ALBERT

Description: Zhao, Y., Wang, E., Cruse, R. M. and Chen, X. 2012. Characterization of seasonal freeze-thaw and potential impacts on soil erosion in northeast China. Can. J. Soil Sci. 92: 567–571. Freeze-thaw cycles are regarded as a critical factor inducing and accelerating gully erosion in the Black soil region (Chernozem) of northeast China. The major objective of this study was to identify the effect of seasonal freeze-thaw processes on soil structure relevant to soil erosion. Perched water due to an argillic horizon brings about higher water potential in the top soil, which lowers the soil shear strength and increases the risk of soil erosion by rainfall and surface flow; and the argillic horizon, with a higher clay content, is more vulnerable to freeze-thaw processes, which break or weaken the structure of the argillic horizon, increasing its vulnerability to gully erosion.

Description: There is a need to provide quantitative relationships that will allow agronomists to estimate accurately the nitrogen-supplying power of soils while taking into account both temperature and soil moisture variations. The procedure for estimating net nitrogen mineralization proposed by Stanford and co-workers was used to determine Arrhenius relationships between the rate constants (k) and absolute temperature (°K) for 33 virgin and cultivated Western Canadian prairie surface (0–15 cm) soils. There was no significant difference in Arrhenius relationship between soils within each soil zone; thus, a single average Arrhenius equation was calculated per soil zone. Average Q10 for the Brown chernozemic soils was 2.75, for the Dark Brown, thin Black and thick Black chernozems, 2.18, and for the Gray luvisols, 2.0. These Q10 values are as high or higher than those reported in other parts of the world and may be related to the degree of degradation of the soil organic matter in these various soils. Culture had no marked effect on Q10 but sandy soils had higher Q10 than loams and clays. An equation for estimating net nitrogen mineralization for the Wood Mountain loam (a Brown chernozem) was tested using data from a previous study. The results were quite satisfactory, especially when the test data were derived under laboratory conditions where moisture was well controlled. The temperature functions presented herein can be used together with moisture functions and potentially mineralizable nitrogen results published earlier to make first estimates of net nitrogen mineralized during the growing season in the soils tested. Key words: Q10, Arrhenius relationship, potentially mineralizable nitrogen

Description: Seedbed temperature and moisture conditions affect crop emergence rate and stand establishment. A 4 × 4 factorial experiment arranged in a split plot design with four replications was conducted for 3 yr at four sites to measure corn emergence rate and stand establishment while monitoring seedbed temperature and soil water content in situ. Four planting dates, beginning as early as the soil could be worked and every 10 d thereafter, were the main plots and four corn (Zea mays L.) hybrids the subplots. Volumetric soil water content in the top 0.10 m was measured a minimum of two times per week using time domain reflectometry (TDR) and estimated daily using a budget model. Measured and estimated soil water contents were similar (R2 = 0.73) and daily estimated values were used in the analysis. Stand establishment for most planting date-site-years ranged from 80 to 99%. Less than 15% of planting date-site-years had stands below 80%, and they were characterized by soil temperatures at or below 12.5°C combined with high soil water contents (〉90% available water). Rate of emergence was not associated with stand establishment (P 〉 0.10) and could not be predicted from soil temperatures below 12.5°C. Results suggest that reduction in stand establishment under conditions of low (12.5°C) soil temperature and high (〉field capacity) soil water content may be a factor in corn yield reductions associated with reduced or no tillage. Key words: Time domain reflectometry, soil water content, soil temperature, maize

Description: The use of commercially available porous cup soil water samplers for soil solution extraction was evaluated. Ortho-P, (NO3 + NO2)-N and potassium (K) were adsorbed by the porous cup during extraction of soil water samples, but the retention of (NO3 + NO2)-N was minimal. The screening of NO3− by the cup was not obvious. The retention of ortho-P and K was a function of solution concentration and the time of contact between soil solution and the cup. A rest period between extractions, during which samplers remained in contact with solution at zero tension, appeared to enhance phosphorus sorption capacity of the ceramic cup. Furthermore, phosphorus sorption was reversible in nature. The porous cup subjected to high solution concentration initially, released phosphorus when flushed with soilsolution of low concentration. It is recommended that several consecutive soil water extractions be carried out at high (0.6 bar) tension, using high flow rate porous cups. The sample collected in the last extraction should be used to determine true soil water quality.

Description: The distribution of lipid S (sulpholipids) in 27 soils was examined in relation to factors which influence its abundance in different soil environments. Lipid S was found in all soils examined, but at levels varying from 1.6 to 291 ppm S. Lipid S content was higher in organic horizons than in mineral horizons, and poorly drained soils had higher lipid S than freely drained soils. Highest levels were observed in poorly drained organic soils. Lipid S accounted for a small proportion of total S (0.5–3.5%) and of total lipid (0.03–1.7%). Lipid S levels were on average three times higher than lipid P. Lipid S was significantly correlated with total S, HI-reducible S and organic C. In a regression analysis, 89% of the variation in soil content of lipid S was accounted for by total lipid and total S contents. The distribution of total lipids confirmed previous reports that higher levels were associated with soils having restricted biological activity.

Description: Content of mercury in organic soil horizons was monitored to ascertain seasonal changes in background levels. L, F, and H horizons were relatively enriched in mercury in early spring. Levels then diminished and reached seasonal low values in August. Content of mercury then increased twofold during September after which levels declined to summer values. F horizons had the highest content of mercury and H horizons had the lowest. Key words: Mercury cycling, mercury dynamics, heavy metal

Description: The sulfur status of rapeseed (Brassica napus and Brassica campestris) plants grown in field studies was assessed using a variety of plant indices; percent sulfur, percent hydriodic acid reducible sulfur (HI-S in plant dry matter), HI-S:total S ratio, and total N:total S ratios. Of these, HI-S:total S determined at the rosette growth stage was the most accurate and consistent index of seed yield. A growth chamber study indicated that the HI-S:total S ratio would not be affected by nitrogen fertilizer application at normal field rates. Key words: Sulfur, deficiency, rapeseed (Brassica spp.), plant analysis

Description: 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.

Description: 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.

Description: The objective of this study was to compare the effects of various pretreatments on the X-ray identification and quantification of clay-sized minerals from some podzolic B horizons. After soil samples were treated with H2O2 to remove organic matter, clay fractions were dispersed, separated, and freeze-dried. A portion of each clay sample was subjected to the following pretreatments: ultrasonic bath, extraction by citrate-dithionite, extraction by 0.5 N NaOH, and extraction by Tiron. Oriented slides were used for identification and quantification of clay minerals after each pretreatment. The X-ray patterns for ultrasonically dispersed samples were used as a basis for evaluating the effectiveness of the three chemical pretreatments. Tiron pretreatment was found to be the most suitable method for removal of amorphous material from clay separates of podzolic B horizons. The traditional citrate-dithionite method was not effective in removing amorphous Si from clays. The 0.5 N NaOH method is not recommended because it resulted in significant destruction of phyllosilicates and it was not effective in removing amorphous Fe.

Description: A study designed to assess gaseous losses of N as N2O and N2 from soils of conventional till fields seeded to wheat in the Chernozemic soil region of Saskatchewan, together with limited supporting laboratory investigations, has confirmed that for the May-November period losses were in the vicinity of 3 kg N∙ha−1 or less. In contrast, total losses from a summer-fallowed field were approximately 300% higher. Comparisons at one site were made of N losses from a conventionally tilled and zero-tilled Dark Brown Chernozemic soil seeded to wheat; the total losses of N were twice as high for the zero till as the conventional till treatments. The N2O fluxes were shown to be the result of both reductive (denitrification) and oxidative (nitrification) processes and generally, under the conditions of these field experiments, both occurred simultaneously. This experiment also confirmed that C2H2 inhibited nitrification in a manner very similar to N-serve, a well-known nitrification inhibitor.

Description: 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.

Description: Li, S., Lobb, D. A., McConkey, B. G., MacMillan, R. A., Moulin, A. and Fraser, W. R. 2011. Extracting topographic characteristics of landforms typical of Canadian agricultural landscapes for agri-environmental modeling. I. Methodology. Can. J. Soil Sci. 91: 251–266. Soil and topographic information are key inputs for many agri-environmental models and there are linkages between soil and topography at the field scale. A major source of soil data is soil databases established based on field soil survey. Although both soil and topographic information are recorded in field soil surveys, the nominal nature of the topographic data has limited their use in agri-environmental models. In this study, we developed a methodology to extract various topographic derivatives and to classify the landscape into landform elements with distinctive topographic characteristics based on detailed analyses of fine resolution digital elevation models. Data obtained from these analyses were used to calculate a representative two-dimensional hillslope of five segments, each with a defined length and slope gradient. A set of modal hillslopes was developed to describe topographic variability. Additional topographic parameters, ratios and indices were calculated to reflect different aspects of topographic characteristics and also to build connections between different agri-environmental models. In particular, a topographic complexity index was developed as a quantitative measure of the degrees of divergence and convergence. This paper describes the methodology using one site as an example. Application of this methodology to other landforms in agricultural land of Canada is reported in a companion paper.

