Quantifying carbon dioxide and methane emissions and carbon dynamics from flooded boreal forest soil

The boreal forest is subject to natural and anthropogenic disturbances, but the production of greenhouse gases as a result of flooding for hydroelectric power generation has received little attention. It was hypothesized that flooded soil would result in greater CO(2) and CH(4) emissions and carbon (C) fractionation compared with non-flooded soil. To evaluate this hypothesis, soil C and nitrogen (N) dynamics, CO(2) and CH(4) mean production rates, and (13)C fractionation in laboratory incubations at 14 and 21 degrees C under non-flooded and flooded conditions and its effect on labile and recalcitrant C sources were determined. A ferro-humic Podzol was collected at three different sites at the Experimental Lakes Area, Canada, with a high (19,834 g C m(-2)), medium (18,066 g C m(-2)), and low (11,060 g C m(-2)) soil organic C (SOC) stock. Soil organic C and total N stocks (g m(-2)) and concentrations (g kg(-1)) were significantly different (p < 0.05) among soil horizons within each of the three sites. Stable isotope analysis showed a significant enrichment in delta(13)C and delta(15)N with depth and an enrichment in delta(13)C and delta(15)N with decreasing SOC and N concentration. The mean CO(2) and CH(4) production rates were greatest in soil horizons with the highest SOC stock and were significantly higher at 21 degrees C and in flooded treatments. The delta(13)C of the evolved CO(2) (delta(13)C-CO(2)) became significantly enriched with time during decomposition, and the greatest degree of fractionation occurred in the organic Litter, Fungal, and Humic forest soil horizons and in soil with a high SOC stock compared with the mineral horizon and soil with a lower SOC stock. The delta(13)C-CO(2) was significantly depleted in flooded treatments compared with non-flooded treatments.     

Tillage and crop residue effects on soil carbon and carbon dioxide emission in corn-soybean rotations

Soil C change and CO2 emission due to different tillage systems need to be evaluated to encourage the adoption of conservation practices to sustain soil productivity and protect the environment. We hypothesize that soil C storage and CO2 emission respond to conservation tillage differently from conventional tillage because of their differential effects on soil properties. This study was conducted from 1998 through 2001 to evaluate tillage effects on soil C storage and CO2 emission in Clarion-Nicollet-Webster soil association in a corn [Zea mays L.]-soybean [Glycine max (L.) Merr.] rotation in Iowa. Treatments included no-tillage with and without residue, strip-tillage, deep rip, chisel plow, and moldboard plow. No-tillage with residue and strip-tillage significantly increased total soil organic C (TC) and mineral fraction C (MFC) at the 0- to 5- and 5- to 10-cm soil depths compared with chisel plow after 3 yr of tillage practices. Soil CO2 emission was lower for less intensive tillage treatments compared with moldboard plow, with the greatest differences occurring immediately after tillage operations. Cumulative soil CO2 emission was 19 to 41% lower for less intensive tillage treatments than moldboard plow, and it was 24% less for no-tillage with residue than without residue during the 480-h measurement period. Estimated soil mineralizable C pool was reduced by 22 to 66% with less intensive tillage treatments compared with moldboard plow. Adopting less intensive tillage systems such as no-tillage, strip-tillage, deep rip, and chisel plow and better crop residue cover are effective in reducing CO2 emission and thus improving soil C sequestration in a corn-soybean rotation.     

Biochar and earthworm effects on soil nitrous oxide and carbon dioxide emissions

Biochar is the product of pyrolysis produced from feedstock of biological origin. Due to its aromatic structure and long residence time, biochar may enable long-term carbon sequestration. At the same time, biochar has the potential to improve soil fertility and reduce greenhouse gas (GHG) emissions from soils. However, the effect of biochar application on GHG fluxes from soil must be investigated before recommendations for field-scale biochar application can be made. A laboratory experiment was designed to measure carbon dioxide (CO) and nitrous oxide (NO) emissions from two Irish soils with the addition of two different biochars, along with endogeic (soil-feeding) earthworms and ammonium sulfate, to assist in the overall evaluation of biochar as a GHG-mitigation tool. A significant reduction in NO emissions was observed from both low and high organic matter soils when biochars were applied at rates of 4% (w/w). Earthworms significantly increased NO fluxes in low and high organic matter soils more than 12.6-fold and 7.8-fold, respectively. The large increase in soil NO emissions in the presence of earthworms was significantly reduced by the addition of both biochars. biochar reduced the large earthworm emissions by 91 and 95% in the low organic matter soil and by 56 and 61% in the high organic matter soil (with and without N fertilization), respectively. With peanut hull biochar, the earthworm emissions reduction was 80 and 70% in the low organic matter soil, and only 20 and 10% in the high organic matter soil (with and without N fertilization), respectively. In high organic matter soil, both biochars reduced CO efflux in the absence of earthworms. However, soil CO efflux increased when peanut hull biochar was applied in the presence of earthworms. This study demonstrated that biochar can potentially reduce earthworm-enhanced soil NO and CO emissions. Hence, biochar application combined with endogeic earthworm activity did not reveal unknown risks for GHG emissions at the pot scale, but field-scale experiments are required to confirm this.     

