Árvores em sistemas agroflorestais: ciclagem de nutrientes e formação da matéria orgânica do solo

• Autor(a) principal: Duarte, Edivânia Maria Gourete
• Data de Publicação: 2011
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1630
• topic: Ciclagem de nutrientes; Matéria orgânica do solo; Sequestro de carbono; Nutrient cycling; Soil organic matter; Carbon Sequestration; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::CIENCIA DO SOLO

The benefits of the agroforestry systems in the quality of the soils they have been evidenced recently in many scientific works. However, there is need to deepen the knowledge about the potential of ciclagem of nutrients and the formation of the organic matter of the soil for native arboreal species of tropical ecossystems, with views to the establishment of use strategies and management of those species in agroforestry systems. This study was demanded by farmers that work with agroforestry systems in region of the Zona da Mata of Minas Gerais, and it had as objective, to evaluate the contribution of residues and nutrients for arboreal species used in these agroforestry systems and still, to evaluate the formation of the organic matter and the disponibilization of nutrients starting from these residues. The species selected to evaluate the contribution of residues and nutrients were: Persea americana, Luehea grandiflora, Zeyheria tuberculosa, Erythrina verna, Aegiphila sellowiana, musa sp, Sollanum mauritianum, Inga subnuda and Senna macranthera. The last two species studies were deepened on the formation of the organic matter of the soil and ciclagem of nutrients. The litter fall were collected during one year, in farmers' agroflorestry systems in the municipal districts of Araponga and Divino. Both located in the Zona da Mata of Minas Gerais. For the m. sp they were made three pruning along the year. The dry mass of residues was quantified. They were determined the tenors of nutrients in these residues. For the m. sp it was also determined the tenors of C, lignin, cellulose, hemicellulose and polyphenol. To evaluate the formation of the organic matter in the soil starting from the fedegoso residues and ingá, it was incubated for of 12 months, soil without residues, soil with 5 g of C-residue of the species incorporated, and maintained to the surface. They were appraised in 4 repetitions: the flow of C-CO2, the dry mass remainder of residues, the total tenors of C and N of the soil, of the microbial biomass and of the substances humics besides the light-free organic matter. To the 12 months, it was also evaluated the relationship 13C/12C in the soil, in the humin fraction and in the light-free organic matter. It was also made the routine analysis. The contribution of residues among the species varied from 0,32 to 5,6 Mg ha-1 year-1. The contributions of N, P and K, through residues of the species, varied from 5 to 112 kg ha-1 year-1 of N; 4,1 to 48,6 kg ha-1 year-1 of K and 0,2 to 6,8 kg ha-1 year-1 of P. The S. macranthera, the S. mauritianum and the I. subnuda are among the three species that contributed the largest amounts residues and of N, P, K. I. subnuda, P. americana and L. grandiflora they presented the largest relationships lignin mais polyphenol/N and lignin/N and larger cellulose tenors, indicating slow rate of decomposition of the residues, compared to the others. In the studies of formation of the organic matter and ciclagem of nutrients, it was evident that in the treatment with residues of incorporate S. macranthera, there was, in short period, great increments in the tenors of C of the fractions of the organic matter from the most label, to the most recalcitrant, resulting in 37,4% of derived organic matter of the residue in your humin fraction. These, with effects also on the pH, the stocks of nutrients, the sum of bases, CEC, besides reductions in the capacity of fixation of P and in the saturation for Al3+ in the soil, The treatment with residues of incorporate I. subnuda, in spite of the slow decomposition presented 33,1% of derived organic matter of the residue in your humin fraction. Already, the treatment with S. macranthera residues incubated in the surface it presented 27% of the derived organic matter of the residue in your humin fraction. In these two treatments improvements were also verified in the characteristics chemistries of the soil. However, for the I. subnuda disposed to the surface, this presented 25% of derived organic matter of the residue in your humin fraction, even so little it was differed of the control in the appraised period, confirming that the S. macranthera residues are more efficient than the I. subnuda, so much in the ciclagem of nutrients as in the formation of the organic matter of the soil, besides in stableer fractions. Such a result evidences the importance of planning the design of agroforestry systems using strategic species to carry out the wanted functions and it shows that is also important to motivate practices that promote a larger diversity of fauna of the soil, responsible for the break and partial incorporation of the residues contributed to the soil.