Rasouli, S., Whalen, J. K. and Madramootoo, C. A. 2014. Review: Reducing residual soil nitrogen losses from agroecosystems for surface water protection in Quebec and Ontario, Canada: Best management practices, policies and perspectives. Can. J. Soil Sci. 94: 109-127. Eutrophication and cyanobacteria blooms, a growing problem in many of Quebec and Ontario's lakes and rivers, are largely attributed to the phosphorus (P) and nitrogen (N) emanating from intensively cropped agricultural fields. In fact, 49% of N loading in surface waters comes from runoff and leaching from fertilized soils and livestock operations. The residual soil nitrogen (RSN), which remains in soil at the end of the growing season, contains soluble and particulate forms of N that are prone to being transported from agricultural fields to waterways. Policies and best management practices (BMPs) to regulate manure storage and restrict fertilizer and manure spreading can help in reducing N losses from agroecosystems. However, reduction of RSN also requires an understanding of the complex interactions between climate, soil type, topography, hydrology and cropping systems. Reducing N losses from agroecosystems can be achieved through careful accounting for all N inputs (e.g., N credits for legumes and manure inputs) in nutrient management plans, including those applied in previous years, as well as the strategic implementation of multiple BMPs and calibrated soil N testing for crops with high N requirements. We conclude that increasing farmer awareness and motivation to implement BMPs will be important in reducing RSN. Programs to promote communication between farmers and researchers, crop advisors and provincial ministries of agriculture and the environment are recommended.

Wile, A., Burton, D. L., Sharifi, M., Lynch, D., Main, M. and Papadopoulos, Y. A. 2014. Effect of nitrogen fertilizer application rate on yield, methane and nitrous oxide emissions from switchgrass (Panicum virgatum L.) and reed canarygrass (Phalaris arundinacea L.). Can. J. Soil Sci. 94: 129-137. This 2-yr (2008-2009) study conducted in Truro, Nova Scotia, measured plant biomass production (yield and ash content) and greenhouse gas emissions (methane and nitrous oxide), from the bioenergy crops switchgrass (SG; Panicum virgatum L.) and reed canarygrass (RCG; Phalaris arundinacea L.) receiving spring application of nitrogen fertilizer at 0, 40 and 120 kg N ha^-1. In both years, crop yields were unresponsive to N fertilizer. In 2008, SG average yields were greater than RCG producing 7.0 vs. 4.6 Mg ha^-1, respectively, while ash content was significantly greater for RCG in both years. Cumulative seasonal (May-November) N₂O emissions were<1 kg N₂O-N ha^-1 in 2008 and<0.2 kg N₂O-N ha^-1 in 2009 with crop (SG>RCG) and N fertilizer (N₁₂₀>N₄₀=N₀) effects found in 2008 only. Nitrate exposure was greater for SG in 2008 only, but responded to N fertilization in both years (N₁₂₀>N₀). These crops were net sinks for methane and the magnitude of the sink was not influenced by crop type, N fertilization or year. Despite lower yields, the greenhouse gas intensity calculated for RCG (-2 to 20 kg CO₂e t^-1 biomass) was lower than for SG (8 - 60 kg CO₂e t^-1 biomass) as a result of lower N₂O emissions.

Caron, J., Rancourt, G. T., Bélec, C., Tremblay, N. and Parent, L.-É. 2014. Nitrogen budget for fertilized carrot cropping systems in a Quebec organic soil. Can. J. Soil Sci. 94: 139-148. After reclamation, organic soils tend to shift from net N immobilization to net N mineralization. The N amounts mineralized annually can be sufficient to cover the N needs of the crop, reducing the need for supplemental N fertilization. The objective of this study was to assess N budgets and to infer the apparent N mineralization in fertilized and unfertilized carrot (Daucus carota L.) crops in an organic soil in southwestern Quebec. Five pre-plant N fertilization treatments (0, 25, 50, 75, and a split 25 25 kg N ha^-1) were applied over a 3-yr period to non-irrigated carrots. Crop yield and plant and soil N contents were measured. Apparent net N mineralization was an important source of N, averaging 117 kg N ha^-1 yr^-1. Crop yield was not affected by the N fertilization rate, by splitting of the fertilizer application or by the previous year's crop. Increasing the N fertilizer rate increased the soil nitrate content below the root zone (~40 cm below the surface), enhancing the risk of nitrate leaching. Thus, because soil N mineralization was sufficient for the carrots' requirements in this organic soil, supplemental N fertilization was found to be unnecessary and could exacerbate the environmental risk of nitrate leaching.

