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
< 0.001), soluble fractions (Fraction A + B1) increased from 363 to 434 g kg
−1
of total CP (
P
= 0.006); neutral detergent fiber (NDF) decreased from 609 to 556 g kg
−1
(
P
= 0.037); indigestible NDF (
P
= 0.046), potentially degradable neutral detergent fiber (
P
= 0.037), and acid detergent fiber decreased (
P
= 0.05), and total digestible nutrient (TDN) increased (
P
< 0.001). Increasing N fertilization decreased the concentrations of Fraction C (
P
= 0.014) and total carbohydrates (
P
< 0.0001), and increased CP:organic matter digestibility (
P
< 0.01). Concentrations of neutral detergent fiber free of ash and protein (P = 0.003), indigestible neutral detergent fiber (
P
< 0.001), neutral detergent fiber potentially degradable (
P
= 0.11), CP (
P
< 0.001), Fraction A + B1 (
P
< 0.001), Fraction B2 (
P
< 0.001), Fraction B3 (
P
< 0.01), and non-structural carbohydrates differed (
P
< 0.001) across years. Therefore, N fertilization can be used to increase CP, soluble protein, and TDN.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Intensification of tropical grassland can be a strategy to increase beef production, but methods for achieving this should maintain or reduce its environmental impact and should not compromise future ...food-producing capacity. The objective of this review was to discuss the aspects of grassland management, animal supplementation, the environment, and the socioeconomics of grassland intensification. Reducing environmental impact in the form of, for example, greenhouse gas (GHG) emissions is particularly important in Brazil, which is the second-largest beef producer in the world. Most Brazilian pastures, however, are degraded, representing a considerable opportunity for the mitigation and increase of beef-cattle production, and consequently increasing global protein supply. Moreover, in Brazil, forage production is necessary for seasonal feeding strategies that maintain animal performance during periods of forage scarcity. There are many options to achieve this objective that can be adopted alone or in association. These options include improving grassland management, pasture fertilization, and animal supplementation. Improving grazing management has the potential to mitigate GHG emissions through the reduction of the intensity of CO2 emissions, as well as the preservation of natural areas by reducing the need for expanding pastureland. Limitations to farmers adopting intensification strategies include cultural aspects and the lack of financial resources and technical assistance.
Background and aims
Prescribed fire is a common management practice in native rangelands that can result in significant losses of C, N, and P from plant and soil. This study evaluated the short-term, ...fire-induced changes in C, N, and P stocks in subtropical native rangelands in Florida, USA.
Methods
Changes in C, N, and P stocks were quantified in aboveground biomass and soil (0-20 cm depth) in locations within native rangelands dominated by either saw-palmetto (
Serenoa repens
Bartr.; Saw-palmetto) or grasses (mixed C
4
grasses; Grass).
Results
Prescribed fire had no impact on soil temperature below 2.5 cm, but peak temperature at soil surface was greater in Saw-palmetto than Grass areas. Despite greater pre-fire aboveground biomass in Saw-palmetto (1115 g m
−2
) vs. Grass (689 g m
−2
), no difference in post-fire net loss (−660 g m
−2
) was observed between vegetation types. This occurred because 97% of biomass in Grass was combusted during fire vs. 65% in Saw-palmetto dominated areas. Similar responses were observed for aboveground C and P stocks. Fire-induced N loss was greater in Saw-palmetto (−6 g N m
−2
) than grass (−2.7 g N m
−2
). Soil C, N, and P stocks were not affected by prescribed fire. This was likely due to limited effects of prescribed fire on soil temperature. Although fire had no effect on soil respiration, ash addition increased soil potentially mineralizable C by 11%.
