Two laboratory incubation studies and a growth room bioassay of forage barley were conducted to investigate nitrogen (N) and phosphorus (P) mineralization, and nitrous oxide emission from two contrasting agricultural soils amended with anaerobically digested cattle manure (ADM). The ADM is a nutrient-rich co-product from manure-based biogas plants which is applied to cropland at rates used for raw manure since scientific information on nutrient release from ADM is lacking. Application of the separated solids fraction of ADM (SS) reduced nitrous oxide emission but resulted in lower N mineralization compared to raw manure in both soils. Raw manure- and SS- treatments had similar biomass yields and P supply capacities while the application of pelletized SS (PSS) caused net N immobilization, lower P release than manure and SS, and depressed barley yields relative to non-amended (control) soils.

Earthworms are well known to increase decomposition of organic matter and release of plant available nutrients. They can also increase CO 2 and N2O fluxes from the soil by stimulating respiration, denitrification, and nitrification caused by soil microorganisms. The objective of this thesis was to examine the influence of different earthworm species and population numbers on CO2 and N2O fluxes from a corn agroecosystem. In the field study, earthworm treatments had a significant effect on CO2 fluxes, but there was no difference between CO 2 fluxes from the two species (Lumbricus terrestris L., Aporrectodea caliginosa Savigny) or from the two population levels (1x and 2x the naturally-occuring population). Also, the earthworm treatments had no significant effect on N2O fluxes. Since all treatments contained mixed species and similar population levels at the end of the study, it is likely that CO2 and N2O fluxes in the field were affected more by soil temperature and moisture fluctuations than by the earthworm treatments. The study was repeated in laboratory microcosms under environmental control. Again, earthworm treatments had a significant effect on CO2 fluxes, but not on N2O fluxes. Interestingly, the N 2O fluxes from microcosms containing L. terrestris came solely from denitrification, while the N2O fluxes from A. caliginosa microcosms were produced mostly by nitrification. It is not known why these species stimulate different groups of microorganisms that can produce N2O, and this remains to be investigated.

Gas phase biofilters are used for controlling odors from animal facilities. Some characteristics can affect their performance and moisture content is one very important. A methodology for controlling and measuring moisture content is required to optimize these systems. An experiment was conducted to determine the appropriate placement of a set of soaker hoses 1.2 m in length for water application. It was found that the soaker hose installed in the lower region of the biofilter coupled with appropriate and timely application of water was able to minimize drying of the compost. Thermal conductance proved to be a reliable indicator for measuring the moisture content. Biofilters using the soaker hoses together with the thermal conductance as a media moisture sensor were able to maintain moisture content above 30% w.b. which provided sufficient water for microbial activity and ammonia abatement. A characterization of the ammonia and nitrous oxide concentrations was performed in order to compare the behavior of the gases when water was applied versus no water addition. These analyses revealed that the overall performance was not significantly different between treatments. But a more detailed assessment inside the biofilter media is performed; it is possible to identify different processes taking place.

Irrigated agriculture in the Canadian Prairies is in a position to play a prominent role in addressing global food demands imposed by a growing world population. Particularly within Saskatchewan there is potential to see large increases in the number of irrigated hectares, due to the large irrigable land base and supply of freshwater resources. Yet, how this increase will influence the agricultural greenhouse gas (GHG) balance is not well understood. Through the quantification and comparison of GHG emissions from a typical irrigated and dryland cropping system in Saskatchewan, this research aimed to better understand the role of irrigated agriculture on GHG dynamics in this region. A field-scale analysis of irrigated soil conditions and resulting soil greenhouse gas emissions identified that soil N availability was likely the dominant factor influencing soil N2O emissions from irrigated systems. Soil moisture was also a key factor in soil GHG fluxes, governing seasonal CH4 uptake and episodic N2O and CO2 emissions. The development of system-specific GHG budgets—incorporating on-site GHG sources and sinks—identified electricity as irrigated cropping’s largest contributor of global warming potential (GWP). Emissions from soil and diesel-combustion sources were less intensive under irrigated production; yet overall greenhouse gas intensity (GHGI) was greater from irrigated cropping. This research provides a first look into GHG dynamics from irrigated agriculture in Saskatchewan and identifies areas for potential mitigation as irrigated crop production expands in the Province.

