Eight years of on-farm trials in Murang’a County, central Kenya, provide evidence on how vermiculture tea performs under the low-input, rainfed conditions typical of many smallholder farms. Researchers from the International Centre of Insect Physiology and Ecology (icipe) and the Research Institute of Organic Agriculture (FiBL) compared vermiculture tea used alone, combined with organic amendments, or integrated with synthetic fertilizers. Ten farmers participated in trials covering 16 cropping seasons between 2016 and 2023, using a maize–legume–potato rotation.

Vermiculture tea alone produced significantly higher maize yields in four of the six seasons with harvests, while combining vermiculture tea with synthetic fertilizers generally resulted in the highest potato yields. Organic combinations containing compost and Tithonia improved some soil nutrients, particularly calcium, although soil organic carbon did not increase under any treatment. Rainfall variability strongly affected performance: maize crops failed completely during the 2019 and 2022 long-rain seasons, and overall crop yields remained well below regional potential.

The findings show that vermiculture tea may offer a locally producible fertilization option, particularly for resource-constrained farmers, but also underline its limitations. At the low application rates tested, none of the systems was sufficient to improve overall soil and crop productivity consistently. The authors recommend further research on optimal application rates, economic viability and the potential for scaling vermiculture-based inputs under tropical farming conditions.