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Cacao: Shade and nutrition effects under Amazonian conditions

Abstract:

This chapter presents recent findings about the response of cacao crop to resources, both nutrients and solar radiation, under Amazonian conditions. Here, we review the results of our studies generated at field trials, and we discuss the crop response to different sources of nitrogen fertilization, as well as the response of cacao to Nitrogen-Phosphorus-Potassium (NPK) interaction. Ammonium sulfate significantly increased yield and fat seed in cacao compared to calcium nitrate and urea. Moreover, leaf nutrient movement during the productive season is described, finding substantial differences among elements and their leaf stages. We also discuss the effect of decreased solar radiation on growth and physiological traits. Mesh was used to reduce solar radiation. Shaded plants significantly reduced stomatal conductance; however, no significant effects on growth and foliar nutritional content were found, but there was an evident genotype effect. Although ammonium sulfate acidifies the soil compared to other N sources, its application improves yield, suggesting crop adaptation to acid soils, typically those of the Amazon region, and ammonium affinity. On the other hand, shade in the Amazon region conditions can alter physiological traits but does not affect plant growth, suggesting acclimatization to radiation modification.