A study was conducted in 2004 and 2005 to determine the effect of liquid hog manure fertilization on greenhouse gas emissions from the surface of a grassland pasture in south-eastern Manitoba. The objectives of this research were to determine the effects of manure application, itstiming and soil moisture on greenhouse gas emissions from pasture soil, cattle dung and urine patches. Nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2) emissions were determined from grassland soil surface, and from cattle dung and artificial urine patches. Liquid hog manure treatments were no manure (Control); 153 kg ha-1 of available-nitrogen (N) (two year average) in spring (Spring); and 149 kg ha-1 as half-rate applications in fall and spring (Split). Four field experiments were conducted on grassland plots. The static-vented chamber technique was used to estimate gas emission rates. Two of the experiments focused on the effects of manure application timing and soil moisture on greenhouse gas emissions from the grassland soil surface. The other two experiments focused on the effects of manure application and soil moisture on greenhouse gas emissions from cattle dung and artificial urine patches. Fresh cattle dung was collected from steers grazing adjacent pastures receiving the same three manure treatments. Artificial cattle urine treatments were generated by converting blood urea concentrations of the steers into urine-N concentrations. Manure application increased (P≤0.01) cumulative N2O emissions from the grassland soil surface with Control, Split and Spring treatments averaging 7, 43 and 120 mg N2O-N m-2, respectively. Of the two manure treatments, the Spring treatment emitted higher (P≤0.10) N2O emissions than the Split treatment. Soil moisture was a major factor influencing the quantity and type of greenhouse gas emissions, with saturated areas emitting CH4 during warm periods, whereas drier areas emitted N2O. Nitrous oxide emissions from these dry areas were higher in manure-treated plots. Spring application increased root density by 45% in the top 5 cm of soil compared to the Control. An increase in soil organic carbon with root density may offset any increase in greenhouse gas emissions caused by manure treatment. Cattle dung from Split and Spring treatments had higher cumulative N2O emissions (30 and 82 mg N2O-N m-2, respectively) compared to dung from Control pastures (6 mg N2O-N m-2) over two study years. Dung from the Spring treatment emitted more N2O (P≤0.01) than the other two treatments. All cattle dung patches emitted CH4 after deposition though unaffected by manure treatment. Artificial urine having highest N concentration had greater (P≤0.05) cumulative N2O emissions (690 mg N2O-N m-2) than urine with the lowest N concentration (170 mg N2O-N m-2). Drier soil locations emitted more N2O from cattle dung and artificial urine patches than wetter areas. This study demonstrated that Split application of liquid hog manure to grassland emitted less N2O than a complete application in spring. Moisture greatly affected the location of N2O and CH4 emissions. Drier areas emitted more N2O than wetter ones. Particularly, the findings indicate a need to assess grassland on periodically saturated soils as sources rather than sinks for CH4. Application of manure increased greenhouse gas emissions from cattle dung and urine patches with urine potentially having the greatest impact because of their higher emissions of N2O. An increase in root growth seems to offset greenhouse gas emissions from manure application.