Methane and carbon dioxide emission from two pig finishing barns

Agricultural activities are an important source of greenhouse gases. However, comprehensive, long-term, and high-quality measurement data of these gases are lacking. This article presents a field study of CH(4) and CO(2) emission from two 1100-head mechanically ventilated pig (Sus scrofa) finishing barns (B1 and B2) with shallow manure flushing systems and propane space heaters from August 2002 to July 2003 in northern Missouri. Barn 2 was treated with soybean oil sprinkling, misting essential oils, and misting essential oils with water to reduce air pollutant emissions. Only days with CDFB (complete-data-full-barn), defined as >80% of valid data during a day with >80% pigs in the barns, were used. The CH(4) average daily mean (ADM) emission rates were 36.2 +/- 2.0 g/d AU (ADM +/- 95% confidence interval; animal unit = 500 kg live mass) from B1 (CDFB days = 134) and 28.8 +/- 1.8 g/d AU from B2 (CDFB days = 131). The CO(2) ADM emission rates were 17.5 +/- 0.8 kg/d AU from B1 (CDFB days = 146) and 14.2 +/- 0.6 kg/d AU from B2 (CDFB days = 137). The treated barn reduced CH(4) emission by 20% (P < 0.01) and CO(2) emission by 19% (P < 0.01). The CH(4) and CO(2) released from the flushing lagoon effluent were equivalent to 9.8 and 4.1% of the CDFB CH(4) and CO(2) emissions, respectively. The emission data were compared with the literature, and the characteristics of CH(4) and CO(2) concentrations and emissions were discussed.     

Monitoring effects of a controlled subsurface carbon dioxide release on vegetation using a hyperspectral imager

A hyperspectral imaging system was used to monitor vegetation during a subsurface controlled release of carbon dioxide (CO₂). From August 3 to 10, 2007, 0.3 tons CO₂/day were released through a 70 m horizontal pipe located at a nominal depth of 1.8 m below the surface. Hyperspectral images of alfalfa plants were collected during the controlled release and used along with classification tree analysis to study changes in the reflectance spectra as a function of perpendicular distance from the horizontal pipe. Changes in the reflectance spectra near the red edge (650–750 nm) were observed over the course of the controlled release experiment for plants within a perpendicular distance of 1 m of the release pipe. These results indicate monitoring vegetation over a carbon sequestration site has the potential to allow monitoring of the integrity of the CO₂ storage.     

Lessons learned from natural and industrial analogues for storage of carbon dioxide

The deployment of CCS (carbon capture and storage) at industrial scale implies the development of effective monitoring tools. Noble gases are tracers usually proposed to track CO₂. This methodology, combined with the geochemistry of carbon isotopes, has been tested on available analogues.At first, gases from natural analogues were sampled in the Colorado Plateau and in the French carbogaseous provinces, in both well-confined and leaking-sites. Second, we performed a 2-years tracing experience on an underground natural gas storage, sampling gas each month during injection and withdrawal periods.In natural analogues, the geochemical fingerprints are dependent on the containment criterion and on the geological context, giving tools to detect a leakage of deep-CO₂ toward surface. This study also provides information on the origin of CO₂, as well as residence time of fluids within the crust and clues on the physico-chemical processes occurring during the geological story.The study on the industrial analogue demonstrates the feasibility of using noble gases as tracers of CO₂. Withdrawn gases follow geochemical trends coherent with mixing processes between injected gas end-members. Physico-chemical processes revealed by the tracing occur at transient state.These two complementary studies proved the interest of geochemical monitoring to survey the CO₂ behaviour, and gave information on its use.     

