Among the main greenhouse gases (CO2, CH4 and N2O), N2O has the highest global warming potential. N2O emission is mainly connected to agricultural activities, increasing as nitrogen concentrations ...increase in the soil with nitrogen fertilizer application. We evaluated N2O emissions due to application of increasing doses of ammonium nitrate and urea in two sugarcane fields in the mid-southern region of Brazil: Piracicaba (São Paulo state) and Goianésia (Goiás state). In Piracicaba, N2O emissions exponentially increased with increasing N doses and were similar for urea and ammonium nitrate up to a dose of 107.9 kg ha−1 of N. From there on, emissions exponentially increased for ammonium nitrate, whereas for urea they stabilized. In Goianésia, N2O emissions were lower, although the behavior was similar to that at the Piracicaba site. Ammonium nitrate emissions increased linearly with N dose and urea emissions were adjusted to a quadratic equation with a maximum amount of 113.9 kg N ha−1. This first effort to measure fertilizer induced emissions in Brazilian sugarcane production not only helps to elucidate the behavior of N2O emissions promoted by different N sources frequently used in Brazilian sugarcane fields but also can be useful for future Brazilian ethanol carbon footprint studies.
Conversion of tropical forest to agricultural management has important implications for C storage in soils and global climate change. The Nova Vida Ranch in the Western Brazilian Amazon basin ...provided a unique opportunity to study the conversion of tropical forests to pastures established in 1989, 1987, 1983, 1979, 1972, 1951, and 1911, in comparison with uncleared forest. Soils were analyzed for organic C, bulk density, total N, pH, clay content, and biomass C. The forest soil contained 34 Mg C ha−1 in the 0‐ to 30‐cm layer: modeling clearance and conversion to pasture caused an initial fall in the C stock, followed by a slow rise. After 88 yr, the pasture soil contained 53% more C than the forest soil. The increase in total N on conversion to pasture was less marked, which led to C/N ratios in the pasture soils being higher than in the forest soil. The Rothamsted C turnover model (RothC‐26.3) was used to simulate changes in the 0‐ to 10‐ and 0‐ to 30‐cm layer of soils when forest was converted to pasture. The model predicted that conversion to pasture would cause a 54% increase in the stock of organic C in the top 30 cm of soil in 100 yr. The modeled input of plant C to the 0‐ to 30‐cm layer of soil under pasture was assumed to be 8.28 Mg C ha−1 yr−1 The model provided a reasonable estimate of the microbial biomass (BIO) C in the 0‐ to 10‐cm soil layer. This was an independent test of model performance, because no adjustments were made to the model to generate output.
The recent agricultural expansion in the Matopiba region, Brazil's new agricultural frontier, has raised questions about the risk of increasing soil organic carbon (SOC) loss as large areas of native ...vegetation (NV; i.e., Cerrado biome) have been replaced by large-scale mechanized agriculture. Although sustainable managements, such as integrated crop-livestock (ICL) systems, are considered strategic to counterbalance the SOC loss associated with land-use change (LUC) while keeping food production, little is known about their long-term effects on SOC stocks in the Matopiba region. To this end, we used the DayCent model to simulate the effects of converting the management commonly used in this region, i.e., soybean-cotton rotation under no-tillage (NT), into ICL systems with distinct levels of intensification (e.g., crop rotations: soybean-pasture and soybean-pasture-cotton; soil and crop management: grass irrigation, scarification/harrowing, and length of grass cultivation) on long term SOC dynamics. Additionally, data from two projected climate scenarios: SSP2-4.5 greenhouse gases emissions (GHG) will not change markedly over time and global temperature will increase by 2.0 °C by 2060 and SSP5-8.5 (marked changes in GHG emissions are expected to occur resulting in an increase of 2.4 and 4.4 °C in global temperature in the middle and at the end of the century) were included in our simulations to evaluate climate change effects on SOC dynamics in this region. Based on a 50-yr-time frame simulation, we observed that SOC stocks under ICL systems were, on average, 23% and 47% higher than in the NV (36.9 Mg ha−1) and soybean-cotton rotation under NT (30.9 Mg ha−1), respectively. Growing grasses interlaid with crops was crucial to increase SOC stocks even when disruptive soil practices were followed. Although the irrigation of grass resulted in an early increase of SOC stocks and a higher pasture stoking rate, it did not increase SOC stocks in the long term compared to non-irrigated treatments. The SSP2-4.5 and SSP5-8.5 climate scenarios had little effects on SOC dynamics in the simulated ICL systems. However, additional SOC loss (∼0.065 Mg ha−1 yr−1) is predicted to occur if the current management is not improved. These findings can help guide management decisions for the Matopiba region, Brazil, to alleviate the anthropogenic pressure associated with agriculture development. More broadly, they confirm that crop-livestock integration in croplands is a successful strategy to regenerate SOC.
