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O aquecimento global é atribuído ao aumento das emissões de gases de efeito estufa (GEE), como dióxido de carbono (CO2), metano (CH4) e óxido nitroso (N2O). As mudanças no uso da terra têm impactos significativos nas emissões de GEE, sendo responsáveis por aproximadamente 44% das emissões do país em 2019. Essa é uma revisão que aborda as principais rotas de formação dos GEE no solo com foco na influência das mudanças do uso da terra nas emissões de GEE. Constata-se que as emissões de CO2 pelo solo estão relacionadas à respiração de raízes, microrganismos e decomposição da matéria orgânica (MO) do solo, assim mudanças no uso da terra podem alterar as características do solo, favorecendo a intensificação das emissões de CO2. As emissões de CH4 pelo solo ocorrem em condições de anaerobiose por microrganismos metanogênicos, no entanto as mudanças no uso da terra, como a conversão de florestas em pastagens, podem aumentar as emissões de CH4 devido a uma maior concentração de microrganismos metanogênicos no solo. Já o N2O é produzido no solo durante o processo de nitrificação e desnitrificação por microrganismos, e a fertilização nitrogenada em áreas agrícolas pode aumentar as emissões de N2O, especialmente quando associada à umidade e disponibilidade de carbono orgânico no solo. Destaca-se a importância de compreender as dinâmicas de formação e emissão de GEE decorrentes das mudanças de uso da terra, pois estratégias eficientes de manejo podem reduzir essas emissões e contribuir para o cumprimento das metas do Brasil em relação à redução de GEE estabelecidas em acordos internacionais.

Grasslands cover about 40% of the Earth's surface, and in addition to forage production, they provide ecosystem services such as carbon storage and soil protection, so they are considered important sinks of greenhouse gases (GHG). Despite this, the dung from grazing animals deposited in the soil, usually unevenly distributed in relatively small areas, can provide favorable conditions for methane (CH4) emissions. The objective of this study was to evaluate the accumulated methane emissions in the dung of different species of herbivores (sheep, goats, beef cattle, dairy cattle, and horses). Incubation was carried out in a greenhouse. Soil collection was carried out in an area of Palisade grass planted more than 10 years ago. The experiment was carried out in a completely randomized design with five treatments and five replications. The treatments used were dung from sheep, goats, beef cattle, dairy cattle, and horses. The amounts added per treatment were 400 g of soil and 100 g of fresh dung. The soil was maintained at a constant temperature and 18% volumetric moisture throughout the experimental period. The remaining vials were kept in the incubator at a constant temperature of 25.0 ± 1.0 °C and 80% relative humidity during the test period. After applying the treatments, samples were collected daily during the first week. From the 8th day after application (DAA) onward, sampling was performed three times a week until 30 DAA, and weekly until 100 days of evaluation. Sampling was performed after closing the chambers (T0) and after 30 minutes (T30). A difference was found between the accumulated emissions of CH4 from the evaluated dung. The highest emissions were released by dairy cattle manure, followed by beef cattle (p

The carbon (C) and nitrogen (N) contents of the soil, when associated through the C:N ratio, make it possible to obtain indices that reveal the quality of soil organic matter (OM), as well as the decomposition efficiency, conversion efficiency of carbon and organic nitrogen into their mineral forms, and the dynamics of these nutrients in the soil. According to the literature, the C:N ratio can be between 30 - 100 in native forest areas and 20 - 30 in cultivated areas. The objective of this work was to evaluate the relationship between soil carbon and nitrogen in integrated systems, monoculture pasture, and native Cerrado forest. Undeformed soil samples were collected once at a site located in the municipality of Barbacena, MG, at depths 0-5 cm, 5-10 cm, 10-20 cm and 20-30 cm in four distinct areas, designated as treatment 1: pasture monoculture (MP) of Urochloa decumbens cv. Basilisk with 27 years of plantation; treatment 2: grass-legume combination (GLC), composed of Urochloa decumbens cv. Basilisk and Arachis pintoi cv. Amarillo with 25 years of plantation; treatment 3: silvopastoral system (SSP), composed of Eucalyptus urophylla planted 13 years ago in an area where Urochloa decumbens cv. Basiliskwas was already established for 14 years; and treatment 4: native forest (NF) of the Cerrado biome with 37 years of regeneration. The quantification of total organic C was performed according to the method proposed by Yeomans and Bremmer (1988); and the determination of total N was performed as proposed by Bremner and Mulvaney (1982) and adapted by Mendonça and Matos (2005). The experimental design completely randomized, with five replications in each treatment. The data were submitted to statistical analysis using the Kruskall-Wallis test and Dunn's test. The NF system showed the highest C:N ratio at all evaluated depths (32.3 – 40.6), being statistically similar to MP (30 – 37) and SSP (25.5 – 28.5). The CGL system did not show statistical similarity with MP and FN, but it was equal to SSP (p

