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Rates of Return to Fertilizer: Evidence from Field Experiments in Kenya
Initial registration date
November 01, 2016
November 01, 2016 4:54 AM EDT
University of California, Santa Cruz
Other Primary Investigator(s)
Massachusetts Institute of Technology
Additional Trial Information
In this paper, we use a series of field trials on Kenyan farms to explore the possibility that, while fertilizer and hybrid seed increase yield on model farms, they are actually not profitable on many small farms, where conditions are less than optimal. Our mean estimates of yield increases due to fertilizer use are in the range of the estimates found on model farms. We find that the mean rate of return to using the most profitable quantity of fertilizer we examined was 36 percent over a season, or 69.5 percent on an annualized basis. However, other levels of fertilizer use, including the combination of fertilizer plus hybrid seed recommended by the Ministry of Agriculture, are not profitable for farmers in our sample.
Duflo, Esther, Michael Kremer and Jonathan Robinson. 2016. "Rates of Return to Fertilizer: Evidence from Field Experiments in Kenya." AEA RCT Registry. November 01.
1/4 teaspoon top-dressing CAN, applied 2 months after farming.
1/2 teaspoon top-dressing CAN, applied 2 months after farming. 1 teaspoon top-dressing CAN, applied 2 months after farming. Full package recommended by the Ministry of Agriculture: Hybrid seeds, 1 teaspoon top-dressing CAN, and 1 teaspoon di-ammonium phosphate, applied 2 months after farming. Comparison: Business as usual farming.
Intervention Start Date
Intervention End Date
Primary Outcomes (end points)
Crop yield, Rates of return to fertilizer
Primary Outcomes (explanation)
Crop yield was measured by the dry weight of harvested maize.
Secondary Outcomes (end points)
Secondary Outcomes (explanation)
A series of six field trials over three years were designed to ascertain the profitability of fertilizer on farms in Busia District, a relatively poor rural district in Western Kenya. Field officers measured out 3 plots of land at a time, and in the first few seasons allocation of the treatments was as follows: the first plot was selected to receive Calcium Ammonium Nitrate (CAN) fertilizer to be applied as top dressing 2 months after planting; the second plot was assigned the full package reccommended by the Ministry of Agriculture (hybrid seeds, Di-Ammonium Phosphate (DAP) fertilizer, and CAN for use at top dressing); and the third plot was a comparison plot, where farmers farmed as usual, with traditional seed and without fertilizer. In the last few seasons, the quantity of fertilizer applied to the plots was also varied.
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
1/4 teaspoon top-dressing fertilizer: 112 farmers
1/2 teaspoon top-dressing fertilizer: 202 farmers
1 teaspoon top-dressing fertilizer: 274 farmers
Full package recommended by the Ministry of Agriculture: 85 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
September 30, 2003, 12:00 AM +00:00
Is data collection complete?
Data Collection Completion Date
September 30, 2003, 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
How High Are Rates of Return to Fertilizer? Evidence from Field Experiments in Kenya
Duflo, Esther, Michael Kremer and Jonathan Robinson. 2008. "How High Are Rates of Return to Fertilizer? Evidence from Field Experiments in Kenya." American Economic Review, 98(2): 482-88.
REPORTS & OTHER MATERIALS