Boczulak, S. A., Hawkins, B. J., Maynard, D. G. and Roy, R. 2015. Long- and short-term temperature differences affect organic and inorganic nitrogen availability in forest soils. Can. J. Soil Sci. 95: 77-86. Soil microbial activity determines rates of decomposition and is strongly influenced by temperature. Soil microbial communities may be adapted to site characteristics, including temperature, through physiological modification of microbial populations or changes in species composition; however, response to short-term changes in temperature may also occur. We searched for evidence of short- and long-term temperature response of microbial communities involved in soil nitrogen (N) cycling by measuring the relative availability of organic and inorganic N forms in forest soils from a high and a low elevation site, incubated at 10, 16 and 20°C for 16 wk. By week 16, ammonium concentrations were greater in soils incubated at 16 and 20°C than at 10°C, and in soil from the low elevation site, compared with high elevation. Nitrate concentrations increased in soil from the low elevation site incubated at 16 and 20°C, but changed little in other treatments. Assessment of autotrophic nitrification potential showed gross nitrification in soil from the low elevation site was likely from classical chemolithotrophic nitrifiers. Organic N concentration increased over time in the 16 and 20°C incubations of soil from the low elevation site, but only increased in the 20°C treatment for soil from the high elevation site. Long-lasting site effects were indicated by the more active microbial community in soil from low elevation, which could be related to site temperature. Evidence of short-term temperature response of N cycling processes was observed in soils from both elevations.

Bolinder, M. A., Kätterer, T., Poeplau, C., Börjesson, G. and Parent, L. E. 2015. Net primary productivity and below-ground crop residue inputs for root crops: Potato (Solanum tuberosum L.) and sugar beet (Beta vulgaris L.). Can. J. Soil Sci. 95: 87-93. Root crops are significant in agro-ecosystems of temperate climates. However, the amounts of crop residues for these crop types are not well documented and they need to be accounted for in the modeling of soil organic carbon dynamics. Our objective was to review field measurements of root biomass left in the soil as crop residues at harvest for potato and sugar beet. We considered estimates for crop residue inputs as root biomass presented in the literature and some unpublished results. Our analysis showed that compared to, for example, cereals, the contribution of below-ground net primary productivity (NPP) to crop residues is at least two to three times lower for root crops. Indeed, the field measurements indicated that root biomass for topsoils only represents on average 25 to 30 g dry matter (DM) m^-2 yr^-1. Other estimates, albeit variable and region-specific, tended to be higher. We suggest relative plant DM allocation coefficients for agronomic yield (R_P), above-ground biomass (R_S) and root biomass (R_R) components, expressed as a proportion of total NPP. These coefficients, representative for temperate climates (0.739:0.236:0.025 for potato and 0.626:0.357:0.017 for sugar beet), should be useful in the modeling of agro-ecosystems that include root crops.

Baker, S. R., Watmough, S. A. and Eimers, M. C. 2015. Phosphorus forms and response to changes in pH in acid-sensitive soils on the Precambrian Shield. Can. J. Soil Sci. 95: 95-108. Soil acidification may explain declines in total phosphorus (TP) levels that have been observed in surface waters in central Ontario, Canada, but much of the research on phosphorus (P) mobility in pH manipulated soils has been performed at high P concentrations (i.e., >500 µM). This study investigated P fractionation in acidic (pH≤4.6) soils in south-central Ontario and relationships between soil pH and P sorption at relatively low P concentrations to test whether long-term declines in soil pH could have increased soil P sorption. Soils from three forested catchments that vary naturally in soil pH and outlet stream [TP] (0.1-0.4 µM in 2008) had very similar soil P concentrations and distributions (Hedley fractionation). Only hydrochloric-acid extractable P (i.e., apatite) differed amongst catchments and was greatest at the catchment with the highest stream [TP]. The fraction of P present as labile/soluble P did not decline with pH as expected and experiments indicated that P sorption at P concentrations between 4.52 and 452.1 µM was insensitive to manipulated solution pH. Soils were, however, able to sorb >90% of P added in sorption experiments at [P]≤452.1 µM. These results suggest that acidification-induced P sorption in upland soils has not contributed to observed decreases in surface water TP concentrations.

