Negative effects of water deficit on cocoa tree yield are partially mitigated by irrigation and potassium application

Summary

Yields of most tropical crops are strongly reduced by drought, but this may be partially mitigated by irrigation and potassium application. Understanding the mechanisms regulating these relationships is essential to select crop varieties reaching high yield under environmental stress. We conducted a 2-year field experiment (2020–2022) to investigate the effects of seasonal irrigation, potassium application and their interaction on cocoa reproduction and yield, using six genotypes in Côte d'Ivoire. Potassium application increased pod number and size, contributing significantly to annual yield, but this effect was conditional to soil water availability. Similarly, irrigation when combined with potassium application almost doubled yield from 1.5 to 3.0 kg/tree (2000 kg ha⁻¹ yr⁻¹ to 4000 kg ha⁻¹ yr⁻¹, respectively). This yield effect was mostly the result of positive effects of irrigation on pod number per tree and, to a lesser extent, due to its positive effects on bean number per pod and bean mass. Irrigation effects on pod number were associated with an increased number of cherelles whereas the larger pod number during the major harvest compared to the minor harvest was associated with lower cherelle wilt. We also found a more than two-fold genotypic difference in yield, with the genotypes CI02 and CI03 and to a lesser extent hybrid M having lower yields having lower yields than the genotype CI01. These genotypic yield differences were associated with differences in both cherelle wilt and initial cherelle production rates. The effects of withholding irrigation on yield were significantly dependent on the genotype, reflecting a potential genotypic difference in drought tolerance. The development of climate adaptive strategies for cocoa production requires integrating effects of irrigation, potassium application and cocoa genotype on yields. Future research should focus on unraveling the underlying genotypic and ecophysiological mechanisms of the results presented here, and identifying other potential approaches to enhance the resilience of cocoa to increasing water deficit under climate change.