•A 23-yr field experiment was used to calibrate and validate the DayCent model.•Integrated crop-livestock (ICL) systems under climate scenarios were simulated.•If not improved, the business-as-usual management (BAU) leads to further SOC loss.•After 50 years, SOC stocks in ICL systems were 1.2–1.7 times higher than in the BAU.•Climate change scenarios had minor effects on decreasing SOC stocks in ICL systems.
Due to the worldwide increase in demand for biofuels, the area cultivated with sugarcane is expected to increase. For environmental and economic reasons, an increasing proportion of the areas are ...being harvested without burning, leaving the residues on the soil surface. This periodical input of residues affects soil physical, chemical and biological properties, as well as plant growth and nutrition. Modeling can be a useful tool in the study of the complex interactions between the climate, residue quality, and the biological factors controlling plant growth and residue decomposition. The approach taken in this work was to parameterize the CENTURY model for the sugarcane crop, to simulate the temporal dynamics of aboveground phytomass and litter decomposition, and to validate the model through field experiment data. When studying aboveground growth, burned and unburned harvest systems were compared, as well as the effect of mineral fertilizer and organic residue applications. The simulations were performed with data from experiments with different durations, from 12 months to 60 years, in Goiana, Timbaúba and Pradópolis, Brazil; Harwood, Mackay and Tully, Australia; and Mount Edgecombe, South Africa. The differentiation of two pools in the litter, with different decomposition rates, was found to be a relevant factor in the simulations made. Originally, the model had a basically unlimited layer of mulch directly available for decomposition, 5,000 g m⁻². Through a parameter optimization process, the thickness of the mulch layer closer to the soil, more vulnerable to decomposition, was set as 110 g m⁻². By changing the layer of mulch at any given time available for decomposition, the sugarcane residues decomposition simulations where close to measured values (R ² = 0.93), contributing to making the CENTURY model a tool for the study of sugarcane litter decomposition patterns. The CENTURY model accurately simulated aboveground carbon stalk values (R ² = 0.76), considering burned and unburned harvest systems, plots with and without nitrogen fertilizer and organic amendment applications, in different climates and soil conditions.
Currently we have little understanding of the impacts of land use change on soil C stocks in the Brazilian Amazon. Such information is needed to determine impacts on the global C cycle and the ...sustainability of agricultural systems that are replacing native forest. The aim of this study was to predict soil carbon stocks and changes in the Brazilian Amazon during the period between 2000 and 2030, using the GEFSOC soil carbon (C) modelling system. In order to do so, we devised current and future land use scenarios for the Brazilian Amazon, taking into account: (i) deforestation rates from the past three decades, (ii) census data on land use from 1940 to 2000, including the expansion and intensification of agriculture in the region, (iii) available information on management practices, primarily related to well managed pasture versus degraded pasture and conventional systems versus no-tillage systems for soybean (
Glycine max) and (iv) FAO predictions on agricultural land use and land use changes for the years 2015 and 2030. The land use scenarios were integrated with spatially explicit soils data (SOTER database), climate, potential natural vegetation and land management units using the recently developed GEFSOC soil C modelling system. Results are presented in map, table and graph form for the entire Brazilian Amazon for the current situation (1990 and 2000) and the future (2015 and 2030). Results include soil organic C (SOC) stocks and SOC stock change rates estimated by three methods: (i) the Century ecosystem model, (ii) the Rothamsted C model and (iii) the intergovernmental panel on climate change (IPCC) method for assessing soil C at regional scale. In addition, we show estimated values of above and belowground biomass for native vegetation, pasture and soybean. The results on regional SOC stocks compare reasonably well with those based on mapping approaches. The GEFSOC system provided a means of efficiently handling complex interactions among biotic-edapho-climatic conditions (>363,000 combinations) in a very large area (∼500
Mha) such as the Brazilian Amazon. All of the methods used showed a decline in SOC stock for the period studied; Century and RothC simulated values for 2030 being about 7% lower than those in 1990. Values from Century and RothC (30,430 and 25,000
Tg for the 0–20
cm layer for the Brazilian Amazon region were higher than those obtained from the IPCC system (23,400
Tg in the 0–30
cm layer). Finally, our results can help understand the major biogeochemical cycles that influence soil fertility and help devise management strategies that enhance the sustainability of these areas and thus slow further deforestation.
