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Potential carbon mineralization (Cmin) is a commonly used indicator of soil health, with greater Cmin values interpreted as healthier soil. While Cmin values are typically greater in agricultural soils managed with minimal physical disturbance, the mechanisms driving the increases remain poorly understood. This study assessed bacterial and archaeal community structure and potential microbial drivers of Cmin in soils maintained under various degrees of physical disturbance. Potential carbon mineralization, 16S rRNA sequences, and soil characterization data were collected as part of the North American Project to Evaluate Soil Health Measurements (NAPESHM). Results showed that type of cropping system, intensity of physical disturbance, and soil pH influenced microbial sensitivity to physical disturbance. Furthermore, 28% of amplicon sequence variants (ASVs), which were important in modeling Cmin, were enriched under soils managed with minimal physical disturbance. Sequences identified as enriched under minimal disturbance and important for modeling Cmin, were linked to organisms which could produce extracellular polymeric substances and contained metabolic strategies suited for tolerating environmental stressors. Understanding how physical disturbance shapes microbial communities across climates and inherent soil properties and drives changes in Cmin provides the context necessary to evaluate management impacts on standardized measures of soil microbial activity.

Potential carbon mineralization (Cmin) is a commonly used indicator of soil health, with greater Cmin values interpreted as healthier soil. While Cmin values are typically greater in agricultural soils managed with minimal physical disturbance, the mechanisms driving the increases remain poorly understood. This study assessed bacterial and archaeal community structure and potential microbial drivers of Cmin in soils maintained under various degrees of physical disturbance. Potential carbon mineralization, 16S rRNA sequences, and soil characterization data were collected as part of the North American Project to Evaluate Soil Health Measurements (NAPESHM). Results showed that type of cropping system, intensity of physical disturbance, and soil pH influenced microbial sensitivity to physical disturbance. Furthermore, 28% of amplicon sequence variants (ASVs), which were important in modeling Cmin, were enriched under soils managed with minimal physical disturbance. Sequences identified as enriched under minimal disturbance and important for modeling Cmin, were linked to organisms which could produce extracellular polymeric substances and contained metabolic strategies suited for tolerating environmental stressors. Understanding how physical disturbance shapes microbial communities across climates and inherent soil properties and drives changes in Cmin provides the context necessary to evaluate management impacts on standardized measures of soil microbial activity.

Returning crop residue may result in nutrient reduction in soil in the first few years. A two-year field experiment was conducted to assess whether this negative effect is alleviated by improved crop residue management (CRM). Nine treatments (3 CRM and 3 N fertilizer rates) were used. The CRM treatments were (1) R0: 100 % of the N using mineral fertilizer with no crop residues return; (2) R: crop residue plus mineral fertilizer as for the R0; and (3) Rc: crop residue plus 83 % of the N using mineral and 17 % manure fertilizer. Each CRM received N fertilizer rates at 270, 360, and 450 kg N ha−1 year−1. At the end of the experiment, soil NO3-N was reduced by 33 % from the R relative to the R0 treatment, while the Rc treatment resulted in a 21 to 44 % increase in occluded particulate organic C and N, and 80 °C extracted dissolved organic N, 19 to 32 % increase in microbial biomass C and protease activity, and higher monounsaturated phospholipid fatty acid (PLFA):saturated PLFA ratio from stimulating growth of indigenous bacteria when compared with the R treatment. Principal component analysis showed that the Biolog and PLFA profiles in the three CRM treatments were different from each other. Overall, these properties were not influenced by the used N fertilizer rates. Our results indicated that application of 17 % of the total N using manure in a field with crop residues return was effective for improving potential plant N availability and labile soil organic matter, primarily due to a shift in the dominant microorganisms.

Reclamation success is highly dependent upon final soil quality of stockpiled soils, such as those found Cold Lake Oil Sands Region. Stockpiled soils, however, are generally poor in quality. Soils were amended with, biochar (BC), humalite (HU), a sub-bituminous coal; and peat (PT), as well as 50:50 blends of biochar:humalite (BCH) and biochar:peat (BCP). These amendments were applied at rates of 0, 6.55, 13.1 and 26.2 g C kg-1 each. Biochar, PT, and BCP applied at the rate of 26.2 g C kg-1 were found to reduce N2O emissions by 34, 54, and 70%, respectively, relative to the control. Within the bioassay, BC and PT amendment resulted in a 38 and 40% increase in dry matter yield (DMY) respectively. Finally, amendment typically resulted in significant net decreases in Olsen P values, while nitrate and ammonium concentrations were high in PT amended soils. In general, PT had the best overall performance.

Reclamation success is highly dependent upon final soil quality of stockpiled soils, such as those found Cold Lake Oil Sands Region. Stockpiled soils, however, are generally poor in quality. Soils were amended with, biochar (BC), humalite (HU), a sub-bituminous coal; and peat (PT), as well as 50:50 blends of biochar:humalite (BCH) and biochar:peat (BCP). These amendments were applied at rates of 0, 6.55, 13.1 and 26.2 g C kg-1 each. Biochar, PT, and BCP applied at the rate of 26.2 g C kg-1 were found to reduce N2O emissions by 34, 54, and 70%, respectively, relative to the control. Within the bioassay, BC and PT amendment resulted in a 38 and 40% increase in dry matter yield (DMY) respectively. Finally, amendment typically resulted in significant net decreases in Olsen P values, while nitrate and ammonium concentrations were high in PT amended soils. In general, PT had the best overall performance.

