Ithaka Institute - Project countries

Ghana

Future of Biochar in Cocoa Systems

Cocoa is one of the major tropical cash crops suffering from degraded and often too acidic soils. Biochar based fertilization has the potential not only to improve yields and crop health but to turn cocoa agroforestry systems into carbon sinks to mitigate climate change. In 2020, Ithaka started a large demonstration project in Ghana to showcase the biochar potential and deliver the scientific data for political and industrial decision-makers.

What advantages may biochar based fertilization procure to cocoa farming?

Conservatively, we can expect at least 20% higher yields though based on our experience with other tropical crops, we are positive that yield increases of 50% are possible. Moreover, significantly improved plant health and thus higher crop quality and reduced fertilizer application (especially phosphate) are expected.

Thanks to the root zone application with compressed air, the pH of the root zone can be controlled, and thus the aluminum toxicity alleviated which makes phosphate again available to the tree roots. As phosphate is currently the main limiting factor, this alone will significantly improve tree performance. Moreover, the injected biochar based fertilizer will improve root aeration, water availability, and the biological activity in the root zone of each cocoa tree.

Moreover, the tested method applying 2 ton of biochar per ha has a carbon-sink potential of about 4.4 t CO2eq with an estimated value of at least 200 Euro per ha.

Injection of the biochar fertilizer slurry in Ghana.

How does it work

One part of the biochar is made from cocoa shells at milling sites. The other part of the biochar is produced on-farm using the Kon-Tiki technique.

The biochar is than milled to 3 mm.

The fertilizer that is currently recommended and used by the farmer is dissolved in water and mixed with the milled biochar.

The biochar-fertilizer slurry is then injected with compressed air 20 - 40 cm deep into the root zone of the cocoa tree. Around the injection probe, the biochar-fertilizer is distributed in an area of 0.5 to 1 m diameters. The injection is done for each tree which takes about 1 to 1.5 min and injects 3 liter of biochar-fertilizer.

Biochar made from cocoa husks and prunning wood.