The role of shelterbelts within prairie agriculture is changing. In the past, shelterbelts have been promoted and adopted to reduce soil erosion and to protect farmsteads and livestock from harsh prairie climates. Production techniques used today have been changed from when shelterbelts were first introduced as a management practice to reduce erosion. Advances in production technology accompanied with increase in farm size and changes to policy have all contributed to a shift in how shelterbelts are considered within management plans. The objective of this research is to identify the private costs and benefits from adoption and retention of shelterbelts. In the summer of 2013, a survey was conducted of producers and land owners chiefly from Saskatchewan, Canada. It was found that many of the benefits of shelterbelts can be classified as noneconomic and, therefore, are more difficult for producers and land owners to recognize or include within their operations management decisions. Conversely, the costs to producers were easily identified and heavily influenced management decisions. As greenhouse gas management and policy become more of a focus, shelterbelts have the potential to play a major role in climate change mitigation by sequestering significant amounts of atmospheric carbon dioxide (CO₂) into the soil and as biomass carbon in above- and belowground parts of planted shelterbelt trees or shrubs. However, most producers do not recognize such benefits within their management decisions, as they are not currently compensated for the benefits that they provide to society.

Shelterbelts provide an opportunity for carbon (C) sequestration and have the potential to mitigate agricultural greenhouse gas (GHG) emissions. However, the influence of shelterbelts on GHG emissions at the farm scale is poorly understood. We estimated the potential of three shelterbelt tree species: hybrid poplar, white spruce, and caragana at five planting densities, to reduce GHG emissions in a model farm (cereal–pulse rotation). The Holos model, a Canadian farm-level GHG calculator developed by Agriculture and Agri-Food Canada, was used to estimate shelterbelt effects on farm GHG emissions over a 60 yr time frame. The planting densities of the shelterbelts represented 0%, 0.5%, 1.0%, 3.0%, and 5.0% of the total area of an average (688 ha) Saskatchewan farm. The greatest reduction in farm GHG emissions was estimated for hybrid poplar (23.0%) followed by white spruce (17.5%) and caragana (8.2%) — all at the highest planting density. The GHG mitigation by the shelterbelts was attributable primarily (90%–95% of GHG reduction) to C sequestration in tree biomass and in soil organic carbon (SOC) pools, with the remainder due to lower N₂O, CH₄ emissions, and a reduction in farm energy use. The GHG estimates from Holos agree with field measurements and suggests that species selection will be important for maximizing C sequestration and GHG mitigation potential of shelterbelt systems; conversely, shelterbelt removal from the agricultural landscape suggests an increase of on-farm GHG emissions.

Shelterbelts sequester and store atmospheric carbon as a direct result of the growth of trees and thus present an opportunity for climate change mitigation. The objectives of this paper were to quantify the growth characteristics and to estimate the carbon stocks of six common shelterbelt species in Saskatchewan: hybrid poplar, Manitoba maple, Scots pine, white spruce, green ash, and caragana. Growth curves (3PG) and carbon dynamics (CBM-CFS3) modelling approaches were used to simulate shelterbelt growth and to estimate the carbon stocks in 50 439 km shelterbelts containing the six species. Shelterbelt width ranged from 6.3 to 14.0 m, age ranged from 5 to 100 yr, and tree density ranged from 356 to 791 trees ha^-1. The r² of the growth curve equations ranged from 28% to 97%, with <50% root-mean-square error and <30% bias. The total ecosystem carbon stocks of all shelterbelts of the six species in Saskatchewan were 10.8 Tg C (1 Tg C = 1 million Mg C), of which 3.77 Tg C was sequestered in the soil and shelterbelt biomass since 1990. The climate mitigation potential of the six shelterbelt species, ranging from 1.78 to 6.54 Mg C km^-1 yr^-1, emphasized the important role that trees can have on the agricultural landscape to mitigate greenhouse gases (GHGs). Planting shelterbelt trees and shrubs on agricultural landscapes is an important strategy for mitigating GHGs.

Tree-based intercropping (TBI) system has been suggested as an alternative to conventional monocropping (CM) for decreasing overall greenhouse gas (GHG) emissions. However, little is known about the advantages of TBI compared with organic CM system with low fertilizer inputs. This project compared CO₂ and N₂O dynamics in replicated TBI and CM in Saint-Paulin (QC, Canada), established about 12 yr prior to this study under organic production, with horse manure and pruning residues as soil amendments. An experimental field, using a complete randomized block design, was instrumented in both systems. A five-point sampling transect was established between tree rows in each of the six plots. Surface CO₂ and N₂O fluxes, CO₂ and N₂O soil concentrations, and other physicochemical properties were analyzed at 0.125 and 0.25 m depths over two growing seasons. CO₂ and N₂O concentrations in TBI soil were similar to or lower than in CM soil. Lower CO₂ and N₂O emissions suggest that TBI would decrease overall GHG mitigation, even when compared with organic production with low fertilizer inputs, in addition to its potential for carbon sequestration in wood and other advantages that are not discussed in this study.

