Journal
SCIENCE OF THE TOTAL ENVIRONMENT
Volume 657, Issue -, Pages 558-567Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.scitotenv.2018.12.050
Keywords
Theobroma cacao; Agroforestry; Organic farming; Cover crop; Root competition; System yield
Categories
Funding
- Swiss Agency for Development and Cooperation (SDC)
- Liechtenstein Development Service (LED)
- Biovision Foundation for Ecological Development
- Coop Sustainability Fund
- Johannes Hubner Stiftung, Giessen, Germany
- Deutsche Forschungsgemeinschaft
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Farmers expect yield reduction of cash crops like cocoa when growing in agroforestry systems compared to monocultures, due to competition for resources, e.g. nutrients and water. However, complementarities between species in the use of resources may improve resource use efficiency and result in higher system performance. Cocoa trees have a shallow rooting system while the rooting characteristics of the associated trees are mainly unknown. This work investigates fine root distribution and production in five cocoa production systems: two monocultures and two agroforestry systems under conventional and organic farming, and a successional agroforestry system. In the organic systems a perennial leguminous cover crop was planted and compost was added, while herbicides and chemical fertilizers were applied in the conventional ones. We measured cocoa fine root parameters in the top 10 cm of soil and annual total fine root production at 0-25 and 25-50 cm depth. We related the root data with both the aboveground performance (tree and herbaceous biomass), and the cocoa and system yields. Cocoa fine roots were homogenously distributed over the plot area. Around 80% of the total fine roots were located in the upper 25 cm of soil. The total fine root production was 4-times higher in the agroforestry systems and the organic monoculture than in the conventional monoculture. The roots of the associated tree species were located in the same soil space as the cocoa roots and, in principle, competed for the same soil resources. The cocoa yield was lower in the agroforestry systems, but the additional crops generated a higher system yield and aboveground biomass than the conventional cocoa monocultures, implying effective resource exploitation. The leguminous cover crop in the organic monoculture competed with the cocoa trees for nutrients, which may explain the lower cocoa yield in this system in contrast with the conventional monoculture. (C) 2018 Elsevier B.V. All rights reserved.
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