Ni, X., Yang, W., Li, H., Xu, L., He, J., Tan, B. and Wu, F. 2014. The responses of early foliar litter humification to reduced snow cover during winter in an alpine forest. Can. J. Soil Sci. 94: 453-461. Snow cover can be reduced by ongoing winter warming in alpine biomes, affecting foliar litter humification, but few reports are available. To quantitatively clarify how early foliar litter humification responds to reduced snow cover in winter, a field litterbag experiment was conducted in an alpine forest in southwestern China. Mass losses, ΔlogK, E4/E6, degrees of humification and humification rates of six typical local foliar litters were investigated at the snow formation, snow cover and snow melt stage under snowpack levels differing in depth (deep snowpack, medium snowpack, thin snowpack, no snowpack) from November 2012 to April 2013. The results indicated that 14-15% of willow (Salix paraplesia), 8-9% of fir (Abies faxoniana), 6-7% of birch (Betula albo-sinensis), 5-8% of cypress (Sabina saltuaria), larch (Larix mastersiana) and azalea (Rhododendron lapponicum) foliar litter was humified, which was about 50% of what decomposed during the first winter. Moreover, the early humification of foliar litter (except for fir and birch) responded positively to the reduced snow cover, but mass loss exhibited negative responses. Such results suggest that reduced snow cover in winter would increase soil carbon or other material sequestration in the scenario of climate change.

Boiteau, G., Goyer, C., Rees, H. W. and Zebarth, B. J. 2014. Differentiation of potato ecosystems on the basis of relationships among physical, chemical and biological soil parameters. Can. J. Soil Sci. 94: 463-476. A study of soil physical, chemical and biological properties of five cultivated agro-ecosystems (two conventional potato, two organic potato and one cereal production systems) and two uncultivated agro-ecosystems (pasture and 20-yr abandoned potato field) was carried out at 21 field sites over 3 yr in New Brunswick, Canada. Twenty-four of the initial 42 variables chosen for their significant response to differences among farming systems were used in a principal component analysis to understand their relationships with the agro-ecosystems studied. The chemical, physical and biological soil properties considered contributed to a single dominant factor (PCI) of agricultural soil health representing soil organic matter dynamics. Conventional, uncertified organic and certified organic potato agro-ecosystems were lowest, intermediate and highest, respectively, on the PCI gradient. Conventional potato systems were characterized by high erosion, high soil bulk density, high soil test sulphur and phosphorus and high bacterial counts. Certified organic potato systems formed a separate group with the reference ecosystems (i.e., pasture and abandoned potato field under long-term rejuvenation). This group was characterized by high soil organic carbon, high soil aggregate stability, high soil water-holding capacity and high meso- and macro-fauna counts. The uncertified organic potato production system and organic barley system were characterized by average values, intermediate between conventional and certified organic potato systems. Results confirmed the strong negative impact of intensive cycles of conventional potato production on soil health. The clear separation observed between conventional, uncertified organic and organic potato ecosystems indicates that the positive impact of rotations and other management practices must be sustained over long periods for full rehabilitation of soils previously under intensive potato production. However, results also revealed that fields under organic certified potato production were retaining the properties of undisturbed reference sites such as pastures and abandoned potato fields under long-term rejuvenation.