Carbon (C) sequestration through the implementation of agroforestry practices is identified as one of the major strategies in the reduction of carbon dioxide (CO₂) emissions from the agricultural sector. The objective of this study was to examine the soil organic carbon (SOC) sequestration potential of major shelterbelt species, including green ash (Fraxinus pennsylvanica), hybrid poplar (Populus spp.), Manitoba maple (Acer negundo), white spruce (Picea glauca), Scots pine (Pinus sylvestris), and caragana (Caragana arborescens), ranging in age from 5 to 63 yr. Soil samples (0–50 cm) were collected for six major shelterbelt species and adjacent agricultural fields, and SOC concentration was determined. Shelterbelts had a significantly higher amount of SOC compared with adjacent agricultural fields, with an average difference of 18.6 Mg C ha^-1 in the top 50 cm soil. An additional 3–8 Mg C ha^-1 was contained in the tree litter layer. Younger shelterbelts (age less than 20 yr) tended to lose SOC in the early years of shelterbelt establishment. However, the SOC accrual was positively related to shelterbelt stand age. Besides stand age, other shelterbelt stand characteristics, including tree height and diameter, crown width, and amount of surface litter, were also positively correlated with the increase in SOC concentration. The findings of this study support the hypothesis that shelterbelts can lead to a significant amount of SOC sequestration in agroecosystems.

Tree-based intercropping (TBI) systems have shown some promise in mitigating greenhouse gas emissions, such as by sequestering carbon and decreasing soil nitrous oxide emissions. However, the effects of TBI on soil methane fluxes remain unknown. In a field study, we failed to show differences in soil CH₄ production between TBI and conventional monocropping (CM) systems. Within TBI plots, however, we found significantly lower CH₄ concentrations near the middle of the alleys than closer to tree rows. Soil CH₄ concentrations also decreased with soil depth, even dipping below mean global atmospheric concentrations. Laboratory assays revealed a higher CH₄ oxidation potential in soils collected from TBI plots compared with CM plots. These assays also revealed a decrease in CH₄ oxidation potential after soils were amended with nitrate. We conclude that TBI could potentially reduce soil CH₄ emissions, whereas fertilizer nitrate may increase them.

Tree-based intercropping (TBI) may increase carbon (C) sequestration in agroecosystems, but may reduce crop yields. In this study of TBI, we used ecosys, a comprehensive mathematical model of terrestrial ecosystems, which represents interspecific competition for light, nutrients, and water, to evaluate the concurrent effects of TBI on C sequestration and crop yields in TBI experiments conducted at St. Paulin and St. Edouard in southern Quebec. Total gains in C sequestration vs. total losses in crop yields over 11 yr relative to monocropping were 682 vs. 396 g C m^-2 at St. Paulin and 841 vs. 168 g C m^-2 at St. Edouard. These gains and losses were generally consistent with the measurements at the two TBI sites and with those at TBI experiments under similar environmental conditions elsewhere. Gains and losses depended on competition for light by trees and crops, and so were affected by different fractions of tree foliage removal used to manage this competition in the model. The modelling protocol developed for this study provides a robust, process-based methodology to evaluate economic and environmental benefits of TBI under diverse climates, soils, and tree and crop management practices. Some of the key assumptions used to model TBI are also discussed.

Shelterbelts represent a significant carbon reserve on the agricultural prairie landscape, and knowledge of their extent can be of importance to atmospheric carbon mitigation strategies. We describe the creation of a detailed inventory of the shelterbelts across the agricultural region of Saskatchewan. A total of 262 000 shelterbelts covering over 51 000 km were identified by species composition, row width, stand condition, and type. This inventory is an important baseline for monitoring changes in prairie agroforestry systems arising from climate change and land use conversion.

Anaerobically digested dairy manure (AD) has been proposed as an alternative nitrogen source to reduce soil nitrous oxide (N₂O) emissions compared with raw dairy manure (RM). The aim of this research was to compare soil N₂O emissions associated with AD and RM according to three application methods: surface broadcasting (SB), incorporation (SBI), and injection (INJ). The field experiment was conducted on a loam soil at Elora, ON, from November 2012 to November 2014, using a randomized block design with four replications. Manure was applied in mid-November (fall), and corn (Zea mays) was planted in late-May of each year. Nitrous oxide flux was measured using nonsteady state chambers sampled weekly or bi-weekly. Cumulative N₂O emissions were significantly affected by the interaction between source and method (F = 3.99, P < 0.01), with the highest value for surface broadcast AD (6.4 kg N₂O-N ha^-1) and the lowest value for injected AD (2.6 kg N₂O-N ha^-1). Manure source affected cumulative N₂O emissions (F = 4.67, P < 0.1), with the largest emissions for AD (4.8 kg N₂O-N ha^-1). Anaerobically digested manure was proven to reduce cumulative N₂O emissions when it was fall injected to corn in cold climates; however, if AD is broadcasted or broadcasted and incorporated, it may result in greater N₂O emissions than those produced by RM.

