Greenhouse gas emissions during cattle feedlot manure composting

The emission of greenhouse gases (GHG) during feedlot manure composting reduces the agronomic value of the final compost and increases the greenhouse effect. A study was conducted to determine whether GHG emissions are affected by composting method. Feedlot cattle manure was composted with two aeration methods--passive (no turning) and active (turned six times). Carbon lost in the forms of CO2 and CH4 was 73.8 and 6.3 kg C Mg-1 manure for the passive aeration treatment and 168.0 and 8.1 kg C Mg-1 manure for the active treatment. The N loss in the form of N2O was 0.11 and 0.19 kg N Mg-1 manure for the passive and active treatments. Fuel consumption to turn and maintain the windrow added a further 4.4 kg C Mg-1 manure for the active aeration treatment. Since CH4 and N2O are 21 and 310 times more harmful than CO2 in their global warming effect, the total GHG emission expressed as CO2-C equivalent was 240.2 and 401.4 kg C Mg-1 manure for passive and active aeration. The lower emission associated with the passive treatment was mainly due to the incomplete decomposition of manure and a lower gas diffusion rate. In addition, turning affected N transformation and transport in the window profile, which contributed to higher N2O emissions for the active aeration treatment. Gas diffusion is an important factor controlling GHG emissions. Higher GHG concentrations in compost windrows do not necessarily mean higher production or emission rates.     

Greenhouse gas emissions from two soils receiving nitrogen fertilizer and swine manure slurry

The interactive effects of soil texture and type of N fertility (i.e., manure vs. commercial N fertilizer) on N(2)O and CH(4) emissions have not been well established. This study was conducted to assess the impact of soil type and N fertility on greenhouse gas fluxes (N(2)O, CH(4), and CO(2)) from the soil surface. The soils used were a sandy loam (789 g kg(-1) sand and 138 g kg(-1) clay) and a clay soil (216 g kg(-1) sand, and 415 g kg(-1) clay). Chamber experiments were conducted using plastic buckets as the experimental units. The treatments applied to each soil type were: (i) control (no added N), (ii) urea-ammonium nitrate (UAN), and (iii) liquid swine manure slurry. Greenhouse gas fluxes were measured over 8 weeks. Within the UAN and swine manure treatments both N(2)O and CH(4) emissions were greater in the sandy loam than in the clay soil. In the sandy loam soil N(2)O emissions were significantly different among all N treatments, but in the clay soil only the manure treatment had significantly higher N(2)O emissions. It is thought that the major differences between the two soils controlling both N(2)O and CH(4) emissions were cation exchange capacity (CEC) and percent water-filled pore space (%WFPS). We speculate that the higher CEC in the clay soil reduced N availability through increased adsorption of NH(4)(+) compared to the sandy loam soil. In addition the higher average %WFPS in the sandy loam may have favored higher denitrification and CH(4) production than in the clay soil.     

Greenhouse gas emissions and soil indicators four years after manure and compost applications

Understanding how carbon, nitrogen, and key soil attributes affect gas emissions from soil is crucial for alleviating their undesirable residual effects that can linger for years after termination of manure and compost applications. This study was conducted to evaluate the emission of soil CO2, N2O, and CH4 and soil C and N indicators four years after manure and compost application had stopped. Experimental plots were treated with annual synthetic N fertilizer (FRT), annual and biennial manure (MN1 and MN2, respectively), and compost (CP1 and CP2, respectively) from 1992 to 1995 based on removal of 151 kg N ha(-1) yr(-1) by continuous corn (Zea mays L.). The control (CTL) plots received no input. After 1995, only the FRT plots received N fertilizer in the spring of 1999. In 1999, the emissions of CO2 were similar between control and other treatments. The average annual carbon input in the CTL and FRT plots were similar to soil CO2-C emission (4.4 and 5.1 Mg C ha(-1) yr(-1), respectively). Manure and compost resulted in positive C and N balances in the soil four years after application. Fluxes of CH4-C and N2O-N were nearly zero, which indicated that the residual effects of manure and compost four years after application had no negative influence on soil C and N storage and global warming. Residual effects of compost and manure resulted in 20 to 40% higher soil microbial biomass C, 42 to 74% higher potentially mineralizable N, and 0.5 unit higher pH compared with the FRT treatment. Residual effects of manure and compost on CO2, N20, and CH4 emissions were minimal and their benefits on soil C and N indicators were more favorable than that of N fertilizer.     

