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Low seed protein content in soybeans [ Glycine max (L.) Merr.] grown in Western Canada can result in soybean meal that does not meet the 48% protein standard. The objectives of this study were to quantify seed composition, agronomic differences between Eastern and Western Canada-grown soybeans, and to determine the yield cost of raising Western soybean protein. Twenty high-to-low protein, including one non-nodulating, genotypes were grown at two locations in Eastern Canada, and eight locations in Western Canada from 2018 to 2021 to determine seed protein, seed composition, and agronomic traits. Over all environments, genotype seed protein ranged from 36.8% to 46.9% with 35.0% for the non-nodulating line. Average seed protein was significantly higher in Eastern Canada (41.6%) compared with Eastern Prairie (39.3%) and Prairie sites (39.7%). There are not separate east–west mega-environments for seed protein in Canada; a high protein genotype is high protein across Canada. With an increase of seed protein by 1%, seed yield dropped by 45.3 kg ha−1 in Eastern Canada, 53.1 kg ha−1 in the Eastern Prairie, and 78.4 kg ha−1 in Prairie sites. In Western Canada, plants were taller but lower yielding with fewer and smaller seeds, and produced lower fixed nitrogen protein yield compared with Eastern Canada. Seed protein quality, quantified with the 11S:7S ratio, was higher in Western Canada compared with Eastern Canada. Plant breeders and growers may need to select higher protein genotypes at the cost of lower yield, if the soybean industry is unable to exploit the protein quality advantage in Western Canada.

Variance analysis was performed on the effect of monthly accumulated precipitation data (May–July) on crop losses between 2005 and 2016 with combined Manitoba and Saskatchewan regional barley grain yield data. A significant negative relationship with total precipitation during May to June was observed. This period coincides with leaf emergence to the booting stage in barley.

Study region This study was carried out in southwestern Manitoba, in the prairie region of Canada. Study focus Mathematical models are routinely used to estimate evapotranspiration (ET) when measurements are lacking. This study was conducted to select the most relevant models for estimating ET in the Canadian Prairies. Eight reference ET models (i.e., Penman-Monteith, Priestley-Taylor, Makkink, Turc, Maule et al., Blaney-Criddle, Hargreaves-Samani, and Hamon models) were evaluated. This study also assessed the applicability and transferability of the growing degree day (GDD)-based crop coefficients for estimating crop ET in the Canadian Prairies. New hydrological insights The equation developed by Maule et al. (2006) was found to be the best reference ET alternative to the Penman-Monteith equation with a mean relative error of 11%. However, when models were validated against measured crop ET, the simpler radiation-based Turc and Makkink models were found to be the most useful models with daily mean relative errors ranging from 16% to 49%, outperforming the widely accepted Penman-Monteith model. Discrepancies in the GDD-based crop coefficients were found to also contribute to errors; however, results show the potential transferability of GDD-based coefficients across different locations and climatic conditions.

The long-term understanding of the carbon budget of cropping systems needs to consider varying meteorological conditions, site/soil conditions, crop selection, and management decisions. On the Canadian Prairies, a variety of crops are used in yearly rotation, often not repeating the same crop within a 3-year period. We measured net ecosystem production (NEP) in two cropping systems in southern Manitoba, Canada, for the 2006–2016 period. One system had continuous annual crops, whereas the other had a perennial phase for 4 years. NEP was calculated using the flux-gradient method, where the carbon dioxide gradient was measured with a tunable-diode laser analyser and the transfer coefficient was based on momentum similarity theory with inputs from sonic anemometer-thermometers. NEP varied from −100 (source) to +300 (sink) g C m−2y−1 among four adjacent 4-ha fields and 10 years, depending on annual crop (corn, faba, spring wheat, barley, rapeseed, soybean) and environmental conditions. There was no period of 3 years or greater when NEP in the continuous annual crop rotation was different from carbon neutral. Inserting a 4-year perennial phase of an alfalfa/grass mix created a statistically significant carbon sink for NEP (P = 0.04), but the perennial period itself was carbon neutral. Enhanced ecosystem respiration was observed following termination of the perennial crop. Harvest practices varied from no harvest (in the establishment year of the perennial crop), grain removal only, grain + straw removal, and straight cutting of green biomass for silage. Once harvest removals were included, 3 of the 4 fields were carbon neutral, but one annual field had net carbon losses for some periods. Ecosystem respiration averaged about twice as large as harvest removals. Net carbon (mean ±S.E.) over the 11-year period for the annual cropping system (−78 ± 51 g C m−2 y−1) was not different from the annual-perennial system (−48 ± 47 g C m−2 y−1).