The production and use of biofuels have increased rapidly in recent decades. Bioethanol derived from sugarcane has become a promising alternative to fossil fuel for use in automotive vehicles. The ...‘savings’ calculated from the carbon footprint of this energy source still generates many questions related to nitrous oxide (N2O) emissions from sugarcane cultivation. We quantified N2O emissions from soil covered with different amounts of sugarcane straw and determined the direct N2O emission factors of nitrogen fertilizers (applied at the planting furrows and in the topdressing) and the by‐products of sugarcane processing (filter cake and vinasse) applied to sugarcane fields. The results showed that the presence of different amounts of sugarcane straw did not change N2O emissions relative to bare soil (control). N‐fertilizer increased N2O emissions from the soil, especially when urea was used, both at the planting furrow (plant cane) and during the regrowth process (ratoon cane) in relation to ammonium nitrate. The emission factor for N‐fertilizer was 0.46 ± 0.33%. The field application of filter cake and vinasse favored N2O emissions from the soil, the emission factor for vinasse was 0.65 ± 0.29%, while filter cake had a lower emission factor of 0.13 ± 0.04%. The experimentally obtained N2O emission factors associated with sugarcane cultivation, specific to the major sugarcane production region of the Brazil, were lower than those considered by the IPCC. Thus, the results of this study should contribute to bioethanol carbon footprint calculations.
Animal production systems are important sources of greenhouse gases (GHG), especially methane (CH4) and nitrous oxide (N2O). Brazilian beef production is almost exclusively (more than 90%) ...pasture-based. GHG emissions from faeces deposited in pastures have been extensively studied in temperate climates, but emissions under tropical conditions are unclear. The aim of this study was to examine the effects of tropical temperature and moisture conditions on GHG emission from manure. We hypothesized that periodical rainfall and high temperature on tropical climates would increase the GHG emission from faeces by maintaining an anaerobic environment within the faeces. We measured the emission of CH4 and N2O from cattle faeces in two different field sites in Brazil: São Paulo (subtropical) and Rondônia (tropical), as well as under controlled conditions, simulating summer conditions. Emissions of CH4 from faeces ranged from 117 to 1007 mg C–CH4 m−2 h−1. In the field, summer emissions were 2.9 (São Paulo) and 2.5 (Rondônia) times higher than winter (p < 0.05). In controlled conditions, prolonged moisture conditions at high temperature (35 °C) resulted in higher emissions (p < 0.05) than the no-rewetted treatment (2831 and 1781 mgCH4 m−2, respectively). Emission factors determined were 0.02 and 0.05 kg CH4 head−1 year−1 (winter and summer São Paulo, respectively) and 0.06 and 0.10 kg CH4 head−1 year−1 (winter and summer Rondônia, respectively), significantly lower than the IPCC default value of 1 kg CH4 head−1 year−1. CH4 emissions from faeces were slightly higher than from others studies in temperate climates. N2O emission from faeces was lower than the control at the Rondônia site during the summer, with net negative fluxes. We conclude that climate is a strong factor controlling GHG emission from faeces. Our study showed that in a continental-size country as Brazil, an average emission factor as proposed by the IPCC is not the best option.
•First data for Brazil relating to CH4 and N2O emissions from manure deposition in grassland.•CH4 emission was correlated with temperature and rainfall.•Low N2O emission related to manure deposition in the soil.•Emission factors determined were lower than the IPCC default.