Biological degradation and greenhouse gas emissions during pre-storage of liquid animal manure

Storage of manure makes a significant contribution to global methane (CH4) emissions. Anaerobic digestion of pig and cattle manure in biogas reactors before outside storage might reduce the potential for CH4 emissions. However, manure pre-stored at 15 to 20 degrees C in buildings before anaerobic digestion may be a significant source of CH4 and could reduce the potential CH4 production in the biogas reactor. Degradation of energy-rich organic components in slurry and emissions of CH4 and carbon dioxide (CO2) from aerobic and anaerobic degradation processes during pre-storage were examined in the laboratory. Newly mixed slurry was added to vessels and stored at 15 and 20 degrees C for 100 to 220 d. During storage, CH4 and CO2 emissions were measured with a dynamic chamber technique. The ratio of decomposition in the subsurface to that at the surface indicated that the aerobic surface processes contributed significantly to CO2 emission. The measured CH4 emission was used to calculate the methane conversion factor (MCF) in relation to storage time and temperature, and the total carbon-C emission was used to calculate the decrease in potential CH4 production by anaerobic digestion following pre-storage. The results show substantial methane and carbon dioxide production from animal manure in an open fed-batch system kept at 15 to 20 degrees C, even for short storage times, but the influence of temperature was not significant at storage times of <30 d. During long-term storage (90 d), a strong influence of temperature on the MCF value, especially for pig manure, was observed.     

The effect of phosphogypsum on greenhouse gas emissions during cattle manure composting

Phosphogypsum (PG), a by-product of the phosphate fertilizer industry, reduces N losses when added to composting livestock manure, but its impact on greenhouse gas emissions is unclear. The objective of this research was to assess the effects of PG addition on greenhouse gas emissions during cattle feedlot manure composting. Sand was used as a filler material for comparison. The seven treatments were PG10, PG20, PG30, S10, S20, and S30, representing the rate of PG or sand addition at 10, 20, or 30% of manure dry weight and a check treatment (no PG or sand) with three replications. The manure treatments were composted in open windrows and turned five times during a 134-d period. Addition of PG significantly increased electrical conductivity (EC) and decreased pH in the final compost. Total carbon (TC), total nitrogen (TN), and mineral nitrogen contents in the final composted product were not affected by the addition of PG or sand. From 40 to 54% of initial TC was lost during composting, mostly as CO(2), with CH(4) accounting for <14%. The addition of PG significantly reduced CH(4) emissions, which decreased exponentially with the compost total sulfur (TS) content. The emission of N(2)O accounted for <0.2% of initial TN in the manure, increasing as compost pH decreased from alkaline to near neutral. Based on the total greenhouse gas budget, PG addition reduced greenhouse gas emissions (CO(2)-C equivalent) during composting of livestock manure by at least 58%, primarily due to reduced CH(4) emission.     

Greenhouse gas emissions along the rural-urban gradient

This paper investigates how land use relates to greenhouse gas emissions, using data sources that are readily available to municipal planners. It presents a causal framework linking settlement patterns to greenhouse gas emissions via landscape impacts (deforestation, carbon sequestration by soils and plants, urban heat island), infrastructure impacts (transportation-related emissions, waste management-related emissions, electric transmission and distribution losses) and buildings (residential, commercial). This is not a full accounting because it does not include impacts from industrial activities, agriculture and consumer behavior not related to land use, such as food consumption and air travel. Exploratory case studies of municipalities lying along a gradient of increasing population density suggest that per-capita carbon dioxide emissions vary widely, following an inverted ‘U’ shape, with post-war suburbs riding the pinnacle. Reflecting their central regional roles, municipalities with good jobs-to-housing ratios have higher per-capita emissions because they host both residential and commercial buildings. Buildings typically contribute more emissions than personal transportation. Vehicle-miles traveled per capita shrink most dramatically at very high population densities and where transit options exist. Changing land-use patterns is a political challenge because localism and outdated zoning ordinances subvert regional solutions. Technical fixes, especially green buildings, must be part of the solution.     

