Remarkable biochar success in Cameroon

A farmer in Malende carries a bag of biochar maize to the collection point. Photos: Laurens Rademakers, Etchi Daniel-JonesTrial data show strong improvement in maize yield

Since December 2008, more than 1500 subsistence farmers in Cameroon's South-West Region (SWR) have been participating in the largest-ever field trial testing the effects of biochar on crop productivity. The first results of this ongoing experiment, based on maize planted in a large series of plots, are now available. The data can be described as 'remarkable', in that they demonstrate how biochar consistently helps boost crop productivity in tropical soils, sometimes in a spectacular manner.

The preliminary results suggest that biochar may offer a solution to hunger and food insecurity amongst the world's poorest, as well as to soil depletion and tropical deforestation.

The Cameroonian farmers are united in 'Common Interest Groups' (CIGs), comprising between 10 and 30 members each. CIGs are the most grassroot of all forms of association in the country. These associations voluntarily dedicated a small plot of their (often scarce) farm land to conduct the experiment.

The participants are subsistence farmers who make less than Euro 300 per year from agriculture, even though some of them are smallholders who are also involved in cash-cropping (mainly cocoa). The majority of the participants are women.

The biochar trials are taking place in and around the town of Kumba, in a region which features a great diversity of tropical soil types ranging from poor, highly weathered oxisols, to fertile volcanic soils. Besides Kumba proper, the following villages are now home to a biochar test plot: Kake, Barombi Kang, Mambanda, Ikiliwindi, Teke, Mabonji, Mbalangi, Malende, Kossala, Ediki and Kendem (see map 1).

The test plots are located in farm land that is commonly used by the peasants to grow root-crops like cassava, yam and cocoyam, and plantain, beans, maize and fruit crops. The typical farming system is one based on mixed cropping.

The Biochar Fund and its local partner, Key Farmers Cameroon, chose to conduct the trials with maize, because this crop can be planted and harvested twice in a single year. This opens the possibility for the partners to collect a large number of data-sets. The growing season for the first maize runs from May to July, that of the second crop from August to October. Because of excellent agro-ecological conditions, maize in this region matures in less than 90 days.

Even though maize is a staple crop for the local population, average yields amongst the participating farmers are low (below 1.7 tons per hectare; see data-page: general data, figure 6 ). The key factors explaining this situation are the low fertility of most soils and a lack of (financial) access to fertilizers, poor farm management, a lack of access to quality seeds, and the absence of modern strategies to deal with pests and diseases.

The results after the first harvest of maize grown on biochar show that char is an effective soil amendment, boosting the yield of the crop, even without the addition of mineral or organic fertilizers.

Maize ready to be harvestedOut of 75 test plots, 41 yielded complete data on biomass development, whereas 37 offer complete data on grain yields. 31 data-sets are complete for both biomass and grain yield data. Incomplete data series can be explained by a range of factors: theft of healthy maize cobs is the most common problem, with some groups whose plots were located deep in the forest reporting that all their maize was stolen (because it looked so good, in their own words).

Other losses were due to observable bird and pest attacks, and misunderstandings on how to conserve and prepare the maize and the biomass correctly for measurements. Some groups sold or consumed the maize before data could be collected.

Despite these losses, we think the series of data are sufficiently large to draw conclusions on the effectiveness of biochar as an agricultural soil amendment in the tropics, and in particular on maize in relatively infertile soils.