
Other Primary Investigator(s)
Massachusetts Institute of Technology
Additional Trial Information
We model farmers as facing small fixed costs of purchasing fertilizer and assume some are stochastically present biased and not fully sophisticated about this bias. Such farmers may procrastinate, postponing fertilizer purchases until later periods, when they may be too impatient to purchase fertilizer. Consistent with the model, many farmers in Western Kenya fail to take advantage of apparently profitable fertilizer investments, but they do invest in response to small, time-limited discounts on the cost of acquiring fertilizer (free delivery) just after harvest. Calibration suggests that this policy can yield higher welfare than either laissez-faire policies or heavy subsidies.
Duflo, Esther, Michael Kremer and Jonathan Robinson. 2016. "Nudging Farmers to Use Fertilizer: Experimental Evidence from Kenya." AEA RCT Registry. November 01.
Basic Savings and Fertilizer Incentive (SAFI): In the first season, a field officer visited farmers immediately after the harvest and offered to sell them a voucher for fertilizer, at the regular price, with free delivery later in the season. The farmer had to decide during the visit whether or not to participate in the program, and could buy any amount of fertilizer. In the second season, a new group of farmers was selected to receive the basic SAFI treatment. The second season also included additional interventions, structured as follows:
SAFI with ex ante choice of timing: A field officer visited the farmers before the harvest and offered them the opportunity to decide when, during the next growing season, they wanted the officer to return to offer them the SAFI program. They were then visited at the specified time, and offered a chance to buy a voucher for future fertilizer use (as in the Basic SAFI program, as described above).
Free delivery visit later in the season: Same as the basic SAFI intervention, but farmers were visited later in the season. A field officer visited farmers 2-4 months after the harvest (when it is time to apply fertilizer as a top-dressing to the next crop), and offered them the opportunity to buy fertilizer, at the regular price, with free delivery. Subsidy later in season: A field officer visited the farmers 2-4 months after the harvest (when it is time to apply fertilizer to the next crop) and offered to sell them fertilizer, at a 50 percent subsidy, with free delivery.
In each of the intervention groups, as well as in the comparison group, a random subset of farmers was offered the option to sell a set quantity of maize at a favorable price to the field officer before the program took place.
Intervention Start Date
Intervention End Date
Primary Outcomes (end points)
Fertilizer use (by season)
Primary Outcomes (explanation)
Secondary Outcomes (end points)
Secondary Outcomes (explanation)
In collaboration with the NGO International Child Support (ICS), researchers designed an intervention to test if providing mechanisms to save harvest income for future fertilizer purchase could be effective in increasing usage. The intervention was called the Savings and Fertilizer Initiative (SAFI). The design of the experiment allowed researchers to test the impact of the SAFI program against various other strategies to improve usage, in particular fertilizer subsidies. The project also investigates whether difficulty in saving harvest income until the time that inputs are needed is a significant barrier to adoption. Finally, the option given to farmers to sell maize before the program took place tests the alternative hypothesis that the SAFI program was seen by the farmers just as a safer way to protect their savings than available alternatives.
Experimental Design Details
Was the treatment clustered?
Sample size: planned number of clusters
Sample size: planned number of observations
Sample size (or number of clusters) by treatment arms
Season 1 -
Basic SAFI: 204 farmers Control: 673 farmers
Season 2 -
Basic SAFI: 179 farmers Basic SAFI with ex ante choice: 208 farmers
Normal price fertilizer with free delivery at top dressing time: 135 farmers
Half price fertilizer with free delivery at top dressing time: 133 farmers
Control: 102 farmers
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
INSTITUTIONAL REVIEW BOARDS (IRBs)
Post Trial Information
Is the intervention completed?
Intervention Completion Date
December 31, 2004, 12:00 AM +00:00
Is data collection complete?
Data Collection Completion Date
December 31, 2005, 12:00 AM +00:00
Final Sample Size: Number of Clusters (Unit of Randomization)
Was attrition correlated with treatment status?
Final Sample Size: Total Number of Observations
Final Sample Size (or Number of Clusters) by Treatment Arms
Reports, Papers & Other Materials
Nudging Farmers to Use Fertilizer: Theory and Experimental Evidence from Kenya
Duflo, Esther, Michael Kremer and Jonathan Robinson. 2011. "Nudging Farmers to Use Fertilizer: Theory and Experimental Evidence from Kenya." American Economic Review, 101(6): 2350-90.
REPORTS & OTHER MATERIALS