ISSN: 1659-2751



Distribution of Fine Roots of Inga edulis and Theobroma cacao in Soils of an Organic Agroforestry System


Agroforestry systems play an important role in the quality of life for millions of people. One of the most economically, socially, and environmentally important agroforestry systems is the association of Theobroma cacao L. with legume trees that form symbiosis with dinitrogen-fixing (N2) bacteria and recycle the nitrogen to the soil. Inga edulis Mart. is one of the most important shade tree species in Central America. Sharing of soil space by these species is poorly known; however, this information would be essential to understand the soil-plant relations and to improve the management of agroforestry systems. This study determined the distribution of fine roots of I. edulis and T. cacao in the soil to a depth of 50 cm during the least rainy (March) and the rainiest season (August) of the year. Two samplings were made, extracting and separating the fine roots from the different layers of the soil profile (0 to 2 cm, 2 to 6 cm, 6 to 10 cm, and to 50 cm by 10-cm-layers). Length, biomass, and necromass of fine roots were measured to study their seasonality and to compare the rooting patterns of T. cacao and I. edulis. The season did not have a statistically significant effect on the length, biomass, nor necromass. The total fine roots length of T. cacao in 0 to 50 cm of soil was 26 762 km ha‑1; 24 % of this length was found in the depth of 0 to 2 cm. The respective numbers were 22 026 km ha-1 and 23 % for I. edulis. The fine root biomass of T. cacao was 3 550 kg ha-1 and that of I. edulis 2 959 kg ha-1. There was no significant difference between the fine root production patterns of T. cacao and I. edulis; this indicates that both species share the same soil resources.

Key words: root biomass, fine root length, nitrogen recycling, humid tropics.

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