Cattle production is a large source of greenhouse gas (GHG) emissions from the Canadian livestock sector. Efforts to reduce CH₄ emissions from enteric fermentation have led to modifications of diet composition for livestock, resulting in a corresponding change in manure properties. We studied the effect of applying manure from cattle fed a barley-based diet with and without the methane inhibitor supplement, 3-nitrooxypropanol (3-NOP), on soil GHG emissions. Three soils common to Alberta, Canada, were used: a Black Chernozem, a Dark Brown Chernozem, and a Gray Luvisol. We compared the supplemented (3-NOPM) and non-supplemented manure (BM) amendments to a composted 3-NOPM (3-NOPC) amendment and a control with no manure amendment (CK). In an 84-day laboratory incubation experiment, 3-NOPM had significantly lower cumulative CO₂ emissions compared to BM in both the Black Chernozem and Gray Luvisol. The cumulative N₂O emissions were lowest for 3-NOPC and CK and highest for 3-NOPM across all soil types. Cumulative CH₄ emissions were only affected by soil type, with a net positive flux from the fine-textured Gray Luvisol and Dark Brown Chernozem and a net negative flux from the coarse-textured Black Chernozem. Cumulative anthropogenic GHG emissions (CO₂-equivalent) from soil amended with 3-NOPM were significantly higher than those for both BM and CK amendments in the Black Chernozem, while the cumulative anthropogenic GHG emissions from the 3-NOPC treatment were similar to or significantly lower than those for the BM and CK treatments across all soil types. We conclude that soil GHG emissions resulting from the 3-NOPM amendment are dependent on soil type and 3-NOPM could potentially increase soil GHG emissions compared to BM or CK. Although we show that the composting of 3-NOPM prior to soil application can reduce soil GHG emissions, the composting process also releases GHGs, which should also be considered in assessing the life-cycle of manure application. Our results provide a first look at the potential effect of the next stage in the life cycle of 3-NOP on GHG emissions. Further research related to the effect of soil properties, particularly in field studies, is needed to assess the best management practices related to the use of manure from cattle-fed diets supplemented with 3-NOP as a soil amendment.

Efforts to reduce greenhouse gas (GHG) emissions from cattle production have led to modifications of livestock diet composition aimed at reducing CH₄ emissions from enteric fermentation. These diet modifications can result in varied manure types that may differentially affect GHG emissions when applied to soil. The purpose of this experiment was to examine the effect of different manure types on GHG emissions. We conducted an incubation experiment, comparing the manure from livestock fed a corn-based diet (CM) to that from livestock fed a traditional barley-based diet (BM). The manures were applied to three soil types (with varied soil fertility and pH) and compared to a control (without manure application). Carbon dioxide (CO₂) emissions were greater from CM than from BM across all soil types (29.1 and 14.7 mg CO₂-C kg⁻¹, respectively). However, CM resulted in lower N₂O emissions relative to BM in the low fertility soil (4.21 and 72.67 μg N₂O-N kg⁻¹, respectively) and in lower CH₄ emissions relative to BM in the two acidic soils (0.5 and 2.5 μg CH₄-C kg⁻¹, respectively). Total GHG emissions (sum of CO₂, N₂O, and CH₄) were similar between CM and BM across all soil types, but CM (unlike BM) had 52–66% lower emissions in the low fertility soil relative to both CM and BM in the high fertility soil. Our study shows that manure and soil type interact to affect GHG emissions and that CM may mitigate N₂O emissions relative to BM when applied to low fertility soils.

Greenhouse gases (GHG) emissions from agricultural practices contribute 14% of anthropogenic emissions to the atmosphere, and novel practices to reduce these emissions, including feeding cattle a modified diet, are of interest. This study examines how additions of manure from cattle fed a regular diet or a diet supplemented with 2% biochar, and biochar at 5 or 10 Mg ha⁻¹, impact GHG emissions in a Gray Luvisol agricultural field experiment. Emissions of CH₄ and N₂O were monitored, and soil samples were collected to analyze exchangeable NPKS, microbial biomass, total C and N, electrical conductivity, and pH. Wheat (Triticum aestivum) was planted, and grain yield measured. We calculated the yield-based emission factor (EF_yield) and cumulative area-based GHG emissions emission factor (EF_area). The results showed an up to 98.5% change in the inhibition of CH₄ oxidation from biochar-manure + biochar at 5 and 10 Mg ha⁻¹ compared to the CT. The biochar in biochar-manure may have acted as a biocide to methanotrophs, causing a reduction in the release of CH₄ over time. Yet, there were no significant differences in N₂O emissions amongst treatments. Therefore, biochar-manure + biochar at 5 and 10 Mg ha⁻¹ applications may impact total GHG emissions and improve grain productivity and protein content compared to BM alone.

Amending soil with manure from cattle fed biochar (BC) (biochar–manure [BM]) is a potential best management practice to improve plant nutrition in the circular economy. Yet, information concerning the agronomic performance of BM under temperate field conditions is scarce. A 2‐year study on a Gray Luvisol was conducted to determine the effect of BM on the crop growth of spring wheat ( Triticum aestivum L.), followed by canola ( Brassica napus L.), soil fertility, and microbial function. Treatments included (i) no amendments (control), (ii) BC at 5 and 10 Mg·ha ⁻¹ (BC5 and BC10), (iii) regular stockpiled manure (RM) at 100 kg total N·ha ⁻¹ , (iv) stockpiled BM at 100 kg total N·ha ⁻¹ , and (v) BC and RM (BC+RM) or BC and BM (BC+BM) at the aforementioned rates. During the wheat growing season in 2020, which had high precipitation, grain yield was 2.4 times greater in BM+BC10 than in BM alone (1416 vs. 579 kg·ha ⁻¹ , p < 0.001), highlighting synergistic effects of BM together with BC application on agronomic performance. Conversely, lower precipitation and warmer temperatures in the canola growing season in 2021 hampered any statistical differences among treatments. While soil microbial biomass did not change by the end of the experiment, shifts toward amino acid utilization with BC additions in both crops potentially influenced crop growth and nitrogen‐use efficiency. In summary, BM+BC at 10 Mg·ha ⁻¹ performed best in this study during the first cropping season under cold and rainy conditions.