Rwanda Agricultural Lime Trial 2018
RWA -17 -1382Last modified on November 10th, 2025 at 1:53 pm
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Abstract
One Acre Fund (OAF) is an agricultural service provider that provides support for smallholder farmers in Africa in accessing agricultural inputs, training, and markets, to help the farmers increase their harvests and income. PxD and OAF began collaborating in 2016 on efforts to increase adoption of agricultural inputs and improve OAF operations in Kenya and Rwanda.
In this experiment we examined the effects of an SMS campaign that promoted the adoption of agricultural lime (a relatively new input) by Rwandan farmers, in a group-based credit and extension program. The campaign sent messages to farmers organized in groups, and we experimentally varied the message diversity and intensity, as well as the message content, framing, and repetition.
On average, receiving SMS messages increased the farmer’s likelihood of purchasing lime through the program by 20% over the adoption rate of 3.4% in the control group. The SMS campaign also had a small and marginally significant effect on the likelihood of lime adoption by farmers who do not own phones; this effect suggests the presence of spillover effects. Further analysis provides tentative evidence that sending diverse messages, instead of identical messages, to farmers within a group is more effective in increasing the likelihood of lime purchase. The overall treatment effect estimated for the full sample of phone owners and non-owners for groups that received diverse messages is twice as large as the estimate for those that received identical messages. An additional SMS message encouraging farmers to share information had no spillover effect. -
Status
Completed
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Start date
Q2 Jun 2017
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End date
Q2 Jun 2017
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Experiment Location
Rwanda
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Partner Organization
One Acre Fund (OAF)
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Agricultural season
Season A
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Experiment type
A/B test
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Sample frame / target population
OAF farmers
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Sample size
196,661
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Outcome type
Input adoption
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Mode of data collection
Partner administrative data
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Research question(s)
1. Do SMS messages promoting the use of lime increase its adoption in Rwanda?
2. Do message campaigns generate spillover effects betweenOAF group members who do not own mobile phones?
3. Do message campaigns sending different messages to different group members, as opposed to sending identical messages to all group members, increase adoption of the recommended input, through information sharing? -
Research theme
Communication technology, Message framing
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Research Design
In order to estimate the effect of SMS messages on travertine (agricultural lime) adoption, we used a randomized controlled trial. The randomization had different treatment arms and they varied along different lines.
Group Randomization:
Farmer groups were randomized into four different categories:
1. A control group, G0: Farmers did not receive any text messages.
2. The same-message group, G1: Farmers belonging to the same group all received the same SMS messages with the same content.
3. The different-message group, G2: Farmers belonging to the same group all received messages with different content.
4. The half-variation group, G3: Half of the farmers of each group were randomly selected to receive messages that differed from individual to individual while the other half did not receive any messages. We used this treatment arm to measure spillovers between farmers who possess a phone and belong to the same treatment group.SMS Variation:
Seven different SMS messages were designed and randomized at the group level in the case of G1 and at the individual level in the cases of G2 and G3. The messages were the following:T1 Is a basic message: Many fields in Rwanda have acidic soil and need TRAVERTINE to increase yields. Order from TUBURA now.
T2 Gives specific information on dosage and impact: Many fields in Rwanda have acidic soil. Applying 25 kg/acre of TRAVERTINE will increase yields by 20%. Order from TUBURA now.
T3 Helps to self-diagnose the need for lime: Do you have fields with poor harvests even when you use fertilizer? You probably have acidity and need TRAVERTINE to increase yields. Order from TUBURA now.
T4 Helps to diagnose via a soil test: Ask your Field Officer for a free soil test to learn if your fields are acidic and you need to order TRAVERTINE to increase yields.
T5 Explains how lime works: Many fields in Rwanda have acidity, which blocks fertilizer uptake. Applying TRAVERTINE solves the problem, increasing crop yields. Order from TUBURA now.
T6 Promotes urgency and need: Many fields in Rwanda have acidic soil and need TRAVERTINE to increase yields. Order it immediately, when signing your TUBURA order form.
T7 Addresses location-targeted acidity: In your site the soil is acidic. If you apply 25 kg/are of TRAVERTINE you can boost yields by 20%. Order from TUBURA now.Framing:
Furthermore, the framing of the message introduced additional variation. Individuals and groups were randomly assigned to receive a loss-framed or gain-framed message. The former highlighted that not using travertine amounted to loss, while the latter explained the possible gains derived from using travertine.Frequency:
We also varied the frequency with which farmers received an SMS message. Farmers received a maximum of four messages. Each farmer always received the same SMS message.Social Nudge:
Some individuals were assigned to receive an additional social nudge, such as an additional message encouraging the recipient to share the message with other farmers, especially those who do not have phones.For further information, see Fabregas et al., 2024.
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Results
Messages increased lime purchases by 0.7 percentage points, a 20% increase over the control mean of 3.4%. Estimated spillover effects are positive but insignificant and small in magnitude. Adoption of recommended practices is marginally higher in groups that received different messages; although only marginally significant at the 10% level, this suggests that there is a possibility of increased information sharing.
The overall treatment effect estimated for the full sample of phone owners and non-owners for groups that received diverse messages is twice as large as the estimate for those that received identical messages. An additional SMS encouraging farmers to share information had no spillover effect.