Description: Tarnocai, C. and Bockheim, J. G. 2011. Cryosolic soils of Canada: Genesis, distribution, and classification. Can. J. Soil. Sci. 91: 749–762. Cryosols are permafrost-affected soils whose genesis is dominated by cryogenic processes, resulting in unique macromorphologies, micromorphologies, thermal characteristics, and physical and chemical properties. In addition, these soils are carbon sinks, storing high amounts of organic carbon collected for thousands of years. In the Canadian soil classification, the Cryosolic Order includes mineral and organic soils that have both cryogenic properties and permafrost within 1 or 2 m of the soil surface. This soil order is divided into Turbic, Static and Organic great groups on the basis of the soil materials (mineral or organic), cryogenic properties and depth to permafrost. The great groups are subdivided into subgroups on the basis of soil development and the resulting diagnostic soil horizons. Cryosols are commonly associated with the presence of ground ice in the subsoil. This causes serious problems when areas containing these soils are used for agriculture and construction projects (such as roads, town sites and airstrips). Therefore, where Cryosols have high ice content, it is especially important either to avoid these activities or to use farming and construction methods that maintain the negative thermal balance.

Description: 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 [Formula: see text]-N and [Formula: see text]-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 [Formula: see text] and increasing [Formula: see text] concentration, in combination with the fact that emissions continued even when soil [Formula: see text] 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.

Description: Fox, C. A. and Tarnocai, C. 2011. Organic soils of Canada: Part 2. Upland Organic soils. Can. J. Soil Sci. 91: 823–842. Soils from upland moderately well-drained environments with thick accumulations (〉10 cm over lithic contact; 〉40 cm over mineral soil) of folic materials (forest materials, branches, roots, and other non-wetland materials) are classified within the Folisol great group in the Organic Order since the 1987 revision of the Canadian System of Soil Classification. The Folisol great group correlates to Folist in Keys to Soil Taxonomy and Folic Histosol in World Reference Base for Soil Resources (FAO). Two subgroups – Hemic and Humic Folisol – account for most Folisols addressing the state of decomposition of folic materials. The Lignic and Histic Folisol subgroups identify specific kinds of folic accumulations. Folisolic soils can occur throughout Canada, in forest, heath, and alpine ecosytems with cool, moist, humid environments, but are most prominent within the Pacific Maritime Ecozone; areal extent in Canada is ∼12 505 km2. The main genetic process is the accumulation and decomposition of the folic materials that lead to distinct F and H horizons. Recommendations for research needs are presented to address outstanding taxonomic questions for: 1. Classification of Folisols as a separate soil order; and 2. Taxonomic protocols for lowercase suffixes for the L, F and H horizons and the need for enhanced humus form classifications. Some of the historical proposals to address these issues are discussed. Folisols should be considered extremely sensitive environmentally because of their markedly different genetic development being dependent on thick accumulations of folic materials, their limited and unique distribution in Canada, and their importance for forest sustainability.

Description: The effects of surface mining for coal on soil respiration (CO2), microbial biomass C, ATP levels, bacterial and actinomycete numbers, bacterial taxa, hyphal lengths, fungal taxa, N2 fixation and decomposition potential were determined for a short-grass prairie site in southern Alberta, Canada. Soil respiration, microbial biomass C, ATP, actinomycete numbers, hyphal lengths and N2-fixing potential were significantly lower in the mined soil particularly when compared to the undisturbed topsoil. Bacterial numbers were, however, greater in the mined soil than in the unmined soil. The bacteria isolated from the undisturbed soil were dominated by Bacillus spp., coryneforms and non-pigmented Gram-negative rods, while those from the disturbed soil belonged mainly to the coryneform group. Mining also caused the fungal community to shift from one dominated by Chrysosporium-Pseudogymnoascus and sterile dark organisms to one dominated by Alternaria spp., Cladosporium spp., sterile dark forms and yeasts. Decomposition of filter paper, 24 mo after their placement in the field, was significantly faster on the disturbed site than on the undisturbed site. Key words: Surface mining, microbiology, prairie soil

Description: Kulasekera, P. B. and Parkin, G. W. 2011. Influence of the shape of inter-horizon boundary and size of soil tongues on preferential flow under shallow groundwater conditions: A simulation study. Can. J. Soil Sci. 91: 211–221. Detailed studies of the impact of soil tongues at soil horizon interfaces are very important in understanding preferential flow processes through layered soils and in improving the accuracy of models predicting water and solute transport through the vadose zone. The implication of having soil tongues of different shapes and sizes created at the soil horizon interface on solute transport through a layered soil horizon was studied by simulating water and solute transport using the VS2DI model. This 2-D simulation study reconfirmed that soil tongues facilitate preferential flow, and the level of activeness of tongues may depend on the number of soil tongues, their spacing and distribution. Also, the size of the soil tongues (length and diameter at the interface between the soil horizons) and their shape influence the rate of preferential flow. Increasing tongue length consistently resulted in an increase in solute velocity across the entire soil profile regardless of the tongue shape; for example, a soil tongue of 0.25 m length increased solute velocity by about 1.5 times over a soil profile without tongues, but this increase might be different for soil types and groundwater conditions other than those considered in this study. Narrowing of tongues increased solute velocity, whereas increasing the number of tongues in a wider soil profile decreased the solute-front's velocity. As tongue length increased, the area containing solutes at prescribed elapsed times decreased. An implication of this study is that soil horizon tongue shape and spacing reduce pollutant residence times, hence inter-horizon boundary morphology should be considered when modelling transport through the vadose zone. As well, since the solute velocity behaviours of a triangular- and a wider rectangular-shaped tongue were nearly identical, simply measuring solute velocity in the field will reveal little information on the shape of a soil tongue.

Description: The morphological expression of podzolization in four Humo-Ferric Podzols increased in a northerly direction over a distance of approximately 74 km from the north shore of Lake Huron. The transect coincided with changes in both geology and vegetation. All the soils were developed in coarse-textured acid tills whose composition was not significantly different to explain the observed variations in soil morphology. Using quartz as an internal standard, the order of mobility from surface horizons was found to be Mg 〉 Fe = Ca 〉 Na = Al 〉 K 〉 Ti. Pyroxenes, amphiboles, chlorite and albite were the most easily weathered minerals. Protocatechuic, p-coumaric, gentisic and gallic acids were found to be the major phenolic acids in water extracts of soil surface horizons. The content of both phenolic acids and carbohydrates in surface horizons increased as the morphological expression of podzolization increased.

Description: Giweta, M., Dyck, M. F., Malhi, S. S., Puurveen, D. and Robertson, J. A. 2014. Long-term S-fertilization increases carbon sequestration in a sulfur-deficient soil. Can. J. Soil Sci. 94: 295–301. We analyzed the change in total soil organic carbon (SOC) in a long-term fertilization experiment (1980–2008) in a wheat–oat–barley–hay–hay rotation system at the University of Alberta Breton Classical plots. Soil samples were taken in 1980, 1990, 1998, 2003 and 2008 from plots that were fertilized with NPKS and NPK. The objective was to compare the relative effect of S fertilization on the SOC stocks in a S-deficient soil. Long-term S fertilization resulted in an increasing trend in soil organic carbon concentrations over 28 yr when N, P and K supply were adequate. The change in SOC with time was significantly different (P

Description: Two separate field experiments were conducted on several crops to determine the effect of selenium (Se) applied to soils with pH levels between 5.7 and 6.6. Tissue Se levels after a single application of Se and lime, were monitored for up to six cropping years or until the tissue Se fell below 0.1 ppm, the level considered to be necessary for animal nutrition. For applications of 1.12 and 2.24 kg Se/ha, the minimal tissue Se concentration (〉 0.1 ppm) was maintained in barley (Hordeum vulgare L.) for two cropping years, but with a very sharp decrease for the first 3 yr. In the case of timothy (Phleum pratense L.), tissue levels greater than 0.1 ppm were maintained for 3 yr at the higher rate of Se without lime and up to 5 yr at high soil pH levels. At the applied rates of 0.28 and 0.56 kg Se/ha, the tissue Se levels above 0.1 ppm in timothy, red clover (Trifolium pratense L.), and alfalfa (Medicago sativa L.) were maintained for one and two cropping years, respectively. In spite of the sharp decrease in plant tissue Se levels, little decrease in total soil Se was noted at rates of 1.12 and 2.24 kg Se/ha after successive croppings of barley and timothy. Although not always significant, liming, in general, increased the plant Se concentration. The Se concentration (log ppm) for tissues (or depletion of Se availability) in the Se-applied plots decreased linearly for at least the first three cropping seasons.

