The productivity of cacao trees decreases with time, forcing farmers to renew their plantations by either cutting down the old trees or establishing a new crop elsewhere. Frequently, new plantations are established in areas of the forest that are thinned out to accommodate new, young cacao trees. However, this comes with high economic and ecological costs. An alternative approach is to graft highly productive and native cultivars onto the existing older cacao trees. An international team led by scientists of the University of Göttingen found that cacao grafting is a useful measure to rejuvenate cacao plants, increasing their yield and profits with minimal impact on biodiversity. The results were published in the Journal of Applied Ecology.
Cacao grafting consists of implanting a shoot from a promising variety into an adult cacao tree. By making use of the adult root system, grafting young and fresh branches completely replaces the old tree crown in a short time period. This approach has long been used for many crops, but its consequences for cacao production and biodiversity had never been simultaneously tested. Researchers from the universities of Göttingen and Würzburg in Germany, with the organization Bioversity International worked with local farmers in Peru to assess this. The technique focused on grafting high-yielding genotypes from the very highly valued, native variety Cacao Blanco de Piura. "These native varieties have already increased crop yield by 45% after just two years," says Dr Carolina Ocampo-Ariza, at Göttingen University's Agroecology group, who led the research. "This is great news for the production of fine flavour cocoa. It shows the value of grafting as a method to improve yields in a short time."
In the first six months after grafting, the researchers monitored the diversity of arthropods – for instance, spiders, mites and insects. "We were afraid that arthropods on the young grafts would be less diverse, because the old voluminous tree crown, including many branches, had been replaced," says Sophie Müller, former MSc student at Göttingen University and co-leader of the research, "but we actually found that, after a small decline in diversity, especially of predatory arthropods, the community quickly recovered in just six months." This recovery is particularly good news for the control of insect pests in cacao agroforests, since predatory arthropods may prevent pest outbreaks.
"Our study demonstrates that grafting is a sustainable alternative which rejuvenates old cacao crops. This prevents the expansion of the agricultural frontier into tropical forests," highlights co-author Professor Teja Tscharntke, Göttingen University.
Original publication: Carolina Ocampo-Ariza, Sophie Müller, et al. Cacao grafting increases crop yield without compromising biodiversity. Journal of Applied Ecology 2025. DoI: 10.1111/1365-2664.14851 . Full text also available in Spanish in the article's supplementary material