The objective of this study was to investigate whether the chemical composition of the dung of different species of herbivores (sheep, goats, beef cattle, dairy cattle and horses) can be an indicator of N2O and CH4 emissions. The incubation was conducted in a greenhouse. Soil collection was carried out in an area of Urochloa brizantha cv. Marandu that has been established for more than 10 years. The experiment was carried out in a completely randomized design with five treatments and five replications. The treatments used were dung from sheep, goats, beef cattle, dairy cattle and horses. The amounts added per treatment were 400 g of soil and 100 g of fresh dung. The soil was maintained at a constant temperature of 18% volumetric moisture throughout the experimental period. The dung samples were dried in forced-air ovens at 55 °C, then ground and analyzed for chemical composition. We evaluated dry matter (DM), volatile solids (VS), total nitrogen (TN), non-protein nitrogen (NPN), neutral detergent fiber (NDF), acid detergent fiber (ADF), insoluble nitrogen content in neutral detergent fiber (NDIN), insoluble nitrogen and total carbon from dung. After the application of the treatments, sampling was carried out daily during the first week. From the 8th day after application (DAA) onward, collections were made three times a week up to 30 DAA, and weekly up to 100 days of evaluation. Sampling was performed after the chambers were closed (T0), and after 30 minutes (T30). To reduce the dimensionality of the data and provide insights into the effect of the chemical composition of dung on N2O and CH4 emissions, principal component analysis (PCA) was performed. For this, the data were evaluated in terms of the assumptions of the test. We utilized a factorial map to describe the effect of the chemical composition of dung on the different animal species with emissions of N2O. The PCA divided the original dataset to achieve high dimensionality of latent hits, namely PC1 and PC2, as a result of orthogonalization. The primary (61.9%) and secondary (19.6%) components together represented 81.5% of the emissions. The first principal component had positive linear correlations with the eigenvalues, namely N2O (r = 0.89, p-value

The aim of this study was to evaluate the cumulative emissions and fraction of N emitted as N2O in dung of different species of herbivores (sheep, goats, beef cattle, dairy cattle and horses). The incubation was conducted in a greenhouse. Soil collection was carried out in an area of Urochloa brizantha cv. Marandu that has been established for more than 10 years. The experiment was carried out in a completely randomized design with five treatments and five replications. The treatments used were dung from sheep, goats, beef cattle, dairy cattle and horses. The amounts added per treatment were 400 g of soil and 100 g of fresh dung. The soil was maintained at a constant temperature and 18% volumetric moisture throughout the experimental period. The remaining Mason jars were kept in the incubator regulated at a constant temperature of 25.0 ± 1.0 ºC and 80% relative humidity. The dung samples were dried in forced-air ovens at 55 °C, then ground and analyzed for dry matter (DM) and total nitrogen (TN). After the application of the treatments, the sampling was carried out daily during the first week. From the 8th day after application (DAA) onward, samples were collected three times a week up to 30 DAA, and weekly up to 100 days of evaluation. Sampling was performed after the chambers were closed (T0), and after 30 minutes (T30). There was a difference in cumulative N2O emissions between the evaluated dung, with the lowest emissions for dung of dairy cattle and horses, and the highest cumulative emission for goat dung (p