Description: Biswas, A., Chau, H. W., Bedard-Haughn, A. K. and Si, B. C. 2012. Factors controlling soil water storage in the hummocky landscape of the Prairie Pothole Region of North America. Can. J. Soil Sci. 92: 649–663. The Prairie Pothole Region (PPR) in North America is unique hummocky landscape containing hydrologically closed topographic depressions with no permanent inlet or outlet. Knowledge about the controls of soil water distribution in the landscape is important for understanding the hydrology in the PPR. In this study, we investigated the correlation between soil water storage and different controlling factors over time. Time domain reflectometry and neutron probe were used to measure soil water storage up to 1.4 m depth over 4 yr along a 576-m long transect at St. Denis National Wildlife Area, Saskatchewan, Canada, which represent a typical landscape of the PPR. Soil and vegetation properties were measured along the transect, and various terrain indices were calculated from the digital elevation map of the study area. Soil texture (e.g., correlation coefficient, r=−0.57 to −0.73 for sand) provided one of the best explanations for the variations in soil water storage by controlling the entry and transmission of water within soil in the semi-arid climate of study area. Bulk density (r=−0.22 to −0.56), depth of A horizon, (r=0.18 to 0.49), C horizon (r=0.29 to 0.69), and CaCO3 layer (r=0.31 to 0.79) influenced the water transmission through soil and were correlated to soil water storage. Beside soil properties, topographic wetness index (r=0.47 to 0.67), slope (r=−0.41 to −0.56), convergence index (r=−0.29 to −0.60), and flow connectivity (r=0.27 to 0.60) were also correlated to soil water storage. However, multiple linear regressions showed a consistent high contribution from soil properties such as sand, organic carbon, depth of CaCO3 layer, and bulk density in explaining the variability in soil water storage. A substantial contribution from topographic variables such as wetness index, gradient, and solar radiation was also observed. Therefore, unlike other geographic regions, the soil-water storage variations in the PPR are controlled by a combination of soil and terrain properties with dominant control from soil characteristics at the field scale.

Description: Drury, C. F., Reynolds, W. D., Yang, X. M., Tan, C. S., Guo, X., McKenney, D. J., Fleming, R. and Denholme, K. 2014. Influence of compost source on corn grain yields, nitrous oxide and carbon dioxide emissions in southwestern Ontario. Can. J. Soil Sci. 94: 347–355. The impacts of compost type on corn grain yields over 10 yr and N2O and CO2 emissions in the first 3 yr after compost application were evaluated on a Brookston clay loam soil in Woodslee, ON. The treatments included yard waste compost (YWC), kitchen food waste compost (FWC), and pig manure compost (PMC), which were applied once in the fall of 1998 to field plots at a rate of 75 Mg ha−1 (dry weight basis) and no further applications occurred thereafter as well as a fertilized control treatment. Large application rates were examined to see if the various compost sources could have a lasting effect on soil C storage, N2O and CO2 emissions and corn yields. Compost application significantly increased corn grain yields by 12.9 to 19.4% over 3 yr. However, after 10 yr, FWC was the only compost source which significantly increased yields by 11.3% compared with the fertilized control. Emissions of N2O and CO2 varied with compost type, soil water content and time. Greater N2O emissions occurred in 1999 from PMC (5.4 kg N ha−1) than YWC (2.7 kg N ha−1) and FWC (1.3 kg N ha−1); however, the N2O emissions from the PMC were less than from YWC and FWC in 2001. The 3-yr average N2O emissions were significantly greater with PMC (2.7 kg N ha−1) and YWC (2.5 kg N ha−1) compared with the control (1.5 kg N ha−1). Hence, the timing of N2O emissions varied by compost type, but the overall losses were similar as the higher N2O losses in the first year with PMC were offset by the reduced losses with PMC in the third year. Significantly more CO2 was produced from the FWC in 2000 and from PMC in 2001 than the control.

Description: Pennock, D., Bedard-Haughn, A. and Viaud, V. 2011. Chernozemic soils of Canada: Genesis, distribution, and classification. Can. J. Soil Sci. 91: 719–747. Chernozemic soils in Canada have a characteristic biomantle that fully expresses the effect of organisms on soil formation. Additions of large amounts of below-ground biomass from grasses are transformed into complex organic compounds through the activities of meso- and macro-fauna, microbial degradation and combustion by fires. Degradation is regulated by (a) climatic influences on plant inputs and microbial activity, (b) the chemical and biochemical nature of the residues, (c) encapsulation of organic matter within aggregates by soil micro-faunal activities and freeze–thaw processes and (d) protection against decomposition by Ca2+ and clay minerals. These organic compounds are mixed with the mineral matrix through the action of organisms from mites to badgers. Regional differences in the regulators cause differences in soil organic carbon (SOC) storage and the colour value of the surface Chernozemic A horizon. The storage of SOC is lowest in the Brown soil zone (≈60 to 80 Mg ha−1) and greatest in the Black soil zone (≈120 to 150 Mg ha−1); this corresponds to a decrease in the annual water deficit from ≈200 mm (Brown) to 70 to 100 mm (Black). Where soil CaCO3 contents are high either through initial concentration in the parent material or by the precipitation of secondary CaCO3, substantially higher SOC storage than the regional norms can result. A repetitive catenary pattern occurs throughout the region. The primary controls on this pattern are hydrological – a lateral component to water flow in hillslopes leads to more developed horizonation downslope, and discharge surrounding wetlands causes precipitation of secondary carbonate minerals and more soluble salts in a fringe surrounding the wetlands. Chernozemic landscapes have been highly altered by humans through their conversion to agricultural production. Loss of the dense root network of the native grasslands causes a substantial decrease in SOC. This loss of carbon and reduction in A horizon thickness is accelerated by erosion; the effects of tillage erosion are now recognized as being ubiquitous through the agricultural region. The substantial amounts of SOC storage and our ability to increase storage through altered management practices make these soils a particular focus of interest in a future made more uncertain by the possibility of human-induced climatic change.

Description: Mineralized soil N from meadow soils will become an important source of N to following crops in low-input biological cropping systems. The C and N mineralization rates of soils from 34 sites situated on dairy farms recently converted to biological cropping systems were evaluated in a 56-wk incubation at 25° C. Data on C and N mineralization were fitted to first-order kinetic models. Carbon and N generally presented similar patterns of mineralization. Total mineralized N (Nm) ranged between 88 and 235 mg N kg-1 soil, which represented 6.6 to 22% of total N. Carbon mineralization (Cm) rate was between 11 and 17 times greater than N mineralization (1523–2638 mg C kg-1 soil ) and C mineralized represented 9 to 19% of soil organic C. The rate constant was between 0.05 and 0.123 wk-1 for C (kC) and ranged from 0.032 to 0.088 wk-1 for N (kN). The half-life for C (TC0) and for N (TN0) varied, respectively, between 5.6 and 13.3 wk and between 15 and 28 wk. Results show that about 80% of total mineralized C and N were mineralized during the first 25 wk of incubation, corresponding to the mineralizable fraction of soil organic matter (OM). Data on C and N mineralization have been adjusted using a bicompartmental model (active and recalcitrant pools), which corresponded, respectively, to first-order and exponential equations. Total mineralizable C and N (Cm and Nm), and the C and N rate constants (kC and kN) were strongly related, whereas the rate constants of the recalcitrant pools (hc and hN) were negatively related to these parameters. This suggests that C and N mineralizable pools were independent of the humified stable OM (recalcitrant pool). Carbon and N mineralization parameters were positively related to the soil clay and silt contents, but inversely to the sand levels. This study indicates that when ploughed, meadow soils contain large mineralizable N pools, which could sustain following crops with N nutrition in low-input biological cropping systems. Key words: Meadow soils, C and N mineralization rates, low-input systems, dairy farms, soil particles sizes

Description: A single batch application of phosphorus once in several years might be a more economical practice for wheat production in Western Canada than the traditional annual application at seeding time. Annual phosphorus applications and batch applications once every 8 yr were compared. Response functions were estimated for annual applications for two locations in Saskatchewan and two in Manitoba. The response functions were used to determine the optimum application rates at each location. These optimums were compared with the profitability of the batch application to determine the economic optimum phosphorus application strategy. Three wheat/fertilizer price ratios were used in the analysis to examine the effect of changes in relative prices. The 100-kg batch application was economically preferred to annual applications for all three price ratios at three of the four locations. Only at Swift Current, Saskatchewan was the batch application not economically justified. The 100-kg batch application was economically superior to the 200-kg application at all locations studied.

Description: The effect of labile inorganic phosphate (Pi) status of the soil on the decomposition of added cellulose and on the immobilization, mineralization, and redistribution of native and added P in soils was studied in a greenhouse incubation experiment. Cellulose was added at 765 μg C∙g−1 soil with and without P (9 μg∙g−1 soil) every 30 days under adequate N, H2O, and constant tempreature to two soils of different available P status. Lack of P eventually slowed down decomposition of added C, but this effect was partially compensated for by increased mineralization of organic P (Po) forms. Added P was redistributed to both P, (58–69%) and Po (42–31%) forms; higher amounts of Po were found in the soil with the highest Pi status. The correlation between microbial P uptake and solution P values was significant, and microbial C:P ratios ranged from 12:1 under high available P conditions to 45:1 where P was in low supply.