Knowing the control of landscape position in greenhouse gas (GHG) emission from the Prairie pothole region is necessary to provide reliable emission estimates needed to formulate strategies for reducing emission from the region. Presented here are results of a study investigating the control of landscape position on the flux of nitrous oxide (N2O) and methane (CH4) from an agricultural soil. Field flux of N2O and CH4 and associated soil parameters from the Upper, Middle, Lower and Riparian slope positions were monitored from spring to fall of 2005, and spring of 2006, at the Manitoba Zero-Tillage Research Association (MTRZA) farm, 17.6km North of Brandon, MB. The field site consisted of a transect of 128 chambers segmented into the four landscape positions, with either all chambers or a subset of the chambers (32) sampled on select days. Spring thaw is an important period for annual inventory of N2O emission, thus, soil samples were also collected from the four slope positions in fall 2005, and treated in the laboratory to examine how antecedent moisture and landscape position affect the freeze-thaw emission of N2O from soil. Daily emissions of N2O and CH4 for 2005 were generally higher than for 2006, the former being a wetter year. There was high temporal variability in N2O and CH4 emission, with high fluxes associated with events like spring thaw and fertilizer application in the case of N2O, and rapid changes in soil moisture and temperature in the case of CH4. There was a high occurrence of hotspots for N2O emission at the Lower slope, associated with its high soil water-filled porosity (WFP) and carbon (C) availability. The Riparian zone was not a source of N2O emission, despite its soil WFP and organic C being comparable with the Lower slope. The hotspot for CH4 emission was located at the Riparian zone, associated with its high soil WFP and C availability. The Upper and Middle slope positions gave low emission or consumed CH4, associated with having low soil WFP and available C. This pattern in N2O and CH4 emission over the landscape was consistent with examination of entire 128 chambers on the transect or the 32 subset chambers. Significantly lowering the antecedent moisture content of soil by drying eliminated the freeze-thaw emission of N2O, despite the addition of nitrate to the soil. This was linked to drying slightly reducing the denitrifying enzyme activity (DEA) of soil. The highest and earliest freeze-thaw emission of N2O was from the Riparian zone, associated with its high antecedent moisture content, DEA and total organic C content. The addition of nitrate to soil before freezing failed to enhance freeze-thaw emission of N2O from the Upper, Middle and Lower slope positions, but increased emission three-fold for the Riparian zone. Despite the greater potential of the Riparian zone to produce N2O at thaw compared to the Upland slopes, there was no spring-thaw emission of N2O from the zone on the field. This was because this zone did not freeze over the winter, due to insulation by high and persistent snow cover, vegetation and saturated condition. The denitrifying potential and freeze-thaw N2O emission increased in going from the Upper to the Lower slope position, similar to the pattern of N2O emission observed on the field. The localization of hotspots for N2O and CH4 emission within the landscape was therefore found to be driven by soil moisture and C availability. When estimating GHG emission from soil, higher emission index for N2O and CH4 should be given to poorly-drained cropped and vegetated areas of the landscape, respectively. The high potential of the Riparian zone for spring-thaw emission of N2O should not be discountenanced when conducting annual inventory of N2O emission at the landscape scale. When fall soil moisture is high, snow cover is low, and winter temperature is very cold, freeze-thaw emission of N2O at the Riparian zones of the Prairie pothole region may be very high.

Agriculture contributes significantly to national and global greenhouse gas (GHG) inventories but there is considerable control over management decisions and changes in production methods could lead to a significant reduction and possible mitigation of emissions from the sector. For example, conservation tillage practices have been suggested as a method of sequestering atmospheric carbon dioxide (CO2), however, many questions remain unanswered regarding the short-term efficacy of the production method and knowledge gaps exist regarding possible interactions with essential nutrient cycles, and the production of non-CO2 GHGs, such as nitrous oxide (N2O). Between autumn 2005 and 2009, a micrometeorological flux system was used to determine net CO2 and N2O exchange from an annual cropping system situated on clay soil in the Red River Valley of southern Manitoba. Four plots (4-ha each) were independently evaluated and planted to corn in 2006 and faba bean in 2007; in 2008, two spring wheat plots were monitored. As well, during the non-growing season in 2006-2007 following corn harvest, a second micrometeorological flux system capable of simultaneously measuring stable C isotopologue (12CO2 and 13CO2) fluxes was operated at the site. Tillage intensity and crop management practices were examined for their influence on GHG emissions. Significant inter-annual variability in CO2 and N2O fluxes as a function of crop and related management activities was observed. Tillage intensity did not affect GHG emissions from the site. After accounting for harvest removals, the net ecosystem C budgets were 510 (source), 3140 (source) and -480 (sink) kg C/ha/year for the three respective crop years, summing to a three-year loss of 3170 kg C/ha. Stable C isotope flux measurements during the non-growing season following corn harvest indicated that approximately 70 % and 20 – 30 % of the total respiration flux originated from crop residue C during the fall of 2006 and spring of 2007, respectively. The N2O emissions at the site further exacerbated the net global warming potential of this annual agroecosystem.

