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Quantifying the emissions of the three main biogenic greenhouse gases (GHGs), carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4), from agroecosystems is crucial. In this study continuous measurements of N2O, and CH4 emissions from potato and pea crops in southwest British Columbia, Canada were made using the eddy‐covariance (EC) technique. Flux footprint analysis, coupled with EC and manual nonsteady state chamber measurements, was used to address the spatial heterogeneity resulting from the field edge at the study site. Flux footprint corrections had a larger effect on N2O fluxes than CO2 fluxes because of a more pronounced difference in N2O fluxes between the crop and edge areas. After flux footprint corrections, the potato and pea crops were both weak CO2 sinks with annual net ecosystem exchange values of −57 ± 9 and −97 ± 16 g C m−2 yr−1, respectively. However, after taking carbon (C) export via crop harvest and C import via seeding into account, the potato crop shifted to being a moderate C source of 284 ± 55 g C m−2 yr−1, while the pea crop became near C neutral, sequestering only 30 ± 26 g C m−2 yr−1. Annual GHG balances, quantified by converting N2O and CH4 to CO2 equivalents as pulse emissions using respective global warming potentials on a 100‐year timescale, were 417 ± 88 and 152 ± 106 g CO2e m−2 yr−1 for the potato and pea crops, respectively, with N2O contributing the largest proportion to annual total GHG balances and outweighing the CO2 uptake from the atmosphere. Plain Language Summary: To better mitigate climate change, quantifying the emissions of the three main biogenic greenhouse gases (GHGs), carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4), from agroecosystems is critical. Therefore, in this study we made continuous half‐hourly measurements of CO2, N2O, and CH4 emissions from potato and pea crops in southwest British Columbia, Canada using micrometeorological instrumentation installed at the field edge. To correct for the effects of the field edge on the micrometeorological measurements, we used supplementary chamber measurements and a footprint model. This enabled us to estimate the actual GHG budgets of the study crop areas. The correction had a larger effect on N2O fluxes than CO2 fluxes because of a more pronounced difference in N2O fluxes between the crop and edge areas. Both crops sequestered CO2 on an annual basis. However, after taking carbon (C) export via crop harvest and C import via seeding into account, the potato crop shifted to being a moderate C source while the pea crop became near C neutral. Even though CH4 emissions were low, substantial N2O emissions outweighed the CO2 uptake from the atmosphere by both crops, resulting in both being GHG sources. Key Points: Combining eddy‐covariance and flux‐chamber data with flux analysis allowed estimation of actual greenhouse gas fluxes from crop fieldsIncluding export (harvesting) and import (seeding), peas were near carbon neutral while potatoes were a moderate carbon sourceFor both potato and pea crops, nitrous oxide contributed the largest proportion of the annual total greenhouse gas emissions [ABSTRACT FROM AUTHOR]

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Soil compaction often limits conifer regeneration on sites degraded by landings and roads, but inadequate understanding of the relationship between compaction and tree growth could lead to inappropriate soil conservation and rehabilitation efforts. We tested liquid and plastic limits, oxidizable organic matter, total carbon, particle size distribution, and iron and aluminum oxides on soil samples collected from five forest experiments in interior British Columbia. These data were used to estimate soil maximum bulk density (MBD) and relative bulk density (RBD); our objective was to relate RBD to tree growth. Height of interior Douglas-fir (Pseudotsuga menziesii var. glauca (Bessin) Franco) was limited when RBD was >0.72. For lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) and hybrid white spruce {Picea glauca (Moench) Voss x Picea engelmannii Parry ex Engelm.), RBDs of 0.60-0.68 corresponded to maximum height, whereas RBDs of 0.78-0.87 appeared to limit height growth. The presence of surface organic material mitigated compaction and was often associated with lower RBD. Our results illustrate the usefulness of RBD to assess compaction and suggest that soil rehabilitation should be considered on disturbed sites where soil RBD is >0.80. [ABSTRACT FROM AUTHOR]

The widespread use of heavy equipment during timber harvesting and site preparation can lead to reduced soil productivity and warrants development of new methods to assess compaction. We evaluated the effects of soil particle density, organic matter, particle size distribution, extractable oxides, and plastic and liquid limits on the maximum bulk density (MBD) of forest soils in British Columbia. Soil samples were collected from 33 sites throughout British Columbia, covering the major forest and soil types of the province. The standard Proctor test was used to determine MBD and related parameters, including the gravimetric water content (WMBD) and porosity (fMBD) at which MBD was achieved. The significance levels of single soil properties in predicting MBD were in the order plastic and liquid limits, organic matter, oxalate-extractable oxides, and particle size distribution. For all samples, liquid limit and clay were most closely related to M BD (R2 = 0.83). Addition of organic matter to the model increased the regression coefficients, and oxidizable organic matter caused a greater increase than did total C. Stratification of the sample set into groups based on plasticity led to higher R2 values in multiple regressions, and different soil properties were important for nonplastic soils than for those with high, moderate, and low plasticity. Prediction with multiple regression explained the most variation in MBD for nonphstic soils, while properties of highly plastic soils explained the least variation in MBD and moderately plastic soils were intermediate. Based on our findings, we propose an approach for using MBD to help better interpret bulk density data in forest soil compaction studies. [ABSTRACT FROM AUTHOR]

