Understanding the dynamics of decomposition and release of nutrients from plant residues of different covers, in association or succession, is essential to define more sustainable management strategies in tropical soils. The objective of this study was to estimate the decomposition rates and the release of nutrients during the decomposition of different crop residues with different chemical compositions when in association (Mix) or in succession as residue management. A study was carried out with the respective treatments in a (2 Â 6) + 1 factorial scheme: (a) without and with the addition of Pennisetum americanum residue (L); and (b) six residue crops (legumes and non-legumes) and one additional treatment with residue of millet only; with destructive samples over time (0; 0.08, 0.25 and 0.41 years after incubation). The treatments were distributed in a randomized block design with four replicates. The plant material was processed, and the contents of macro-and micronutrients were determined. The decomposition rates and release of nutrients from the residues were estimated by fitting nonlinear regression models. Residues of only non-legumes, with the exception of sunflower, tend to accumulate and degrade more slowly, resulting in a slow release of nutrients to the soil. Legume residues are more easily decomposed, enabling faster delivery of the nutrients available to the soil. Despite the faster degradation of legume residues, brown hemp was more resistant to decomposition. A combined supply of legume and non-legume residues favoured a diversified pattern of decomposition and release of nutrients among the different residues studied. The knowledge of
The choice of a forage species is one of the most important factors when raising ruminants as a source of income. The objective of this study was to analyze the growth and development of Manihot seedlings as a function of different diameters and lengths of manioc subjected to irrigation in the municipality of Serra Talhada-PE, in the Brazilian semi-arid region. The plant material used for propagation analysis was the maniçoba forage species (Manihot glaziovii Müll. Arg.). The experimental design was completely randomized, in a 3x3 factorial arrangement, with three diameters of maniva (2.0; 3.0 and 4.0 cm) and three lengths of maniva (10; 15 and 20 cm), with eight replications. The analyzed characteristics were: number of shoots, length of shoots and number of leaves. Manihot glaziovii Müll. Arg. seedlings can be produced by asexual propagation, using mantras with a diameter of 3.0 cm and a length of 15 to 20 cm. The use of vegetative propagation presents a good sprouting rate, thus aiding in the propagation of the species.
The knowledge about the dynamics of soil organic matter (SOM) in Antarctica is fundamental to better understand the functioning of terrestrial ecosystems and to analyze the possible impacts of global climate change. Despite this, information on SOM in Maritime Antarctica is still incipient. Thus, we aimed to: i) analyze the elemental and biochemical constitution of the SOM; ii) calculate the soil C and N stocks; iii) perform the dating of the C present in the soils of the Byers Peninsula, Maritime Antarctica; iv) evaluate the soil microbial composition and activity, and; v) identify possible formation routes of the SOM present in the Antarctic biome. The Byers Peninsula with about 60 km 2 - is the largest ice-free area in Maritime Antarctica. It is designated a Specially Protected Antarctic Area (ASPA N° 126) due to its identification as a habitat of global importance, since it hosts breeding colonies of several birds and intense occupation of elephant seals. It is also considered the most important limnological site in the region and the most vulnerable to human interference. Thirteen soil profiles were opened and classified to represent vegetational, geological, geomorphological diversity and distance from the Rotche Dome glacier. The profiles were described and classified according to Soil Taxonomy and World Reference Base for Soil Resources (WRB). Samples were collected from all horizons for chemical and physical characterization. Vegetation material surrounding the profiles was also collected. The characterization of the SOM was done by physical fractionation, determining the POM and MAOM fractions. From these, the determination of the contents of C, N, C/N ratio and the isotopic signatures of δ 13 C and δ 15 N was made, as well as in the collected vegetal materials. In order to biochemically characterize the SOM present in these fractions and the vegetation, thermochemolysis analysis was performed with identification of the compounds by GC/MS to analyze whether there is a correlation between the composition of these vegetables and the biochemical composition of the SOM. Nuclear magnetic resonance spectroscopy ( 13 C NMR CP/MAS) analysis was also performed in order to characterize the SOM at the molecular level and to identify the abundance of functional groups present in it. The C dating by the 14 C method was also performed to assess whether there is a correlation of this with glacier retreat. To understand the microbiological activity present in the Antarctic soils and its relationship with SOM and soil attributes, DNA was extracted from selected samples for identification of the organisms. The high diversity of biotic and abiotic factors acting in Maritime Antarctica directly affects the accumulation, transformation, and stabilization of SOM. Due to the greater presence of ecological niches, greater plant diversity with the presence of vascular plants, and the marked action of avifauna, these factors differentiate the processes involved in the redistribution of SOM between Maritime and Continental Antarctica, in addition to the humidity factor (in the form of net precipitation) being a key factor in the most active humification processes in the soils studied. Keywords: Dynamics of soil organic matter. Elemental and biochemical composition. C and N stocks. Microbial composition. Formation routes of the SOM.
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