Campeau, A. B., Lafleur, P. M. and Humphreys, E. R. 2014. Landscape-scale variability in soil organic carbon storage in the central Canadian Arctic. Can. J. Soil Sci. 94: 477-488. Arctic soils constitute a vast, but poorly quantified, pool of soil organic carbon (SOC). The uncertainty associated with pan-Arctic SOC storage estimates - a result of limited SOC and land cover data - needs to be reduced if we are to better predict the impact of future changes to Arctic carbon stocks resulting from climate warming. In this study landscape-scale variability in SOC at a Southern Arctic Ecozone site in the central Canadian Arctic was investigated with the ultimate goal of up-scaling SOC estimates with a land cover classification system. Total SOC was estimated to depths of 30 cm and 50 cm for 76 soil pits, together representing eight different vegetation communities in seven different broad landscape units. Soil organic carbon to 50 cm was lowest for the xerophytic herb community in the esker complex landscape unit (7.2±2.2 SD kg m^-2) and highest in the birch hummock terrain in the lowland tundra landscape unit (36.4±2.8 kg m^-2), followed by wet sedge and dry sedge communities in the wetland complex (29.8±9.9 and 22.0±2.0 kg m^-2, respectively). The up-scaled estimates of mean SOC for the study area (excluding water) were 15.8 kg m^-2 (to 50 cm) and 11.6 kg m^-2 (to 30 cm). On a landscape scale, soil moisture content was found to have an important influence on SOC variability. Overall, this study highlights the importance of SOC variability at fine scales and its impact on up-scaling SOC in Arctic landscapes.

Dobrovolskaya, Y. V., Chau, H. W. and Si, B. C. 2014. Improving water storage of reclamation soil covers by fractionation of coarse-textured soil. Can. J. Soil Sci. 94: 489-501. Mining operations cause considerable land disturbance as well as the accumulation of large amounts of waste rock. Capping waste rock with a soil cover has proven to be a reliable, long-term reclamation technique. This study examines the question of whether it is possible to attain a considerable increase in water storage capacity (WSC) by separating coarse-textured soil into particle size fractions and layering them into a soil cover. Additionally, this study investigated whether preferential flow can be mitigated by increasing the number of layers and extending the interlayer transitions in fine-over-coarse-textured soil systems. Intermittent and constant infiltration experiments were conducted on homogeneous covers composed of natural sand, two-layered covers with abrupt and gradual interlayer transitions as well as on a four-layered cover under initially air-dry and field capacity (FC) conditions. Water storage capacities were determined from a sampling of soil covers′ water content at FC. Infiltration experiments showed that all tested covers under all initial and boundary conditions had limited susceptibility to preferential flow. Increasing the number of layers and extending the interlayer transitions had a stabilizing effect on the wetting front. Water storage capacities and residence time increased with the increased number of layers. Overall, it has been shown that it is possible to improve the WSC of coarse-textured soil by fractionation and layering of it into a relatively fine-over-coarse soil system.

She, D., Xuemei, G., Jingru, S., Timm, L. C. and Hu, W. 2014. Soil organic carbon estimation with topographic properties in artificial grassland using a state-space modeling approach. Can. J. Soil Sci. 94: 503-514. Knowledge of the distribution of soil organic carbon (SOC) in artificial grasslands in semiarid areas is helpful in optimizing management for soil fertility recovery and carbon sequestration. Accurate estimation of SOC with easy-to-obtain topographic properties can save considerable labor and cost as well as protect the grassland from being disturbed by intensive soil sampling. In our study, a total of 113 sampling points were setup within a patch of artificial grassland in a small catchment located in the north Loess Plateau of China. State-space modeling and traditional linear regression were used to estimate the localized variation of SOC in the 0- to 20-cm surface soil layer using five selected topographic properties (elevation, slope, aspect, plan curvature, and surface soil roughness). Soil surface roughness and plan curvature were identified as the most effective variables for SOC estimation in state-space models. Soil surface roughness and plan curvature explained 92.5% and 84.5% of the total variation of SOC, respectively. The best state-space model was the one using both plan curvature and surface soil roughness, explaining 94.5% of the total variation of SOC, whereas the best linear regression model could only explain 15.9% of the total variation of SOC. The results indicate that all the derived state-space models performed better than the equivalent linear regression models. Our study provides an insight into the possibility of accurate estimation of SOC only using one or two easy-to-obtain topographic properties with state-space modeling approach.

