Assessing the Impact of Leaf Color Charts on Cotton Farmers
IND -24 -2997Last modified on December 19th, 2025 at 10:42 am
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Abstract
Farmers in low- and middle-income countries face multiple barriers to optimizing agricultural decisions, and often lack access to actionable information to adapt their practices. These challenges are particularly salient in fertilizer application: Returns to fertilizer application are highly heterogeneous, which makes it difficult for farmers to observe the effectiveness of their actions. With large fertilizer subsidies in South Asia, many farmers overuse nitrogen fertilizers. A Leaf Color Chart (LCC), a simple plastic strip with graduated green shades, provides both real-time estimates of a crop’s nitrogen status and rule-of-thumb guidance on the correct timing and quantities of urea fertilizer application.
We evaluate whether access to LCCs, paired with in-person training and digital advisory messages throughout the season, can improve nitrogen management for cotton farmers in Maharashtra, India, and examine how alternative financial incentive designs affect LCC adoption. Using a random-walk sampling method, we recruited 1,253 cotton farmers across 60 villages during Kharif 2024 and individually randomized them (stratified by block) into five arms: control; LCC + training + digital advisory; and three variants that add small financial incentives (~$5/acre) delivered either ex-post conditional on use, ex-ante unconditional, or ex-ante conditional on use. To evaluate impacts, we collected both objective nitrogen-use-efficiency measures using mid-season chlorophyll meter checks, and farmers’ self-reported use of fertilizer and cotton yield using an endline survey, to analyze the outcomes of LCC adoption, nitrogen application behavior, and cotton yield. -
Status
Completed
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Start date
Q1 Mar 2024
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Experiment Location
India / Maharashtra
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Partner Organization
J-PAL South Asia
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Agricultural season
Kharif
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Experiment type
Impact Evaluation
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Sample frame / target population
Cotton farmers in Maharashtra
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Sample size
1,253
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Outcome type
Farming practices, Service engagement, Input adoption, Knowledge, Agricultural production / yield, Agricultural profits / revenues
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Mode of data collection
PxD administrative data, In-person survey, Phone survey
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Research question(s)
1. Does providing farmers with an LCC (plus training and digital advisory) change nitrogen fertilizer application (quantity, timing, and frequency), yields, and total production costs?
2. How effective are different financial incentives (conditional vs. unconditional and ex-ante vs. ex-post) to adopt LCCs? -
Research theme
Agricultural management advice, Input recommendations, Service design, Soil fertility
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Research Design
Using a random-walk sampling method, we recruited 1,253 cotton farmers across 60 villages in six blocks in three eastern districts of Maharashtra.
Eligible participants were the primary agricultural decision-makers in their household, aged 18–75. Their primary crop for Kharif 2024 (the intervention year) was cotton, grown on land they own (not solely rented or sharecropped). They applied urea to cotton in the Kharif 2023 season, possessed a verifiable 10-digit mobile number, and had at least one plot that was under cotton cultivation in each of the past two Kharif seasons and would be under cotton again in Kharif 2024. Eligible participants were willing to accompany the enumerator for GPS area measurement and soil sampling for this plot.
We stratified recruited farmers by block of residence, and randomly assigned the farmers to one of five experimental arms:
1. Treatment 1 (T1, n = 208 farmers): LCC distribution and in-person training, plus digital extension support via Interactive Voice Response (IVR) and WhatsApp.
2. Treatment 2 (T2, n = 208 farmers): Same as T1, plus a conditional payment of ~$5 per acre at the end of the season for verified LCC use.
3. Treatment 3 (T3, n = 209 farmers): Same as T1, plus an unconditional upfront payment of ~$5 per acre (no usage conditions).
4. Treatment 4 (T4, n = 207 farmers): Same as T1, plus an upfront payment of ~$5 per acre for LCC use, with the provision that the payment might be rescinded if the farmer does not use the LCC.
5. Control (n = 421 farmers): No intervention.We collected baseline survey data, soil samples, and GPS coordinates of the monitored plots prior to randomization. We collected chlorophyll meter and LCC readings two times during the cotton growing season at approximately 55 and 75 days after sowing (DAS). The endline survey measured self-reported fertilizer quantities and timing, LCC use and knowledge, yields, and production costs. We used administrative data to measure user engagement with the digital advisory services (IVR/WhatsApp).
The integrated data collection and intervention timeline was as follows:
1. Baseline—Survey, soil samples, GPS (March 29–May 2, 2024).
2. Training and distribution—LCC training, LCC distribution, contract offer (May 21–June 6, 2024).
3. Ex-ante payments—Groups paid before June 30, 2024.
4. Digital advisory—IVR/WhatsApp messages (June–July 2024).
5. Sowing/resowing phone checks—Scheduled monitored-plot field visits (July–August 2024).
6. Monitored plot visit 1 (~55 DAS)—Chlorophyll meter and LCC readings (July 17–October 16, 2024).
7. Monitored plot visit 2 (~75 DAS)—Chlorophyll meter and LCC readings (August 14–October 29, 2024).
8. Phone survey on LCC use; ex-post conditional payments (September 18–October 31, 2024).
9. In-person endline survey A—Fertilizer use, LCC use (December 14, 2024–January 10, 2025).
10. In-person endline survey B—Yield, production costs, contract recall (April 28–June 3, 2025).Primary Outcomes of Interest:
1. LCC panel reading.
2. Chlorophyll meter reading.
3. Self-reported urea use (kg/acre).
4. Self-reported nitrogen use (kg/acre).Secondary outcomes of interest:
1. Pick-up and listening rates of voice push messages over the phone.
2. Index of Correct LCC-Use Knowledge.
3. Self-reported cotton fiber yield (kg/acre).
4. Self-reported fertilizer cost (INR/acre).
5. Self-reported production cost (INR/acre).
6. Self-reported profit (INR/acre).See the American Economic Association’s registry for randomized controlled trials for this study: https://www.socialscienceregistry.org/trials/14033