Short-term grassland set-asides (GLSA) have been incorporated into intensive annual crop rotations to improve soil quality. The legacy of the GLSA to subsequent annual crops, however, is not well understood. The objective of this study was to determine the impacts of 3-year-old GLSA on nitrogen (N) dynamics and the yield of the subsequent cash crop. A regional analysis was conducted over two years, utilizing eight production fields transitioning from GLSA, paired with fields in continuous annual crop rotation (ACR) with matching management. A controlled plot-scale experiment was also conducted on a single 3-year-old GLSA, comparing fertilizer types, rates, and timing of incorporation. In each experiment, soils were sampled every 10–14 days for ammonium (NH4+-N) and nitrate (NO3−-N), along with ion probes, installed near the rooting zone to track plant available nitrogen (PAN) throughout the season. The results from the regional analysis are confounding, in 2015 showing that GLSA supplied an additional 18 kg PAN ha−1 compared to ACR but showed no PAN benefits in 2016. The controlled plot-scale experiment highlighted the importance of fertilizer type to subsequent PAN, showing synthetic treatments consistently supplied more PAN than organic. The results from this study suggest that 3-year-old GLSAs can potentially improve PAN to subsequent crops depending on how they are managed. [ABSTRACT FROM AUTHOR]

• Soil water regulation was improved by enrollment in stewardship programs. • Greater soil carbon was observed with enrollment in stewardship programs. • Grassland set-aside with winter cover cropping improved soil organic carbon storage potential. • Enrollment in stewardship programs can lead to regenerative outcomes. Agricultural stewardship programs that incentivize practices such as winter cover cropping (WCC), grassland set-asides (GLSA), and hedgerows (HR) for intensive annual agricultural production are often implemented to improve both soil conditions and provision of wildlife habitat in coastal agricultural systems of the Fraser River Delta, British Columbia (BC). Although these programs have been shown to support numerous ecosystem services, it is unclear how they contribute to regenerative agricultural outcomes. Regenerative agricultural practices aim to increase soil carbon inputs and reduce carbon dioxide losses which in turn improves soil structure, optimizes soil water regulation, and provides climate mitigation and resiliency of agricultural systems. The objectives of this study were to quantify the effects of agricultural stewardship programs for regenerative outcomes through indicators of climate mitigation and adaptation. Twenty-six fields in the southwestern, BC were grouped by those that participated in stewardship programs between 1992 and 2016 and those that did not. In the spring of 2018, soil samples were collected; soil organic carbon (SOC) concentrations were measured, and stocks were calculated; pedo-transfer functions were used to estimate soil water regulation indicators; and differences among stewardship program and non-program fields were statistically analyzed using a linear mixed effects model. The SOC (mg kg−1) from 0 to 15 cm was greater with implementation of stewardship programs. Topsoil equivalent soil mass SOC stocks (t/ha) were 71 % and 63 % greater in HR and WCC + GLSA program fields, respectively, compared to non-program fields. Soil workability threshold was 25 % and 14 % greater in HR and WCC + GLSA program fields, respectively, compared to non-program. Our results indicate that stewardship programs that include hedgerows and grassland set-asides promote accrual of soil carbon and improved soil water regulation and show that these programs can effectively enhance regenerative outcomes and improve agroecosystem resilience in this important agricultural region. [ABSTRACT FROM AUTHOR]

• We report eddy-covariance measured GHG fluxes over a highbush blueberry field. • The field emitted more CO 2 relative to N 2 O and CH 4 in CO 2 equivalents. • The field was a source of CO 2 but a net carbon sink in the carbon balance. • Annual N 2 O emissions were underestimated by default and Canada-specific equations. • Changes in soil moisture and rainfall were associated with higher N 2 O emissions. Agricultural fields can be significant sources of carbon dioxide (CO 2), nitrous oxide (N 2 O) and methane (CH 4), with implications for climate change. This paper reports continuous half-hourly CO 2 , CH 4 and N 2 O fluxes over a conventionally-managed highbush blueberry field on Westham Island in Delta, British Columbia (BC), Canada, measured using the eddy-covariance (EC) method for a 1-year period. Field management, including fertilization and mowing interrow grass, was associated with substantial changes in GHG exchange. With emissions of N 2 O and CH 4 totaling 0.61 ± 0.03 g N 2 O m−2 year−1 and 0.81 ± 0.4 g CH 4 m−2 year−1, corresponding to 182 ± 9 g and 30 ± 13 g CO 2 equivalent (CO 2 e) m−2 year−1, respectively, based on their 100-year global warming potentials, the field was a net source of 840 ± 126 g CO 2 e m−2 year−1. The annual net ecosystem exchange of CO 2 (NEE c) was the largest component of the GHG balance at 171 ± 28 g C m−2 year−1 (628 ± 104 g CO 2 m−2 year−1), indicating the field was a net carbon (C) source. After accounting for inputs and outputs of C in sawdust and harvested fruit, respectively, the agroecosystem gained a net of 233 ± 88 g C m−2 year−1, primarily controlled by the application of sawdust mulch. Both soil temperature and soil moisture were important environmental factors controlling GHG emissions, which has implications for future feedback cycles and climate change. Our results suggest that agricultural management strategies can be targeted for GHG mitigation. [ABSTRACT FROM AUTHOR]