Canada's climate is warming faster than the global average, but the warming is unevenly distributed. This study analyzes historical and future climate change in dairy-producing regions across Canada to better understand how Canada's dairy cows are affected. Historical changes (i.e., 1960–2019) were assessed using temperature and humidity data from 29 weather stations across the country. The temperature–humidity index (THI) was used as an indicator of dairy cattle at risk of heat stress, and three THI metrics evaluated the frequency, severity, and duration of potential heat stress. Future scenarios were investigated using five global climate models to project daily THI under three Shared Socioeconomic Pathways (SSPs). Projections were grouped into three time periods (2020–2049, 2040–2069, and 2060–2089). Historical climate trends show an increase in temperature, humidity, and THI exceedance in most west coast and eastern Canada locations, affecting 84% of the national dairy herd. Future scenarios project that 90% of the national herd will experience a large increase in the frequency, severity, and duration of THI exceedance under all but the most optimistic SSP. These findings highlight the need for Canadian dairy farmers to consider heat-stress adaptation strategies.

The health, longevity, and performance of dairy cattle can be adversely affected by heat stress. This study evaluated the in-barn condition [i.e., temperature, relative humidity, and resulting temperature-humidity index (THI)] at 9 dairy barns with various climates and farm design-management combinations. Hourly and daily indoor and outdoor conditions were compared at each farm, including both mechanically and naturally ventilated barns. On-site conditions were compared with on-farm outdoor conditions, meteorological stations up to 125 km away, and NASA Power data. Canadian dairy cattle face periods of extreme cold and periods of high THI, dependent on the regional climate and season. The northernmost location (53°N) experienced about 75% fewer hours of THI >68 compared with the southernmost location (42°N). Milking parlors had higher THI than the rest of the barn during milking times. The THI conditions inside dairy barns were well correlated with THI conditions measured outside the barns. Naturally ventilated barns with metal roofs and without sprinklers fit a linear relationship (hourly and daily means) with a slope <1, indicating that in-barn THI exceeded outdoor THI more at lower THI and reached equality at higher THI. Mechanically ventilated barns fit nonlinear relationships, which showed the in-barn THI exceeded outdoor THI more at lower THI (e.g., 55–65) and approached equality at higher THI. In-barn THI exceedance was greater in the evening and overnight due to factors such as decreased wind speed and latent heat retention. Eight regression equations were developed (4 hourly, 4 daily) to predict in-barn conditions based on outdoor conditions, considering different barn designs and management systems. Correlations between in-barn and outdoor THI were best when using the on-site weather data from the study, but publicly available weather data from stations within 50 km provided reasonable estimates. Climate stations 75 to 125 km away and NASA Power ensemble data gave poorer fit statistics. For studies involving many dairy barns, the use of NASA Power data with equations for estimating average in-barn conditions in a population is likely appropriate especially when public stations have incomplete data. Results from this study show the importance of adapting recommendation on heat stress to the barn design and guide the selection of appropriate weather data depending on the aim of the study.

Micrometeorological methods are ideally suited for continuous measurements of N2O fluxes, but gaps in the time series occur due to low-turbulence conditions, power failures, and adverse weather conditions. Two gap-filling methods including linear interpolation and artificial neural networks (ANN) were utilized to reconstruct missing N2O flux data from a corn–soybean–wheat rotation and evaluate the impact on annual N2O emissions from 2001 to 2006 at the Elora Research Station, ON, Canada. The single-year ANN method is recommended because this method captured flux variability better than the linear interpolation method (average R2 of 0.41 vs. 0.34). Annual N2O emission and annual bias resulting from linear and single-year ANN were compatible with each other when there were few and short gaps (i.e., percentage of missing values <30%). However, with longer gaps (>20 d), the bias error in annual fluxes varied between 0.082 and 0.344 kg N2O-N ha−1 for linear and 0.069 and 0.109 kg N2O-N ha−1 for single-year ANN. Hence, the single-year ANN with lower annual bias and stable approach over various years is recommended, if the appropriate driving inputs (i.e., soil temperature, soil water content, precipitation, N mineral content, and snow depth) needed for the ANN model are available.