Study region This study used data collected from three cropland sites (two in Manitoba and one in Prince Edward Island) in Canada. Study focus In efforts to accurately describe the water dynamics in agricultural soils, most of the agri-hydrological models developed are highly complex, such that they require detailed input data, of which most of them are not always measured or otherwise readily available. However, the comprehensive and complex representations of the processes may not be justified when data is scarce. Thus, this study developed a soil water budget model that could describe the movement of water through Canadian agricultural soils using a few parameters only. The model was developed by selecting algorithms from various existing models, whose data requirements are readily available in literature and public Canadian databases. New hydrological insights The model developed in this study can simulate evapotranspiration, runoff, deep percolation, and soil moisture content for various seasons (i.e., growing, non-growing/dormant, and pre-planting/post-harvest) with minimum data requirement, which addresses the limited availability of data in the country for crop and hydrological modeling. Moreover, the model is simple and easy to use, and can work without calibration. It was tested using three site-specific datasets, and results show that despite its simplicity, its overall performance was comparable with those of other agricultural models that use cascade flow framework for hydrology.

Consumptive use of shallow groundwater by phreatophytic vegetation is a significant part of the water budget in many regions, particularly in riparian areas. The influence of vegetation type on groundwater level fluctuations and evapotranspiration has rarely been quantified for contrasting plant communities concurrently although it has implications for downstream water yield and quality. Hourly groundwater evapotranspiration (ETG) rates were estimated for grass and tree riparian vegetation in southwestern Manitoba, Canada using two modified White methods. Groundwater table depth was monitored in four 21 m transects of five 3 m deep monitoring wells in the riparian zone of a stream reach including tree (Acer negundo; boxelder) and grass (Bromus inermis; smooth brome) dominated segments. The average depths to the groundwater table from the surface were 1.4 m and 1 m for the tree and grass segments, respectively, over the two-year study. During rain free periods of the growing season ETG was estimated for a total of 70 days in 2014 and 79 days in 2015 when diurnal fluctuations were present in groundwater level. Diurnal groundwater level fluctuations were observed during dry periods under both segments, however, ETG was significantly higher (p

In the northern Great Plains, most runoff transport of N, and P to surface waters has historically occurred with snowmelt. In recent years, significant rainfall runoff events have become more frequent and intense in the region. Here, we examine the influence of landscape characteristics on hydrology and nutrient export in nine tributary watersheds of the Assiniboine River in Manitoba, Canada, during snowmelt runoff and with an early summer extreme rainfall runoff event (ERRE). All watersheds included in the study have land use that is primarily agricultural, but with differing proportions of land remaining as wetlands, grassland, and that has been artificially drained. Those watersheds with greater capacity for storage of water in surface depressions (noneffective contributing areas) exhibited lower rates of runoff and nutrient export with snowmelt. During the ERRE, higher export of total P (TP), but not total N, was observed from those watersheds with larger amounts of contributing area that had been added through artificial surface drainage, and this was associated primarily with higher TP concentrations. Increasing or restoring the storage of water on the landscape is likely to reduce nutrient export; however, the importance of antecedent conditions was evident during the ERRE, when small surface depressions were at or near capacity from snowmelt. Total P concentrations observed during the summer ERRE were as high as those observed with snowmelt, and N/P ratios were significantly lower. If the frequency of summer ERREs increases with climate change, this is likely to result in negative water quality outcomes.