Chemical and physical changes following co-composting of beef cattle feedlot manure with phosphogypsum

Nitrogen (N) loss during beef cattle (Bos taurus) feedlot manure composting may contribute to greenhouse gas emissions and increase ammonia (NH(3)) in the atmosphere while decreasing the fertilizer value of the final compost. Phosphogypsum (PG) is an acidic by-product of phosphorus (P) fertilizer manufacture and large stockpiles currently exist in Alberta. This experiment examined co-composting of PG (at rates of 0, 40, 70, and 140 kg PG Mg(-1) manure plus PG dry weight) with manure from feedlot pens bedded with straw or wood chips. During the 99-d composting period, PG addition reduced total nitrogen (TN) loss by 0.11% for each 1 kg Mg(-1) increment in PG rate. Available N at the end of composting was significantly higher for wood chip-bedded (2180 mg kg(-1)) than straw-bedded manure treatments (1820 mg kg(-1)). Total sulfur (TS) concentration in the final compost increased by 0.19 g kg(-1) for each 1 kg Mg(-1) increment in PG rate from 5.2 g TS kg(-1) without PG addition. Phosphogypsum (1.6 g kg(-1) P) addition had no significant effect on total phosphorus (TP) concentration of the final composts. Results from this study demonstrate the potential of PG addition to reduce overall N losses during composting. The accompanying increase in TS content has implications for use of the end-product on sulfur-deficient soils. Co-composting feedlot manure with PG may provide an inexpensive and technologically straightforward solution for managing and improving the nutrient composition of composted cattle manure.     

Greenhouse gas and alcohol emissions from feedlot steers and calves

Livestock's contributions to climate change and smog-forming emissions are a growing public policy concern. This study quantifies greenhouse gas (GHG) and alcohol emissions from calves and feedlot steers. Carbon dioxide (CO) methane (CH), nitrous oxide (NO), ethanol (EtOH), and methanol (MeOH) were measured from a total of 45 Holstein and Angus steers and 9 Holstein calves representative of four different growth stages commonly present on calf ranches and commercial feedlots. Individuals from each animal type were randomly assigned to three equal replicate groups of nine animals per group. Steers were fed a high concentrate diet and calves a milk replacer and grain supplement. Cattle and calves were housed in groups of three animals in an environmental chamber for 24 h. The CO, NO, EtOH, and MeOH concentrations from the air inlet and outlet of the chamber were measured using an INNOVA 1412 monitor and CH using a TEI 55C methane analyzer. Emission rates (g head h) were calculated. The GHGs were mainly produced by enteric fermentation and respiration and differed across life stages of cattle. Compared with dairy cows, feedlot steers produce relatively less GHG. In general, ethanol and methanol, the most important volatile organic compound (VOC) group in the dairy sector, were below the lower limit of detection of the gas analyzer. The present data will be useful to verify models and to enhance GHG emission inventories for enteric fermentation, respiration, and fresh excreta for numerous cattle life stages across the beef industry.     