Larney, F. J., Olson, A. F., Miller, J. J. and Tovell, B. C. 2014. Soluble salts, copper, zinc, and solids constituents in surface runoff from cattle manure compost windrows. Can. J. Soil Sci. 94: 515-527. Composting has become widely adopted by the beef cattle feedlot industry in southern Alberta. Compost windrows subjected to heavy rainfall can lead to runoff whose properties may vary with compost maturity. A rainfall simulator generated runoff on days 18, 26, 40, 54, 81, 109 and 224 of manure composting. Runoff was collected in timed 5-L increments to 30 L, creating the variable “time during runoff event” (TDRE). Calcium, K and S showed significant maturity×TDRE interactions, especially earlier in the composting process, e.g., on day 18, Ca values increased from 34 mg L^-1 for the initial 0- to 5-L runoff increment to 43 mg L^-1 for the final 25- to 30-L increment. Most significant changes in runoff concentrations occurred between days 26 and 40, e.g., Cu levels fell by 67% and Zn levels by 78%. Even though compost Cu and Zn concentrations were higher during the latter stages of composting, their transport potential in runoff was curtailed due to binding with stable organic matter (OM). The C:N ratio of runoff solids decreased from 10.5 on day 18 to only 4.9 on day 224, suggesting the transport of very stable OM after compost curing. The study showed that runoff quality was influenced by compost maturity, which has implications for the timing of rainfall events relative to the maturity spectrum and the potential risk to surface water quality if runoff is not contained.

Carson, A. W., Rutherford, P. M. and Burton, P. J. 2014. Desulphurized tailings serve as a useful soil supplement for mine reclamation. Can. J. Soil Sci. 94: 529-541. Soil is often in limited supply for use in mine reclamation activities; it may be necessary to build soils (Anthroposols) using locally available substrates. Eight test plots were established at Huckleberry Mine, Houston, BC, to investigate soil properties and evaluate the performance and metal uptake of plants established on stockpiled soils that were or were not supplemented with non-acid generating sand (NAGS) and fertilizer. Concentrations of total and extractable trace elements (including base metals) were lower in NAGS-supplemented soils than in non-supplemented soils. Supplementing soils with NAGS reduced cation exchange capacity and exchangeable base cations, yet plant performance was not significantly lower than that observed in non-supplemented soils. When combined with a fertilizer application, plant performance on NAGS-supplemented soils significantly increased. For heavy metals analyzed in plant tissues, only molybdenum (Mo) concentrations exceeded the National Research Council's (NRC) recommended maxima for beef cattle. The copper (Cu):Mo ratio for all treatments was above a suggested adverse-health threshold value for ruminant feeds (with lesser values leading to adverse health effects). The use of NAGS (combined with fertilizer) as a supplement to stockpiled mine soil can increase the quantity of growth media for reclamation and is not expected to have any adverse effects on plant growth or the metal content in above-ground vegetation.

Irshad, M., Khan, R. U., Jadoon, S., Hassan, A. and Egrinya Eneji, A. 2014. Effect of phosphate rock on the solubility of heavy metals in soils saturated with industrial wastewater. Can. J. Soil Sci. 94: 543-549. An in situ technology for immobilizing metals in polluted soils could be a more effective approach to managing their toxicity to the environment, especially plants. The aim of this study was to investigate the effect of milled phosphate rock (PR) on the sorption of Ni, Cd and Cu ions in differently textured soils polluted with industrial wastewater. For this purpose, soils were mixed with two particle size fractions (0.2 mm and 1 mm) of PR material. Each material was applied at the rate of 0, 2.5 and 5%. Results showed that PR amendment reduced the solubilization of heavy metals in the order sandy clay loam>sandy loam>loamy sand. Metal concentrations in soils saturated with industrial wastewater were in the order Ni>Cd>Cu. Solubilization of metal ions in soils also reduced with the increase in the amount of rock phosphate added. This occurred more with the finer PR fraction. The concentrations of heavy metals in soils varied directly with their respective concentrations in the wastewater. Saturating soil with wastewater for a longer time increased the solubility of heavy metals. The adsorptive capacity of heavy metals from the respective aqueous solution also increased with increasing shaking time. The finer PR particles better enhanced the sorption capacity of heavy metals. This study indicated that the retention of heavy metals by PR mineral in contaminated soils may reduce the contamination risk in surface and subsurface waters.

