TY - JOUR

T1 - Combined effects of shade and drought on physiology, growth, and yield of mature cocoa trees

AU - Mensah, Eric Opoku

AU - Ræbild, Anders

AU - Asare, Richard

AU - Amoatey, Christiana A.

AU - Markussen, Bo

AU - Owusu, Kwadwo

AU - Asitoakor, Bismark Kwesi

AU - Vaast, Philippe

N1 - Publisher Copyright: © 2023 The Authors

PY - 2023

Y1 - 2023

N2 - Climate models predict decreasing precipitation and increasing air temperature, causing concern for the future of cocoa in the major producing regions worldwide. It has been suggested that shade could alleviate stress by reducing radiation intensity and conserving soil moisture, but few on-farm cocoa studies are testing this hypothesis. Here, for 33 months, we subjected twelve-year cocoa plants in Ghana to three levels of rainwater suppression (full rainwater, 1/3 rainwater suppression and 2/3 rainwater suppression) under full sun or 40 % uniform shade in a split plot design, monitoring soil moisture, physiological parameters, growth, and yield. Volumetric soil moisture (ϴw) contents in the treatments ranged between 0.20 and 0.45 m3m−3 and increased under shade. Rainwater suppression decreased leaf water potentials (ѱw), reaching −1.5 MPa in full sun conditions indicating severe drought. Stomatal conductance (gs) was decreased under the full sun but was not affected by rainwater suppression, illustrating the limited control of water loss in cocoa plants. Although pre-dawn chlorophyll fluorescence (Fv/Fm) indicated photoinhibition, rates of photosynthesis (Pn) were highest in full sun. On the other hand, litter fall was highest in the full sun and under water stress, while diameter growth and carbon accumulation increased in the shade but was negatively affected by rainwater suppression. Abortion of fruits and damage to pods were high under shade, but dry bean yield was higher compared to under the full sun. The absence of interactions between shade treatments and rainwater suppression suggests that shade may improve the performance of cocoa, but not sufficiently to counteract the negative effects of water stress under field conditions.

AB - Climate models predict decreasing precipitation and increasing air temperature, causing concern for the future of cocoa in the major producing regions worldwide. It has been suggested that shade could alleviate stress by reducing radiation intensity and conserving soil moisture, but few on-farm cocoa studies are testing this hypothesis. Here, for 33 months, we subjected twelve-year cocoa plants in Ghana to three levels of rainwater suppression (full rainwater, 1/3 rainwater suppression and 2/3 rainwater suppression) under full sun or 40 % uniform shade in a split plot design, monitoring soil moisture, physiological parameters, growth, and yield. Volumetric soil moisture (ϴw) contents in the treatments ranged between 0.20 and 0.45 m3m−3 and increased under shade. Rainwater suppression decreased leaf water potentials (ѱw), reaching −1.5 MPa in full sun conditions indicating severe drought. Stomatal conductance (gs) was decreased under the full sun but was not affected by rainwater suppression, illustrating the limited control of water loss in cocoa plants. Although pre-dawn chlorophyll fluorescence (Fv/Fm) indicated photoinhibition, rates of photosynthesis (Pn) were highest in full sun. On the other hand, litter fall was highest in the full sun and under water stress, while diameter growth and carbon accumulation increased in the shade but was negatively affected by rainwater suppression. Abortion of fruits and damage to pods were high under shade, but dry bean yield was higher compared to under the full sun. The absence of interactions between shade treatments and rainwater suppression suggests that shade may improve the performance of cocoa, but not sufficiently to counteract the negative effects of water stress under field conditions.

KW - Agroforestry

KW - Carbon accumulation

KW - Climate change

KW - Cocoa

KW - Drought adaptation

KW - Shade

U2 - 10.1016/j.scitotenv.2023.165657

DO - 10.1016/j.scitotenv.2023.165657

M3 - Journal article

C2 - 37478928

AN - SCOPUS:85166241527

VL - 899

JO - Science of the Total Environment

JF - Science of the Total Environment

SN - 0048-9697

M1 - 165657

ER -