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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.

ABSTRACT: In Brazil, urea is the most used nitrogen (N) fertilizer to improve forage production. However, their excessive use can cause environmental impacts through N losses, such as ammonia (NH3) volatilization. Therefore, the current study adjusted and estimated the NH3 volatilization from urea applied on tropical pastures in three rainfall conditions using mathematical models. Data were collected from Marandu grass (Brachiaria brizantha) fertilized with 50 kg N ha-1 during wet, intermediate, and dry conditions. Ammonia volatilization was measured in five semi-open chambers for 21 days. The linear, quadratic, exponential, Gompertz, Groot, and Richards models were tested for fitting and estimating the NH3 volatilization. The Gompertz, Groot, and Richards models generated predictions similar to the observed data, with a high determination coefficient, indicating a better fit of these equations to data, with precision and accuracy. However, the Groot model was selected due to the lowest root mean square error of prediction (0.29 % total N lost as NH3). The greatest N loss as NH3 volatilization occurred in the wet, followed by intermediate and dry conditions (20.2, 17.0, and 11.3 % total N lost as NH3, respectively). Therefore, nitrogen losses as NH3 volatilization after application of 50 kg N ha-1, as urea source, are altered according to the weather conditions, reaching 20% of N added in the wet rainfall period. The Groot model is recommended for fitting and estimating the NH3 volatilization from urea applied on Marandu grass pastures in the wet and dry rainfall conditions.

Methane emissions (CH4) from the soil increase according to changes made in forest soils and adverse edaphoclimatic factors. Soil temperature and nutrients will impact the activity of microorganisms, depending on land use. The objective of this study was to evaluate the impacts of land use, temperature, and nitrogen application on CH4 emissions from soils within the Amazon region. Three experiments were conducted in a completely randomized design. Each experiment consisted of five replicates to measure CH4 emissions. The variables examined in these experiments were: 1) three distinct land uses (forest, pasture, or agriculture; 2) soil temperatures (25, 30, 35, or 40°C); and 3) input of nitrogen to the soil (0, 90, 180, or 270 kg of N ha−1). In this study, the highest emissions occurred in pasture soils, with values of 470 μg of CH4 g−1 of dry soil, while forest and agricultural soils suffer the effects of CH4 oxidation. Temperature is a factor that contributes to CH4 emissions, and temperatures above 30°C tended to reduce gas emissions in the systems studied, since the highest emission was observed in pasture soil kept at 25°C (∼1,130 μg of CH4 g−1 of dry soil). Nitrogen fertilization in pasture soils reduces CH4 emitted nearly 140% as the dose increased. As a result, the pasture soils tended to emit higher concentrations of CH4 into the atmosphere. However, reducing these emissions from the pasture management employed is possible.

Typical successions in land use affect the dynamics of carbon (C) and nitrogen (N) in the soil. This study aimed to determine the effects of land use change on soil organic carbon and N content and stocks in pastures, crops, and forests in the Amazon. Soil C and N stocks were assessed at depths of 30 and 100 cm to determine 13C isotopic abundance. The concentrations of C and N in crops were lower (p < 0.05) than those in other land use types. Soil organic C and soil N stocks for pasture (67.6, 144.8, 5.7, and 13.3) and forest (77.1, 137.5, 6.3, and 13.8) systems were similar, but greater than those of the crop area (36.4, 63.9, 3.0, and 6.0), regardless of depth (30 and 100 cm for C and N). Land use change for pastures in the Arc of Deforestation region of the Amazon maintains SOC and N stocks in the soil and is more sustainable than the agricultural system with black pepper, as long as the conditions of soil, climate, and cultivation are similar. Part of the C3-derived carbon from the forest was replaced by C4-derived C from grasses at soil depths up to 100 cm.

ABSTRACT: The use of nitrogen (N) in pastoral ecosystems leads to increased productivity, as it allows the plant to elongate its leaves and, therefore, grazing herbivores harvest the green leaves. However, there are very volatile N sources, which can be replaced by ammonium nitrate, which is less volatile and less dependent on the application in rainy days. The treatments are compound of Marandu palisade grass pastures managed under continuous stocking at a canopy height of 25 cm, with different levels of N fertilizer: 0, 75, and 150 kg ha-1year-1, as ammonium nitrate (32% of N), with four replicates (pastures) in a completely randomized design. Nitrogen uptake (54.9, 96.5, 113.8 kg N ha-1) and N nutrition index (0.67, 0.98, 1.15) were different between N level, respectively, 0, 75 and 150 kg ha-1 year-1. The N recovery (58.3, 40.9 %) differed between 75 and 150 kg ha-1 year-1, respectively. The dose of 75 kg N kg ha-1 year-1 results in better N utilization, while the dose of 150 kg N ha-1 year-1 enables greater stocking rate; therefore, requiring less grazing area.

