Tropentag, September 16 - 18, 2026, Göttingen "Towards multi-functional agro-ecosystems promoting climate-resilient futures"

Spatial nutrient dynamics in ecuadorian cacao agroforestry

¹University of Rostock, Faculty of Agricultural and Environmental Sciences, Dept. of Agronomy, Germany
²Universidad Regional Amazónica Ikiam, Biomass to Resources Group, Ecuador
³University of Rostock, Agricultural and Environmental Faculty, Germany

Abstract

Agroforestry systems represent a sustainable alternative to conventional land-use systems, particularly in tropical regions affected by deforestation, soil degradation, and nutrient losses. This study investigated the spatial variability of nutrient dynamics in an Ecuadorian cacao agroforestry system established on volcanic ash-derived Andosol. The study focused on two shade-tree species, Cedrelinga cateniformis and Erythrina amazonica —and their influence on soil carbon, nitrogen, phosphorus, and alkaline nutrient pools. A standardised transect-based sampling design was applied to capture spatial gradients between cacao trees (Theobroma cacao) and the respective shade-tree species. Soil samples were collected at two depths, 0–20 cm and 20–40 cm, and analysed for carbon and nitrogen stocks, C/N ratios, phosphorus fractions, Mehlich^-3 extractable nutrients, total concentrations of K, Mg, and Ca, and soil pH. Statistical analyses were performed using linear mixed-effects models and principal component analyses. The results showed only weak and inconsistent spatial differentiation of carbon and nitrogen stocks. This was likely caused by the high background nutrient levels due to strong organo- mineral stabilisation typical of Andosols, which may have masked species-specific effects. In contrast, phosphorus dynamics displayed more pronounced spatial patterns. Local increases in labile and moderately labile P fractions were observed particularly near E. amazonica and, to a lesser extent, near cacao. Alkaline nutrients, especially K, Mg, and Ca, also showed partially elevated total or extractable concentrations near E. amazonica and cacao. C. cateniformis, however, showed no clear measurable effects on the investigated soil parameters. Overall, the study demonstrates that transect-based sampling designs are suitable for detecting fine-scale biotic influences in tropical agroforestry systems. The findings also highlight the dominant role of Andosol properties in shaping nutrient dynamics. Nevertheless, E. amazonica appears to have potential to enhance local phosphorus and nutrient cycling, providing valuable insights for shade-tree selection and nutrient management in cacao agroforestry systems.

Keywords: Shade-tree species

Contact Address: Franz Weingärtner, University of Rostock, Faculty of Agricultural and Environmental Sciences, Dept. of Agronomy, Justus-von-Liebig-Weg 6b, 18059 Rostock, Germany, e-mail: franz.weingaertneruni-rostock.de