Greenhouse gas emissions from forestry operations: a life cycle assessment

Most forest carbon assessments focus only on biomass carbon and assume that greenhouse gas (GHG) emissions from forestry activities are minimal. This study took an in-depth look at the direct and indirect emissions from Pacific Northwest (PNW) Douglas-fir [Pseudotsuga menziesii (Mirbel) Franco] forestry activities to support or deny this claim. Greenhouse gas budgets for 408 "management regimes" were calculated using Life Cycle Assessment (LCA) methodology. These management regimes were comprised of different combinations of three types of seedlings (P + 1, 1 + 1, and large plug), two types of site preparation (pile and burn, and chemical), 17 combinations of management intensity including fertilization, herbicide treatment, pre-commercial thinning (PCT), commercial thinning (CT), and nothing, and four different rotation ages (30, 40, 50, and 60 yr). Normalized to 50 yr, average direct GHG emissions were 8.6 megagrams (Mg) carbon dioxide equivalents (CO2e) ha(-1), which accounted for 84% of total GHG emissions from the average of 408 management regimes. Harvesting (PCT, CT, and clear cutting) contributed the most to total GHG emissions (5.9 Mg CO2e per 700 m3 harvested timber), followed by pile and burn site preparation (4.0 Mg CO2e ha(-1) or 32% of total GHG emissions) and then fertilization (1.9 Mg CO2e ha(-1) or 15% of total GHG emissions). Seedling production, seedling transportation, chemical site preparation, and herbicide treatment each contributed less than 1% of total GHG emissions when assessed per hectare of planted timberland. Total emissions per 100 m3 averaged 1.6 Mg CO2e ha(-1) over all 408 management regimes. An uncertainty analysis using Monte Carlo simulations revealed that there are significant differences between most alternative management regimes.     

Greenhouse gas emissions from conventional, agri-environmental scheme, and organic Irish suckler-beef units

The problems of overproduction within the European Union countries and the environmental impact of agriculture have lead to the introduction of schemes that aim to reduce both. Beef (Bos taurus) production forms a large component of the Irish agricultural industry and accounts for more than one quarter of agricultural economic output. Recently, the European CAP (Common Agricultural Policy) has been re-evaluated to include supplementary measures that encompass the environmental role of agriculture rather than just the production role. A life cycle assessment (LCA) method was adopted to estimate emissions per kilogram of CO2 equivalent per kilogram of live weight (LW) leaving the farm gate per annum (kg CO2 kg(-1) LW yr(-1)) and per hectare (kg CO2 ha(-1) yr(-1)). Fifteen units engaged in suckler-beef production (five conventional, five in an Irish agri-environmental scheme, and five organic units) were evaluated for emissions per unit product and area. The average emissions from the conventional units were 13.0 kg CO2 kg(-1) LW yr(-1), from the agri-environmental scheme units 12.2 kg CO2 kg(-1) LW yr(-1), and from the organic units 11.1 kg CO2 kg LW yr(-1). The average emissions per unit area from the conventional units was 5346 kg CO2 ha(-1) yr(-1), from the agri-environmental scheme units 4372 kg CO2 ha(-1) yr(-1), and from the organic units 2302 kg CO2 ha(-1) yr(-1). Results indicated that moving toward extensive production could reduce emissions per unit product and area but live weight production per hectare would be reduced.     

Greenhouse gas emissions and poverty alleviation nexus in the Economic Commission of West African States

This paper investigates the nexus between greenhouse gas emissions and poverty alleviation in the Economic Commission of West African States between 1985 and 2020 applying autoregressive distributed lag and Granger causality techniques. The results reveal that carbon dioxide non-significantly relates to gross domestic product per capita positively while nitrous oxide and foreign direct investment impacts gross domestic product per capita positively. Methane negatively impacts gross domestic product per capita. The governments should use conventions to regulate greenhouse gas emissions’ effects on environmental degradation regionally and globally. The study underscores that countries should diversify to cleaner energy sources. This would reduce greenhouse gas emissions in the atmosphere. Massive technological investment is required to mitigate the greenhouse gas emissions’ negative impacts on the environment which create poverty. This policy implication ensures environmental sustainability and reverses the ugly trend of greenhouse gas emissions on poverty.     

