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Araujo A.P.,Federal Rural University of Rio de Janeiro | Del Pin B.,Federal Rural University of Rio de Janeiro | Teixeira M.G.,Embrapa Agrobiologia
Field Crops Research | Year: 2012

Leaf senescence and its concomitant remobilization of nutrients supplies part of seed demand, and leaf decay also contributes to nutrient cycling. However, a nutrient budget of common bean (Phaseolus vulgaris) crop that considers senescent leaves is lacking. The purpose of this study was to measure the amounts of N and P in senescent leaves of common bean cultivars and their contribution to the crop nutrient budget. Seven bean cultivars were grown in a field experiment, where shoot biomass was sampled at each week after flowering and senesced leaves were collected twice weekly. Grain yield and the actual and apparent harvest indices (respectively including or not senescent leaves) were measured at maturity. Leaf decay in bean crop was low until 3 weeks after flowering and increased until grain maturity. Senesced leaves collected throughout the growth cycle reached 96.4, 1.94 and 0.15gm -2 of dry mass, N and P, respectively, which corresponded to 29%, 28% and 19% of the total biomass, N and P accumulated by the crop. Bean cultivars differed in the amounts of mass, N and P deposited by senesced leaves, for apparent harvest indices of biomass, N and P, but not for actual harvest indices. Of the amount present in the leaf canopy 2 weeks after flowering, 44% of N and 51% of P was further remobilized to seeds, which corresponded to 33% of N and 25% of P accumulated by grains at maturity. A subsequent decomposition study with litterbags provided half-lives of 80, 179 and 64 days, respectively, for senesced leaves, stems and podwalls produced after pod threshing, with similar patterns of N and P release. The results illustrate the remobilization of N and P from leaves to seeds during pod-filling and stress the relevance of senescent leaves in the nutrient budgets of legume crops. © 2011 Elsevier B.V. Source

dos Reis Martins M.,Embrapa Agrobiologia | Angers D.A.,Agriculture and Agri Food Canada
Geoderma | Year: 2015

Sequestration of atmospheric carbon (C) and erosion prevention are two ecosystem services that can be provided by plants through their impact on soil aggregation and organic matter. We propose a conceptual model aimed at generalizing the effect of plant material decomposition on C sequestration and soil water-stable macroaggregation (WSMA). We characterized plant material mineralization using a first order exponential plus linear equation in which parameter b describes the mineralization rate of the labile C pool, followed by a low mineralization rate of the non-labile C pool (parameter k). We propose that there are two selected types of plant materials that have differential positive effects on soil organic C (SOC) or soil WSMA: type-. B and type-. K plant materials. During decomposition in soil, type-. B plant materials present a high b parameter followed by low k and have a positive effect on SOC, whereas type-. K plant materials show an inverse mineralization pattern and favor longevity of soil WSMA. In our field and laboratory experiments, the model for type-. B plant material was pigeon pea [. Cajanus cajan (L.) Millsp.] which was characterized by high lignin and N contents, and the model for type-. K plant material was mature corn (. Zea mays L.) residue which contained high levels of pentoses, the main component of hemicellulose. According to this model, type-. B plants would be adequate in strategies aiming primarily at soil C sequestration, while type-. K would be more appropriate in reducing a soil's susceptibility to physical degradation. Cropping or reclamation systems involving both plant types would contribute to both ecosystem services. © 2014. Source

da Silva R.F.,State University of Mato Grosso do Sul | de Fatima Guimaraes M.,State University Londrina | de Aquino A.M.,Embrapa Agrobiologia | Mercante F.M.,Embrapa Agropecuaria Oeste
Pesquisa Agropecuaria Brasileira | Year: 2011

The objective of this work was to evaluate the effects of the integrated crop-livestock system on the morphological, physical and biological properties of soil. The experiment was carried out in Dourados, Mato Grosso do Sul State, Brazil, in a typic Hapludox soil. The following systems were sampled: grain crop under conventional soil tillage system, integrated crop-livestock system under no-tillage, continuous Urochloa decumbens (Syn. Brachiaria decumbens) pasture and natural system. In each system, a trench was opened in order to detect morphological changes caused by different management, using the cultural profile method. Assessments of soil macroinvertebrates were done according to the method Tropical Soil Biology and Fertility. Undisturbed soil samples were also used to assess the physical attributes of soil (soil density, total porosity, macro and microporosity). Among the cultivated systems, better soil structure was observed in the integrated crop-livestock system, in the layers 0.0.1 and m. The systems under crop-livestock and pasture continuously cultivated favored a more biologically active soil environment, among the other agricultural systems. The visualization of soil attributes showed that crop-livestock integration is a promising strategy to develop sustainable production systems and that the period of two years of management is considered suitable for crop-pasture rotation. Source

