A trial in Tanzania of the effectiveness of a highly porous charcoal made from organic waste has demonstrated its potential to significantly improve coffee yields while reducing input costs.

Project Black Earth, which was run by US-registered non-profit Radio Lifeline in partnership with with Tembo Coffee and MIICO, a network of community-based agricultural development organizations based in Mbeya, compared the efficacy of biochar with more conventional farming approaches.

Six mature coffee plots were treated with various combinations of biochar, compost and different formulations of nitrogen, phosphorus and potassium

(NPK) fertiliser, with weekly results monitored by field technicians and agronomists associated with Tembo and MIICO. In a separate trial, coffee seedlings planted in both full sun and shade were treated with applications of either biochar or NPK to evaluate the impact of biochar on the early stages of coffee tree development.

After the first round of harvest, results demonstrated significant yield increases in those trees treated with amendments of biochar vs trees treated with traditional NPK fertiliser applications. Among the trees treated with a combination of biochar and compost, yield increases amounted to more than 43 times over those trees with traditional NPK fertiliser treatments.

This is consistent with results from a trial run in Rwanda in 2012.

In that trial, 18 test plots were constructed among six partner cooperatives, representing each of the major coffee growing regions in the country. Results of these trials demonstrated an average of 35 per cent increase in yield and a 50 per cent reduction in input costs within the first year among coffee trees treated with an application of biochar.