Fencing cattle from watercourses and providing alternative drinking water sources is recommended for optimizing herd health and decreasing degradation effects on aquatic systems. The challenge is that complete exclusion of livestock from watercourses is often costly and requires considerable oversight. Two inexpensive access ramps, differing in their degree of accessibility were constructed at fenced-off waterways and evaluated as alternative options for cattle watering. At Site I (Upper Falmouth, Nova Scotia), cattle were allowed a narrowed region of direct access to enter the watercourse via a gradually sloping gravel ramp (controlled access). At Site II (Antigonish, Nova Scotia), an access ramp was constructed such that cattle were prohibited from directly entering the watercourse and only their noses could access the system for drinking (restricted access). Water samples were collected from upstream and downstream locations both before (pre-Beneficial Management Practices-when cattle had direct access to the watercourses) and after the access modification (post-Beneficial Management Practices). Sites were monitored over three grazing seasons which included both before and after site modification for several water quality parameters with an emphasis on Escherichia coli (E.coli). At Site I, where controlled access was established, no significant differences (p>0.05) were observed in the E. coli concentrations upstream and downstream of the stream access both before (pre-BMP) and after (post-BMP) ramp improvements. In contrast, E. coli concentrations declined significantly (p<0.01) downstream of the restricted water access at Site II between pre- and post-BMP. Furthermore mean daily E. coli loads were reduced by similar to 99%. This suggests that when cattle are allowed to drink from but not enter a watercourse, they do not promote degradation of waterways. Finally, total suspended solid concentrations displayed a qualitatively similar trend to that observed for E. coli concentrations. However, other water quality parameters (i.e., nitrogen, phosphorus, pH, and BOD5) were unaffected by access modification at either of the sites.

Phosphorus (P) loading from poorly designed or hydraulically failed residential on-site wastewater treatment systems (OWS) into neighbouring surface water systems is typically an unquantified process in many rural and suburban watersheds. The transport of P from OWS to surface waters is typically related to the subsoil conditions surrounding the OWS disposal field (DF), which impact lateral movement of the wastewater plume and P sorption capacity, and the level of OWS management by the homeowner (Gold and Sims, 2000). In Nova Scotia (NS), Canada there is a wide abundance of low permeability soils, shallow bedrock and high water tables that can cause failure and improper functioning of OWS DFs (Havard et al., 2008). McCray et al. (2005) identified a need for quantitative approaches, such as watershed computer models, to assess OWS pollutant loads because of the increased importance of total maximum daily load (TMDL) planning and watershed management. Current updates to the Soil and Water Assessment Tool (SWAT) watershed scale model (version 2009) include algorithms for simulating OWS using a biozone based treatment process (Jeong et al., 2011). However, there are no specific algorithms within SWAT (version 2009) to simulate P transport via lateral subsurface flow to surface water systems, demonstrating a need for an integrated approach to simulate P fate and transport from OWS at the watershed scale.

A wetland-reservoir wastewater treatment and reuse systems is an integrated water management system constructed on farms to conserve water and to help mitigate water pollution from agricultural drainage. This research assesses such a system in Nova Scotia and provides recommendations for adapting its location, design, construction, and operation to a cold climate. Water quality, hydraulic, and meteorological data was collected between November 2007 and January 2009. The system collected approximately 15500 m3 (8700 m3 ha-1 of drained land) annually, potentially enough water to irrigate more than the drained area. A tracer study was conducted in the constructed treatment wetland to assess residence time. Little difference was observed between the actual residence time (15.0 d) and the nominal residence time (14.5 d). This is attributed to a high length to width ratio (10:1). Annual nitrate-nitrogen and E. coli reductions by the constructed treatment wetland were 52% and 33%, respectively. Significant monthly variation was observed, and is attributed to the dynamic hydraulic and pollutant loading of tile drainage water. Total phosphorus and soluble reactive phosphorus concentrations were typically below detectable levels (0.10 mg L-1 and 0.05 mg L-1 respectively) at all sampling locations. Reservoir water quality exceeded irrigation water quality guidelines for E. coli (100 CFU 100 mL-1) during summer months and is attributed to environmental factors. At a cost of approximately $50,000 ha-1 the system may require economic incentives or drainage water disposal regulations before it can be adopted by farmers.