Gao, X., Tenuta, M., Buckley, K. E., Zvomuya, F. and Ominski, K. 2014. Greenhouse gas emissions from pig slurry applied to forage legumes on a loamy sand soil in south central Manitoba. Can. J. Soil Sci. 94: 149-155. Information regarding the greenhouse gas (GHG) emissions resulting from the application of pig slurry to forage in western Canada is limited. This study examined the effects of addition of pig slurry and soil water content with landscape position on nitrous oxide (N₂O) and methane (CH₄) emissions from forage legumes [sainfoin (Onobrychis viciifolia) and alfalfa (Medicago sativa)] on a sandy loam soil in Brandon, Manitoba, over two growing seasons. Pig slurry was surface applied with a rolling aerator-type tine at a rate of 35000 L ha^-1 and 38000 L ha^-1, providing 62-15-50 and 205-45-86, actual N-P-K kg ha^-1, in 2006 and 2007, respectively. Emissions were measured on and between surface bands of the slurry applied to soil. Soil concentrations of -N and -N, moisture, and temperature were also monitored. In both years, slurry application increased growing season cumulative N₂O emissions. Net increase in cumulative N₂O-N emissions with slurry treatment ranged from 0.04 to 0.05% of total N ha^-1 applied in 2006 but from 0.7 to 0.9% in 2007. The coherence of rapidly increasing N₂O emissions following slurry application with decreasing soil and increasing concentration, in combination with the fact that emissions continued even when soil concentrations were undetectable, suggest nitrification and denitrification were sources of N₂O. Emissions of CH₄ were generally slightly negative and unaffected by addition of slurry. Higher soil water content at lower landscape position did not affect emissions of CH₄ but did increase those of N₂O in 2007. The current study was conducted at one field location. Examination of slurry additions to additional sites is required for reliable estimation of N₂O emissions from slurry applied to perennial legume forages in prairie Canada.

Preston, C. M., Norris, C. E., Bernard, G. M., Beilman, D. W., Quideau, S. A. and Wasylishen, R. E. 2014. Carbon and nitrogen in the silt-size fraction and its HCl-hydrolysis residues from coarse-textured Canadian boreal forest soils. Can. J. Soil Sci. 94: 157-168. Improving the capacity to predict changes in soil carbon (C) stocks in the Canadian boreal forest requires better information on the characteristics and age of soil carbon, especially more slowly cycling C in mineral soil. We characterized C in the silt-size fraction, as representative of C stabilized by mineral association, previously isolated in a study of soil profiles of four sandy boreal jack pine sites. Silt-size fraction accounted for 13-31% of the total soil C and 12-51% of the total soil N content. Solid-state ¹³C nuclear magnetic resonance spectroscopy showed that silt C was mostly dominated by alkyl and O,N-alkyl C, with low proportions of aryl C in most samples. Thus, despite the importance of fire in this region, there was little evidence of storage of pyrogenic C. We used HCl hydrolysis to isolate the oldest C within the silt-size fraction. Consistent with previous studies, this procedure removed 21-74% of C and 74-93% of N, leaving residues composed mainly of alkyl and aryl C. However, it failed to isolate consistently old C; 11 out of 16 samples had recent ¹⁴C ages (fraction of modern ¹⁴C > 1), although C-horizon samples were older, with Δ¹⁴C from -17 to -476‰. Our results indicate relatively young ages for C associated with the silt-size fractions in these sites, for which mineral soil C storage may be primarily limited by good drainage and coarse soil texture, exacerbated by losses due to periodic wildfire.