Goetz, J. D. and Price, J. S. 2015. Role of morphological structure and layering of Sphagnum and Tomenthypnum mosses on moss productivity and evaporation rates. Can. J. Soil Sci. 95: 109-124. Morphological structures of peatland mosses control moss water relations and the rate of water loss by drainage and evaporation, thus influencing their physiological functions. While many of these mechanisms are understood for Sphagnum mosses, there is a limited understanding of how these processes operate in Tomenthypnum nitens, a dominant brown moss species in northern rich fens. This study contrasts how different hydrophysical characteristics of Tomenthypnum and Sphagnum species affect capillary water flow that supports evaporation and productivity. Laboratory investigations indicate that volumetric water content (), gross ecosystem productivity, and evaporation decreased with water table depth for both mosses, with Sphagnum capitula retaining 10-20% more water ( range of 0.18-0.32 cm³ cm^-3) than Tomenthypnum (0.07-0.16 cm³ cm^-3). Despite lower and a smaller fraction of pores between 66 and 661 µm to retain water within the Tomenthypnum structure (10%) compared with Sphagnum (27%), both mosses had similar fractions of water conducting pore spaces and were able to maintain capillary rise throughout the experiment. While there was a larger difference in the bulk density and porosity of the Tomenthypnum moss compared with its underlying peat than there was in the Sphagnum profile, a layer of partially decomposed moss of intermediate properties was sufficient to provide a connection between the moss and peat under low water table conditions. In trying to characterize the soil-water pressure (ψ) in near-surface mosses of Tomenthypnum based on measurements of vapour pressure, we found disequilibrium conditions that severely underestimated ψ (i.e., very large negative pressures). It is this disequilibrium that drives evaporation and draws up capillary water to the moss surface for peatland-atmosphere carbon and water transfers.

Whitson, I. R. 2015. Equivalent latitude for prediction of soil development in a complex mapunit. Can. J. Soil Sci. 95: 125-137. Soil pattern in the Hillwash complex mapunit from Saskatchewan is too variable to be resolved spatially with conventional mapping approaches. The equivalent latitude metric allows identification of an index based on gradient and aspect that ranks sites based on differences in direct radiant energy inputs. Effects on soil development with reference to surface horizon color and soil classification were investigated at three study areas in southern Saskatchewan. At the first, sites with equivalent latitude greater than local latitude (north group) had a higher frequency of darker soil colors than sites where equivalent latitude was less than local latitude (south group). Black Chernozemic profiles made up nine of 13 profiles from the north group compared with none in the south group or in local controls. Similar color and classification trends in a north sample group were found at a second study area. Results from a third study area more than 200 km away and in a drier ecoregion found similar differences albeit a different set of subgroups between north and south group soils at that location. The equivalent latitude metric could be used in a GIS context to better resolve soil characteristics within this complex mapunit, but only after additional work to include a climate parameter such as potential transpiration into the model.

Miller, J. J., Curtis, T., Chanasyk, D. S. and Reedyk, S. 2015. Influence of mowing and narrow grass buffer widths on reductions in sediment, nutrients, and bacteria in surface runoff. Can. J. Soil Sci. 95: 139-151. Little research has been conducted on the effect of mowing and buffer width on the effectiveness of short-width (< 10 m) native grass buffers to filter sediment, nutrients, and bacteria. A 2-yr (2011-2012) field study was conducted on native rangeland in southern Alberta. The treatments of mowing and buffer width (1.5, 3, 6 m) were evaluated using a randomized complete block design with four replicates. The buffer plots were pre-wet with distilled water. A spiked solution was then applied to each plot using a run-on distribution device and the runoff collected every 10 min for 30 min once the runoff started discharging from the plot. The volume of runoff, and percent reduction in concentration and mass of sediment [total dissolved solids (TSS)], phosphorus [dissolved reactive P (DRP), total P], nitrogen (total N), and bacteria (Escherichia coli, total coliforms) in runoff were determined. The findings did not support our hypothesis that percent reductions in concentrations and mass for sediment, nutrients, and bacteria were greater for mowed than unmowed buffers. In contrast, the findings supported our hypothesis that increasing buffer width would significantly (P≤0.05) decrease mass (but not concentration) of sediment, nutrients, and bacteria in runoff. The significant mass reduction was attributed to a reduced runoff ratio caused by longer residence time and greater infiltration in the wider buffers. Mass reductions for the three buffer widths ranged from 29 to 92% for TSS, 22 to 93% for DRP, 38 to 93% for total P, 23 to 92% for total N, and between 61 and 94% for E. coli and total coliforms. These findings suggest that buffer width but not mowing may reduce runoff quantity and improve runoff quality over the short term.