Description: A field study was conducted to measure the effect of soil salinity on barley grown under irrigated conditions in Alberta. Salinity was measured by the saturated paste extract, 1:2 soil-to-water extract, vertical probe and horizontal surface array methods. Correlation coefficients were determined between salinity measurements and the yield of barley to establish the suitability of these methods for predicting the growth of barley. Nineteen fields over 2 yr were monitored and soil salinity and the yield of barley were determined at a number of sites in each field. All methods of measuring salinity were significantly correlated (P = 0.01) with the yield of barley. At an EC of 7.8, yields of barley were reduced by 50%. Sodium concentration and sodium adsorption ratio were closely correlated with yield of barley and with saturated-paste-extract salinity. Soil moisture and pH were not as effective as salinity and sodium measurements in predicting the yield of barley. The saturated-paste-extract salinity was more closely correlated with the 1:2 soil-to-water extract than with the vertical probe or the horizontal surface array. The latter three methods were effective for rapid determination of the yield reductions which would occur on saline soils. No difference in tolerance to salinity was found between Klages (two-row) and Galt (six-row) cultivars of barley. Key words: Salinity tolerance of barley, methods of measuring salinity, vertical probe EC, horizontal array EC, saturated paste EC, 1:2 soil-to-water extract EC

Description: Iverson, M. A., Holmes, E. P. and Bomke, A. A. 2012. Development and use of rapid reconnaissance soil inventories for reclamation of urban brownfields: A Vancouver, British Columbia case study. Can. J. Soil Sci. 92: 191–201. As a result of suburban growth and abandonment and relocation of industrial facilities, vacant lots are becoming common in most urban centers in North America. These neglected, derelict, and often contaminated brownfields are receiving attention as a public liability since they are not productive and detract from the environmental quality of urban centres. Soils at these urban sites have been negatively impacted by anthropogenic activities. A prerequisite to effective reclamation is knowledge about the soil conditions on these sites. Most urban areas do not have soil survey or soil inventory information. Soil physical factors such as compaction are common problems at sites and are difficult and expensive to modify. A soil inventory provides the initial information for remediation and reclamation strategies that incorporate inherent soil properties. A soil inventory was conducted in Vancouver, British Columbia, by interpreting and extrapolating surficial geologic and regional soil survey information. The resulting soil inventory is presented as a series of topographical cross sections through the city, and displays information to stakeholders by reference to cultural features including street addresses. The soil inventory is compiled into soil management groups for general descriptions of the soil units and for initial recommendation for reclamation strategies.

Description: Engel, R., Jones, C. and Wallander, R. 2013. Ammonia volatilization losses were small after mowing field peas in dry conditions. Can. J. Soil Sci. 93: 239–242. Ammonia losses following termination of peas (Pisum sativum L.) by mowing were measured using a micrometeorological mass-balance approach. Field trials were conducted during two seasons in a semiarid climate. Plant N in the above ground biomass was 105 and 79 kg N ha−1 in 2011 and 2012, respectively. Vertical NH3 flux estimates were nominal (0.3 to 1.7 g N ha−1 h−1) in the 2 wk following mowing. Cumulative NH3 loss represented 0.3 to 0.5% of the N in plant biomass, indicating that N fertility was not diminished by NH3 volatilization in this dry climate.

Description: Remediation of excessive soil metals in situ is receiving new attention because the alternative, soil removal and replacement, is very expensive, requires disposal of the removed soil and may achieve no better environmental remediation than the in situ treatments. A factorial pot experiment was conducted with two muck soils contaminated by a Ni refinery; we tested the effectiveness of making the soil calcareous and addition of freshly precipitated hydous ferric oxide (HFO) in reducing soil Ni phytotoxicity to the Ni-sensitive crops, oat and redbeet, and a Ni-resistant crop, wheat. Fertilized but otherwise untreated soil caused significant Ni phytotoxicity to oats and redbeet, but not to wheat, on both soils. Adding limestone reduced the concentration of Ni in shoots of all species and alleviated the symptoms specific to Ni phytotoxicity in oat (banded chlorosis). The addition of HFO was more effective in reducing shoot Ni concentration in the redbeets than in crops from the Poaceae family. Both amendments induced phosphorus and/or manganese deficiency depending on the crop tested. The experiment indicates that some combination of limestone and Fe oxides can readily remediate Ni phytotoxicity of the tested soils, but that Mn and P fertilizers would be needed to achieve practical in situ remediation of Ni phytotoxicity of Quarry muck (Terric Mesisol). Key words: Nickel, soil, plant, phytotoxicity, remediation

Description: A theory is presented for the distribution of load pressures over the different phases in an unsaturated soil. It provides differential and integral relations between the equilibrium liquid pressure, the equilibrium solid pressure and the load pressure. Mechanical and thermodynamic models are presented by which the effective stress in unsaturated soils is defined. The value of the effective stress is then calculated for a certain state of a clay soil.

Description: Soils cultivated for 60 yr were compared with uncultivated forested soils at 10 sites in Appalachian Quebec. All soils belonged to the Humo-Ferric Podzol Great Group, five sets of comparisons being located on the Ascot soil series and five on the Greensboro. Comparisons were made between corresponding soil horizons, analytical data being derived from the bulking and analysis of six sample cores per horizon. Cultivation increased weight of soil in the solum and in the whole profile of both the Greensboro and the two soil series combined; bulk density was slightly affected. Field capacity, permanent wilting point and available water of the surface and sub-surface layers, in the solum and in the whole profile, were significantly increased by cultivation. The increase of available water was accompanied by a corresponding decrease in gravitational water. The content fine clay was significantly decreased in the surface layer and in the solum, while it was increased significantly in the C horizon by cultivation which also decreased the acidity of the surface and sub-surface in both series. There was a marked increase in organic matter content, but the level of fulvic acid was relatively unaffected by cultivation, indicating that the increased H/F ratio was primarily due to an increase in humic acid. Generally, Al content was not significantly changed, while significant increases in Fe and Mn were observed in the surface and solum of cultivated profiles. A deduction is made that cultivation has regraded podzol profiles into Dystric Brunisol ones which have started to evolve already toward kinds of Luvisolic profiles.

Description: An important economic concept in the evaluation of soil conservation is the ease with which production inputs can be substituted for one another. This concept and economic optimum application rates of N and P fertilizer for wheat grown after fallow were applied to three artificially eroded soils in southern Alberta. Each site had topsoil removed to depths of 0, 10 and 20 cm. Four rates of N (0, 50, 75 and 100 kg ha−1) and three rates of P (0, 11 and 22 kg ha−1) were applied to each eroded depth. There were four replications. Fertilizer N and P did not easily substitute for the loss of topsoil. The economic optimum level of N and P was nearly constant across depths of eroded topsoil. Increases in fertilizer N and P applied to eroded soils were primarily to replace lost soil nutrients. It was not economical to apply inorganic fertilizer on these eroded soils at rates that would restore grain yields. Key words: Eroded soil, economics, inorganic fertilizer, wheat

Description: The biodiversity of soil-inhabiting nematodes in Canada is incompletely known, as large areas of Canada’s landmass have not been surveyed for nematode fauna. Nematodes considered as indigenous are generally well adapted to a variety of ecological niches and climatic zones. Much of the available information is based on agricultural ecosystems and agricultural species, and thus is biased toward conditions in disturbed ecosystems and away from “primeval” ecology. Introduced nematode species are frequently quite pathogenic, even to exotic host plants from the same geographic point of origin. Estimates of crop loss due to single species infestations of pathogenic nematodes and the costs of nematode control using chemicals are reasonably well known, averaging about 10% of crop value, but ranging to 100% depending on the situation; the cost of damage by multiple-species infestations is less defined. Nematode-suppressive mechanisms are understood in only a few plant species; sulfur appears to be important as a constituent of active compounds in suppressive plants of agricultural origin. Similarly, some native plants are equally adapted with allelopathic chemicals that suppress nematodes. Management of nematode populations in agricultural soils by integrated crop management methods is at an early stage, requiring research to quantify effects of nematode-suppressive plants and soil amendments containing nitrogen. An integrated program could include nematode-suppressive plants, appropriate soil amendments, and the promotion of microbial antagonists. Different mathematical methods may be required to analyze and explain multi-factor nematode control systems. Less-toxic management systems could benefit the soil-inhabiting nematodes that predate arthropod soil pests. Further research on soil-borne nematodes may demonstrate the value of nematodes as indicators of agroecosystem health and environmental pollutants. Key words: Biocontrol, biodiversity, nematode distribution, nematode management, soil ecology

Description: Organic residues resulting from crop and animal production either become incorporated in the soil or remain on the surface and, thus, provide much of the nutrient and energy sources for many soil organisms. Characterizing the response of soil biota to these organic materials is a challenging undertaking due to the complexity of the soil ecosystem with respect to the magnitude of biodiversity involved, the possibilities for interrelationships with biochemical and biophysical processes, and the immense range of scale of observation from particle, through to aggregate, field, landscape and regional levels. The objectives of this paper were to review the available research pertaining to Canadian agroecosystems, which characterize the response of soil biota to soil organic matter dynamics, and to identify the issues, challenges and knowledge gaps. The response by soil organisms is discussed from two approaches: (1) their state of occurrence in terms of population response to soil organic matter as a nutrient and carbon/energy source, and (2) the extent of their influence in contributing to organic matter dynamics, that is, assessing their functional role. For the most part, Canadian research has emphasized comparative studies based on population responses by broad soil biota groups to soil organic matter additions or losses as an outcome of undertaking various agronomic practices. Studies that evaluate the extent of contributions by soil biota to soil organic matter dynamics are few, and rare at the species level. For Canadian agroecosystems, there is currently a great need for research initiatives that address the immense knowledge gaps that exist in relation to (a) identifying the specific contributions to soil organic matter processes and interactions of soil biota both at species and community level, (b) predicting outcomes of the contributions of soil biota groups in regulating or controlling soil organic matter processes both spatially and temporally across landscapes, and (c) assessing the risk to soil biodiversity in various agroecosystems in being able to sustain these functional roles. Key words: Soil biota, functional role, soil organic matter, agroecosystems, ecosystem services