Integrated production systems can stimulate the growth and reproduction of soil microbiota responsible for nutrient cycling. The use of quality indicators such as soil microbial biomass carbon (SMBC) can help formulate strategies that preserve organic matter and enable more sustainable production systems. The objective of this study was to evaluate soil microbial biomass carbon in integrated production systems, a monoculture system of pasture, and native Cerrado forest. Undeformed soil samples were collected at a site located in the municipality of Barbacena, MG, at depths 0-5 cm, 5-10 cm, 10-20 cm and 20-30 cm in four distinct areas, formed by treatment 1: monoculture to pasture (MP) of Urochloa decumbens cv. Basilisk; treatment 2: combination of legumes and grasses (CLG) composed of Urochloa decumbens cv. Basilisk and Arachis pintoi cv. Amarillo, with a history of conventional cultivation; treatment 3: silvopastoral system (SSP), composed of Urochloa decumbens cv. Basilisk and Eucalyptus urophylla; and treatment 4: native forest (NF) of the Cerrado biome, with 37 years of regeneration. To determine the carbon in the biomass, the fumigation-extraction method proposed by Vance et al. (1987) was applied, with fumigation and the addition of chloroform (without alcohol) in the sample, as suggested by Brookes et al. (1982) and Witt et al. (2000). The experimental design was completely randomized, with five replications in each treatment. The data obtained were submitted to statistical analysis using the Kruskall-Wallis test and Dunn's test. The microbial biomass carbon reached the lowest level in CLG and highest in FN, with statistical differences in the deeper layers and no statistical difference just in the surface layer (0-5cm). MP and SSP treatments did not differ from FN. In the CLG system, the results found corresponded to 153.1, 152.9, 132.6, 91.3 in layers 0-5, 5-10, 10-20 and 20-30 respectively, while in the FN system, the values were 295. 7, 265.5, 235 and 235 in the corresponding layers. The CLG system contained on average 49% less carbon in the microbial biomass compared to NF, while the silvopastoral system averaged 8%, and the pasture monoculture had a 12% difference. The higher carbon content of the microbial biomass in the areas of native vegetation, silvopastoral system and monoculture pasture may be a reflection of the continuous supply of organic materials from the litter and rhizosphere, associated with the absence of soil disturbance, constituting a favorable factor for survival and growth of different groups of microorganisms; while the low SMBC in CLG can be explained by the rapid decomposition of organic matter, which has low C:N ratio, and also can be associated with lower litter deposition, limiting microbial activity. Since there was no difference in CBMS between treatments in the 0-5 cm layer, where there is a greater predominance of Arachis pintoi roots, we infer that the fibrous root component present in SSP, MP and NF substantially contributed to the growth of microbial biomass in the subsurface soil layers, providing these systems with better nutrient cycling.

The aim of this study was to characterize four corn and sorghum co-products (DDG) in terms of their protein and carbohydrate fractions; we also evaluated the effects of substituting the protein source of the conventional supplement by DDG on consumption and nutrient digestibility in confined finishing cattle. Thirty-six male Nellore cattle with a mean age of 24 months were used. The treatments were: FA: concentrate with corn as an energy source and cottonseed meal as a protein source; DDG50: concentrate with a 50% substitution of the FA protein source by DDG; DDG100: concentrate with 100% substitution of the FA protein source by DDG. The experimental design was completely randomized with three treatments and three replicates (pens) containing four animals per pen. We found that the use of DDG in the finishing phase did not interfere with the animals’ food intake or the digestibility of the nutrients (p > 0.05). Nutrients were used by the animals; therefore, DDGs may be viable substitutes of cottonseed meal. We conclude that the bromatological composition of this co-product is influenced a lot during processing; therefore, the nutritional values of this co-product present in the composition tables may not be true.