A study was conducted to examine the impact of diet and cold weather on the excretion of nitrogen (N) and phosphorus (P) from beef cows, and the potential for these nutrients to be lost to waterways or as greenhouse gases (GHG). Feces and urine were collected from mature cows fed low-quality forage supplemented with DDGS to 0%, 10%, and 20% ww-1 in the fall of 2008 and winter of 2009. A detailed nutrient analysis was performed to determine forms of N and fractions of P in excreta. Feces, urine, and a simulated bedding pack were then applied to grassland to determine soil GHG emission. Cattle receiving DDGS supplementation excreted greater proportions of labile P in feces and greater concentrations of P in urine. The 20% DDGS diets had greater nitrous oxide emission from urine patches and greater proportions of available N in urine and feces.

Two laboratory incubation studies and a growth room bioassay of forage barley were conducted to investigate nitrogen (N) and phosphorus (P) mineralization, and nitrous oxide emission from two contrasting agricultural soils amended with anaerobically digested cattle manure (ADM). The ADM is a nutrient-rich co-product from manure-based biogas plants which is applied to cropland at rates used for raw manure since scientific information on nutrient release from ADM is lacking. Application of the separated solids fraction of ADM (SS) reduced nitrous oxide emission but resulted in lower N mineralization compared to raw manure in both soils. Raw manure- and SS- treatments had similar biomass yields and P supply capacities while the application of pelletized SS (PSS) caused net N immobilization, lower P release than manure and SS, and depressed barley yields relative to non-amended (control) soils.

Micro-organisms living in the soils of the Canadian High Arctic produce and consume the greenhouse gases (GHGs) CO2, CH4, and N2O, contributing to global nutrient and GHG cycles; however, different vegetation and soil communities differ in their net productions of each gas and the total emissions from the ecosystem. The range of Arctic vegetation communities spans wetlands, tundras, and deserts differing in their soil water contents and other properties such as organic matter content. Previous estimates of total GHG emissions are often imprecise relative to the scale of microbial processes that result in these emissions. Deserts have extremely low levels of both water and organic matter, yet I found that deserts produce nearly as much GHGs as wetter, more fully vegetated tundras. To test the hypothesis that this unexpectedly strong source of GHGs in deserts was a consequence of recently-thawed, organic-rich permafrost, I measured GHG net production throughout the active layer of polar desert soils; both production and consumption of CH4 and N2O, as well as soil respiration were found throughout the profile, indicating no link to thawed permafrost and suggesting these high GHG activities are characteristic features of Arctic polar deserts rather than transient effects of recent warming. I studied the community of microorganisms of the Arctic deserts by examining DNA from soil samples collected from three deserts on Ellesmere Island using DNA microarrays targeted for the functional genes AmoA and pmo. Using Structural Equation Modeling (SEM) I evaluated the hypotheses that the community of ammonia-oxidizers would be causally linked to the observed patterns of N2O net production, and that methane-oxidizers would be causally linked to CH4 net production. The SEM showed the expected link for CH4 production, but not N2O production. Available nitrogen in Arctic desert soils is primarily in the form of ammonia/ammonium, thus I find it surprising that no link could be found to the nitrifying community. Subsequent analysis of the occurence patterns of nitrous oxide reductase, a gene present in denitrifying bacteria and the only known biological sink for N2O, revealed only a weak association. Thus it remains unknown which organisms are responsible for the high levels of N2O emitted from Arctic polar desert soils. Furthermore, I observed several cases of unusual GHG processes, including a positive correlation between net CO2 and net N2O production in only some soils and some soil layers that consumed both CH4 and N2O.