Life cycle assessment of carbon dioxide capture and storage from lignite power plants

In this article, we present a life cycle assessment (LCA) of CO₂ capture and storage (CCS) for several lignite power plant technologies. The LCA includes post-combustion, pre-combustion and oxyfuel capture processes as well as subsequent pipeline transport and storage of the separated CO₂ in a depleted gas field.The results show an increase in cumulative energy demand and a substantial decrease in greenhouse gas (GHG) emissions for all CO₂ capture approaches in comparison with power plants without CCS, assuming negligible leakage within the time horizon under consideration. Leakage will, however, not be zero. Due to the energy penalty, CCS leads to additional production of CO₂. However, the CO₂ emissions occur at a much lower rate and are significantly delayed, thus leading to different, and most likely smaller, impacts compared to the no-sequestration case. In addition, a certain share of the CO₂ will be captured permanently due to chemical reactions and physical trapping.For other environmental impact categories, the results depend strongly on the chosen technology and the details of the process. The post-combustion approach, which is closest to commercial application, leads to sharp increases in many categories of impacts, with the impacts in only one category, acidification, reduced. In comparison with a conventional power plant, the pre-combustion approach results in decreased impact in all categories. This is mainly due to the different power generation process (IGCC) which is coupled with the pre-combustion technology.In the case of the oxyfuel approach, the outcome of the LCA depends highly on two uncertain parameters: the energy demand for air separation and the feasibility of co-capture of pollutants other than CO₂. If co-capture were possible, oxyfuel could lead to a near-zero emission power plant.     

Effect of nitrogen fertilizer application on growing season soil carbon dioxide emission in a corn-soybean rotation

Nitrogen application can have a significant effect on soil carbon (C) pools, plant biomass production, and microbial biomass C processing. The focus of this study was to investigate the short-term effect of N fertilization on soil CO(2) emission and microbial biomass C. The study was conducted from 2001 to 2003 at four field sites in Iowa representing major soil associations and with a corn (Zea mays L.)-soybean (Glycine max L. Merr.) rotation. The experimental design was a randomized complete block with four replications of four N rates (0, 90, 180, and 225 kg ha(-1)). In the corn year, season-long cumulative soil CO(2) emission was greatest with the zero N application. There was no effect of N applied in the prior year on CO(2) emission in the soybean year, except at one of three sites, where greater applied N decreased CO(2) emission. Soil microbial biomass C (MBC) and net mineralization in soil collected during the corn year was not significantly increased with increase in N rate in two out of three sites. At all sites, soil CO(2) emission from aerobically incubated soil showed a more consistent declining trend with increase in N rate than found in the field. Nitrogen fertilization of corn reduced the soil CO(2) emission rate and seasonal cumulative loss in two out of three sites, and increased MBC at only one site with the highest N rate. Nitrogen application resulted in a reduction of both emission rate and season-long cumulative emission of CO(2)-C from soil.     

Kinetic of formation for single carbon dioxide and mixed carbon dioxide and tetrahydrofuran hydrates in water and sodium chloride aqueous solution

A laboratory-scale reactor system is built and operated to measure the kinetic of formation for single and mixed carbon dioxide–tetrahydrofuran hydrates. The T-cycle method, which is used to collect the kinetic data, is briefly discussed. For single carbon dioxide hydrate, the induction time decreases with the increase of the initial carbon dioxide pressure up to 2.96 MPa. Beyond this pressure, the induction time is becoming relatively constant with the increase of initial carbon dioxide pressure indicating that the liquid phase is completely supersaturated with carbon dioxide. Experimental results show that the inclusion of tetrahydrofuran reduces the induction time required for hydrate formation. These observations indicate hydrate nucleation process and onset growth are more readily to occur in the presence of tetrahydrofuran. In contrast, the presence of sodium chloride prolongs the induction time due to clustering of water molecules with the ions and the salting-out effects. It is also shown that the degree of subcooling required for hydrate formation is affected by the presence of tetrahydrofuran and sodium chloride in the hydrate forming system. The presence of tetrahydrofuran in the hydrate system significantly reduces the amount of carbon dioxide uptake. The apparent rate constant, k, for those systems are reported.     