Understanding economic scenarios is crucial in all production chains. Tropical pastures are Brazil’s primary food source for beef cattle production, and current pasture management is not ideal due to land degradation. An economic evaluation assists farmers with improving pasture management using novel techniques, such as nitrogen (N) fertilization, which is straightforward and practical. The economic effects of different N fertilizer levels in beef cattle production were evaluated. This study was conducted over three years (2014/2015, 2015/2016, and 2016/2017) using four concentrations of urea fertilizer (0, 90, 180, and 270 kg N/ha). A principal component analysis and sensitivity analysis were performed using financial data. A financial pattern was observed, with increases in some variables, such as cost-effective operating and cost-total operating from those measuring costs and gross revenue, operating profit, and net income from those estimating revenues. Treatment with 180 kg N/ha fertilizer resulted in increased profitability, payback, internal rate of return, and net present value (at 6% and 12% tax) of 17.76%, 2.79 years, 35.79%, and USD 5926.03 and USD 1854.35, respectively. For this study, the main costs associated with profitability were supplementation, animal purchases, and sale prices. The best treatment to achieve excellent grazing pressure in tropical areas with oxisol is 180 kg/ha per year.

Abstract The effects of sources of rumen undegradable protein (RUP) in diets on methane (CH4), nitrous oxide (N2O) and ammonia (NH3) emissions from the manure of feedlot-finished cattle were evaluated. We hypothesized that the use of different RUP sources in diets would reduce N loss via urine and contribute to reduced N2O, CH4 and NH3 emissions to the environment. Nellore cattle received different diets (18 animals/treatment), including soybean meal (SM, RDP source), by-pass soybean meal (BSM, RUP source) and corn gluten meal (CGM, RUP source). The protein source did not affect the N and C concentration in urine, C concentration in feces, and N balance (P > 0.05). The RUP sources resulted in a higher N2O emission than the RDP source (P = 0.030), while BSM resulted in a higher N2O emission than CGM (P = 0.038) (SM = 633, BSM = 2521, and CGM = 1153 g ha−2 N–N2O); however, there were no differences in CH4 and NH3 emission (P > 0.05). In conclusion, the use of RUP in diets did not affect N excretion of beef cattle or CH4 and NH3 emission from manure, but increased N2O emission from the manure.

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.

Pastures are important environments worldwide because they offer many ecosystem services and sustain meat and milk production. However, pastures ecosystems are responsible for greenhouse gas (GHG) emission. The major GHGs include CO2, CH4, and N2O. The present review summarizes GHG emission from pasture ecosystems and discusses strategies to mitigate this problem. In pastures, emissions originate from animal excretion, fertilization, and organic matter decomposition. Emissions of specific gases can be measured based on certain factors that were recently updated by the United Nation’s Intergovernmental Panel on Climate Change in 2019. Urine is the main source of N2O emission. Forage structure is an important factor driving GHG transport. Forage fiber content and animal intake are the key drivers of enteric CH4 emission, and the introduction of forage legumes in pasture systems is one of the most promising strategy to mitigate GHG emission.

Animal supplementation during the background phase may increase greenhouse gas emissions (GHG). The inclusion of tannins in the diet of Nellore bulls can mitigate nitrous oxide (N2O), methane (CH4), and ammonia (NH3) production. The objective of this study was to quantify the effect of energy supplementation associated with sources of tannins in the diet of young Nellore bulls backgrounded in pastures with N2O, CH4, and NH3 emissions. Two experiments were conducted in a completely randomized design. The treatments were three supplementation strategies: (1) soybean hulls 0.3% of body weight (BW), (2) sorghum grain 0.3% of the BW, and (3) peanut peel 0.3% of BW, the last two being sources of tannin. The static closed chambers method was used to quantify N2O and CH4 emissions and the semi-open chamber technique to estimate NH3 volatilization. Supplementation strategies did not affect the N2O emissions (p = 0.9116). The soil water-filled pore space explained the variation in the N2O fluxes (p = 0.0071). The treatments did not change the total CH4 emissions (p = 0.3599), and no explanatory variable was correlated with the CH4 fluxes. The NH3 volatilization did not vary according to the supplements or tannin inclusion (p = 0.5170). However, the type of excreta affected the NH3 volatilization (p < 0.0001). Ammonia volatilization averaged 14.05, 4.16, and 2.25% of the applied N for urine, urine + dung, and dung, respectively. The energetic supplementation of Nellore bulls containing sources of tannins in the evaluated dosages was not a mitigation strategy for the emissions of N2O, CH4, and NH3.

