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Rates of Return to Fertilizer: Evidence from Field Experiments in Kenya
Last registered on November 01, 2016

Pre-Trial

Trial Information
General Information
Title
Rates of Return to Fertilizer: Evidence from Field Experiments in Kenya
RCT ID
AEARCTR-0001750
Initial registration date
November 01, 2016
Last updated
November 01, 2016 4:54 AM EDT
Location(s)
Region
Primary Investigator
Affiliation
University of California, Santa Cruz
Other Primary Investigator(s)
PI Affiliation
Harvard University
PI Affiliation
Massachusetts Institute of Technology
Additional Trial Information
Status
Completed
Start date
2000-06-01
End date
2003-09-30
Secondary IDs
Abstract
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.
External Link(s)
Registration Citation
Citation
Duflo, Esther, Michael Kremer and Jonathan Robinson. 2016. "Rates of Return to Fertilizer: Evidence from Field Experiments in Kenya." AEA RCT Registry. November 01. https://doi.org/10.1257/rct.1750-1.0.
Former Citation
Duflo, Esther et al. 2016. "Rates of Return to Fertilizer: Evidence from Field Experiments in Kenya." AEA RCT Registry. November 01. https://www.socialscienceregistry.org/trials/1750/history/11584.
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Experimental Details
Interventions
Intervention(s)
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
2000-06-01
Intervention End Date
2003-09-30
Primary Outcomes
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
Secondary Outcomes (end points)
Secondary Outcomes (explanation)
Experimental Design
Experimental Design
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
Randomization Method
Stata
Randomization Unit
Individual (farmer)
Was the treatment clustered?
No
Experiment Characteristics
Sample size: planned number of clusters
673 farmers
Sample size: planned number of observations
673 farmers
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)
IRB
INSTITUTIONAL REVIEW BOARDS (IRBs)
IRB Name
IRB Approval Date
IRB Approval Number
Post-Trial
Post Trial Information
Study Withdrawal
Intervention
Is the intervention completed?
Yes
Intervention Completion Date
September 30, 2003, 12:00 AM +00:00
Is data collection complete?
Yes
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?
No
Final Sample Size: Total Number of Observations
Final Sample Size (or Number of Clusters) by Treatment Arms
Reports and Papers
Preliminary Reports
Relevant Papers
Abstract
How High Are Rates of Return to Fertilizer? Evidence from Field Experiments in Kenya
Citation
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.