The effects of soil carbon on phosphorus and sediment loss from soil trays by overland flow

Soil chemical constituents influence soil structure and erosion potential. We investigated manure and inorganic fertilizer applications on soil chemistry (carbon [C] quality and exchangeable cations), aggregation, and phosphorus (P) loss in overland flow. Surface samples (0-5 cm) of a Hagerstown (fine, mixed, semiactive, mesic Typic Hapludalf) soil, to which either dairy or poultry manure or triple superphosphate had been applied (0-200 kg P ha(-1) yr(-1) for 5 yr), were packed in boxes (1 m long, 0.15 m wide, and 0.10 m deep) to field bulk density (1.2 g cm(-3)). Rainfall was applied (65 mm h(-1)), overland flow collected, and sediment and P loss determined. All amendments increased Mehlich 3-extractable P (19-177 mg kg(-1)) and exchangeable Ca (4.2-11.5 cmol kg(-1)) compared with untreated soil. For all treatments, sediment transport was inversely related to the degree of soil aggregation (determined as ratio of dispersed and undispersed clay; r = 0.51), exchangeable Ca (r = 0.59), and hydrolyzable carbohydrate (r = 0.62). The loss of particulate P and total P in overland flow from soil treated with up to 50 kg P ha(-1) dairy manure (9.9 mg particulate phosphorus [PPI, 15.1 mg total phosphorus [TP]) was lower than untreated soil (13.3 mg PP, 18.1 mg TP), due to increased aggregation and decreased surface soil slaking attributed to added C in manure. Manure application at low rates (<50 kg P ha(-1)) imparts physical benefits to surface soil, which decrease P loss potential. However, at greater application rates, P transport is appreciably greater (26.9 mg PP, 29.5 mg TP) than from untreated soil (13.3 mg PP, 18.1 mg TP).     

Dissolved organic carbon and disinfection by-product precursor release from managed peat soils

A wetland restoration demonstration project examined the effects of a permanently flooded wetland on subsidence of peat soils. The project, started in 1997, was done on Twitchell Island, in the Sacramento-San Joaquin Delta of California. Conversion of agricultural land to a wetland has changed many of the biogeochemical processes controlling dissolved organic carbon (DOC) release from the peat soils, relative to the previous land use. Dissolved organic C in delta waters is a concern because it reacts with chlorine, added as a disinfectant in municipal drinking waters, to form carcinogenic disinfection byproducts (DBPs), including trihalomethanes (THMs) and haloacetic acids (HAAs). This study explores the effects of peat soil biogeochemistry on DOC and DBP release under agricultural and wetland management. Results indicate that organic matter source, extent of soil organic matter decomposition, and decomposition pathways all are factors in THM formation. The results show that historical management practices dominate the release of DOC and THM precursors. However, within-site differences indicate that recent management decisions can contribute to changes in DOC quality and THM precursor formation. Not all aromatic forms of carbon are highly reactive and certain environmental conditions produce the specific carbon structures that form THMs. Both HAA and THM precursors are elevated in the DOC released under wetland conditions. The findings of this study emphasize the need to further investigate the roles of organic matter sources, microbial decomposition pathways, and decomposition status of soil organic matter in the release of DOC and DBP precursors from delta soils under varying land-use practices.     

Synthesis and characterization of zwitterionic carbon dioxide fixing reagents

The synthesis of three amine-based carbon dioxide fixing reagents is presented. The reagents were designed so that they would be able to bind CO₂ reversibly through the formation of the well known carbamates that was stabilized through forming a zwitterion. CO₂ fixing experiments were performed with ¹³CO₂ labeling and medium pressure NMR. The experiments showed that two of the three reagents were able to form carbamates and thus bind CO₂. In addition we investigated this particular class of molecules for the possible formation of neutrally charged spiro compounds and we show that these did not form under the conditions studied.     

Grey relation analysis of carbon dioxide emissions from industrial production and energy uses in Taiwan