In northern regions, a high proportion of annual runoff and phosphorus (P) export from cropland occurs with snowmelt. In this study, we analyze 57 site-years of field-scale snowmelt runoff data from 16 small watersheds draining fine-textured soils (clay or clay loam) in Manitoba, Canada. These fields were selected across gradients of soil P (2.4 to 26.7 mg kg, 0- to 15-cm Olsen P), tillage intensity (high frequency to long-term no-till), and fertilizer input. The strongest predictor of flow-weighted mean concentrations of total dissolved P (TDP) in snowmelt runoff was Olsen P in the top 5 cm of soil ( = 0.45, < 0.01). Residual variation in this relationship related positively to volumetric soil moisture and negatively to water yield. Although Olsen P levels were relatively consistent from year to year, suggesting control by long-term fertilization and tillage history, Olsen P stratification (ratio of 0-5/0-15 cm) increased with rates of fertilizer application. Particulate P (PP) comprised

Precision farming methods such as variable rate or site-specific nitrogen (N) fertilizer application based on field management zones may represent a mechanism to mitigate soil nitrous oxide (N2O) emissions. To investigate the impact of site-specific N fertilization on soil N2O fluxes a study was conducted from spring 2013 through summer 2015 on no-till cropland under canola (Brassica napus) production near Brandon, Manitoba, Canada. The static chamber method was used to measure soil N2O fluxes across three management zones (low yield, average yield, and high yield) with three N application rates (50%, 100%, and 150% of target seed yields for each management zone) and unfertilized control treatments. A machine-learning approach (random forest analysis) for analyzing soil N2O fluxes confirmed conditions related to soil temperature, moisture, and nitrate availability were the most important predictors of individual flux events. Similarly, soil N availability and moisture content were found to be the most important variables in regression models of cumulative growing season emissions. Nitrogen fertilizer-induced N2O emission factors were lower for the high yield management zone (≈0.1% both growing seasons) compared to the low yield management zone (0.9% in 2013 and 0.2% in 2015) confirming that variable rate application can mitigate N2O fluxes from cropland soils. The high yield zones had the lowest emission factors despite receiving 50% more fertilizer than field average target yields suggesting more efficient crop N use in these areas with greater production potential. Conversely, the low yield zones had higher emission factors despite receiving 50% less fertilizer than field average target yields indicating a greater environmental burden associated with annual cropping these portions of the agricultural landscape. More studies are required to investigate the generality of these findings for different crops, soils and climatic conditions.

© 2016 Elsevier B.V. Across a global network of eddy covariance flux towers, two relatively new open-path infrared gas analyzers (IRGAs), the IRGASON and the EC150, are increasingly used to measure net carbon dioxide (CO2) fluxes (Fc_OP). Differences in net CO2fluxes derived from open- and closed-path IRGAs in general remain poorly constrained. In particular, the performance of the IRGASON and the EC150 for measuring Fc_OPhas not been characterized yet. These IRGAs measure CO2absorption, which is scaled with air temperature and pressure before converting it to instantaneous CO2density. This sensor-internal conversion is based on a slow-response thermistor air temperature measurement. Here, we test if the high-frequency temperature attenuation causes selectively systematic Fc_OPerrors that scale with kinematic temperature fluxes. First, we examine the relationship between wintertime Fc_OPand kinematic temperature fluxes for eight northern ecosystems. Second, we investigate how residuals between Fc_OPand CO2fluxes from co-located closed-path IRGAs (FC_CP) are related to kinematic temperature fluxes for three different ecosystem types (i.e., boreal forest, grassland, and irrigated cropland). We find that kinematic temperature fluxes, but not mean ambient air temperatures or CO2flux regime, consistently determine the absolute magnitude of Fc_OPerrors. This selectively systematic bias causes the most pronounced relative Fc_OPerrors to occur when “true” CO2fluxes are low and kinematic temperature fluxes are high (e.g., northern ecosystems during the winter). The smallest relative errors occur during periods with large “true” CO2fluxes and low kinematic temperature fluxes. To address this bias, we replace the slow-response air temperature in the absorption-to-CO2density conversion with a fast-response air temperature derived from sonic anemometer measurements. The use of the fast-response air temperature improves the agreement between half-hourly Fc_OPand FC_CPfor all open- versus closed-path IRGA comparisons. Additionally, cumulative Fc_OPand Fc_CPsums are more comparable as differences drop from 63 %–13 % to 20 %–8 %. The improved IRGASON and EC150 performance enhances the ability and confidence to synthesize flux measurements across multiple sites including these two relatively new IRGAs.