Greenhouse gas emissions in Canada and Japan: sector-specific estimates and managerial and economic implications

Many firms generate large amounts of carbon dioxide and other greenhouse gases when they burn fossil fuels in their production processes. In addition, production of raw materials and other inputs the firms procure for their operations also generates greenhouse gases indirectly. These direct and indirect greenhouse gas emissions occur in many sectors of our economies. In this paper, we first present sector-specific estimates for such greenhouse gas emissions. We then show that estimates for such sector-specific greenhouse gas emissions are often required for various types of corporate as well as public policy analyses in both domestic and international contexts. Measuring greenhouse gas emissions resulting from firms' multi-stage production processes in a multi-sector context is relevant for policies related to the Kyoto protocol, an international agreement to limit global greenhouse gas emissions. For example, since the protocol allows firms to engage in trading and offsetting of their greenhouse gas emissions across national borders, provided that emissions are correctly measured, the firms can take advantage of such trading schemes by placing their energy-intensive production facilities globally and strategically. We present several case studies which illustrate the importance of this and other aspects of greenhouse gas emissions in firms' environmental management. We also argue that our modeling and estimation methods based on input-output analyses are suitable for the types of research goals we have in this paper. Our methods are applied to data for Canada and Japan in a variety of environmental management circumstances.     

Application technique and slurry co-fermentation effects on ammonia,nitrous oxide,and methane emissions after spreading: II. Greenhouse gas emissions

The aim of this study was to investigate the effect of different application techniques on greenhouse gas emission from co-fermented slurry. Ammonia (NH3), nitrous oxide (N2O), and methane (CH4) emissions were measured in two field experiments with four different application techniques on arable and grassland sites. To gather information about fermentation effects, unfermented slurry was also tested, but with trail hose application only. Co-fermented slurry was applied in April at a rate of 30 m3 ha(-1). Measurements were made every 4 h on the first day after application and were continued for 6 wk with gradually decreasing sampling frequency. Methane emissions were <150 g C ha(-1) from co-fermentation products and seemed to result from dissolved CH4. Only in the grassland experiment were emissions from unfermented slurry significantly higher, with wetter weather conditions probably promoting CH4 production. Nitrous oxide emission was significantly increased by injection on arable and grassland sites two- and threefold, respectively. Ammonia emissions were smallest after injection or trail shoe application and are discussed in the preceding paper. We evaluated the climatic relevance of the measured gas emissions from the different application techniques based on the comparison of CO2 equivalents. It was evident that NH3 emission reduction, which can be achieved by injection, is at least compensated by increased N2O emissions. Our results indicate that on arable land, trail hose application with immediate shallow incorporation, and on grassland, trail shoe application, bear the smallest risks of high greenhouse gas emissions when fertilizing with co-fermented slurry.     

Carbon, nitrogen balances and greenhouse gas emission during cattle feedlot manure composting

Carbon and N losses reduce the agronomic value of compost and contribute to greenhouse gas (GHG) emissions. This study investigated GHG emissions during composting of straw-bedded manure (SBM) and wood chip-bedded manure (WBM). For SBM, dry matter (DM) loss was 301 kg Mg(-1), total carbon (TC) loss was 174 kg Mg(-1), and total nitrogen (TN) loss was 8.3 kg Mg(-1). These correspond to 30.1% of initial DM, 52.8% of initial TC, and 41.6% of initial TN. For WBM, DM loss was 268 kg Mg(-1), TC loss was 154 kg Mg(-1), and TN loss was 1.40 kg Mg(-1), corresponding to 26.5, 34.5, and 11.8% of initial amounts. Most C was lost as CO2 with CH4 accounting for <6%. However, the net contribution to greenhouse gas emissions was greater for CH4 since it is 21 times more effective at trapping heat than CO2. Nitrous oxide (N2O) emissions were 0.077 kg N Mg(-1) for SBM and 0.084 kg N Mg(-1) for WBM, accounting for 1 to 6% of total N loss. Total GHG emissions as CO2-C equivalent were not significantly different between SBM (368.4 +/- 18.5 kg Mg(-1)) and WBM (349.2 +/- 24.3 kg Mg(-1)). However, emission of 368.4 kg C Mg(-1) (CO2-C equivalent) was greater than the initial TC content (330.5 kg Mg(-1)) of SBM, raising the question of the net benefits of composting on C sequestration. Further study is needed to evaluate the impact of composting on overall GHG emissions and C sequestration and to fully investigate livestock manure management options.     