Dil, M., Oelbermann, M. and Xue, W. 2014. An evaluation of biochar pre-conditioned with urea ammonium nitrate on maize (Zea mays L.) production and soil biochemical characteristics. Can. J. Soil Sci. 94: 551-562. Biochar can enhance soil fertility, plant nutrient uptake and crop production. Using a potted study, we quantified the effects of adding biochar at 1 t ha^-1 (Char), biochar pre-conditioned with urea ammonium nitrate [UAN (Char )], or UAN only to a control (Contr) with no amendments on maize (Zea mays L.) biomass production, tissue carbon (C) and nitrogen (N) concentrations, N uptake (NU), N utilization efficiency (NUtE), and soil chemistry and biology in coarse-, medium- and fine-textured soils over 6 wk. Soil pH decreased (P<0.05) in Char and UAN treatments for all soil textures. Soil organic carbon (SOC) increased (P<0.05) in the coarse and medium textured soil in Char and Char treatments. Soil ammonium and soil nitrate were different (P<0.05) among treatments; increasing or decreasing depending upon soil texture. Soil microbial biomass C was lowest (P<0.05) in the UAN treatment for all soil textures. Soil potential microbial activity was significantly greater in the coarse-textured soil in only the Char and Char treatments. Maize biomass, tissue N concentration, and NU increased (P<0.05) in soils amended with Char or UAN only. NUtE was lower (P<0.05) in Char and UAN treatments in the coarse- and medium-textured soils, but this was reversed for the fine-textured soil.

Roy, A. K., Wagner-Riddle, C., Deen, B., Lauzon, J. and Bruulsema, T. 2014. Nitrogen application rate, timing and history effects on nitrous oxide emissions from corn (Zea mays L.). Can. J. Soil Sci. 94: 563-573. Nitrous oxide (N₂O) emissions resulting from application of nitrogen (N) fertilizer contribute to the greenhouse gas footprint of corn production. In eastern Canada, corn is a major crop with most N fertilizer applied pre- or at planting. This timing of application results in a lack of synchrony of soil N supply and crop N demand. Matching the amount and timing of application to crop uptake has been suggested as a mitigation measure to reduce N losses, and is an integral part of the 4R Nutrient Stewardship program. This study examined the effect of timing, rate and history of urea-ammonium nitrate application on N₂O emissions in corn in 2011 and 2012 at Elora, ON, Canada. Treatments were three N rates (30, 145 and 218 kg N ha^-1); two timings (N injected in mid-row at planting and at the 8th leaf stage, V8); two histories (short-term: applying N rate treatments on plots that had received 145 kg N ha^-1 in the previous year, and long-term: applying the same N rate to a given plot over the duration of the trial). N₂O emissions were measured using static chambers. History of N application did not have an effect on N₂O emissions or grain yield. In both years, cumulative N₂O emissions during the growing season and corn yields increased significantly with increasing N application rates. In 2011, cumulative N₂O emissions were significantly lower when N was applied as side-dress at V8 (0.88 kg N ha^-1) compared with planting (2.12 kg N ha^-1), with no significant impact on corn grain yield (average 9.1 Mg ha^-1). In contrast, in 2012, limited rainfall reduced both N₂O emissions and corn grain yield, and neither N₂O emission (average 0.17 kg N ha^-1) nor grain yield (average 6.7 Mg ha^-1) was affected by timing of N application. Applying N as side-dress at V8 instead of at planting and using the recommended N rate were shown to be effective N₂O emission mitigation practices without affecting corn yield during a typical wet spring in Ontario.