Conclusion
Prescribed fire reduces C, N, and P stocks in aboveground vegetation, but limited impacts are expected to occur in soil pools.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Greenhouse gases are known to play an important role in global warming. In this study, we determined the effects of selected soil and climate variables on nitrous oxide (N2O), methane (CH4), and ...carbon dioxide (CO2) emissions from a tropical grassland fertilized with chicken slurry, swine slurry, cattle slurry, and cattle compost. Cumulative N2O emissions did not differ between treatments and varied from 29.26 to 32.85 mg N m−2. Similarly, cumulative CH4 emissions were not significantly different among the treatments and ranged from 6.34 to 57.73 mg CH4 m−2. Slurry and compost application induced CO2 emissions that were significantly different from those in the control treatment. The CH4 conversion factors measured were 0.21%, 1.39%, 4.39%, and 5.07% for cattle compost, chicken slurry, swine slurry, and cattle slurry, respectively, differing from the recommendations of the Intergovernmental Panel on Climate Change (IPCC). The fraction of added N emitted as N2O was 0.39%, which was lower than the IPCC default value of 2%. Our findings suggest that N2O emissions could be mitigated by replacing synthetic fertilizer sources with either biofertilizer or compost. Our results indicate the following: N2O emission was mainly controlled by soil temperature, followed by soil moisture and then soil NH4+ content; CH4 fluxes were mainly controlled by soil moisture and chamber headspace temperature; and CO2 fluxes were mainly controlled by chamber headspace temperature and soil moisture.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Using condensed tannins (CT) in ruminant nutrition yields many benefits, especially regarding better dietary protein utilization and decreased methane (CH4) emission by altering ruminal fermentation ...kinetics. A meta-analysis was conducted to develop and analyze a database from published studies and verify the effects of CT inclusion on enteric CH4 emission by cattle, nutrient digestibility and ruminal parameters, and their interactions. The study aimed to develop regression equations based on the significant components and their interactions to target a specific ruminal CH4 mitigation when correctly associating CT inclusion level and diet composition. A database was developed from 40 published studies that measured cattle CH4 emission using in vitro or in vivo methods and reported the source and inclusion levels of CT as well as typical diet characteristics, including crude protein (CP), organic matter (OM), neutral detergent fiber (NDF), and ether extract (EE). Other related parameters were also included in the database when reported, such as dry matter intake (DMI) and digestibility, OM digestibility, NDF digestibility, and ruminal parameters, including pH, ruminal ammonia nitrogen, total volatile fatty acids (VFA), acetate, propionate, butyrate, and the acetate-to-propionate ratio. The meta-analysis was conducted by multiple linear regression, using the nlme package of R 4.2.1, in which studies were assumed as random variables affecting the intercept and slopes. The CH4 emission, expressed in L/kg of DMI, decreased with increasing levels of dietary CT when in vitro and in vivo were analyzed together (P < 0.001) or in vivo alone (P < 0.001). Total VFA concentration (P = 0.049), propionate (P = 0.042), and butyrate (P = 0.047) increased with increasing levels of dietary CT on in vitro + in vivo methods, suggesting improved fermentability. When analyzing all chemical components of the diet, OM (P = 0.043) and CP (P = 0.010) decreased CH4 production with in vitro methods, EE decreased CH4 production on in vivo method (P = 0.001), while dietary NDF increased CH4 production on in vitro + in vivo (P = 0.016), and also separately for in vivo (P = 0.058) and in vitro method (P = 0.022). There was an interaction between CT and CP for in vivo experiments (P = 0.010): CH4 = 35.64 – 6.87 ×CT – 0.49 ×CP + 0.33 ×CT*CP. Across many experiments, increasing the level of dietary CT led to a decrease in ruminal CH4 concentrations for in vitro and in vivo fermentation conditions and an increase in molar proportions of propionate, butyrate, and total VFA, indicating that it is an efficient natural alternative to reduce environmental impacts of ruminant production systems possibly. Our meta-analysis identified diet components that significantly affect enteric CH4 emissions by cattle and developed a prediction model based on these components, including OM, CP, NDF, and EE. The in vivo CH4 method showed that an interaction between CT and CP diet content affects CH4 emissions. Future research and meta-analysis must focus on CT biological activity along with percent content to dictate ideal diet inclusion to suppress CH4 emissions without depressing animal performance.
•Condensed tannins are an efficient natural, organic additive to mitigate CH4 emissions from cattle.•Diet composition directly influences CH4 emissions.•Prediction models of CH4 emissions based on CT and diet composition can determine mitigation strategies.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The effects of sources of rumen undegradable protein (RUP) in diets on methane (CH
), nitrous oxide (N
O) and ammonia (NH
) 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 N
O, CH
and NH
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 N
O emission than the RDP source (P = 0.030), while BSM resulted in a higher N
O emission than CGM (P = 0.038) (SM = 633, BSM = 2521, and CGM = 1153 g ha
N-N
O); however, there were no differences in CH
and NH
emission (P > 0.05). In conclusion, the use of RUP in diets did not affect N excretion of beef cattle or CH
and NH
emission from manure, but increased N
O emission from the manure.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Greenhouse gases (GHG) can be affected by grazing intensity, soil, and climate variables. This study aimed at assessing GHG emissions from a tropical pasture of Brazil to evaluate (i) how the grazing ...intensity affects the magnitude of GHG emissions; (ii) how season influences GHG production and consumption; and (iii) what are the key driving variables associated with GHG emissions. We measured under field conditions, during two years in a palisade-grass pasture managed with 3 grazing intensities: heavy (15 cm height), moderate (25 cm height), and light (35 cm height) N₂O, CH₄ and CO₂ fluxes using static closed chambers and chromatographic quantification. The greater emissions occurred in the summer and the lower in the winter. N₂O, CH₄, and CO₂ fluxes varied according to the season and were correlated with pasture grazing intensity, temperature, precipitation, % WFPS (water-filled pores space), and soil inorganic N. The explanatory variables differ according to the gas and season. Grazing intensity had a negative linear effect on annual cumulative N₂O emissions and a positive linear effect on annual cumulative CO₂ emissions. Grazing intensity, season, and year affected N₂O, CH₄, and CO₂ emissions. Tropical grassland can be a large sink of N₂O and CH₄. GHG emissions were explained for different key driving variables according to the season.