Understanding spatial patterns of soil phosphorus is critical for efficient nutrient management and for the design of soil sampling in agricultural watersheds. This study describes patterns of soil test phosphorus (Olsen-P) concentration and variability for undulating/dissected agricultural landscapes in southwestern Manitoba under a range of management systems (no-input organic, organic with manure application, no-till, fertilized and tilled). Sampling occurred at 504 locations located in 16 small watersheds draining eight different fields. At a regional scale, most variance in Olsen-P for the 0–15 cm depth was associated with differences among fields (0.344 [log (mg kg− 1)]2, 47%). However, significant variance (0.263 [log (mg kg− 1)]2, 36%) was associated with differences among sampling plots within each field. Olsen-P for the 15–60 cm depth was lower and variance was more strongly associated with differences in field. Among-field differences in Olsen-P for 0–15 cm were strongly associated with management. Elevated Olsen-P was observed for fields that historically received application of fertilizer or manure in combination with tillage and lower Olsen-P was observed for low input organic and no-till fields. For six of eight fields sampled, a high proportion of variance in Olsen-P at the 0–15 cm depth was predicted by the Topographic Wetness Index (TWI) (r2 = 0.46–0.96, p

Net CO₂ exchange data of legume crops at 17 flux tower sites in North America and three sites in Europe representing 29 site-years of measurements were partitioned into gross photosynthesis and ecosystem respiration by using the nonrectangular hyperbolic light-response function method. The analyses produced net CO₂ exchange data and new ecosystem-scale ecophysiological parameter estimates for legume crops determined at diurnal and weekly time steps. Dynamics and annual totals of gross photosynthesis, ecosystem respiration, and net ecosystem production were calculated by gap filling with multivariate nonlinear regression. Comparison with the data from grain crops obtained with the same method demonstrated that CO₂ exchange rates and ecophysiological parameters of legumes were lower than those of maize (Zea mays L.) but higher than for wheat (Triticum aestivum L.) crops. Year-round annual legume crops demonstrated a broad range of net ecosystem production, from sinks of 760 g CO₂ m–² yr–¹ to sources of –2100 g CO₂ m–² yr–¹, with an average of –330 g CO₂ m–² yr–¹, indicating overall moderate CO₂–source activity related to a shorter period of photosynthetic uptake and metabolic costs of N₂ fixation. Perennial legumes (alfalfa, Medicago sativa L.) were strong sinks for atmospheric CO₂, with an average net ecosystem production of 980 (range 550–1200) g CO₂ m–² yr–¹.

a b s t r a c t We analyzed net CO2 exchange data from 13 flux tower sites with 27 site-years of measurements over maize and wheat fields across midcontinent North America. A numerically robust "light-soil temperature- VPD"-based method was used to partition the data into photosynthetic assimilation and ecosystem respiration components. Year-round ecosystem-scale ecophysiological parameters of apparent quantum yield, photosynthetic capacity, convexity of the light response, respiration rate parameters, ecological light-use efficiency, and the curvature of the VPD-response of photosynthesis for maize and wheat crops were numerically identified and interpolated/extrapolated. This allowed us to gap-fill CO2 exchange com- ponents and calculate annual totals and budgets. VPD-limitation of photosynthesis was systematically observed in grain crops of the region (occurring from 20 to 120 days during the growing season, depend- ing on site and year), determined by the VPD regime and the numerical value of the curvature parameter of the photosynthesis-VPD-response, � VPD. In 78% of the 27 site-years of observations, annual gross pho- tosynthesis in these crops significantly exceeded ecosystem respiration, resulting in a net ecosystem production of up to 2100 g CO2 m−2 year−1. The measurement-based photosynthesis, respiration, and net ecosystem production data, as well as the estimates of the ecophysiological parameters, provide an empirical basis for parameterization and validation of mechanistic models of grain crop production in