This study aims to identify key factors affecting energy-induced CO₂emission changes from 34 industries in Taiwan, in order to have an integrated understanding of the industrial environmental-economic-energy performance and to provide insights for relevant policy making in Taiwan. Grey relation analysis was used in this paper to analyse how energy-induced CO₂emissions from 34 industries in Taiwan are affected by the factors: production, total energy consumption, coal, oil, gas and electricity uses. The methodology was modified by taking account of the evolutionary direction among relevant factors. Furthermore, tests of sensitivity and stability, which are seldom discussed in most grey relation analyses, were conducted to ensure the reliability of outcomes. We found that values ranging from 0·3 to 0·5 are appropriate, and the analytical results with value of 0·5 offer moderate distinguishing effects and good stability. Results indicate that industrial production has the closest relationship with aggregate CO₂emission changes; electricity consumption the second in importance. It reveals that the economy in Taiwan relied heavily on CO₂intensive industries, and that electricity consumption had become more important for economic growth. The relational order of fuels is electricity, coal, oil then gas, accordant with their CO₂emission coefficients in Taiwan. The positive relational grade of aggregate production implies that the aggregate industrial CO₂intensity tended to decline. The total energy consumption had a smaller and negative relational grade with CO₂emissions, and implies an improvement on aggregate energy intensity, while the CO₂emission coefficient increased. For industries with significant influence on CO₂emissions, the total energy consumption had the largest relational grades. It is important to reduce the energy intensity of these industries. Nevertheless, it is also critical to decouple energy consumption and production to reduce the impacts of CO₂mitigation on economic growth.     

Atmospheric emissions of nitrous oxide, methane, and carbon dioxide from different nitrogen fertilizers

Alternative N fertilizers that produce low greenhouse gas (GHG) emissions from soil are needed to reduce the impacts of agricultural practices on global warming potential (GWP). We quantified and compared growing season fluxes of NO, CH, and CO resulting from applications of different N fertilizer sources, urea (U), urea-ammonium nitrate (UAN), ammonium nitrate (NHNO), poultry litter, and commercially available, enhanced-efficiency N fertilizers as follows: polymer-coated urea (ESN), SuperU, UAN + AgrotainPlus, and poultry litter + AgrotainPlus in a no-till corn ( L.) production system. Greenhouse gas fluxes were measured during two growing seasons using static, vented chambers. The ESN delayed the NO flux peak by 3 to 4 wk compared with other N sources. No significant differences were observed in NO emissions among the enhanced-efficiency and traditional inorganic N sources, except for ESN in 2009. Cumulative growing season NO emission from poultry litter was significantly greater than from inorganic N sources. The NO loss (2-yr average) as a percentage of N applied ranged from 0.69% for SuperU to 4.5% for poultry litter. The CH-C and CO-C emissions were impacted by environmental factors, such as temperature and moisture, more than the N source. There was no significant difference in corn yield among all N sources in both years. Site specifics and climate conditions may be responsible for the differences among the results of this study and some of the previously published studies. Our results demonstrate that N fertilizer source and climate conditions need consideration when selecting N sources to reduce GHG emissions.     

Adsorption of carbon dioxide using impregnated activated carbon promoted by Zinc

The effect of impregnation of activated carbon with Cr₂O and Fe₂O₃ and promotion by Zn²⁺ on its adsorptive properties of carbon dioxide was studied using a volumetric adsorption apparatus at ambient temperature and low pressures. Slurry and solution impregnation methods were used to compare CO₂ capture capacity of the impregnated activated carbon promoted by Zinc. The obtained adsorption isotherms showed that amount of CO₂ adsorbed on the samples impregnated by Cr₂O was increased about 20% in compare to raw activated carbon. The results also showed that Fe₂O₃ was not an effective impregnating species for activated carbon modification. Moreover slurry impregnation method showed higher CO₂ adsorption capacity in comparison with solution impregnation method. Samples prepared by co-impregnation of two metal species showed more adsorption capacity than samples impregnated by just one metal species individually. Washing the impregnated samples by metal oxide resulted in 15% increase in CO₂ adsorption capacities of activated carbons which can be attributed to the metal oxides removal covering the adsorption surface. Decreasing impregnation temperature from 95 to 25 °C in solution method showed a significant increase in CO₂ adsorption capacity. Sips equation was found a suitable model fitting to the adsorption data in the range studied.     