Description: It is becoming common for soil surveys to be made of the same area at different intensities and published at different scales. The principles of cartographic generalization are discussed that control the relationships between the map units and delineations on maps made from such surveys. A study of two sets of maps showed that almost no lines were coincident. Up to 20% of the small scale delinations could be ’inliers’ of different soils and about 15% of the large scale delineations would be outside their small scale equivalents. The same discrepancies are to be expected between large scale soil maps and the smaller scale maps of physiography or vegetation that are often used to stratify soils. Reasons for these discrepancies are discussed under the headings of simplification and classification. Recommendations arc made to guide the preparation of maps and legends for different intensities and scales of survey in the same area. These recommendations have practical implications for the planning of surveys and the designs of computer-based autocartography systems.

Description: Fujii, K., Morioka, K., Hangs, R., Funakawa, S., Kosaki, and Anderson, D. W. 2013. Rapid turnover of organic acids in a Dystric Brunisol under a spruce–lichen forest in northern Saskatchewan, Canada. Can. J. Soil Sci. 93: 295–304. Organic acids released by lichen play an important role in mineral weathering and podzolization in the Boreal–Tundra transition zone of Canada; however, importance of low-molecular-weight organic acids in the soil carbon (C) cycle in the black spruce–lichen forests remains unclear. We examined soil solution composition and mineralization kinetics of 14C-radiolabelled oxalate and citrate to quantify the C fluxes from organic acid mineralization in a Dystric Brunisol under a spruce–lichen forest in northern Saskatchewan. Oxalate concentration in soil solution was greatest in the lichen layer, while the high levels of citrate were observed in the lichen and organic (O) layers to the Ae horizon with the lowest sorption capacity. Oxalate and citrate were rapidly mineralized within the lichen and O layers and had short mean residence times (0.5 to 2.7 h). Substantial C fluxes due to citrate mineralization were observed both within the lichen and O layers, but oxalate mineralization led to C flux in the lichen layer only. The contribution of citrate and oxalate to microbial respiration was large (up to 57%) in the surface soil layers. Citrate was the dominant substrate for microbial respiration of the surface soil; however, it appears that oxalate could also be an important microbial substrate within the lichen layer, at least in summer months. We conclude that the exudation of low-molecular-weight organic acids by lichenous fungi, followed by their rapid mineralization, could play an important role in the C cycles of the sandy soils under spruce–lichen forest.

Description: A 3-yr field study was conducted on two texturally different tailings sites at the Highland Valley Copper Partnership mine in south-central British Columbia to determine the effects of fertilizer and biosolids amendments on selected soil physical, chemical and microbiological properties. Soil bulk density and penetration resistance decreased in the upper 15 cm of tailings with increasing dry biosolids application rates of 50, 100, 150, 200 and 250 Mg ha-1. The addition of biosolids increased gravimetric water retention at field capacity and wilting point, but no significant changes occurred in the gravimetric water-holding capacity as both field and wilting point increased proportionally. Increasing biosolids decreased volumetric water-holding capacity on the silt loam, but had no effect at the sandy site because of decreased bulk density. Soil pH was not impacted by the treatments while electrical conductivity, soil organic matter, total carbon and cation exchange capacity increased with increasing levels of biosolids applied. Biosolids enhanced biological activity by increasing total aerobic, total anaerobic, iron reducing, sulfate reducing and denitrifying microorganisms near the surface. The fertilizer amendment did not alter soil physical or chemical properties from those of the control. The addition of biosolids was more effective at enhancing properties related to soil quality and fertility and therefore more effective for building soil organic matter on reclaimed tailings sites than the traditional use of inorganic fertilizer.

Description: Quantification of the effects of organic carbon (OC) addition to reclaimed soils is an important reclamation issue. Such effects on soil texture, field capacity (FC), wilting point (PWP) and water-holding capacity (WHC), all expressed both on a gravimetric and volumetric basis, were quantified using both in situ soil samples and laboratory-prepared peat:mineral mixes. Soil samples were collected from both natural and reclaimed areas within the Oil Sands region of Alberta; peat was obtained from the same area. Organic carbon was determined for laboratory-created mixtures and expressed as volume ratios; for the in situ samples it was expressed as % OC. Bulk density, an important factor in the effects of OC on water retention, was measured in situ.Water retention parameters of in situ samples on a gravimetric basis were significantly related to % OC, but those on a volume basis were not. Trends in volumetric WHC for in situ, coarse-textured samples were similar to those for gravimeteric WHC, due to similar bulk densities ranging from 1.30 to 1.40 Mg m–3. However, for in situ peaty soils, trends in volumetric water retention did not mimic those expressed on a gravimetric basis due to low and irregular bulk densities. For laboratory-constructed peat:mineral mixes, FC and WHC were significantly impacted by % OC, however, PWP was not.  The addition of peat material resulted in minor textural changes for sand and loamy sand; hence, the change in texture could not be responsible for the increases in WHC as the result of peat additions. The results for sandy loam were variable. Key words: Bulk density, field capacity, reclamation, water-holding capacity

Description: Ozturk, M., Salman, O. and Koc, M. 2011. Artificial neural network model for estimating the soil temperature. Can. J. Soil Sci. 91: 551–562. Although soil temperature is a critically important agricultural and environmental factor, it is typically monitored with low spatial resolution and, as a result, methods are required to estimate soil temperature at locations remote from monitoring stations. In this study, cost-effective, feed-forward artificial neural network (ANN) models are developed and tested for estimating soil temperature at 5-, 10-, 20-, 50- and 100-cm depths using standard geographical and meteorological data (i.e., altitude, latitude, longitude, month, year, monthly solar radiation, monthly sunshine duration and monthly mean air temperature). These data plus measured monthly mean soil temperature were collected for 2006–2008 from 66 monitoring stations distributed throughout Turkey to obtain a total of 2376 data records (36 months×66 monitoring stations) for each of the five soil depths. At each soil depth, 1800 randomly selected data records were used to develop and train a separate ANN model, and the remaining 576 records at each depth were used to test and validate the resulting models. Good agreement was obtained between ANN-estimated soil temperature and measured soil temperature, as evidenced by correlation coefficients of 98.91, 97.99, 99.03, 98.26 and 95.37% for the 5-, 10-, 20-, 50- and 100-cm soil depths, respectively. It was concluded that ANN modeling is a reliable method for predicting monthly mean soil temperature in regions of Turkey where soil temperature monitoring stations are not present.

Description: The variability of forest floor properties over short distances and the number of samples required to achieve desired levels of precision for estimation of property means have received little attention. The importance of the forest floor for forest management is well known and increasingly forest floor characteristics are being used to classify forest sites. Highly variable forest floor properties require more intensive sampling and often have less predictive value for characterization and classification purposes. A study site at Port Hardy was used to characterize forest floors for selected physical and chemical properties. The three sites chosen represented xeric, mesic and hygric positions along a hygrotopic gradient. A stratified random sampling procedure was used to obtain 15 samples at each site. Fifteen samples were adequate to characterize the means at 10% allowable error with a 95% confidence level for total nitrogen, organic carbon, pH and cation exchange capacity. Greater than 15 samples were required for exchangeable bases and forest floor thickness for the same level of accuracy and confidence. Even at 25% allowable error and 90% confidence, 40 samples and 16 samples, respectively, were required for exchangeable Ca and Mg.