Climate change is a major constraint on the sustainability of the humid tropics, maintaining ecosystem services, food production, and social functioning. Humid tropics play an essential role in C ...storage and greenhouse gas (GHG) emission reduction. Unfortunately, unplanned economic exploration, human occupation, and lack of knowledge of techniques to maintain ecosystem services negatively affect the humid tropics. In this study, we focused on the mechanisms of GHG emissions, C storage, and their mitigation strategies. This review indicated technologies that can be adopted by farmers in humid tropics to maintain or increase their capacity to store C stocks and reduce GHG emissions. The adoption of climate-smart agriculture technologies and the regulation of ecosystem services markets will accelerate the progress of preserving the humid tropics. Improved management practices, such as proper N fertilizer management and the introduction of N2-fixing legumes, can increase soil C sequestration, providing economic and environmental trade-offs associated with these management strategies. Public and private investments toward knowledge dissemination and technology adoption regarding GHG emissions reduction and soil C storage are needed to allow humid tropics to maintain their critical function of generating environmental and societal benefits.
•We reviewed GHG emissions and soil C in humid grasslands.•Brazilian humid grasslands can act as a carbon sink.•Pasture management is fundamental to increase soil C sequestration.•Nitrogen inputs increase net primary production in grassland ecosystems.•Technologies to mitigate GHG emissions in humid tropics need to be investigated.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Soil moisture and compaction, and source of N and bovine urine can reduce methane (CH
4
) rates from agricultural soils. However, the magnitude of the effect is unknown in tropical soil under ...different conditions, as well as the potential of different urine-N concentration, volume, and sources of N in such an effect. This study aimed to investigate the effects of different soil conditions (moist, dry, compacted, moist-dung, moist-dung-compacted), N concentration in urine (2.5, 5.0, 10.0, and 15.0 g N L
−1
), volume of urine (25, 50, 100, and 200 ml kg
−1
dry soil), and source of N (ammonium, nitrate, and urea) on CH
4
emissions. A tropical Ferralsol soil from marandu-grass pasture was incubated during 106 days and the CH
4
concentration determined by gas chromatography. The CH
4
rates varied significantly according to the soil conditions when manipulated the urine-N (
p
< 0.01) and averaged 0.75, − 0.50, 1.14, 6.23, and 8.17 μg C–CH
4
m
−2
h
−1
for the moist, dry, compacted, moist-dung, and moist-dung-compacted soil, respectively, and, not responded to the level of N (
p
= 0.73) averaging 2.57 μg C–CH
4
m
−2
h
−1
. When evaluated, the volumes of urine cumulative CH
4
averages were − 0.52, − 1.24, − 0.88, 14.48, and 18.56 μg C–CH
4
m
−2
h
−1
for the moist, dry, compacted, moist-dung, and moist-dung-compacted, respectively. Soils were affected by soil treatments (
p
< 0.001) but not by urine volumes (
p
= 0.30). The source of N did not influence the CH
4
rates (
p
= 0.1) averaging 0.88, − 1.26, and − 1.19 μg C–CH
4
m
−2
h
−1
respectively, for urea, nitrate, and ammonium. The CH
4
fluxes in tropical Ferralsols are controlled by the soil characteristics and dung addition.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Beef cattle production is an important agricultural activity in Brazil, which influences environmental and resource consumption. This study analyzed greenhouse gas (GHG) emission impacts from 17 ...farms, representing the Brazil’s productive system and determined possible improvements in the production chain. Methane, nitrous oxide, and carbon dioxide emissions were evaluated using the updated Intergovernmental Panel on Climate Change (IPCC) guidelines for national inventories. The GHG inventory included emissions from animals, feeds, and “cradle-to-farm-gate” operations for animal management. Regression analyses of carbon dioxide equivalent (CO2eq) emissions and productive indices were performed to identify possible GHG emission hotspots. The results varied considerably among the farms. The GHG yield ranged from 8.63 to 50.88 CO2eq kg carcass−1. The productive indices of average daily gain (p < 0.0001), area productivity (p = 0.058), and slaughtering age (p < 0.0001) were positively correlated with GHG yield. However, no correlation was found with the stocking rate (p = 0.21). The production chain could be improved through accurate animal management strategies that reduce the slaughtering age and daily weight gain individually or per area using pasture management and strategic animal supplementation, which could subsequently reduce GHG emissions in beef cattle production.
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