De Carvalho F.,Federal University of Minas Gerais | de Souza F.A.,Embrapa Milho e Sorgo Nucleo de Biologia Aplicada | Carrenho R.,State University of Maringa | Moreira F.M.D.S.,Federal University of Lavras | And 2 more authors.
Applied Soil Ecology | Year: 2012

The high diversity in rupestrian field vegetation has been attributed to the mosaic of environments formed by several soil classes, rugged relief and microclimatic variation. Although advances in the knowledge of some biological areas in rupestrian fields have been made, little is known about the relevance of soil microorganisms and their relationships with the vegetation. Symbiosis with arbuscular mycorrhizal fungi (AMF) is one of the most studied interactions between microorganisms and plants, because they are ubiquitous and contribute to the sustainability of ecosystems. This study aimed to investigate the occurrence and diversity of AMF species and to evaluate their relationship with soil physicochemical attributes and plant diversity in different habitats of the rupestrian fields from the Cadeia do Espinhaço, Serra do Cipó, Brazil. These rupestrian fields were delimited into five distinct habitats: rock outcrop, quartz gravel fields, sandy bogs, peat bogs and the Cerrado. Forty-nine AMF species were identified as belonging to nine families and twelve genera. Among them, Acaulospora colossica and Pacispora dominikii were found for the first time in Brazil. The results of this study suggest that the diversity of AMF is related to the heterogeneity of habitats and that the soil texture (coarse sand, gravel and silt) is better related to the structure of these fungi communities than to the soil chemical attributes. Plant species richness was related to AMF richness only in the quartz gravel field, rocky outcrop, and sandy bog habitats. Considering these habitats constitute one of the most menaced ecosystems on the planet, our survey provides information to improve knowledge about rupestrian field biodiversity, thus supporting policy actions for its conservation and preservation. © 2011 Elsevier B.V. Source

Ferreira D.A.,Federal University of Goais | Carneiro M.A.C.,UFG | Saggin Jr. O.J.,Embrapa Agrobiologia
Revista Brasileira de Ciencia do Solo | Year: 2012

The alterations in the communities of arbuscular mycorrhizal fungi (AMF) induced by changes in land use and different agricultural uses are still insufficiently studied, particularly in the Cerrado biome. This study evaluated how human interference by management and land use change affect the AMF density and diversity in a Cerrado Oxisol. The study evaluated five areas: Riparian Forest (MC), Riparian Forest Edge (BM), Pasture (Past), no-till monoculture (PD) and Riparian Deforested Area (AD). In each area, 20 plots of 250 m2 were marked. Within each plot, 10 subsamples were randomly collected to form a composite soil sample. The density and diversity of AMF spores, by morphological characteristics, were determined for each composite sample. In the PD and AD areas, the density of recovered spores and mycorrhizal colonization were lower than in the other areas due to the low density of living plants. The AMF families with highest abundance in the study areas were Acaulosporaceae, Glomeraceae and Gigasporaceae, the first two dominant in the areas with leass anthropogenic influence MC and BM. The most frequent AMF species were Acaulospora scrobiculata, Glomus macrocarpum and Acaulospora tuberculata, of which the first two appeared in all areas and the third was absent only in PD. These species have great capacity to adapt to changing environments. The occurrence of the species Acaulospora rehmii, Acaulospora sp.3, Glomus etunicatum, Glomus tortuosum, Glomus sp.1, Gigaspora sp.2 and Scutellospora heterogama was low, and were recovered in only one of the study areas. The area with highest density and species occurrence was Past with 414 spores (individuals) and 11 AMF species. The highest and lowest Shannon diversity (H') index were calculated for Past and BM, respectively. Principal component analysis indicated the formation of three groups, the first with MC and BM, the second with PD and AD and the third with only Past. It was concluded that land use changes modify the AMF community, which may increase spore density and diversity, as in the case of Pasture, or reduced, in the case of deforestation. Source

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