Frações oxidáveis do carbono orgânico de latossolo cultivado com cafeeiro em diferentes espaçamentos de plantio

Abstract

RESUMOObjetivou-se com este estudo avaliar a suscetibilidade à oxidação pelo permanganato de potássio do carbono presente em Latossolo Vermelho distroférrico típico, cultivado com cafeeiro (Coffea arabica L.), em diferentes espaçamentos de plantio, em experimento localizado na Fazenda Experimental da EPAMIG, em Machado (MG). Os tratamentos avaliados, instalados a campo em 1992, consistiram na combinação de quatro espaçamentos entre linhas (2,0, 2,5, 3,0 e 3,5 m), com três espaçamentos entre plantas (0,5, 0,75 e 1,0 m). Uma área de mata próxima ao experimento foi amostrada e usada como referência. Para a avaliação do grau de oxidação do carbono orgânico (CO), as amostras de solo foram coletadas na entrelinha (EL) e na projeção da copa (PC) do cafeeiro, nas camadas de solo de 0-0,05 e 0-0,1 m. Na camada superficial do solo (0-0,05 m), os teores de C lábil na entrelinha são, em geral, maiores do que os observados nas amostras coletadas na projeção da copa do cafeeiro. A amplitude de variação dos teores de C nas frações orgânicas obedece à seguinte ordem decrescente: C lábil> C não lábil > C orgânico, o que indica o maior potencial do C lábil em avaliar o impacto de diferentes sistemas de adensamento e manejo do cafeeiro, sobre os compartimentos de matéria orgânica. Os teores de C lábil e C não lábil não são influenciados pelo número de plantas por área, mas são dependentes da largura de rua do cafeeiro, da profundidade e do local de coleta das amostras de solo. Termos para indexação:Coffea arabica L., densidade de plantio, matéria orgânica do solo, carbono lábil. ABSTRACTThe present work was carried out to evaluate soil carbon susceptibility to oxidation by potassium permanganate in adystroferric Red Latosol (Oxisol) cultivated with coffee (Coffea arabica L.) at different planting spacings. The experiment was installed in 1992 at the Experimental Farm of EPAMIG, in Machado (Minas Gerais State-Brazil). Treatments consisted of a combination of four row spacings (2.0, 2.5, 3.0, and 3.5 m) with three spacings within the row (0.5, 0.75, and 1.0 m). As a reference, soil samples were also collected in an area under native forest. For assessing the degree of oxidation of the organic carbon (OC), soil samples were collected at the inter-row and in the coffee canopy projection, at the 0-0.05 and 0-0.1 m soil depths. Labile C in inter-row samples located at the soil surface layer(0-0.05 m) is, in general, higher than that measured in samples collected in the coffee canopy projection. The amplitude of variation of C in different soil organic fractions follows the order: labile C > non labile C > Organic C.Thus, labile C could be used as a sensitive index to evaluate the impact of different coffee planting systems and management practices on soil organic matter pools. Labile and non labile C contents are not influenced by the number of coffee plants per area. However, these indexes are dependent on coffee plants inter-row spacings, soil depth and sampling location.

Microbiological properties and oxidizable organic carbon fractions of an oxisol under coffee with split phosphorus applications and irrigation regimes

“…The values for the different oxidizable fractions are within the range of values published elsewhere in studies with different soils under different uses (Rangel et al, 2008;Loss et al, 2010;Barreto et al, 2011). With the exception of F4, in the 5-10 cm layer, irrigation resulted in higher contents of TOC and of the fractions in both layers.…”

“…In general, the results of research with fractions of OC oxidation show that management systems and/or crops that favor frequent additions of organic material to the soil tend to have a higher proportion of C in this fraction at the expense of the more recalcitrant fractions (F3 and F4) (Chan et al, 2001;Andrade et al, 2005;Rangel et al, 2008;Loss et al, 2010;Barreto et al, 2011).…”

Physical properties and particle-size fractions of soil organic matter in crop-livestock integration

“…No significant differences were observed for CMI between the rotation systems and NF, showing that the tested systems can increase the preservation and restore the levels and/or quality of the organic fractions in the studied area. When computing the CMI, the distribution patterns and carbon contents of compartments related to the chemical composition of SOM may differ from one site and one crop to another and not reflect the conditions observed in areas with natural vegetation, which are almost always the best to ensure the functionality of the matrix soil (Rangel et al, 2008).…”

“…However, even when cotton is used, which usually acts as a C source for the atmosphere when grown in monoculture, planted in rotation with other crops, there seems to be a mechanism of restoration of the C levels in the soil promoted by the other crops of the systems studied. For Rangel et al (2008), reductions in C pools and changes in the SOM composition affect the sustainability of agroecosystems. Corazza et al (1999) studied different management systems as C source or deposit for cerrado vegetation and concluded that in relation to the natural system, more C was accumulated in systems without soil disturbance (no-tillage, planted pasture and eucalyptus reforestation) and lowest in the tilled systems (disk plow and heavy disk harrow), which acted as a CO 2 deposit and source to the atmosphere, respectively.…”

“…It is assumed that the fraction that passes through the sieve contains the MOM fraction, which was calculated as the difference between SOM and POM and the C content in it was also determined by subtraction (Salton et al, 2005). These data were used to compute some indices, as proposed by Rangel et al (2008) Accumulated carbon/carbon pool was computed as the product of its contents (g kg -1 of soil) and soil density in the corresponding area and layer (in g dm -3 ) and transformed into Mg ha -1 , when a specific layer is considered: e) Stock C = Ct x Ds x layer thickness (cm) The results were subjected to analysis of variance and when significant, the Tukey test was applied at 5 % for mean comparison. Simple linear correlations for pair combinations were also established, with the soil physical and chemical properties studied.…”