This study aimed to evaluate the forage mass and nutritional value (NV) of Guinea Massai grass (Megathyrsus maximus × Megathyrsus infestum) in an open pasture (OP) or the silvopastoral system (SPS) at different stages of development (SDs). The experimental design was completely randomized, with five replications. The treatments were distributed in a factorial scheme 2 × 4, corresponding to types of systems (OP and SPS) and four SD (vegetative stage—S1, pre-flowering—S2, full flowering—S3 and maturity after flowering—S4). There was no interaction of the system × stage of plant development in any of the variables evaluated. The production of forage mass and Guinea Massai grass morphological components did not differ (p > 0.05) between SPS and OP. However, they differed between the SDs (p ≤ 0.05), with an increasing linear effect for forage mass, percentage of the stem, and dead material, and decreasing for leaf percentage and leaf: stem ratio. Only protein content differed (p < 0.05) among the chemical composition variables between culture systems. The shading caused by the SPS did not decrease the forage mass, NV, and in vitro dry matter digestibility of Guinea Massai grass compared to the system in OP. The advance of the SD of Guinea Massai grass increases the forage mass, with higher proportions of morphological components of low NV, such as stem and dead material. Silvopastoral system of Guinea Massai grass and eucalyptus is effective to prolongate the grazing season, with a greater amount of green leaves in the sward and better NV, without compromising herbage mass production in the forage growing season.

Abstract The effects of nitrogen (N) fertilization levels on protein and carbohydrate fractions in Marandu palisadegrass pasture [Urochloa brizantha (Hochst. ex A. Rich.) R.D. Webster] were investigated in a pasture over five years. The experimental design was completely randomized with four levels of N (0, 90, 180, and 270 kg N ha-1, as urea) for five years, and with three replicates. The study was conducted in a continuously stocked pasture during the forage growing season (December to April) in a tropical region. The effects of N fertilization were similar across the five years. With increasing N fertilization, the concentrations of crude protein (CP) increased from 103 to 173 g kg−1 (P

The objective of this study was to evaluate the effect of the addition of a phytogenic compound blend (PHA) containing hydrolyzable tannins, carvacrol, and cinnamaldehyde oil to mineral salt or energy supplementation on the rumen microbiota and nitrogen metabolism of grazing Nellore cattle. Eight castrated Nellore steers were distributed in a double-Latin-square 4 × 4 design, with a 2 × 2 factorial arrangement (two types of supplements with or without the addition of the PHA), as follows: energy supplement without the PHA addition (EW); energy supplement with the PHA addition (EPHA); mineral supplement without the addition of the PHA (MW); mineral supplement with the PHA addition (MPHA). Steers that received supplements with the PHA have a lower ruminal proportion of valerate (with the PHA, 1.06%; without the PHA, 1.15%), a lower ruminal abundance of Verrucomicrobia, and a tendency for lower DM digestibility (with the PHA, 62.8%; without the PHA, 64.8%). Energy supplements allowed for higher ammonia concentrations (+2.28 mg of NH3-N/dL), increased the propionate proportion (+0.29% of total VFA), and had a higher ruminal abundance of Proteobacteria and Spirochaetae phyla in the rumen. The PHA addition in the supplement did not improve nitrogen retention, reduced the ruminal proportion of valerate, and had a negative impact on both the total dry-matter digestibility and the abundance of several ruminal bacterial groups belonging to the Firmicutes and Verrucomicrobia phyla.

This study aimed to evaluate the emission factor of N2O, CH4, and the volatilization of NH3 for the combination of feces or urine with increasing doses of ammonium nitrate in tropical palisade grass pastures. The emission of greenhouse gases was assessed in eight treatments combining feces and urine with doses (75 and 150 kg of N ha−1) of ammonium nitrate, (32% N). The emission factor of N2O was 0.11, 0.19, and 0.17% for feces, urine, and 75 kg N ha−1 year−1 (as ammonium nitrate) and showed an additive linear effect when feces or urine were combined with increasing doses of N fertilizer. The emission factor of CH4 of feces (0.18 kg CH4 animal−1 year−1) was similar irrespective of combination with ammonium nitrate. The N loss by volatilized NH3 has a decreasing linear effect (p < 0.05) for the combination of feces or urine with ammonium nitrate. We concluded that N2O and CH4 emission factors of feces and urine in tropical climate conditions are lower than those reported by the IPCC. However, their N2O emission factors are sharply enhanced when combined with ammonium nitrate. These results may contribute to improvements in national and regional greenhouse gas inventories of livestock production.