Agricultural soils are a significant anthropogenic source of nitrous oxide (N 2 O) to the atmosphere. Despite likely having large emissions of N 2 O, there are no continuous multi-year studies of emissions from poorly drained floodplain soil. In the present study, the micrometeorological flux of N 2 O ( F N ) was measured over three years (2006–2008) in a maize ( Zea mays L.)/faba ( Vicia faba minor L.)/spring-wheat ( Triticum aestivum L.) rotation in the Red River Valley, Manitoba, Canada on a gleyed humic verticol soil. Comparison of newly established reduced and intensive tillage treatments showed no difference in F N within the constraints of the high variability between duplicate plots. The annual gap-filled Σ F N across tillage treatments was 5.5, 1.4, and 4.3 kg N ha −1 in the maize, faba, and spring-wheat crop years, respectively. Emissions from fertilizer N addition and soil thaw the following spring was responsible for the greater Σ F N in the maize and spring-wheat years. Using four approaches to approximate background Σ F N resulted in estimates of 3.5–3.8% and 1.4–1.8% of applied fertilizer N emitted as N 2 O for the maize and spring-wheat crops, respectively. The CO 2 global warming potential equivalent of Σ F N over the three study years was an emission of 5.4 Mg CO 2 -equiv. ha −1 which adds to the previously determined C balance emission of 11.6 Mg CO 2 -equiv. ha −1 .

Net carbon dioxide ecosystem exchange (NEE) was measured over three years (2006–2008) in a maize/faba/spring-wheat crop rotation in the Red River Valley of southern Manitoba, Canada using the flux-gradient method. The turbulent transfer coefficients were obtained using a similarity-theory, eddy-covariance based aerodynamic method and the carbon dioxide vertical gradient was measured with a tunable diode laser analyzer. The system measured 30-min-average fluxes over each of four plots sequentially to test reduced and intensive tillage treatments. Annual cumulative NEE was −720, 70 and −2400 kg C ha −1 yr −1 in the maize, faba and spring-wheat crop years, respectively. Enhanced respiration in the faba year was largely responsible for the loss, whereas the large gain in the spring-wheat year was a combination of high photosynthetic activity and reduced respiration. The three years experienced sequentially cooler and wetter years that likely affected the crops. After accounting for harvest removals, the net ecosystem loss was 510, 3140 and −480 (gain) kg C ha −1 yr −1 for the respective crop years, summing to a three-year loss of 3170 kg C ha −1 . A recent conversion from intensive tillage to a reduced tillage practice showed no difference because of relatively large variability among the four plots.

Net ecosystem carbon dioxide exchange was measured in two contrasting peatlands in northern Alberta, Canada using the eddy covariance technique during the growing season (May–October). Sphagnum spp. made up approximately 66% of the total LAI (1.52 m2 m−2) at the poor fen and the total N content of Sphagnum capitula was 7.8 mg g−1 at the peak of the growing season. In contrast, the dominant plant species at the extreme-rich fen site, the perennial sedge, Carex lasiocarpa, accounted for approximately 60% of the total LAI (1.09 m2 m−2), and had leaf total N content of 19.3 mg g−1 at peak biomass. In addition, the peak aboveground biomass was higher at the poor fen (230.9 g m−2) than at the extreme-rich fen (157.1 g m−2). Both sites had maximum daily rates of net CO2 uptake of approximately 5 μmol m−2 s−1, and typical nighttime rates of CO2 loss of approximately 2 μmol m−2 s−1 during the peak of the growing season. Calculations of maximum photosynthetic and respiratory capacity were consistently higher at the extreme-rich fen. The poor fen was a net sink for CO2 during 4 of the 6 months (peaking at 44 g C m−2 in July), while only slight net losses of CO2 (3 g C m−2) occurred in May and September. In contrast, the extreme-rich fen was calculated to be a significant net sink for CO2 only during 2 months of the growing season (peaking at 30 g C m−2 in August), while significant net losses of CO2 occurred in May (8 g C m−2) and in October (13 g C m−2). The plant species at the poor fen site were active earlier and later in the growing season, while it took longer for C. lasiocarpa to develop leaf tissue, and leaf senescence and reduction in photosynthetic activity occurred earlier in the fall at the extreme-rich fen. When integrated over the 6-month growing season, the poor fen was a net sink (90 g C m−2) that was three times larger than the extreme-rich fen (31 g C m−2). The ratio of cumulative total ecosystem respiration to gross primary production was 0.7 at the poor fen and 0.9 at the extreme-rich fen.

