Wednesday, 8 October 2008

George R. Brown Convention Center, Exhibit Hall E

Antonio C. Gama-Rodrigues, Soil Laboratory, Universidade Estadual do Norte Fluminense, CEP 28013-602, Campos dos Goytacazes, RJ, CEP 28013-60, Brazil, Emanuela F. Gama-Rodrigues, Soil Laboratory, Universidade Estadual do Norte Fluminense, CEP 28013-602, Campos dos Goytacazes, RJ, Campos dos Goytacazes, CEP 28013-60, Brazil, P.K. Ramachandran Nair, School of Forest Resources & Conservation, University of Florida, PO Box 110410, Gainesville, FL 32611-0410, Nicholas B. Comerford, Soil and Water Science Department, University of Florida, 2169 McCarty Hall, PO Box 110290, Gainesville, FL 32611, Virupax Baligar, Bldg 001 Rm 225 BARC-W, USDA - ARS, USDA ARS ACSL, 10300 Baltimore Ave, Beltsville, MD 20705 and Regina C. R. Machado, Research Station of Almirante Cacau, Bahia, Brazil

In Brazil, cacao (Theobroma cacao) agroforestry systems are adopted and promoted mostly in highly weathered soils with acidic pH and low fertility. Therefore, it is important to optimize nutrient cycling in these systems to maintain sustainable production. The objectives of this study were to determine the soil carbon (C) content; soil microbial biomass C, nitrogen (N), and phosphorus (P) contents; extent of soil C and N mineralization; and total and labile (fast mineralization) soil organic P in different cacao agroforestry systems in southern Bahia, Brazil. Three systems were selected: cacao under Erythrina poeppigiana, cacao under natural forest (‘Cabruca’), and a cacao germplasm collection area, all in reddish yellow Oxisols or Inceptisols. Soil samples were collected from four depth classes (0 – 5, 5 – 15, 15 – 30, and 30 – 50 cm) for soil C analysis. Microbial attributes and organic P were measured on only the 0 – 5 cm depth. Mean soil C ranged from 70 to 108 Mg ha^-1, microbial C from 173 to 356 kg ha^-1, microbial N from 117 to 212 kg ha^-1, and microbial P from 3 to 9 kg ha^-1. The amount of soil C mineralized in 111 days ranged from 23 to 61 kg ha^-1and that of N from 61 to 81 kg ha^-1. Total organic P content ranged from 11 to 195 kg ha^-1 and labile organic P from 5 to 10 kg ha^-1. This study shows that cacao agroforestry systems store relatively high amounts of C in the soil and consequently have a potential to increase the soil quality and reduce the atmospheric CO₂ emission. Furthermore, the high amounts of soil microbial biomass and organic P could be relevant for cacao nutrition considering the low amount of N (24 kg ha^-1) and P (5 kg ha^-1) exported through cacao seed harvest.

See more of: Manures, Cover Crops, and Soil Amendments (Posters)
See more of: S04 Soil Fertility & Plant Nutrition

2008 Joint Annual Meeting (5-9 Oct. 2008): Soil Carbon and Nutrient Contents under Cacao Agroforestry Systems in Bahia, Brazil.

748-14 Soil Carbon and Nutrient Contents under Cacao Agroforestry Systems in Bahia, Brazil.