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.

Two experiments were conducted to evaluate the effect of replacing cottonseed meal with DDG on ruminal parameters, methane (CH4) emissions (Experiment 1), and animal performance (Experiment 2) of young Nellore bulls grazing Marandu grass during the rainy season. Four supplementation strategies were used in both experiments: (1) Mineral supplementation (MS); (2) conventional multiple supplement (energy/protein) with cottonseed meal and citrus pulp (CMS); (3) CMS with 50% cottonseed meal replaced by DDG (50DDG); and (4) CMS with 100% cottonseed meal replaced by DDG (100DDG). The 50DDG condition resulted in greater intake of dry matter (p = 0.033), organic matter (OM) (p = 0.050), forage (p = 0.035), and digestible OM (p = 0.031) than 100DDG. The supplemented animals presented greater final body weight (BW) and average daily gain than the animals consuming MS (p = 0.011), and lower pH, acetate, and acetate:propionate (p < 0.05). However, the treatments had no influence on stocking rate, gain per area, and enteric CH4 emissions (p > 0.05). Replacing cottonseed meal with DDG does not result in great variations in ruminal parameters, animal performance, and enteric CH4 emissions of grazing Nellore cattle during the rearing phase in the wet season. Both protein sources in 0.3% BW supplementation can be used to intensify beef cattle production in pastures.

Pasture intensification through higher stocking rates, nitrogen fertilization and intensified grazing management in beef cattle production optimizes pasture use by increasing the forage harvested. We aimed to assess its effects on the morphogenesis and canopy structure of Urochloa brizantha ‘Marandu’ (marandu palisadegrass) pastures. The treatments consisted of marandu palisadegrass pastures managed under continuous stocking and a canopy height of 25 cm, with different levels of intensification: extensive, semi-intensive, and intensive systems N-fertilized with 0 kg, 75 kg, and 150 kg N ha−1 year−1, respectively, as ammonium nitrate (32% of N), with four replicates (paddocks) in a completely randomized design. Phyllochron (9.8 days) and leaf lifespan (34.7 days) were shorter in intensified pastures, whereas herbage mass was similar among treatments. Extensive pastures had a higher proportion of senescent material; thus, more intensive systems showed higher proportions of leaves and stems, although the leaves-to-stem ratio remained similar across production systems. The defoliation interval was lower in intensive (14.4 days) and higher in extensive (18.7 days) treatments. Thus, pasture intensification accelerates leaf appearance, decreases leaf lifespan, shortens the tiller defoliation interval and increased herbage accumulation rate but does not change herbage mass. The extensive system produces excessive forage losses due to dead material.

The reduction in ammonia (NH3) losses from volatilization has significant implications in forage production. The objective of this study was to evaluate the impact of N fertilizers (urea, ammonium nitrate, and ammonium sulfate) and four doses (0, 90, 180 and 270 kg N ha−1) on N losses by NH3 volatilization, accumulation, and forage chemical composition of Urochloa brizantha cv Marandu. Two field experiments were conducted to measure NH3 losses using semi-open chambers. The forage accumulation and chemical composition were evaluated in the third experiment; the response variables included forage accumulation, crude protein (CP), and neutral detergent fiber (NDF). Compared to urea, ammonium nitrate and ammonium sulfate reduced NH3 losses by 84% and 87% and increased total forage accumulation by 14% and 23%, respectively. Forage accumulation rate and CP increased linearly with the N levels, while NDF contents decreased linearly with the N levels. In both experiments, NH3 losses and forage characteristics were different according to the rainfall pattern and temperature variations. Our results indicate that the use of nitric and ammoniacal fertilizers and the application of fertilizer in the rainy season constitute an efficient fertilizer management strategy to increase forage yield and decrease losses from volatilization of NH3.