Peatlands cover about 21% of the landscape and contain about 80% of the soil carbon stock in western Canada. However, the current rates of carbon accumulation and the environmental controls on ecosystem photosynthesis and respiration in peatland ecosystems are poorly understood. As part of Fluxnet-Canada, we continuously measured net ecosystem carbon dioxide exchange (NEE) using the eddy covariance technique in a treed fen dominated by stunted Picea mariana and Larix laricina trees during August 2003–December 2004. The total carbon stock in the ecosystem was approximately 51,000 g C m −2 , with only 540 g C m −2 contributed by live above ground vegetation. The NEE measurements were used to parameterize simple physiological models to assess temporal variation in maximum ecosystem photosynthesis ( A max ) and ecosystem respiration rate at 10 °C ( R 10 ). During mid-summer the ecosystem had a relatively high A max (approx. 30 μmol m −2 s −1 ) with relatively low R 10 (approx. 4 μmol m −2 s −1 ). The peak mid-day NEE uptake rate during July and August was 10 μmol m −2 s −1 . The ecosystem showed large seasonal variation in photosynthetic and respiratory activity that was correlated with shifts in temperature, with both spring increases and fall decreases in A max well predicted by the mean daily air temperature averaged over the preceding 21 days. Leaf-level gas exchange and spectral reflectance measurements also suggested that seasonal changes in photosynthetic activity were primarily controlled by shifts in temperature. Ecosystem respiration was strongly correlated with changes in ecosystem photosynthesis during the growing season, suggesting important links between plant activity and mycorrhizae and microbial activity in the shallow layers of the peat. Only very low rates of respiration were observed during the winter months. During 2004, the peatland recorded a net annual gain of 144 g C m −2 year −1 , the result of a difference between gross photosynthesis of 713 and total ecosystem respiration of 569 g C m −2 year −1 .

[1] Northern peatlands are a diverse group of ecosystems varying along a continuum of hydrological, chemical, and vegetation gradients. These ecosystems contain about one third of the global soil carbon pool, but it is uncertain how carbon and water cycling processes and response to climate change differ among peatland types. This study examines midsummer CO2 and H2O fluxes measured using the eddy covariance technique above seven northern peatlands including a low-shrub bog, two open poor fens, two wooded moderately rich fens, and two open extreme-rich fens. Gross ecosystem production and ecosystem respiration correlated positively with vegetation indices and with each other. Consequently, 24-hour net ecosystem CO2 exchange was similar among most of the sites (an average net carbon sink of 1.5 ± 0.2 g C m−2 d−1) despite large differences in water table depth, water chemistry, and plant communities. Evapotranspiration was primarily radiatively driven at all sites but a decline in surface conductance with increasing water vapor deficit indicated physiological restrictions to transpiration, particularly at the peatlands with woody vegetation and less at the peatlands with 100% Sphagnum cover. Despite these differences, midday evapotranspiration ranged only from 0.21 to 0.34 mm h−1 owing to compensation among the factors controlling evapotranspiration. Water use efficiency varied among sites primarily as a result of differences in productivity and plant functional type. Although peatland classification includes a great variety of ecosystem characteristics, peatland type may not be an effective way to predict the magnitude and characteristics of midsummer CO2 and water vapor exchanges.