Effects of reed straw, zeolite, and superphosphate amendments on ammonia and greenhouse gas emissions from stored duck manure

Stored poultry manure can be a significant source of ammonia (NH) and greenhouse gases (GHGs), including nitrous oxide (NO), methane (CH), and carbon dioxide (CO) emissions. Amendments can be used to modify physiochemical properties of manure, thus having the potential to reduce gas emissions. Here, we lab-tested the single and combined effects of addition of reed straw, zeolite, and superphosphate on gas emissions from stored duck manure. We showed that, over a period of 46 d, cumulative NH emissions were reduced by 61 to 70% with superphosphate additions, whereas cumulative NO emissions were increased by up to 23% compared with the control treatment. Reed straw addition reduced cumulative NH, NO, and CH emissions relative to the control by 12, 27, and 47%, respectively, and zeolite addition reduced cumulative NH and NO emissions by 36 and 20%, respectively. Total GHG emissions (as CO-equivalents) were reduced by up to 27% with the additions of reed straw and/or zeolite. Our results indicate that reed straw or zeolite can be recommended as amendments to reduce GHG emissions from duck manure; however, superphosphate is more effective in reducing NH emissions.     

Greenhouse gas emissions and energy balance of sunflower biodiesel: Identification of its key factors in the supply chain

The production of first generation biofuels, such as sunflower-based biodiesel, is potentially an option for diversifying the energy matrix in several South American countries. However, biofuels present environmental challenges, especially concerning the reduction of greenhouse gas (GHG) emissions. This study, using a life-cycle approach, evaluates the GHG emissions and energy balance of the future nationwide production of sunflower-based biodiesel in Chile. Direct land use change is included in the analysis. The overall findings indicate that sunflower biodiesel, under the most likely production conditions, will have better environmental performance than fossil diesel in terms of both indicators. The agricultural stage is associated to key factors such as land use change, and nitrogen fertilizers. These factors contribute significantly to GHG emissions or energy demand in the biodiesel life cycle. The sensitivity analysis shows that no GHG emission saving could occur if nitrogen fertilizers rate exceeds 330 kg N/ha. In order to reduce the environmental impacts of this biofuel, improvement measures are suggested.     

Effect of cattle slurry separation on greenhouse gas and ammonia emissions during storage

Storage of cattle slurry leads to emissions of methane (CH(4)), nitrous oxide (N(2)O), ammonia (NH(3)), and carbon dioxide (CO(2)). On dairy farms, winter is the most critical period in terms of slurry storage due to cattle housing and slurry field application prohibition. Slurry treatment by separation results in reduced slurry dry matter content and has considerable potential to reduce gaseous emissions. Therefore, the efficiency of slurry separation in reducing gaseous emissions during winter storage was investigated in a laboratory study. Four slurry fractions were obtained: a solid and a liquid fraction by screw press separation (SPS) and a supernatant and a sediment fraction by chemically enhanced settling of the liquid fraction. Untreated slurry and the separated fractions were stored in plastic barrels for 48 d under winter conditions, and gaseous emissions were measured. Screw press separation resulted in an increase of CO(2) (650%) and N(2)O (1240%) emissions due to high releases observed from the solid fraction, but this increase was tempered by using the combined separation process (CSP). The CSP resulted in a reduction of CH(4) emissions ( approximately 50%), even though high emissions of CH(4) (46% of soluble C) were observed from the solid fraction during the first 6 d of storage. Screw press separation increased NH(3) emissions by 35%, but this was reduced to 15% using the CSP. During winter storage greenhouse gas emissions from all treatments were mainly in the form of CH(4) and were reduced by 30 and 40% using SPS and CSP, respectively.     