The intensification of pasture production has increased the use of N fertilizers—a practice that can alter soil greenhouse gas (GHG) fluxes. The objective of the present study was to evaluate the fluxes of CH4, CO2, and N2O in the soil of Urochloa brizantha ‘Marandu’ pastures fertilized with different sources and doses of N. Two field experiments were conducted to evaluate GHG fluxes following N fertilization with urea, ammonium nitrate, and ammonium sulfate at doses of 0, 90, 180, and 270 kg N ha−1. GHG fluxes were quantified using the static chamber technique and gas chromatography. In both experiments, the sources and doses of N did not significantly affect cumulative GHG emissions, while N fertilization significantly affected cumulative N2O and CO2 emissions compared to the control treatment. The N2O emission factor following fertilization with urea, ammonium nitrate, and ammonium sulfate was lower than the United Nations’ Intergovernmental Panel on Climate Change standard (0.35%, 0.24%, and 0.21%, respectively, with fractionation fertilization and 1.00%, 0.83%, and 1.03%, respectively, with single fertilization). These findings are important for integrating national inventories and improving GHG estimation in tropical regions.

The study aimed to evaluate the effect of replacing cottonseed meal by dried distiller’s grains (DDG) in terms of efficiency in the productive aspects of beef cattle finishing in pasture versus feedlot. The experiment was conducted in a completely randomized design in a 2 × 3 factorial arrangement, with two production systems (pasture versus feedlot) and three supplements: CM, conventional supplement with cottonseed meal (CM) as a protein source; 50DDG: supplement with 50% replacement of CM by DDG; and 100DDG: 100% replacement. The effect of replacing CM by DDG on dry matter and nutrients intake and nutrients digestibility depends on the finishing system (p < 0.05). While in the pasture system animal consumed more nutrients in the CM, a greater intake was observed in the 100DDG in feedlot. The nutrients digestibility was lower in the pasture (p < 0.05). Animal performance and final body weight were higher in the feedlot (p < 0.0001), with averages of 1.57 kg/d and 566 kg of final body weight (FBW) for feedlot, and 0.99 kg/d and 504 kg FBW for pasture. The use of DDG does not change the animal performance finished in pasture or feedlot, and it is a viable alternative to replace conventional supplements in finishing phase in both systems in tropical environment.

A 7 year experiment (2008–2014) evaluated cattle grazing intensity (sward height) effects on herbage mass, forage quality, and greenhouse gas emissions in continuously stocked pastures containing the tropical ‘Marandu’ palisade grass (Brachiaria brizantha (Hochst. ex A. Rich) Stapf cv. Marandu). The experiment consisted of three sward height treatments (15, 25, and 35 cm) and six replicates. There were four periods each year during the rearing phase. Significant effects were found for herbage mass, proportions of leaf and stem, crude protein, neutral detergent fiber, acid detergent fiber, lignin, animal performance, enteric methane (CH4), and greenhouse gas (GHG) emissions from soils. When the canopy height increased from 15 to 35 cm, the herbage mass rose from 5.23 to 9.86 kg t ha−1, leaf percentage decreased, and stem percentage increased. Crude protein content averaged 14.2%, and neutral detergent fiber averaged 58%. Average daily gain averaged 0.67, 0.81, and 0.90 kg −1 head−1, while live weight gain ha–1 was 649, 530, and 439 kg for the 15, 25, and 35 cm treatments, respectively. The weather variables explained the GHG emissions, interannual herbage mass, and structure variations.

We quantified nitrous oxide (N2O) fluxes and total denitrification (N2O + N2) in an acidic (Ferralsol) and a near-neutral pH soil (Cambisol) to determine whether biochar’s alkalinization effect could be the mechanism inducing potential reductions in N2O fluxes. In Ferralsol, decreases in N2O emissions and in the N2O to N2O + N2 ratio were observed in both biochar and lime treatments. In Cambisol, neither biochar nor lime decreased N2O emissions, despite significantly increasing soil pH. The abundance and community structure of nosZ gene-bearing microorganisms indicated that gene abundances did not explain biochar effects, but a higher diversity of nosZ gene-bearing microorganisms correlated to lower total denitrification. Overall, our results suggest that biochar’s potential to decrease N2O emissions, through soil alkalinization, may be more effective in acidic soils.

The objective of this work was to evaluate the effect of biochar application on soil nitrous oxide emissions. The experiment was carried out in pots under greenhouse conditions. Four levels of ground commercial charcoal of 2 mm (biochar) were evaluated in a sandy Albaqualf (90% of sand): 0, 3, 6, and 9 Mg ha-1. All treatments received 100 kg ha-1 of N as urea. A cubic effect of biochar levels was observed on the N2O emissions. Biochar doses above 5 Mg ha-1 started to mitigate the emissions in the evaluated soil. However, lower doses promote the emissions.