Baugé, S. M. Y., Lavkulich, L. M., Wilson, J. E. and Schreier, H. E. 2014. Comparison of surface properties of synthetic and soil struvite. Can. J. Soil Sci. 94: 169-176. X-ray, Raman and nuclear magnetic resonance (NMR) analyses of intensively managed agricultural soils in southwestern British Columbia reported the presence of the Mg-phosphate mineral, struvite. Soils are heterogeneous, thus analytical techniques based on single minerals require calibration in order to provide reliable results. A synthetic struvite was used to compare the properties of the soil phosphate with struvite. The results confirmed the presence of struvite and possibly additional species of Mg. Time of flight-secondary ion mass spectroscopy (TOF-SIMS) revealed that the surface of struvite, to 2nm depth, is dominated by Mg with other cations, notably Fe and NH₄ that were measured in minor amounts and were associated with the Mg rich surface layer. The results suggest that P is located within the struvite structure. Chemical reactions of struvite and phosphorus chemistry in these soils appear to be governed by the Mg surface layer.

Liu, M., Du, W. and Zhang, H. 2014. Changes of preferential flow path on different altitudinal zones in the Three Gorges Reservoir Area, China. Can. J. Soil Sci. 94: 177-188. Preferential flow in soil macropores plays an important role in runoff control and soil and water conservation. The aim of this study was to investigate the distribution of preferential flow paths in the soil profile of various altitudinal belts, analyze its variation among different soil horizons, and define the cause of soil macropores. A dye tracer method combined with photographic analysis was conducted for four hillslope sites in the Three Gorges Reservoir Area of China (TGRA). The results show that stained area proportion, as well as its vertical distribution in soil sections, presented varied patterns due to changes of forest vegetation and soil type with altitude. Stained area ratio of soil profiles increased, while stained depth decreased with increasing altitude. For soil sections in the subalpine belt, mid-mountain belt, and low-mountain belt of TGRA, stained area ratios were 62, 42, and 45%, and stained depths were 52.4, 56.4, and 69.5 cm, respectively. For brown earth covered with subalpine temperate deciduous broad-leaved forest, stained area ratios were the largest, but dyed patches were concentrated in the humus horizon. For yellow earth covered with low-mountain warm coniferous forest, stained depth reached 69.5 cm, and stained patches existed in the total soil profile. Compared with forest soil, stained depth and stained area ratio of abandoned farmland in low-mountain belt were lower, and the depth of dye infiltration was even shallower.

Fox, C. A., Tarnocai, C., Broll, G., Joschko, M., Kroetsch, D. and Kenney, E. 2014. Enhanced A Horizon Framework and Field Form for detailed field scale monitoring of dynamic soil properties. Can. J. Soil Sci. 94: 189-208. Taxonomic protocols for A horizon description are limited when detailed monitoring of soil change in dynamic soil properties is required for determining the effectiveness of best management practices, remediation efforts, and assessing subtle impacts on soil properties from environmental and anthropogenic stressors. The A Horizon Framework was designed by consolidating protocols from national and international description systems and expert opinion to optimize descriptive capability through use of additional enhanced lowercase designators. The Framework defines new protocols and syntax resulting in a unique soil fingerprint code. Five levels of enhanced lowercase A horizon designators are defined: Level 1, Soil processes and environmental context; Level 2, Soil structure-bulk density; Level 3, Organic carbon; Level 4, pH and electrical conductivity; and, Level 5, Soil and landscape context (i.e., soil texture, surface conditions, current land use, slope character). An electronic Field Form based on the new Framework syntax automatically records the soil fingerprint code in an enhanced (all Levels included) and a minimum detail mode focused on the key dynamic properties. The soil fingerprint codes become a powerful tool by which to identify trends of soil change and small alterations in the dynamic soil properties. Examples of soil fingerprint codes from selected Canada and Germany long-term experimental studies are presented.