Description: The Maillard reaction between carbohydrates and nitrogenous compounds originally investigated in 1912 has subsequently been proposed as a possible pathway for the formation of humic substances in natural environments. However, the role of mineral catalysis of the Maillard reaction is little understood and the promoting effect of light on such catalysis is not known. Birnessite (δ-MnO2), which is commonly present in soil environments, was investigated for its activity in promoting the Maillard reaction between glucose and glycine at a light intensity of 168 µE s–1 m–2 or in the dark. The presence of substantial quantities of Mn(II) was detected in both the supernatant and solid phase of the glucose-glycine-birnessite systems. The spectroscopic evidence indicates that birnessite, in the presence of light, is a very effective catalyst in abiotic browning of solutions of glucose and glycine. Furthermore, birnessite significantly promoted the reaction even in the absence of light. Therefore, the abiotic heterogeneous catalytic role of soil minerals such as birnessite in polycondensation of simple sugars and amino acids merits close attention in the formation of humic substances in natural environments. Key words: Maillard reaction, heterogeneous catalysis, light, birnessite, humic substance formation, XANES

Description: Dagesse, D. F. 2013. Freezing cycle effects on water stability of soil aggregates. Can. J. Soil Sci. 93: 473–483. The freezing process is commonly implicated as a key factor in defining the state of soil structural stability following the winter months. Controversy exists, however, regarding the efficacy, and even the net effect, of this process. The objective of the study was to establish the separate effects of the freezing, freeze–thaw and freeze-drying processes in defining soil structural stability following the over-winter period. Aggregates from soils of varying clay content (0.11, 0.33, 0.44 kg kg−1) and initial water content (0.10, 0.20 or 0.30 kg kg−1) were subjected to freeze-only (F), freeze–thaw (FT) and freeze-dry (FD) treatments. Post-treatment aggregate stability determination was via wet aggregate stability (WAS) and dispersible clay (DC). Freezing alone and freeze-dry treatments generally resulted in greater aggregate stability, while the freeze–thaw generally resulted in lower aggregate stability as compared with a control, not frozen treatment (T). These data suggest the freezing-induced desiccation process improves aggregate stability, while the addition of a thaw component following freezing, with the attendant liquid water, is responsible for degradation of aggregate stability. Clay content and initial water content are important factors governing the magnitude of this process.

Description: Bedard-Haughn, A. 2011. Gleysolic soils of Canada: Genesis, distribution, and classification. Can. J. Soil Sci. 91: 763–779. This review examines the pedogenesis of Gleysolic soils, including how they affect and are affected by land use and climate change. In the Canadian System of Soil Classification, the Gleysolic Order includes all those soils with morphologic features that provide dominant physical evidence of oxidation-reduction processes or gleying. Gley features include dull coloured soil matrices and/or brightly coloured mottles, which arise due to periodic or permanently saturated conditions. Under saturated conditions, oxygen is rapidly depleted and alternative terminal electron acceptors (such as iron, Fe3+) are used by microorganisms in the decomposition of organic matter. Gleysolic soils are found throughout Canada, either in low-lying landscape positions in association with better-drained soil orders (e.g., Prairie Pothole region), or as the dominant soil type where topography and/or a slowly permeable substrate prolong the period of saturation (e.g., Clay Belt of northern Ontario and Quebec). These soils are often highly fertile agricultural land and are commonly drained for production, altering the soil-forming environment. Gleysolic soils have also been found to be potentially significant sources of greenhouse gas emissions due to high levels of denitrification and methanogenesis under their characteristic reducing conditions. Given their economic, ecologic, and environmental significance, further research is required to refine our understanding and classification of Gleysolic soils, particularly with respect to (1) how Gleysols are affected by human- or climate-change-induced changes to the drainage regime (either progressing towards reducing conditions or regressing to a non-redoximorphic state), (2) classification of carbonated and saline Gleysols, and (3) pseudogley versus groundwater Gleysols.

Description: Peralta, N. R., Costa, J. L., Balzarini, M. and Angelini, H. 2013. Delineation of management zones with measurements of soil apparent electrical conductivity in the southeastern pampas. Can. J. Soil Sci. 93: 205–218. Site-specific management demands the identification of subfield regions with homogeneous characteristics (management zones). However, determination of subfield areas is difficult because of complex correlations and spatial variability of soil properties responsible for variations in crop yields within the field. We evaluated whether apparent electrical conductivity (ECa) is a potential estimator of soil properties, and a tool for the delimitation of homogeneous zones. ECamapping of a total of 647 ha was performed in four sites of Argentinean pampas, with two fields per site composed of several soil series. Soil properties and ECawere analyzed using principal components (PC)–stepwise regression and ANOVA. The PC–stepwise regression showed that clay, soil organic matter (SOM), cation exchange capacity (CEC) and soil gravimetric water content (θg) are key loading factors, for explaining the ECa(R2≥0.50). In contrast, silt, sand, extract electrical conductivity (ECext), pH values and [Formula: see text]-N content were not able to explain the ECa. The ANOVA showed that ECameasurements successfully delimited three homogeneous soil zones associated with spatial distribution of clay, soil moisture, CEC, SOM content and pH. These results suggest that field-scale ECamaps have the potential to design sampling zones to implement site-specific management strategies.

Description: Paré, M. C. and Bedard-Haughn, A. 2011. Optimum liquid density in separation of the physically uncomplexed organic matter in Arctic soils. Can. J. Soil Sci. 91: 65–68. Using an appropriate density to separate the soil light fraction (LF) and heavy fraction (HF) is an important aspect of the density fractionation technique. The effect of liquid density when separating the physically uncomplexed Arctic soil organic matter (SOM) was tested on three Arctic sites: High-Arctic, Low-Arctic, and Sub-Arctic. Our results showed that selecting the right density to use for Arctic soils is not unequivocal. Nevertheless, based on these two criteria: (1) the difference between the C:N values of the LF and HF needs to be as large as possible, and (2) the C:N value of the whole soil needs to be different from the C:N values of the LF and HF, the optimum density for all of our Arctic sites was between 1.49 and 1.55 g mL−1. We concluded that 1.55g mL−1 was the conservative optimum liquid density to use to separate Arctic SOM light and heavy fractions.

Description: Pipeline construction on the Canadian boreal plain occurs on woodland and/or agricultural fields, but soil recovery from its impact is not well documented. Therefore, we quantified changes over 3 yr (1992 to 1994) in the chemical properties of two Grey soils and the physical properties of a Grey soil that were subjected to pipeline burial and cropped to barley. The pipeline right-of-way (RoW) was divided into three zones: a road (or work) area used for vehicular traffic, a trench area for burying pipeline, and a pile (or spoil) area where soil was stockpiled during excavation. Pipeline construction resulted in mixing of subsoil material with topsoil, and the chemical properties most affected were those that varied most with depth. The pH, electrical conductivity, soluble sulphate, and exchangeable Ca and Na were increased in the surface 20 cm of soil, particularly the road and trench areas. The affected properties moderated 2 or 3 yr after pipeline construction as soluble components were dissolved or dispersed and translocated back to lower soil depths. The RoW zones had increased soil strength and compaction, and reduced water retention and infiltration rates. However, the deterioration in soil physical condition was similar across the RoW zones, indicating that it was due mainly to land clearing, a requirement to convert woodland to agricultural land. Improvement in bulk density, and water infiltration and retention in 1993 and 1994 indicated that the RoW was undergoing rehabilitation with time as a result of natural processes and annual cropping. Key words: Chemical properties, exchangeable cations, sulphate, physical properties, soil-water, pipelines

Description: Elliott, J. 2013. Evaluating the potential contribution of vegetation as a nutrient source in snowmelt runoff. Can. J. Soil Sci. 93: 435–443. On the Canadian prairies, most nutrient transport to surface waters takes place during snowmelt. The potential for a range of 11 residue types to release nitrogen (N), phosphorus (P) and carbon (C) was assessed by snowmelt simulation. Interactions between soils and residues were measured for two contrasting residues. Samples (taken in late fall) were frozen prior to snowmelt simulations that consisted of three diurnal temperature cycles from −5°C to +9°C followed by a final melt at +5°C. Releases of total and total dissolved P (TP and TDP), total dissolved N (TDN), and dissolved organic C (DOC) during simulated snowmelt were greater from actively growing residues than from crop stubble and were significantly related to plant moisture and nutrient contents. Nutrient release from wheat stubble (WS) was statistically similar to that from the underlying surface soil but releases of P and ammonia (NH3) from winter wheat (WW) were at least four times greater than for the corresponding soil. When combined samples of residue and soil were tested, releases of most nutrients were less than when the residue and soil were tested separately. Potential release of nutrients from vegetation is a factor for consideration in the design of practices to reduce nutrient transport.

Description: The objectives of this study were to find ways to improve the accuracy of soil fertilizer recommendations by taking into account the variation in bulk density (BD) of organic soils. To achieve this end, field BD values of 30 organic soils (0.100–0.504 g/mL) were used to evaluate methods of measuring the BD in the laboratory by means of correlation and regression techniques. A simple and rapid procedure using the reconstituted BD of field-moist soils was the most accurate means of determining the average field BD in the laboratory, as indicated by the correlation coefficient obtained between the BD values obtained by this method and those in the field (r = 0.975**). The second most accurate method relied upon the exponential relationship between the water content of soils and their BD (R2 = 91.1 %). The least exact method of correcting for BD variations was to scoop a volume of dried (65 °C) and sieved (2-mm) soils, as is done in some soil test laboratories. Although the values obtained by this method were related (r = 0.502**) to the field data, drying caused shrinkage of soils, thereby increasing their BD about twofold. Soil pH (r = 0.716**) and percentage ash contents (r = 0.851**) were also related to the field BD of soils. These tests could be used to estimate the BD of soils when the preferred method cannot be used. Regression equations are provided for relating appropriate test values to the BD of organic soils.