Lagoon-biogas emissions and carbon balance estimates of a swine production facility

Gaseous emissions from animal manure storage facilities can contribute to global greenhouse gas inventories. Biogas fluxes were measured for one year from a 2-ha anaerobic lagoon that received waste from a 10500-head swine (Sus scrofa) finishing operation in southwestern Kansas. During 2001, ebullition of biogas was measured continuously by using floating platforms equipped with gas-collection domes. Periodically, the composition of the biogas was determined by using gas chromatography. Detailed records of feed quality and quantity and animal weights and gains also were obtained to determine the carbon budget of the facility (barns and lagoon). Flux of biogas was very seasonal, with peak emission (18.7 mol m(-2) d(-1)) occurring in early June. Nearly 50% of the annual biogas losses occurred during a 30-d period beginning on day of year (DOY) 146. Flux patterns suggest that the start of the high biogas production period was governed by temperature, while the decline in production in mid-June was caused by substrate limitations. Average biogas composition was 0.71 L CH4 L(-1). The quantity of CH4 released from the lagoon was 86.3 Mg yr(-1), which represents about 38 g of CH4 per kg of animal weight gain. The average flux density of biogas from the lagoon was 382 mol m(-2) yr(-1) or 728 mol yr(-1) per resident animal where the resident animal population was 10500. Flux rates of CH4 were 1.7 to 3.4 times less than predictions made with Intergovernmental Panel on Climate Change (IPCC) models. Additional research is needed on the carbon budgets of other animal feeding operations so that better estimates of greenhouse gas emissions can be determined.     

Environment and productivities in developed and developing countries: The case of carbon dioxide and sulfur dioxide

We propose a productivity index for undesirable outputs such as carbon dioxide (CO₂) and sulfur dioxide (SO₂) emissions and measure it using data from 51 developed and developing countries over the period 1971–2000. About half of the countries exhibit the productivity growth. The changes in the productivity index are linked with their respective per capita income using a semi-parametric model. Our results show technological catch up of low-income countries. However, overall productivities both of SO₂ and CO₂ show somewhat different results.     

CO2 transportation for carbon capture and storage: Sublimation of carbon dioxide from a dry ice bank

Climate change is being caused by greenhouse gases such as carbon dioxide (CO₂). Carbon capture and storage (CCS) is of interest to the scientific community as one way of achieving significant global reductions of atmospheric CO₂ emissions in the medium term. CO₂ would be captured from large stationary sources such as power plants and transported via pipelines under high pressure conditions to underground storage. If a downward leakage from a surface transportation system module occurs, the CO₂ would undergo a large temperature reduction and form a bank of “dry ice” on the ground surface; the sublimation of the gas from this bank represents an area source term for subsequent atmospheric dispersion, with an emission rate dependent on the energy balance at the bank surface. Gaseous CO₂ is denser than air and tends to remain close to the surface; it is an asphyxiant, a cerebral vasodilator and at high concentrations causes rapid circulatory insufficiency leading to coma and death. Hence a subliming bank of dry ice represents safety hazard. A model is presented for evaluating the energy balance and sublimation rate at the surface of a solid frozen CO₂ bank under different environmental conditions. The results suggest that subliming gas behaves as a proper dense gas (i.e. it remains close to the ground surface) only for low ambient wind speeds.     

Rototillage,disking, and subsequent irrigation: effects on soil nitrogen dynamics,microbial biomass,and carbon dioxide efflux

Spring and summer tillage are usually followed by irrigation before planting crops in California's summer-dry Mediterranean-type climate. Tillage treatments such as rototillage or disking are known to disturb the soil structure to different extents, but little is known about how the intensity of a tillage event and subsequent irrigation affect the microbial biomass, respiration, CO2 efflux, and mineral N of agricultural soils. We carried out an experiment with a Yolo silt loam (fine-silty, mixed, superactive, nonacid, thermic Mollic Xerofluvent) with two tilled treatments (rototillage and disked and rolled) and a nontilled control. The soil was subsequently sampled throughout a 17-d period. Nine days after tillage, all treatments were lightly sprinkler-irrigated to bring the soil water potential above -10 kPa. After tillage, the soil ammonium and nitrate content increased rapidly relative to the control with highest increases in the disked soil. Mineral N remained higher in the tilled treatments after irrigation. Rototillage and disking increased the CO2 efflux of the soil within 24 h of the disturbance. The increase was higher in the disked soil, which was more than three times the CO2 efflux of the control soil at 0.25 h after tillage. This effect may be due to degassing of dissolved CO2 since microbial respiration did not increase in tilled soils. Irrigation increased the CO2 efflux of all treatments but this was most pronounced in the control soil, which had an order of magnitude increase in CO2 efflux after irrigation. An ancillary experiment carried out under similar conditions but with more frequent sampling showed that increases in CO2 efflux after irrigation were accompanied by increases in soil respiration. This study shows that different tillage implements affect CO2 efflux, nitrate accumulation, and microbial activity, and thus have different effects on soil and atmospheric environmental quality.