Olatuyi, S. O. and Leskiw, L. A. 2015. Evaluation of soil reclamation techniques at the Key Lake uranium mine. Can. J. Soil Sci. 95: 153-176. Adequate soil nutrients and water supply are critical to vegetation establishment and creation of sustainable ecosystems in post-disturbed mining sites. This study investigated effects of various amendments and capping techniques on soil quality and moisture distribution on a reclaimed waste rock pile at the Key Lake uranium mine in northern Saskatchewan, Canada. Soil profiles were reconstructed in 2010 using locally available sandy glacial materials to create soil covers of 1 m thickness. The reclamation treatments consisted of a Control plot, commercial peat (Peat), a local lake sediment (Sediment), underlying flax straw (Straw), mulched forest floor and Ae (LFH), fertilizer (NPK), manure pellets (Pellets), and a demonstration plot (Demo) comprised of Sediment, LFH and Pellets. Soil amendments were applied by various techniques as broadcast, surface incorporation, below the surface or surface mounding. Annual plot monitoring was conducted from 2011 to 2013 and soil samples were analyzed for pH, electrical conductivity (EC), sodium adsorption ratio (SAR), available nutrients, cation exchange capacity (CEC), total organic carbon (TOC), total nitrogen (TN), and regulated metals. Volumetric moisture contents were measured periodically to examine soil moisture response to growing-season precipitation. In 2013, the topsoil of the Control plot was slightly acidic (pH of 6.3) while the Sediment and Demo plots had the lowest pH of 4.0. The EC and SAR values were below 1.0 in all treatment plots. The highest levels of available N, TN, TOC and CEC were in the Sediment and Demo plots, followed by the Peat. The concentration of arsenic exceeded the regulatory limit by 3.4- and 2.6-fold in the Sediment and Demo topsoil, respectively, while concentrations of other metals were below the limits in all treatment plots. The Sediment and Demo treatments were most effective in retaining water in the topsoil, while application of soil amendment by mounding enhanced infiltration and water transmission in the profile. In terms of soil fertility and moisture storage, the combination of organic amendments in multi-layers plus surface mounding, as in the Demo plot, is the most promising capping technique for restoring soil health, vegetative cover and ecosystem functions on the waste rock pile.

Smith, E. G., Janzen, H. H. and Larney, F. J. 2015. Long-term cropping system impact on quality and productivity of a Dark Brown Chernozem in southern Alberta. Can. J. Soil Sci. 95: 177-186. Long-term cropping system studies offer insights into soil management effects on agricultural sustainability. In 1995, a 6-yr bioassay study was superimposed on a long-term crop rotation study established in 1951 at Lethbridge, Alberta, to determine the impact of past cropping systems on soil quality, crop productivity, grain quality, and the relationship of yield productivity to soil quality. All plots from 13 long-term crop rotations were seeded to wheat (Triticum aestivum L.) in a strip plot design [control, nitrogen (N) fertilizer]. Prior to seeding, soils were sampled to determine soil chemical properties. Total wheat production for the last 4 yr of the study was used as the measure of productivity. The 1995 soil analysis indicated crop rotations with less frequent fallow and with N input had higher soil quality, as indicated by soil organic carbon (SOC) and light fraction carbon (LF-C) and N (LF-N). SOC had a positive relationship to total wheat yield, but was largely masked by the application of N in this bioassay study. Frequent fallow in the previous crop rotation lowered productivity. The concentration of LF-C had a negative relationship, whereas LF-N had a positive relationship to total wheat yield, with and without N fertilization in this bioassay study. Grain N concentration was higher with applied N and when the long-term rotation included the addition of N by fertilizer, livestock manure, annual legume green manure or legume hay. This study determined that long-term imposition of management practices have lasting effects on soil quality and crop productivity.

Ouimet, R., Pion, A.-P. and Hébert, M. 2015. Long-term response of forest plantation productivity and soils to a single application of municipal biosolids. Can. J. Soil Sci. 95: 187-199. After 16 to 19 yr, we revisited four experimental trials set up in the early 1990s to evaluate the long-term impact of municipal biosolids applied in forest plantations. Tree growth and the soil were sampled to determine the effects of a single application of biosolids applied at (liquid equivalent) rates of 0, 130, 200, and 400 m³ ha^-1. Tree radial growth responded markedly to biosolids in the young plantations, increasing from 18 % for Pinus resinosa to 62 % for Picea glauca, and up to 700 % for Quercus sp. Increases in phosphorus (P) concentrations in the tree foliage in response to biosolids could still be detected in the conifer trials. In the top 0-5 cm soil layer, organic carbon (C), total nitrogen (N), P, and copper (Cu) concentrations and pools increased, while soil compaction and bulk density decreased. In the deepest soil layer sampled (20-40 cm depth), the total N and calcium (Ca) pools were reduced by the biosolids treatments, while the pool of exchangeable acidity increased. Our observations indicate that a single application of liquid biosolids up to 400 m³ ha^-1 (30 t ha^-1 DM) in young forest plantations is a sustainable practice without undue risk to such podzolic soils.