Adubos verde na quantidade e qualidade da matéria orgânica do solo de cafezais em sistema de cultivo orgânico

• Autor(a) principal: Coelho, Marino Salgarello
• Data de Publicação: 2009
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/5431
• topic: Agricultura orgânica; Substâncias húmicas; Café orgânico; Organic agriculture; Humic substances; Organic coffee; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::CIENCIA DO SOLO

The use of leguminous as green manure is a widespread practice among family farms of Zona da Mata of Minas Gerais, contributing to the maintenance of the organic systems. With the addition of organic materials in the soil, the humic substances (HS) formation is a important process that increase the cycling time and contribute for soil C and N stocks maintenance. Beyond of the stocks, the constant addition of vegetal waste provides larger biological activity, increase of loads capable to minimize the loss of nutrients of the soil, it increases the aggregation and it reduces the erosion. The leguminous present different characteristics amongst themselves as the biomass production accumulate of nutrients and chemical characteristics. Those ones influence in the formation of the HS in the soil. Those characteristics can also be influenced by the climate of the place and, consequently, influencing in the formation and stabilization of the HS of the soil. The objective of this stud was quantity the C and N contents and the stocks of soil and on HS and evaluate the impact of the leguminous use as green manure in the quality of the HS under cultivation of organic coffee in two different edaphic conditions. Four leguminous species were cultivated between the coffee lines: Arachis pintoi, Calopogonium mucunoides, Stylozanthes guyanensis, Stizolobium aterrimum and spontaneous species, with prevalence of the Brachiaria plantaginea, during 4 years in family farmers of Araponga-MG (northwest exposure) and Pedra Dourada-MG (south exposure) in the area of the Zona da Mata of Minas Gerais. After 4 years of manure, was collected the soil in two depths (0-5 and 5-20 cm) and analyzed the content of Total Organic Carbon (TOC) and Total Nitrogen (TN) in the soil and on HS. In the farms were collected soil samples in volumetric rings to calculate the soil density. For the qualitative evaluation of the HS, they were extracted and purified for obtaining of the fulvic acids (FA) and humic acids (HA). FA and HA were accomplished elementary analysis (CHNO), UV-visible spectroscopy, Infra Red spectroscopy and termogravimetric of the purified material. The manure with leguminous and spontaneous species used as green manure can maintain the content of TOC, TN and the content of C and N on SH in the soil, maintaining the close values to the native forest. In the handling after 4 years of cultivation, just the humic fraction more labile (fulvic acids fraction - FAF) had effect in the treatments, what wasn t observed in the content of the most recalcitrant fractions (humic acids fraction HAF and humin fraction - HF). The content of C and N in HF were more the other fractions. The edaphic conditions promoted effect in the formation and in the stock of C and total N and of HS, and in the farm under conditions of smaller sunstroke (Pedra Dourada), the soil presented larger stocks of C and N. The effect of the position in the landscape (face exposure) it was superior to the effect of the clay content. The analyses to evaluate the quality, was verified that HA possesses larger weight molecular, larger hidrofobicity and larger condensation, for the presence of larger proportion of aromatic compositions and with larger content of C, checking larger structural stability in relation to FA. The farm under larger light incidence and temperature and smaller humidity, due to face of exposure northwest solar presented in FA, larger relationship O/C, relationship E4/E6, relationship 3300/1700 and value of inferior ITG, favoring the formation of FA with larger mass molar in relation to the found in the farm under smaller light incidence and temperature and larger humidity. In HA, the treatments obtained little effect due to the time of handling of the leguminous that they were for only 4 years. Among the leguminous, in FA, the treatment with Calopogonium mucunoides presented low content of C and high content of O in his composition, corroborating for the mass loss the temperature lowers, characterizing a material of easy mineralization. Already the treatment with Stylozanthes guyanensis provided FA with smaller molecular weight.