Drivers of Cocoa Yield and Growth in Young Monoculture and Agroforestry Systems

Abstract

CONTEXT: Agricultural extension, including cocoa expansion, has been linked to deforestation and biodiversity loss in West Africa, notably in Côte d’Ivoire, the world’s leading cocoa producer. Agroforestry systems could potentially increase the sustainability of cocoa production. However, despite the long history of cocoa cultivation in agroforestry systems, the exact mechanism or the combination of factors that drive cocoa growth and yield in these agroecosystems, especially at the cocoa establishment stage, is unclear.OBJECTIVE: The present study aims to analyse how resource availability, stand characteristics and cocoa tree morphology interact to determine the performance of cocoa during the establishment phase among different cocoa cultivation systems.METHODS: We studied seven different agroforestry systems and one monoculture system in 53 plots located in a 12-ha cocoa agroforestry trial recently established in Côte d’Ivoire. We characterized each system with 16 variables that described five system components: 1) cocoa yield (number of pods, pods weight, number of productive trees) and cocoa growth (basal diameter), 2) cocoa tree morphology (crown depth, diameter, area, and volume), 3) stand characteristics (number and size of shade trees), 4) light (leaf area index) and 5) water (soil volume water content). We used a Structural Equation Modelling approach to understand and quantify interactions between the five components.RESULTS AND CONCLUSIONS: We observed improved cocoa establishment in certain designs of agroforestry systems compared to monoculture. However, Structural Equation Modelling revealed that stand characteristics (i.e. increase in the number and height of shade trees) had a negative effect on cocoa yield, growth, and tree morphology. Cocoa tree morphology were more important than stand characteristics, leaf area index, and soil volume water content in controlling cocoa early yield and juvenile growth. Taken together, our results suggest a competition for space between shade trees and cocoa plants. Finding the optimal design of agroforestry systems can help enhance cocoa establishment in the first years, improving the long-term performance of the system.SIGNIFICANCE: This finding suggests that the competition effect depends on spatial planting pattern and species composition, offering an opportunity to meet the goals of a sustainable intensification of cocoa plantations through the design and management of optimal agroforestry systems.

Keywords: Cocoa agroforestry systems, Sustainable cocoa production, Plant interactions, Structural Equation Modelling