Decomposition and nutrient release of leguminous plants in coffee agroforestry systems

• Published in: Revista Brasileira de Ciência do Solo 2011-02, Vol.35 (1), p.141-149
• Main Authors: Matos, Eduardo da Silva, Mendonça, Eduardo de Sá, Cardoso, Irene Maria, Lima, Paulo César de, Freese, Dirk
• Format: Article
• Language: English
• Subjects: agroecologia; ciclagem de nutrientes; qualidade do resíduo vegetal; SOIL SCIENCE
• ISSN: 1806-9657; 1806-9657
• DOI: 10.1590/S0100-06832011000100013

Leguminous plants used as green manure are an important nutrient source for coffee plantations, especially for soils with low nutrient levels. Field experiments were conducted in the Zona da Mata of Minas Gerais State, Brazil to evaluate the decomposition and nutrient release rates of four leguminous species used as green manures (Arachis pintoi, Calopogonium mucunoides, Stizolobium aterrimum and Stylosanthes guianensis) in a coffee agroforestry system under two different climate conditions. The initial N contents in plant residues varied from 25.7 to 37.0 g kg-1 and P from 2.4 to 3.0 g kg-1. The lignin/N, lignin/polyphenol and (lignin+polyphenol)/N ratios were low in all residues studied. Mass loss rates were highest in the first 15 days, when 25 % of the residues were decomposed. From 15 to 30 days, the decomposition rate decreased on both farms. On the farm in Pedra Dourada (PD), the decomposition constant k increased in the order C. mucunoides < S. aterrimum < S. guianensis < A. pintoi. On the farm in Araponga (ARA), there was no difference in the decomposition rate among leguminous plants. The N release rates varied from 0.0036 to 0.0096 d-1. Around 32 % of the total N content in the plant material was released in the first 15 days. In ARA, the N concentration in the S. aterrimum residues was always significantly higher than in the other residues. At the end of 360 days, the N released was 78 % in ARA and 89 % in PD of the initial content. Phosphorus was the most rapidly released nutrient (k values from 0.0165 to 0.0394 d-1). Residue decomposition and nutrient release did not correlate with initial residue chemistry and biochemistry, but differences in climatic conditions between the two study sites modified the decomposition rate constants. Leguminosas utilizadas como adubos verdes são consideradas uma fonte importante de nutrientes para a cultura do cafeeiro, especialmente em solos com baixa disponibilidade de nutrientes. Experimentos de campo foram realizados com o objetivo de avaliar as taxas de decomposição e liberação de nutrientes de leguminosas empregadas como adubos verdes em cafezais sob sistemas agroflorestais na Zona da Mata de Minas Gerais. Os teores iniciais de N e P nos materiais vegetais variaram de 25,7 a 37,0 e de 2,4 a 3,0 g kg-1, respectivamente. As relações lignina/N, lignina/polifenol e (lignina+polifenol)/N apresentaram baixos valores para todas as espécies estudadas. As maiores perdas de matéria seca ocorreram nos primeiros 15