Description: Miller, J. J., Curtis, T. W., Bremer, E., Chanasyk, D. S. and Willms, W. D. 2013. Evaluation of selected soil properties for indicating cattle activity at off-stream watering and river access sites in southern Alberta. Can. J. Soil Sci. 93: 343–358. Off-stream watering troughs may reduce surface water pollution by shifting nutrient distribution from natural watering sites along the river to around artificial water troughs some distance from the river. The objective of our study was to evaluate the suitability of nine soil properties for assessing the impacts of cattle activity adjacent to eight watering sites. Nine surface (0–5 cm) soil properties were evaluated along four 100-m transects at the five off-stream water troughs and three river access sites along the Lower Little Bow River in southern Alberta over 4 yr (2007–2010). The properties included P (total P, soil test P or STP), N (total N, NO3-N, NH4-N), total C, total C:total N ratio (TC:TN), chloride (Cl), and soil bulk density. Soil test P was significantly (P≤0.05) enriched at 65% of site-year comparisons, followed by total C (63%), NO3-N (55%), total P and TC:TN (50%). This suggested that these soil properties were relatively good indicators of cattle activity at the majority (〉50%) of watering sites. Chloride was a valid indicator only in non-saline areas (100% of four non-saline sites). Total C and TC:TN ratios were not valid indicators in the calcareous soils at all sites because of possible confounding influence of inorganic C. Overall, we recommend Cl as an indicator of cattle activity at watering sites not affected by soil salinity and high natural Cl levels, and STP as the best overall indicator of cattle activity at off-stream watering sites and river access sites. Certain soil properties were also influenced by distance from watering site, stocking rate, precipitation, and age of water trough.

Description: Huffman, T., Coote, D. R. and Green, M. 2012. Twenty-five years of changes in soil cover on Canadian Chernozemic (Mollisol) soils, and the impact on the risk of soil degradation. Can. J. Soil Sci. 92: 471–479. Agricultural soils that are covered by vegetation or crop residue are less susceptible to degradation by wind and water erosion, organic matter depletion, structural degradation and declining fertility. In general, perennial crops, higher yields, reduced tillage and continuous cropping provide more soil cover than annual crops, lower yields, intensive tillage, residue harvesting and fallowing. This study presents a model for estimating the number of days in a year that the soil surface is protected and demonstrates its application on the Canadian prairies over the period from 1981 to 2006. Over the 25-yr study period, the average soil cover on Canadian prairie soils increased by 4.8% overall. The improvement came primarily as a result of widespread adoption of no-till and a decline in the use of summerfallow, but the gains were offset to a great deal by a shift from higher-cover crops such as wheat, oats and barley to more profitable but lower-cover crops such as canola, soybeans and potatoes. The implication of these trends is that, even though protection of prairie agricultural soils has improved over the past 25 yr, soil cover could decline dramatically over the next several decades if crop changes continue, the adoption of conservation tillage reaches a peak and residue harvesting for biofuels becomes more common.

Description: Risk, N., Snider, D. and Wagner-Riddle, C. 2013. Mechanisms leading to enhanced soil nitrous oxide fluxes induced by freeze–thaw cycles. Can. J. Soil Sci. 93: 401–414. The freezing and thawing of soil in cold climates often produces large emissions of nitrous oxide (N2O) that may contribute significantly to a soil's annual greenhouse gas emission budget. This review summarizes the state of knowledge of the physical and biological mechanisms that drive heightened N2O emissions at spring melt. Most studies of freeze–thaw N2O emissions have concluded that denitrification is the dominant process responsible for the large thaw fluxes. Soil moisture, availability of carbon and nitrogen substrates, and freeze temperature and duration are the major factors identified as controlling freeze–thaw cycle (FTC) N2O emissions. Two mechanisms are proposed to lead to enhanced N2O emissions at thaw: (1) the physical release of N2O that is produced throughout the winter and trapped under frozen surface layers and/or within nutrient-rich water films in the frozen layers, and (2) the emission of newly produced (de novo) N2O at the onset of thaw, which is stimulated by increased biological activity and changes in physical and chemical soil conditions. Early studies implicated the physical release of N2O from subsurface soil layers as the main mechanism contributing to spring thaw emissions, but most current studies do not support this hypothesis. Mounting evidence suggests that most of the emitted N2O is produced de novo. This may be fueled by newly available denitrification substrates that are liberated from dead microbes, fine roots, and/or the disintegration of soil aggregates. The release of N2O trapped in shallow surface layers may represent a small, but important contribution of the total emissions. Application of new techniques to study microbial communities in their natural environments, such as metagenomics and stable isotope studies, have the potential to enhance our understanding of the soil N cycle and its linkages to FTC N2O emissions. Future field studies of N2O emissions ought to quantify both overwinter accumulation/release and the de novo production of N2O so that the contribution of each mechanism to the annual emission budget is known.

Description: An understanding of emissions from liquid manure facilities during winter, spring thaw and agitation is needed to improve national emissions inventories in Canada. In this study, liquid dairy manure was stored in six pilot-scale tanks (1.8 m deep × 6.6 m2 surface area) covered by steady-state chambers that enabled greenhouse gas (GHG) and ammonia (NH3) flux measurement. After 158 d of undisturbed storage, three tanks were agitated for 5 d (8 h per day) consecutively. During storage, methane (CH4) flux was correlated with manure temperature at 30 cm depth (P 

Description: Tenuta, M. and Sparling, B. 2011. A laboratory study of soil conditions affecting emissions of nitrous oxide from packed cores subjected to freezing and thawing. Can. J. Soil Sci. 91: 223–233. A series of laboratory experiments using a packed core soil assay was carried out to test several soil conditions affecting the emission of N2O (nitrous oxide) during thawing of soil. The assay consisted of a sandy loam soil packed to 1.1 Mg m−3, moistened to 80% water-filled pore space, and temperature treated to 4 or −20°C for 2.5 d; the emissions from thawing soil were then determined as the differences in N2O release rates of the temperature-treated soils when placed at 15°C. Nitrate addition to surface soil (0–10 cm) enhanced thaw emission. Thaw emissions, averaged for deeper collected soil (10–30 and 30–60 cm), was 0.3% with NO3− treatment and 1.2% without NO3− treatment of that for surface soil treated similarly. Higher thaw emission for surface soil was related to greater organic matter and microbial biomass C contents and denitrifying enzyme activity than deeper collections of soil. Increasing the bulk density of soil from 1.1, 1.2, and 1.25 Mg m−3 decreased thaw emission. A second freeze-thaw cycle of the highest compaction treatment resulted in an emission of 2.3% of the first freeze-thaw cycle. Acetylene increased thaw emission of N2O and more so for NO3− untreated than treated soil. Using the acetylene inhibition method, the N2O:N2 ratio of gas produced was higher for frozen (0.17) than cold (0.07) treated soil, respectively, without the addition of NO3−. The addition of NO3− increased the N2O:N2 ratio of gas produced with the ratio being 2.45 and 0.53 for frozen and cold-treated soil. The results are consistent with biological denitrification being a source of N2O with conditions promoting N2O production rather than consumption enhancing thaw emissions.

Description: A growth chamber study was conducted using two Saskatchewan soils to evaluate how addition of urea and swine manure affects the supply of plant-available nitrogen (ammonium and nitrate) and its relationship with plant N uptake. Treatments consisted of two different N rates applied as urea and manure (100 and 800 mg N kg−1) and a control. Ion exchange membrane probes were used to measure plant-available N supply rate. Canola was grown under the same environmental conditions to determine plant N uptake. Additions of fertilizer and manure significantly increased the supply of plant-available N measured in the soil. Over an 84-d period the available N supply in the manured soil was about 40% lower than in the urea-fertilized soil at equivalent rates of total N addition due to incomplete mineralization of organic N in the manure. However, plant N uptake was similar between manure and urea-treated soils, which was attributed to other nutrients present in the manure that may have enhanced root growth and plant N uptake. High proportions of ammonium N were measured initially, especially at the high rates of urea and manure. However, inorganic N in the form of ammonium rapidly decreased with time and nitrate N became the main inorganic N form supplied. Overall, there was good correlation (r value 0.79 to 0.96) between plant N uptake and available N supply rate in the soil as measured by ion exchange membrane. Key words: Ion exchange membrane, available N supply rate, urea, swine manure, canola, plant N uptake

Description: Potassium deficiency in grapes, as well as in other fruit crops grown on soils in the Niagara peninsula, is a common and often serious problem. Ap horizon samples from 12 of these soils and grape petiole samples from nine of the soil locations were analyzed to elucidate the behavior of the soil K and its availability to grapes. The soils ranged in texture from sandy loam to silty clay and their clay mineralogy was relatively uniform with mica as the main layer silicate. Vermiculite was quantified by potential K fixation methods and was concentrated in the clay. Up to 5.8% vermiculite was present in the soils which seemed to be sufficient to reduce K availability by K fixation. Amounts of exchangeable K extracted with NaCl or NH4Cl were relatively high (0.46–2.09 meq/100 g) but were not correlated with K uptake by grapes. Energies of K exchange obtained from immiscibly displaced soil solutions were closely related to vermiculite contents and amounts of K fixed after air drying. Energies of K exchange and ratios of exchangeable K over exchangeable Ca + Mg were highly correlated with K uptake by grapes. Soils with energies of K exchange less than or equal to −2800 cal/equiv. or K exch./(Ca + Mg) exch. equal to or more than 7% appeared to have adequate amounts of available K for grapes. These two analyses therefore show promise for predicting K availability to grapes. Key words: Exchangeability of K, energy of K exchange, fixation of K, soil mineralogy, availability of K to grapes