No information regarding the management of manure from beef cattle feedlots is available for Brazil. To fill this knowledge gap, a survey of 73 feedlots was conducted in 7 Brazilian states. In this ...survey, questions were asked regarding animal characteristics, their diets, and manure handling management from generation to disposal. These feedlots finished 831,450 animals in 2010. The predominant breed fed was Nellore, with average feeding periods of 60 to 135 d. Corn was the primary source of grain used in the feedlot diets (76% of surveyed animals) with concentrate inclusion levels ranging from 81 to 90% (38% of surveyed animals). The most representative manure management practice was the removal of manure from pens only at the end of the feeding period. Subsequently, the manure was stored in mounds before being applied to crop and pasture lands. Runoff, mainly from rainwater, was collected in retention ponds and used for agriculture. However, the quantity of runoff was not known. Manure was composted for only 20% of the animals in the survey and was treated in anaerobic digesters for only 1% of the animals. Manure from 59% of the cattle surveyed was used as fertilizer, providing a cost savings over the use of synthetic fertilizers. Overall, chemical analysis of the manure before application to fields was conducted for the manure of 56% of the surveyed animals, but the exact quantity applied (per hectare) was unknown for 48%. Feedlots representing 48% of the surveyed animals noted similar or greater crop and pasture yields when using manure, rather than synthetic fertilizers. In addition, 32% mentioned an increase in soil organic matter. Feedlots representing 88% of the surveyed cattle indicated that information concerning management practices that improve manure use efficiency is lacking. Feedlots representing 93% of the animals in the survey reported having basic information regarding the generation of energy and fertilizer with anaerobic digesters. However, only 1 feedlot implemented this technology. In conclusion, the manure management evaluated in this study represents an important indirect economic benefit that was represented by decreased use of synthetic fertilizers in crops. However, little attention was given to the specific treatments and environmental impacts of handling manure. This survey provides information that should assist in the development of better research practices and broader application of future models.
Grassland management affects soil organic carbon (SOC) content and a variety of management options have been proposed to sequester carbon. However, studies conducted in Brazilian pastures have shown ...divergent responses for the SOC depending on management practices. Our objective was to evaluate the effects of management on SOC stocks in grasslands of the Brazilian states of Rondônia and Mato Grosso, and to derive region-specific factors for soil C stock change associated with different management conditions. Compared to SOC stocks in native vegetation, degraded grassland management decreased SOC by a factor of 0.91
±
0.14, nominal grassland management reduced SOC stock for Oxisols by a relatively small factor of 0.99
±
0.08, whereas, SOC storage increased by a factor of 1.24
±
0.07 with nominal management for other soil types. Improved grassland management on Oxisols increased SOC storage by 1.19
±
0.07, relative to native stocks, but there were insufficient data to evaluate the impact of improved grassland management for other soil types. Using these results, we also evaluated the potential for grassland management to sequester or emit C to the atmosphere, and found that degraded grassland management decreased stocks by about 0.27–0.28 Mg C ha
−
1
yr
−
1
; nominal management on Oxisols decreased C at a rate of 0.03 Mg C ha
−
1
yr
−
1
, while nominal management on others soil types and improved management on Oxisols increased stocks by 0.72 Mg C ha
−
1
yr
−
1
and 0.61 Mg C ha
−
1
yr
−
1
, respectively. Therefore, when well managed or improved, grasslands in Rondônia and Mato Grosso states have the potential to sequester C.
•We evaluated the effects of DCD and pyrazole derivatives on N2O emission.•Laboratory and field experiments were conducted under UK summer conditions.•N2O emissions showed similar temporal dynamics ...in both experiments.•The nitrification inhibitors did not significantly reduce N2O emissions.•The lack of effectiveness was presumably due to the higher soil temperature.
Nitrous oxide (N2O) has become the prime ozone depleting atmospheric emission and the third most important anthropogenic greenhouse gas, with a global warming potential approximately 300 times higher than CO2. Nitrification and denitrification are processes responsible for N2O emission from the soil after nitrogen input. The application of a nitrification inhibitor can reduce N2O emissions from these processes. The objective of this study was to assess the effect of two different nitrification inhibitors (dicyandiamide (DCD) and a commercial formulation containing two pyrazole derivatives (PD), 1H-1,2,4-triazole and 3-methylpyrazole) on N2O emissions from cattle urine applications for summer grazing conditions in the UK. Experiments were conducted under controlled conditions in a laboratory incubator and under field conditions on a grassland soil. The N2O emissions showed similar temporal dynamics in both experiments. DCD concentration in the soil showed an exponential degradation during the experiment, with a half-life of the order of only 10d (air temperature c. 15°C). DCD (10kgha−1) and PD at the highest application rate (3.76kgha−1) reduced N2O emissions by 13% and 29% in the incubation experiment and by 33% and 6% in the field experiment, respectively, although these reductions were not statistically significant (P>0.05). Under UK summer grazing conditions, these nitrification inhibitors appear to be less effective at reducing N2O emissions than reported for other conditions elsewhere in the literature, presumably due to the higher soil temperature.
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