By Felix Ochieng Akech

Shamba Assistant has relaunched its handheld soil testing device as a $400 one-off purchase, ending its subscription model, in a move it says will help farmers apply fertiliser more accurately by working with agronomists.

The device, developed by engineering students at Kenyatta University, was built to stop farmers relying on guesswork, by measuring the levels of nitrogen, phosphorus and potassium already in the soil.

“The reason we developed the Shamba Assistant was to bring data-driven agriculture to smallholder farmers,” said engineer Derrick, one of the developers. “Where I grew up, in Naivasha, farming decisions were based on copying neighbours. If one farmer applied a fertiliser, everyone else followed without knowing whether their soils were the same. Yet soil can be different even in the same village.”

The different levels of these main nutrients from plot to plot can mean the same fertiliser levels even harm some farms, yet “for a smallscale farmer, lab testing was out of reach,” said Derrick. “So we asked ourselves: what if there was a very simple device, available within the community, that could give basic soil information and immediate guidance?”

“The sensor we made measures nitrogen, phosphorus, and potassium. It also measures soil pH and electrical conductivity, which helps interpret nutrient availability. Moisture and temperature are included too, mainly for greenhouse and controlled environments.”

This remains a basic test. It doesn’t equip farmers to adjust the micronutrients critical to plant health and many yields. But it does give the right information to stop farmers wasting money on the wrong fertiliser, which can even harm their harvests.

“Our thinking was that once farmers improved yields and profit margins using basic data, they could then afford full laboratory tests later,” said Derrick.

“For example, if nitrogen levels are already high but phosphorus is low, a farmer can avoid buying a blanket NPK fertiliser and instead target what the soil actually needs,” he said. “That alone can reduce fertiliser costs significantly while improving crop performance.”

But while the team first tried monthly rental subscriptions for the device, offered to farmers through agrovets and NGOs, the model became difficult to run. “Adoption took much longer than we thought it woukd,” said Derrick. “Education was also a major barrier. Many users struggled with the technology, and consistent training was required. Software updates, connectivity issues, and maintenance also made the subscription model difficult to keep going.”

“It became clear that ownership by individual farmers just wouldn’t work,” he said. “Training mattered more than we had thought. If users weren’t properly trained, the data could be misinterpreted. But where agronomists were involved, results were much stronger. It made more sense for agronomists or agrovets within the community to own the device. That way, a farmer can get their soil tested and receive recommendations within 15 minutes.”

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“We moved away from the rental model to selling the device outright at around $400, so that the price includes the hardware, the software, and the service support.”

“Our main customers now are NGOs working with farmers, agronomists supporting producer groups, and agrovets,” he said. 

“The device works best this way, as an extension tool, especially in large farms and greenhouse operations, because it is built as a data and advisory platform, supported by hardware, so now our focus is on building reliability, making sure the product works consistently across different regions and conditions across the country.”

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