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Organic Material Decomposition and Mineral Nutrient Dynamics in a Leguminous Tree-Enriched Mulch System in Amazon

Josť Henrique Cattanio, UFPA, (Presenting)
Ronald Kuehne, University of Goettingen,
Paul Vlek, University of Bonn,

The new technique proposed for Amazonian agriculture includes rotational fallow systems with planted leguminous trees and replacing burning by mulching of biomass. Decomposition and nutrient release from mulch were studied using fine-mesh litterbags with five different leguminous enrichment species and the natural fallow vegetation as the control. The samples from each treatment were analysed for total C, N, P, K, Ca, Mg, lignin, cellulose content and soluble polyphenol at different sampling times during the course of one year. The decomposition rate constant varied with species and time. Weigh losses from the decomposed litter bag material after 96 days was 30.1% for A. angustissima, 32.7% for S. paniculatum, 33.9% for I. edulis and the Fallow vegetation, 45.2% for A. mangium and 63.6% for C. racemosa. All studied treatments exhibited immobilisation of N and P. N mineralisation showed a negative correlation with phenol, C-to-N ratio, lignin + phenolto-N ratio, and phenol-to-phosphorus ratios and with nitrogen content in the litterbags material. After 362 days of field incubation, on average (pooled over all treatments), 3.3% of the K, 32.2% of Ca and 22.4% of Mg remained in the mulch. The result confirms that low quality and high amount of organic carbon as mulch application limits the quantity of energy available for microorganism and it increases de immobilisation of nutrient for biomass decomposition. The increase of agriculture productivity needs cannot be met by a major expansion of cultivated areas so intensification and improvement of currently managed land is unavoidable. Enriched fallow management with slash and mulch system can be an option to restore soil organic matter and maintain nutrients in the humid tropic ecosystem

Science Theme:  ND (Nutrient Dynamics)

Session:  1B: Nutrient Cycling in Terrestrial and Aquatic Systems

Presentation Type:  Oral

Abstract ID: 96

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