The Impact of Site Specific Soil Fertility Recommendations: experimental evidence from Malawi

A first treatment (T1) entails a soil report based on a soil test conducted on a plot chosen by the farmer. This report includes key characteristics of the soil, along with a customized recommendation for a fertilizer blend tailored to the specific crop selected by the farmer. The soil report is delivered to the farmer by an extension agent that explains the soil report.
A second treatment (T2) is a subsidy will be provided to farmers that can be used to purchase the recommended fertilizer blend.

In the first treatment, a random sample of farmers is visited by an enumerator accompanied by an agronaut and is offered the opportunity for a soil on a plot chosen by the farmer. The farmer is also asked what crop the farmer plans to cultivate on this plot, as well as the target yield that the farmer would like to get from the crop on that plot. This information is registered in a CAPI app, and an appointment is made at a later date when the farmer will visit the farmer to go the the plot and take the soil sample. The soil sample is then analyzed, which results in a soil report (see example in Appendix 1) that is provided to the farmer. The report indicates the soil’s texture, pH level, cation exchange capacity, percentage organic matter, total nitrogen, carbon to nitrogen ratio, as well as the parts per million of available P, exchangeable K, calcium, magnesium, iron, manganese, boron, copper and zinc. Beyond the exact measurements each soil property is given a score on a 4-point Likert scale (very low, low, high, very high), with emojis, color coding and bar charts indicating where the soil is deficient and where the levels are sound. An extension worker (agronout) then discusses the soil report with the farmer to derive a recommended nutrient package specific to the crop the farmer wants to grow. The farmer is then informed where and how to obtain these nutrients (in the form of a particular fertilizer blend).

The second treatment consists of a subsidy that the farmer receives in the from of a voucher that can be redeemed at a nearby Farmer World agro-input shop. The subsidy is tied to T1 in that it will be specific for the recommended fertilizer blend. The value of the subsidy will be model on Malawi's Agricultural Input Program (AIP) which allows farmers to buy one bag of fertilizer at a reduced rate (30 percent of full price). In particular, our subsidy will be equal to 70 percent of the AIP fertilizer bag value minus the cost of the soil test. This will allow us to directly compare our bundle as an alternative to Malawi's AIP.

2024-09-22

2024-10-13

yield, profit.

outcomes are measured at the household level (as the treatment may affect which plot is chosen by the farmer which complicates identifying an appropriate plot in the control group). In other words, we will collect information on all plots.

crops grown by the farmer, soil health management practices used by the farmer (eg fertilizer blends used)

application error (soil management practices used versus those recommended)

Cluster randomized control trail with incremental treatments (1 control arm, one T1 arm, and one T1+T2 arm)

Cluster randomize control trial with clustering at the village level. We use an incremental design with one control group,

randomization done in office by a computer

villages

Yes

113 villages

2034 (16 households in 113 villages plus 2 households in 113 villages to account for attrition)

41 villages in T1, 42 villages in T2 and 30 villages in the Control

Simulation was used to determine sample size. We simulated treatment effects by drawing samples from real data collected in April and May 2024. We model 13 percent increase over baseline yield (average yield is 2,574 kilogram per hectare with standard deviation of 1145) for both T1 and T2.