Examining Barriers to Fertilizer Use in Kenya

Last registered on August 29, 2017


Trial Information

General Information

Examining Barriers to Fertilizer Use in Kenya
Initial registration date
May 31, 2016

Initial registration date is when the trial was registered.

It corresponds to when the registration was submitted to the Registry to be reviewed for publication.

First published
May 31, 2016, 4:07 AM EDT

First published corresponds to when the trial was first made public on the Registry after being reviewed.

Last updated
August 29, 2017, 3:38 PM EDT

Last updated is the most recent time when changes to the trial's registration were published.



Primary Investigator

University of California, Santa Cruz

Other Primary Investigator(s)

PI Affiliation
PI Affiliation
PI Affiliation
Harvard University

Additional Trial Information

On going
Start date
End date
Secondary IDs
Insufficient knowledge of appropriate use can hamper technology adoption. In the agricultural context, if farmers do not observe each others' inputs, diffusion of both information on the optimal input mix and of the technology itself may be slow. In a large-scale field experiment, we introduced a simple and salient tool, a blue measuring spoon, to help farmers remember how much fertilizer to use. A randomly selected subset of farmers received the technology for free, and the remaining farmers could purchase it at fertilizer stores at a nominal price. Farmers who were randomly assigned to receive a measuring spoon subsequently improved knowledge of how much fertilizer to use, and were more likely to use fertilizer. Unlike fertilizer adoption itself, purchase and use of measuring spoons diffused rapidly through social networks. We find that the formation of farmers' cooperatives sped the diffusion of the spoons. Finally, a time-limited discount coupon for fertilizer increased fertilizer use in the season of the program.
External Link(s)

Registration Citation

Duflo, Esther et al. 2017. "Examining Barriers to Fertilizer Use in Kenya." AEA RCT Registry. August 29. https://doi.org/10.1257/rct.1306-3.0
Former Citation
Duflo, Esther et al. 2017. "Examining Barriers to Fertilizer Use in Kenya." AEA RCT Registry. August 29. https://www.socialscienceregistry.org/trials/1306/history/20979
Experimental Details


We worked with the parents of schoolchildren in 184 schools in Western Kenya, to examine the diffusion of a new agricultural technology, and to examine the impact of farmers' cooperatives and time-limited coupons on diffusion and fertilizer adoption. The experiment was conducted with small-scale farmers over two agricultural seasons (short rains 2010 and long rains 2011). To reach a large number of farmers at aff ordable costs, we leveraged a large social network: the parents of school children in 184 rural primary schools. Children in these schools were given a letter inviting their parents inviting them to a meeting at the school. Every parent who participated in a meeting at a particular school was eligible for the treatment administered at this school. At the meeting, the experimental treatments (if any) were explained, and enumerators completed a short baseline survey with each participant. We enrolled approximately 27,000 farmers into the program.

We cross-randomized three main treatments. First, we subsidized the creation of farmers' cooperatives in which farmers could discuss agricultural issues. Second, we provided farmers with time-limited coupons which could be redeemed for a small discount on the cost of fertilizer. Third, we provided a randomly selected subset of farmers with 1/2 teaspoon measuring spoons, painted blue, which could be used to measure out a quantity of fertilizer which we found profit-maximizing in prior work (Duflo et al. 2008).
Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
adoption of fertilizer, adoption of bluespoons, redemption of coupons, membership in agricultural cooperatives
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
At the school level, we cross-randomized farmers at the school level into two main treatment conditions. First, to lower costs of communicating and sharing knowledge about fertilizer and other agricultural practices, we encouraged farmers to form farmers' cooperatives to talk about agriculture. While we facilitated organizing the groups and coordinated the fi rst few meetings, we did not provide any information directly to farmers.

Second, in previous work, we fou nd that providing farmers with small incentives to invest in fertilizer when they have money (right after harvest) can substantially increase usage (Duflo et al. 2011). Hence, to increase usage exogenously, we implemented a scalable version of a program to provide farmers with small, time-limited discounts which were valid within a short window (3 to 4 weeks) right after harvest, redeemable at a local shop. Farmers received coupons for a discount of 15% of the price of fertilizer. The coupon was valid for discounts to either diammonium phosphate fertilizer (DAP), used at planting, and calcium ammonium nitrate fertilizer (CAN), used at top dressing, when the maize plant is knee high, approximately one to two months after planting. Farmers could choose any combination of DAP and CAN up to 25 kilograms in total. Moreover, to evaluate the e ectiveness of text message reminders, we randomly selected half of the schools that received fertilizer discount coupons into a text message reminder program. In these schools, we randomized a subset of individuals who either owned a cellphone or had access to a cellphone to receive a text message reminder two days before the expiration date of their time-limited discount.

At each school meeting, we asked about 25% of farmers in each school to provide names and contact information of up to 3 individuals outside their own household with whom they discussed agriculture whom we refer to as agricultural contacts" below. About two thirds of these individuals were randomly selected to receive a "Bluespoon," a half-teaspoon, painted blue, which farmers could use to apply fertilizer to their maize. We chose this simple technology because in earlier work we had found 1/2 teaspoon of CAN to yield the highest profits on average among four di fferent quantities (Duflo et al. 2008). We delivered these spoons in an additional short meeting
(at the same schools) to which we had invited the randomly selected subset of farmers. In addition, farmers were given the information that in earlier work we had found that this quantity of CAN resulted in the highest pro ts on average. Again due to logistical constraints, the timing of these meetings was randomized. Bluespoons were also made available to anyone for a nominal
fee ($0.05) in the local market center at the same shops which handled the coupon redemption.
Experimental Design Details
Randomization Method
randomization was done in office by a computer
Randomization Unit
The coupon and cooperative treatments were randomized at the school level (this included all the parents of schoolchildren in that school); the bluespoon treatment was randomized at the individual level.
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
184 schools
Sample size: planned number of observations
approximately 27,000 individuals
Sample size (or number of clusters) by treatment arms
46 schools got not coupons nor cooperatives
46 got no coupons but got cooperatives
47 got coupons but not cooperatives
45 got both

approximately 4,056 respondents received bluespoons
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)

Institutional Review Boards (IRBs)

IRB Name
Harvard University-Area Committee on the Use of Human Subjects
IRB Approval Date
IRB Approval Number
IRB Name
MIT Committee on the Use of Humans as Experimental Subjects
IRB Approval Date
IRB Approval Number
IRB Name
University of California, Santa Cruz IRB
IRB Approval Date
IRB Approval Number
IRB Name
University of California, Santa Cruz IRB
IRB Approval Date
IRB Approval Number


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