Nongrowing season (NGS) greenhouse gas (GHG) emissions may be significant in cold agricultural regions, but the influence of winter conditions, soil type, and fall manuring must be better documented. We monitored NGS N₂O and CO₂ fluxes and soil atmosphere composition from 2009 to 2013, on sandy loam and silty clay soils, with and without fall-applied pig slurry. Early-winter emission peaks indicated that soil respiration and biogenic N₂O production were stimulated during active soil freezing. Soil atmosphere GHG concentrations increased throughout winter, whereas O₂ concentration declined, especially when surface fluxes were low. Therefore, soil respiration and denitrification were not stopped by cold temperatures, and low surface fluxes were mainly due to restriction of gas diffusion. Nitrous oxide emissions varied from 0.4 to 8.5 kg N ha^-1 and were generally greater in the presence of pig slurry. Emissions were of similar magnitude between soil types, likely because O₂ restrictions on denitrification typically found in sandy soils during the growing season were eliminated by high soil moisture content in the NGS. This multiyear assessment highlights the need to include NGS GHG emissions to properly estimate yearly emissions and refine inventories in cold regions, particularly for sandy soils.

Nitrous oxide (N₂O) production in four soils with unique fertilization management histories — collected from long-term fertility treatments receiving no fertilizer, NPKS, PKS, and NPK in a 5 yr cereal–forage rotation — in response to three sources of added N [100 kg N ha^-1 urea, NH₄Cl, Ca(NO₃)₂] with and without co-addition of elemental S (20 kg S ha^-1) plus a 0-N and 0-S control was investigated in a 7 wk laboratory incubation in a loamtextured soil at 40% water-filled pore space. In all soils, cumulative N₂O emissions and apparent, cumulative, net nitrification were significantly higher following addition of urea compared with other N fertilizers with and without co-addition of elemental S. Lower N₂O emissions were observed in soils without a history of long-term N fertilization following addition of urea compared with soils that had historically received urea. Because the preincubation soil total N levels were similar in soils with a history of urea application (NPKS) and without urea (PKS), the results of this investigation suggest that the higher N₂O production in the NPKS soil may be the result of a priming effect and (or) changes in microbial community composition induced by long-term urea applications rather than differences in the long-term soil N balance.

A field study conducted over three growing seasons (2013–2015) assessed the effect of long-term fertilization history and crop rotation on growing season nitrous oxide (N₂O) and carbon dioxide (CO₂) emissions, wheat yield, wheat N uptake, N₂O emission intensity, and soil properties on a Gray Luvisol soil. Long-term fertility treatments included check, manure, NPKS, NPK, and PKS fertilizers in two contrasting crop rotations: 2 yr wheat (Triticum aestivum L.) – fallow (WF), and 5 yr wheat (T. aestivum L.) – oat (Avena sativa) – barley (Hordeum vulgare L.) – alfalfa (Medicago sativa) – brome (Bromus tectorum) hay (WOBHH). Rotation significantly affected cumulative growing season N₂O emissions, and within each rotation, long-term fertilizer or manure N additions increased N₂O emissions over the check. Average, cumulative growing season N₂O emissions in the 5 yr rotation were 1.29 kg N₂O-N ha^-1, significantly higher than the 0.58 kg N₂O-N ha^-1 in the WF rotation, but N₂O emission intensities were comparable between the two rotations. Cumulative N₂O emissions were positively correlated to total soil N (0–15 cm) and wheat N uptake, but N₂O emission intensities were negatively correlated to total soil N. However, it is uncertain whether this result extends to annual emission intensities because of a lack of nongrowing season measurements.

Forages are an important part of crop rotations in many agricultural systems. In Manitoba, Canada, almost 40% of the 7 million ha agricultural area is devoted to forage crops and pastures. Use of legume forages to reduce fertilizer cost to producers can improve soil quality and productivity and may provide more options for diversification of the agricultural production system. We tested that whether a twofold increase in forage production for feeding beef cattle would change greenhouse gas (GHG) emissions for the agriculture and agri-food system and economic returns at the farm in the year 2011. The forage resulting from the increased production was fed to beef cattle. The GHG emissions were calculated using Intergovernmental Panel on Climate Change Tiers 1 and 2 methodologies and economic returns through an optimization algorithm maximizing net financial margin. The results suggest that the economic effects, in terms of farm-level profitability, may be minimal (decrease of 0.6%) but are likely sensitive to the market conditions in different years. Doubling the forage area and increasing the cattle herd increased GHG emissions from agriculture by 7.6%, mostly because of methane from enteric fermentation by cattle. The GHG emissions were mitigated by carbon sequestration in soil, but this is likely ephemeral, suggesting that the longer term emissions would be even greater. However, a twofold increase in forage production implies less energy use, change in water dynamics, and a reduction in the use of nitrogenous fertilizer, which could be beneficial for ecosystem services, and needs to be assessed.