Two laboratory incubation studies and a growth room bioassay of forage barley were conducted to investigate nitrogen (N) and phosphorus (P) mineralization, and nitrous oxide emission from two contrasting agricultural soils amended with anaerobically digested cattle manure (ADM). The ADM is a nutrient-rich co-product from manure-based biogas plants which is applied to cropland at rates used for raw manure since scientific information on nutrient release from ADM is lacking. Application of the separated solids fraction of ADM (SS) reduced nitrous oxide emission but resulted in lower N mineralization compared to raw manure in both soils. Raw manure- and SS- treatments had similar biomass yields and P supply capacities while the application of pelletized SS (PSS) caused net N immobilization, lower P release than manure and SS, and depressed barley yields relative to non-amended (control) soils.

Two laboratory incubation studies and a growth room bioassay of forage barley were conducted to investigate nitrogen (N) and phosphorus (P) mineralization, and nitrous oxide emission from two contrasting agricultural soils amended with anaerobically digested cattle manure (ADM). The ADM is a nutrient-rich co-product from manure-based biogas plants which is applied to cropland at rates used for raw manure since scientific information on nutrient release from ADM is lacking. Application of the separated solids fraction of ADM (SS) reduced nitrous oxide emission but resulted in lower N mineralization compared to raw manure in both soils. Raw manure- and SS- treatments had similar biomass yields and P supply capacities while the application of pelletized SS (PSS) caused net N immobilization, lower P release than manure and SS, and depressed barley yields relative to non-amended (control) soils.

Phosphate availability and movement is very low in acid soil due to fixation reactions of aluminum with phosphate. This research proposed that P fixation reactions are controlled, among other factors, by hydrogen ion production/consumption. A series of experiments were designed to demonstrate the proposed research model through the study of one-dimensional diffusive movement and precipitation reactions of applied P fertilizer (and associated cations). The effects of exchangeable Al, gibbsite, lignosulphonate, and type of P fertilizer ($\rm KH\sb2PO\sb4,\ K\sb2HPO\sb4$ and $\rm K\sb3PO\sb4$) were investigated in a simulated soil consisting of acid-washed sand and various levels of Al-saturated cation exchange resin. The diffusive transport of P and associated cations were also studied in a limed and unlimed gibbsite-rich Oxisol. When $\rm KH\sb2PO\sb4$ was applied to the surface of columns with different levels of exchangeable Al, gibbsite, and lignosulphonate and incubated for various times, the soluble amount and movement of P decreased as levels of exchangeable Al increased. Gibbsite alone did not reduce movement of P, but the combination of gibbsite with exchangeable Al greatly reduced the movement of P. Lignosulphonate decreased the soluble amount and movement of P in columns with exchangeable Al, but the opposite effect occurred in columns with both exchangeable Al and gibbsite, especially after four weeks. Studies using $\rm KH\sb2PO\sb4$ in unlimed and limed gibbsite-rich Oxisol showed that P movement was very limited in both; liming had very little effect. Among the three P fertilizers tested, P movement was greatest with $\rm KH\sb2PO\sb4$ and least with $\rm K\sb3PO\sb4$ in columns with exchangeable Al without gibbsite. But there was little difference among the three P fertilizers in columns with both exchangeable Al and gibbsite. However, P concentration was the highest for $\rm K\sb3PO\sb4$ as time increased. Tripotassium phosphate and $\rm K\sb2HPO\sb4$

Phosphate availability and movement is very low in acid soil due to fixation reactions of aluminum with phosphate. This research proposed that P fixation reactions are controlled, among other factors, by hydrogen ion production/consumption. A series of experiments were designed to demonstrate the proposed research model through the study of one-dimensional diffusive movement and precipitation reactions of applied P fertilizer (and associated cations). The effects of exchangeable Al, gibbsite, lignosulphonate, and type of P fertilizer ($\rm KH\sb2PO\sb4,\ K\sb2HPO\sb4$ and $\rm K\sb3PO\sb4$) were investigated in a simulated soil consisting of acid-washed sand and various levels of Al-saturated cation exchange resin. The diffusive transport of P and associated cations were also studied in a limed and unlimed gibbsite-rich Oxisol. When $\rm KH\sb2PO\sb4$ was applied to the surface of columns with different levels of exchangeable Al, gibbsite, and lignosulphonate and incubated for various times, the soluble amount and movement of P decreased as levels of exchangeable Al increased. Gibbsite alone did not reduce movement of P, but the combination of gibbsite with exchangeable Al greatly reduced the movement of P. Lignosulphonate decreased the soluble amount and movement of P in columns with exchangeable Al, but the opposite effect occurred in columns with both exchangeable Al and gibbsite, especially after four weeks. Studies using $\rm KH\sb2PO\sb4$ in unlimed and limed gibbsite-rich Oxisol showed that P movement was very limited in both; liming had very little effect. Among the three P fertilizers tested, P movement was greatest with $\rm KH\sb2PO\sb4$ and least with $\rm K\sb3PO\sb4$ in columns with exchangeable Al without gibbsite. But there was little difference among the three P fertilizers in columns with both exchangeable Al and gibbsite. However, P concentration was the highest for $\rm K\sb3PO\sb4$ as time increased. Tripotassium phosphate and $\rm K\sb2HPO\sb4$