Reducing ammonia gas from chicken manure with lime and soybean plants

This research is aimed at addressing the complaints of local people living near chicken farms who are disturbed by odors caused by livestock activities, and specifically, by the generation of ammonia gas from chicken manure. Methods that are expected to reduce the intensity of ammonia gas odors include both scattering lime on the surface of the soil and planting soybeans around the cages. The results obtained showed a reduction in the levels of ammonia gas by 57.48%–from 1.67 parts per million (ppm) near an untreated cage to 0.71 ppm near the cage that achieved the best results. The study found that spreading lime evenly over the chicken manure was the most effective method that farmers could use to reduce ammonia odors. The sample area treated by the addition of soybean plants showed a reduction in the levels of ammonia gas from 1.67 to 0.78 ppm.     

Manipulation of dietary protein and nonstarch polysaccharide to control swine manure emissions

Odor and greenhouse gas (GHG) emissions from stored pig (Sus scrofa) manure were monitored for response to changes in the crude protein level (168 or 139 g kg(-1), as-fed basis) and nonstarch polysaccharide (NSP) content [i.e., control, or modified with beet pulp (Beta vulgaris L.), cornstarch, or xylanase] of diets fed to pigs in a production setting. Each diet was fed to one of eight pens of pigs according to a 2 x 4, full-factorial design, replicated over three time blocks with different groups of animals and random assignment of diets. Manure from each treatment was characterized and stored in a separate, ventilated, 200-L vessel. Repeated measurements of odor, carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) emissions from the vessels were taken every two weeks for eight weeks. Manure from high-protein diets had higher sulfur concentration and pH (P < or = 0.05). High-NSP (beet pulp) diets resulted in lower manure nitrogen and ammonia concentrations and pH (P < or = 0.05). Odor level and hedonic tone of exhaust air from the storage vessel headspaces were unaffected by the dietary treatments. Mean CO2 and CH4 emissions (1400 and 42 g d(-1) m(-3) manure, respectively) increased with lower dietary protein (P < or = 0.05). The addition of xylanase to high-protein diets caused a decrease in manure CO2 emissions, but an increase when added to low-protein diets (P < or = 0.05). Nitrous oxide emissions were negligible. Contrary to other studies, these results do not support the use of dietary protein reduction to reduce emissions from stored swine manure.     

Soil nitrous oxide emissions following band-incorporation of fertilizer nitrogen and swine manure

Treatment of liquid swine manure (LSM) offers opportunities to improve manure nutrient management. However, N2O fluxes and cumulative emissions resulting from application of treated LSM are not well documented. Nitrous oxide emissions were monitored following band-incorporation of 100 kg N ha(-1) of either mineral fertilizer, raw LSM, or four pretreated LSMs (anaerobic digestion; anaerobic digestion + flocculation: filtration; decantation) at the four-leaf stage of corn (Zea mays L.). In a clay soil, a larger proportion of applied N was lost as N2O with the mineral fertilizer (average of 6.6%) than with LSMs (3.1-5.0%), whereas in a loam soil, the proportion of applied N lost as N2O was lower with the mineral fertilizer (average of 0.4%) than with LSMs (1.2-2.4%). Emissions were related to soil NO3 intensity in the clay soil, whereas they were related to water-extractable organic C in the loam soil. This suggests that N2O production was N limited in the clay soil and C limited in the loam soil, and would explain the interaction found between N sources and soil type. The large N2O emission coefficients measured in many treatments, and the contradicting responses among N sources depending on soil type, indicate that (i) the Intergovernmental Panel on Climate Change (IPCC) default value (1%) may seriously underestimate N2O emissions from fine-textured soils where fertilizer N and manure are band-incorporated, and (ii) site-specific factors, such as drainage conditions and soil properties (e.g., texture, organic matter content), have a differential influence on emissions depending on N source.