Nutrient and pathogen export from agricultural drainage water is a major source of surface water quality degradation. Wetland-reservoir drainage water treatment and reuse systems have the potential to mitigate this pollution, as well as conserve water, improve crop yields, and increase bio-diversity. This study will assess the viability of this type of system in a colder climate. Specific objectives are to assess (i) system hydraulics and water balances; (ii) wetland treatment efficiencies; and (iii) reservoir water quality.

Constructed wetlands are used throughout North America to treat various types of wastewater in warm climates; however, little has been documented about their treatment processes and efficiencies during winter periods in Atlantic Canada. Two small-scale constructed wetlands (100 m2) of differing operational depth (wetland 1: 0.15 m shallow zone depth and wetland 2: managed water level) were designed to treat agricultural wastewater at the Bio-Environmental Engineering Center of the Nova Scotia Agricultural College. Both wetlands were monitored from November 2000 through March 2002 to evaluate treatment efficiencies and mass reductions of five-day biological oxygen demand (BOD5), total suspended solids (TSS), total phosphorus (TP), and ammonia-nitrogen (NH3-N). An average loading rate of 44.7 kg BOD ha−1 d−1 was loaded into each wetland, even during winter months. Percent removal and mass reductions for BOD5, TSS, TP, and NH3-N in both wetlands, irrespective of water levels, ranged from 62 to 99%. The treatment of TP was not found to be as effective as the other parameters, especially during high loading periods. Results show promise for the operation of constructed wetlands on a year-round basis in Atlantic Canada.

Pentachlorophenol (PCP) is a toxic compound commonly found as a soil contaminant atwood preservation facilities. Laboratory studies were conducted to determine the effects ofenvironmental parameters on the degradation of PCP by indigenous soil microorganisms. Theobjective of the first experiment was to determine the effect of selected nutrient amendments andincubation temperatures on the biodegradation of PCP in contaminated soil. This was accomplishedby monitoring microbial populations, the concentration of PCP and the release of inorganic Cl- ions.The temperature factor consisted of three levels, 10, 15 and 20C. The three nutrient amendmentschosen were an ammonium nitrate fertilizer, Municipal Solid Waste (MSW) compost and an ageddairy manure, along with a control (no nutrient additions). It was found that the temperature levelsused had no significant effect on the microbial populations and the % PCP remaining in the soil.However, the nutrient factor levels did have a significant effect on the parameters measured. Thedairy manure, ammonium nitrate fertilizer and the control experienced fluctuations in % PCPremaining in the soil and may have been due to the release of initially unextractable bound residues.It was found that the treatments that received the MSW compost amendment were significantlyhigher in bacterial and fungal populations. The% PCP remaining in the MSW amended soildecreased by 76%, while the concentration of inorganic Cl- ions increased in the soil. The objectiveof the second experiment was to determine the effects of supplemental aeration and moisture. Thethree moisture levels chosen were 40, 60 and 80% of the soils field capacity (FC). The threeaeration levels used were: no supplemental aeration (control), 150 cm3 min-1 of supplementalaeration pumped through for 1 h d-1, and 150 cm3 min-1 of supplemental aeration pumped through for2 h d-1. The moisture levels used were found to have no significant effect on the parametersmeasured with the exception of a significant increase in bacterial populations in treatments remainingat a 60% FC. In terms of the supplemental aeration factor it was found that in order to get astatistically significant decrease of PCP, a minimum of 150 cm3 min-1 of supplemental aeration for 2 hd-1 would be required. The results of this study were implemented into the construction of a soilbiopile at a wood preservation facility.