Miller, J. J., Curtis, T., Chanasyk, D. S. and Willms, W. D. 2014. Influence of streambank fencing and river access for cattle on riparian zone soils adjacent to the Lower Little Bow River in southern Alberta, Canada. Can. J. Soil Sci. 94: 209-222. Cattle grazing in riparian pastures adjacent to rivers may increase soil compaction and increase soil nutrients, such as N and P. We conducted a 4-yr study with sampling in 3 yr (2009, 2010, 2012) of riparian zone soils adjacent to fenced and unfenced reaches of the Lower Little Bow River in southern Alberta. We examined the effect of grazing, access of cattle to the river (access versus no-access), and distance (0.25, 1, 2, 4, 6, 8, 10 m) from the river on surface soil bulk density, volumetric water content, NH₄-N, NO₃, and soil test P. Penetration depth was also measured in 2012. The three grazing treatments consisted of one fenced reach (ungrazed treatment), one unfenced and grazed reach with high cattle impact (high-impact grazed treatment), and one unfenced and grazed reach with low cattle impact (low-impact grazed treatment). We hypothesized that soil compaction would be greater, soil nutrients would be enriched, and soil water content would be lower for grazed compared with ungrazed treatments, and that this same trend would occur for access compared with no-access locations. The soil properties in our study were generally significantly (P≤0.05) influenced by grazing, access, and distance from the riverbank. However, treatment effects were generally dependent on two- or three-way interactions with the other factors. Soil bulk density in 2009 and 2012 was 8 to 20% greater at access compared with no-access locations within 2 m of the riverbank, suggesting soil compaction by cattle was confined close to the wetter riverbank soils. Most soil properties generally supported our hypothesis of greater soil compaction and nutrient enrichment for unfenced compared with fenced reaches, as well as for access compared with no-access locations. The exceptions were soil water content and soil test P results that did not support the grazing hypothesis, and soil water content and NH₄-N results that did not support the cattle-access hypothesis.

Kröbel, R., Lemke, R., Campbell, C. A., Zentner, R., McConkey, B., Steppuhn, H., De Jong, R. and Wang, H. 2014. Water use efficiency of spring wheat in the semi-arid Canadian prairies: Effect of legume green manure, type of spring wheat, and cropping frequency. Can. J. Soil Sci. 94: 223-235. In the semi-arid Canadian prairie, water is the main determinant of crop production; thus its efficient use is of major agronomic interest. Previous research in this region has demonstrated that the most meaningful way to measure water use efficiency (WUE) is to use either precipitation use efficiency (PUE) or a modified WUE that accounts for the inefficient use of water in cropping systems that include summer fallow. In this paper, we use these efficiency measures to determine how cropping frequency, inclusion of a legume green manure, and the type of spring wheat [high-yielding Canada Prairie Spring (CPS) vs. Canada Western Red Spring (CWRS)] influence WUE using 25 yr of data (1987-2011) from the “New Rotation” experiment conducted at Swift Current, Saskatchewan. This is a well-fertilized study that uses minimum and no-tillage techniques and snow management to enhance soil water capture. We compare these results to those from a 39-yr “Old Rotation” experiment, also at Swift Current, which uses conventional tillage management. Our results confirmed the positive effect on WUE of cropping intensity, and of CPS wheat compared with CWRS wheat, while demonstrating the negative effect on WUE of a green manure crop in wheat-based rotations in semiarid conditions. Furthermore, we identified a likely advantage of using reduced tillage coupled with water conserving snow management techniques for enhancing the efficiency of water use.

Raut, N., Sitaula, B. K., Bakken, L. R. and Dörsch, P. 2014. Fluxes of CH₄, N₂O, and kinetics of denitrification in disturbed and undisturbed forest soil in India. Can. J. Soil Sci. 94: 237-249. Soil disturbance due to grazing has been severe in Indian forests. This may alter ecosystem functions such as the cycling of nitrogen, and may hence affect the emission of greenhouse gases. We measured fluxes of CH₄ and N₂O with a closed chamber technique throughout one year in a forest of Western Ghats, Karnataka state, southwest India and determined the product stoichiometry of denitrification under standard anoxic incubations in soil samples from disturbed and undisturbed forest. In both areas, there was a net flux of CH₄ from the atmosphere to the soil, and the undisturbed forest soil was a stronger sink for CH₄ than the disturbed (P<0.05). The accumulated CH₄ uptake averaged for all four seasons was 1.5 times higher in undisturbed than disturbed forest. Contrary to our expectation, the N₂O emission was significantly higher for undisturbed than for disturbed forest (P<0.05). The accumulated N₂O emission averaged for all four seasons was 1.6 times higher in undisturbed than disturbed forest. Together our data suggest that increase of N₂O release and decrease in CH₄ sink in soil induced by grazing disturbance can affect the global warming potential (GWP) of forest in this region. The incubation study showed a strong correlation between oxic respiration rate (R) and subsequent denitrification rate (D) and the ratio D/R was 1:3 and 1:6 for soil from undisturbed and disturbed soils, respectively. The N₂O/(N₂ N₂O) product ratio of denitrification tended to be higher in undisturbed than disturbed site, despite lower soil pH.