Since the process of gas dynamics in agricultural soils is mainly studied during plant growth, only a few studies have focused on these dynamics in frozen soils covered with snow. Nevertheless, gas dynamics during the cold season is important to quantify the yearly mass balance of gas emitted to the atmosphere. Spatiotemporal concentrations of CO₂ and N₂O have been measured from the prefreezing to the thawing period in a pasture soil during two cold seasons along with soil temperature and other soil properties. The spatial dynamics of these gases differed from each other and depended on the spatial and temporal variability of soil temperature as long as the soil surface temperature was above 0 °C. Two main occurrences of gas release occurred during thawing, one related to trapped gases, similar for both gases, and the other to reactivation of microorganisms, different between both gases. Once the soil was frozen, both gas concentrations increased throughout the frozen period, even during very cold conditions, indicated a gases production faster than the loss. Under frozen condition, their spatial variability was independent of soil temperature during which their correlation was up to 90%. Three periods related to gas dynamics were observed during both cold seasons: freezing with spatiotemporal trends different between both gases, completely frozen with similar trends, and partial to complete thawing with trends different between both gases.

Current approaches for estimating greenhouse gas (GHG) emissions from manure storages do not consider contributions due to bedding materials. Compared with sand, wood-based bedding has the potential to increase volatile solids and total solids concentrations and favour crust formation in liquid dairy manure. In this study, the GHG emissions from wood and sand bedding slurries were evaluated monitored continuously for 207 d (1 May–24 Nov. 2014) under “warm season” storage conditions. For both slurries, methane (CH₄) made up >95% of the GHG emissions. The sand bedding slurry had minimal crust, which also led to more evaporation and higher ammonia volatilization losses when scaled by nitrogen content. The wood bedding slurry emitted 51% more CH₄, eight times more nitrous oxide, and 53% more total GHG emissions (CO₂-eqivalents). However, these differences were reduced if only the initial 123 d (1 May–31 Aug. 2014) of storage was considered. This was presumably related to the slower degradability of the wood bedding. Given these differences bedding choice should be considered in GHG emissions estimates.

The N₂O and CO₂ emissions from soil amended with cattle manure and compost from animals fed a diet including wheat dried distillers’ grains with solubles (DDGS) were evaluated in a 105 d aerobic incubation study in the laboratory. Manure (BM) and compost (BC) from cattle fed a typical finishing diet containing barley, and manure (DDGSM) and compost (DDGSC) from cattle fed a diet containing 60% wheat DDGS replacing barley grain, were used. A nonamended control (soil without manure or compost) was included for comparison. Organic amendments significantly increased N₂O and CO₂ emissions compared with the control, and manure resulted in significantly higher CO₂ emissions than compost. Adding DDGS to cattle diet resulted in significantly higher N₂O emission amounts and emission factors from soil regardless of whether the amendment was manure or compost, mainly due to increased NH₄ -N content. While N₂O emissions were lower in soil amended with DDGSC than DDGSM, there was no difference in N₂O emissions when soils were amended with BM and BC. Our results suggest that across diet types and management approaches, application of compost from cattle fed a typical diet could be less detrimental to the environment with relatively lower emissions of CO₂ and N₂O.

Soil nitrous oxide (N₂O) fluxes are commonly measured with nonsteady state chambers using slope values derived from linear or quadratic regression, fitted to the change in N₂O concentration over time (dC/dt); however, these methods frequently underestimate N₂O flux values. Here, we propose a decision tree-based model (DTBM) to better match curve shape with linear and nonlinear models to estimate dC/dt. The DTBM was compared with linear, quadratic regression, and the Hutchinson–Mosier (H–M) equation. The objectives were to (i) evaluate curve shape classification; (ii) evaluate dC/dt response to uncertainty, and (iii) determine method effect on cumulative N₂O emissions and emission factor. Curve shapes with increasing N₂O concentration over time had the highest proportion of data (52%–55%). Mean N₂O flux calculated with DTBM showed to be less responsive to data variability, and therefore, more stable than the other methods. Data classification included in DTBM offered an improved method for calculating cumulative N₂O emissions in low-flux situations, whereas under a high-flux situation, all methods tested were acceptable to calculate N₂O emissions. The DTBM proved to be a robust method of matching each data type with the best model for calculating an individual flux and to accurately calculate cumulative N₂O emissions.