Description: This study was conducted to provide a better understanding of the relationship between foliar nutrient status, maple dieback and soil quality. Fieldwork was conducted in four maple stands, two of which were located in the Appalachians at Tingwick and two in the Laurentians at Duchesnay. All stands were characterised by a mound and depression microrelief. In one of the Tingwick maple stands (T1) the predominant soil type was found on mounds, and was well to moderately well-drained (Leeds and Woodbridge series). At the other site (T2), the predominant soil type was in depressions, and imperfectly to poorly drained (Sainte-Marie and Brompton series). At the first Duchesnay site (D1) the predominant soil type was found on mounds and was well to rapidly drained (Ste Agathe series). At the second Duchesnay site (D2), the predominant soil type was also found on mounds, but was well to moderately well-drained (Sergent series). On all sites, the soils were acidic and nutrient poor. The lowest pH values and nutrient concentrations (in the H-Ah horizons) were found in maple stands with well-drained soils (T1 and D1) (P 〈 0.05). On these sites, maple dieback was less than 10%. It was on the poorly to imperfectly drained soils at Tingwick (T2), as well as on the moderately drained soils at Duchesnay (D2), that we observed the lowest biological activity. Although these soils were the most nutrient rich, we observed foliar nutrient deficiencies, and maple dieback in excess of 25%. Our results suggest that maple dieback is the result of a poor physiological adaptation of sugar maple to poor drainage conditions in the areas studied. Key Words: Dieback, Acer saccharum, forest soils, biological activity index

Description: The range of soil properties associated with soil taxonomic class results from natural soil formation and soil-changing effects of human activity. My goal was to assess cultivation effects on soil formation and soil organic carbon (SOC) at four cultivated and two native hummocky till sites from the same climatic region of Saskatchewan. A revised landform segmentation procedure was used for comparisons across sites. Neither A horizon thickness nor SOC was related to topographical attributes at the native sites, but both had significant relationships (P = 0.001) with profile curvature (Pearson r= −0.53 and −0.57 for A horizon thickness and SOC, respectively), specific dispersal area (r = −0.40 and −0.54) and plan curvature (r = −0.24 and −0.34) at the cultivated sites. The greatest decreases in A horizon thickness (16 cm) and SOC (56 Mg ha-1) at the cultivated sites occurred in divergent shoulder elements, which have high rates of tillage-induced soil loss. Increases in soil thickness (including depth to calcium carbonate) occurred in concave footslope and depressional elements, but in situ losses of SOC outweighed the effects of SOC deposition. Soil thinning caused increases in the proportion of Orthic Regosols and decreases in the proportion of Calcareous Chernozems, but horizonation changes in the dominant Orthic Chernozems were minor. The self-terminating nature of the horizonation changes and improved conservation measures suggest that the future rate of soil change in these landscapes may be lower than in the past. Key words: organic carbon, topography, landscape-scale, erosion, tillage redistribution, digital elevation model, cesium

Description: There is little information on the effects of S management strategies on soil microorganisms under zero tillage systems o n the North American Prairies. Experiments were conducted to examine the effects of tillage and source and placement of S on soil microbial biomass (substrate induced respiration) and functional diversity (substrate utilization patterns) in a canola-wheat rotation under conventional and zero tillage systems at three sites in Gray Luvisolic and Black Chernozemic soils. Conventional tillage significantly reduced microbial biomass and diversity on an acidic and C-poor Luvisolic soil, but it had mostly no significant effects on the near-neutral, C-rich Luvisolic and Chernozemic soils, which underlines the importance of soil C in maintaining a healthy soil. Sulphur had no significant effects on soil microbial biomass, and its effects on microbial diversity were more frequent on the near-neutral Luvisol, which was more S-deficient, than on the acidic Luvisol or the Chernozem. Significant S effects on microbial diversity were observed both in the bulk soil (negative effects, compared with the control) and rhizosphere (positive effects) of the acidic Luvisol, but all significant effects (positive) were observed in root rhizospheres in the other soils. Sulphur by tillage interactions on acidic Luvisolic soil indicated that the negative effects of S in bulk soil occurred mostly under zero tillage, presumably because the fertilizer is concentrated in a smaller volume of soil than under conventional tillage. Sulphate S effects, either negative or positive, on microbial diversity were usually greater than elemental S effects. Therefore, S application can have direct, deleterious effects on soil microorganisms or indirect, beneficial effects through crop growth, the latter presumably due to increased root exudation in the rhizosphere of healthy crops. Key Words: Biolog, conservation tillage, microbial biodiversity, rhizosphere, soil biological quality, S fertilizer type and placement

Description: The P dynamics in soils should be quantified in agricultural soils to improve fertilizer P (FP) efficiency while limiting the risk of P transfer from soils to water bodies. This study assessed P transformations following FP addition to Gleysolic soils. A pot experiment was conducted with five soils varying in texture from sandy loam to heavy clay, and receiving four FP rates under barley (Hordeum vulgare L.)-soybean (Glycine max L.) rotations. A modified Hedley procedure was used for soil P fractionation. Soil resin-P and NaHCO3-Pi contents were interactively affected by texture and FP. The NaHCO3-Po, NaOH-Po, HCl-P and H2SO4-P were only affected by soil texture. Proportions of 78 and 90% of the variation in labile and total P were, respectively, related to soil clay content. The FP addition increased resin-P, NaHCO3-Pi and NaOH-Pi and -Po contents in coarse-textured soils, but the amount added was not sufficient to mask the initial influence of soil texture on the sizes of soil P pools. Plant P uptake was proportional to FP rate but less closely linked to clay content. The average increase in labile P per unit of total FP added in excess of plant exports was 0.85, 0.8 2 , 0.73, 0.55 and 0.24 for the sandy loam, loam, clay loam, clay and heavy clay soil, respectively. The results of this study stress the important of considering soil texture in Gleysolic soils when assessing P accumulation and transformations in soils, due to commercial fertilizers applied in excess of crop removal. Key words: P fractions, clay content, fertilizer P, plant P uptake, soil texture

Description: The recommended method for N fertilization to winter wheat (Triticum aestivum L.) on the Canadian prairies has been to broadcast ammonium nitrate (AN) during early spring. In the Chinook region of southern Alberta, considerable interest exists in alternative formulations (particularly urea), times of application and placements. To determine the effect of alternative N fertilizer practices on winter wheat in southern Alberta, two field experiments were conducted over 2 consecutive years (1998-1999 and 1999-2000) at three locations. In the first experiment, fall applications of urea or coated urea, seed-placed or banded, were compared to the standard practice of spring-broadcast AN. At five of six sites, there was no difference between fall-banded urea and coated urea in plant stand, grain yield or protein concentrations when compared to spring-broadcast AN. In 1998-1999, fall-banded urea reduced grain yield by 13% at the site in the Brown soil. Seed-placed N was only safe for urea at 30 kg N ha-1 and for coated urea at rates up to 60 kg N ha-1. In the second experiment, urea and coated urea were broadcast in spring for comparison with AN. Coated urea was ineffective in dry years due to poor N release. Urea was equally effective as AN in this study, possibly due to the cool, dry conditions at the time of application and the relatively low surface soil pH levels at these reduced tillage sites. Further research will be required to confirm the effectiveness of this practice for this region. Key words: Ammonium nitrate, urea, coated urea, nitrogen fertilizer placement, nitrogen timing, grain protein

Description: Use of controlled-release P fertilizers to match the fertilizer P availability to crop requirement has potential for improvement of P uptake and crop production. Greenhouse experiments were conducted to evaluate the concept of controlled-release P fertilizer by using different coatings to regulate the release of P and to compare the growth and P uptake of barley (Hordeum vulgare L.) in three Alberta soils. Testing of different coatings in one experiment was followed by further evaluation of the promising treatments in two experiments. Commercial monoammonium phosphate (MAP) and diammonium phosphate (DAP) were coated with a polymer (thin-coated, 1.8% by weight or thick-coated, 2.2%) or enveloped in commercial packaging polyethylene film (shrink wrap, SW) with two, four or six pin-holes to control P release. Thin-coated treatment showed greater dry matter yield (DMY), P uptake (PU), net fertilizer P efficiency (NFPE) and net fertilizer releases efficiency of MAP compared to the uncoated, thick-coated or SW treatments in many cases. Coating of DAP did not consistently improve any of the above-mentioned parameters. In some cases, uncoated fertilizer had greater DMY, PU and NFPE than the polymer-coated treatments in early stages of crop growth (at the 13th, 26th, and 30th days), but coated treatments generally performed better during later stages of crop (at the 39th, 45th, 60th and 90th days). At 31.4 mg P pot-1 for example, thick-coated treatment had about 25% of its total PU during the 60th to 90th day, which resulted in greater spike yield accumulation in this treatment (8.4 g pot-1) compared to uncoated fertilizer (5.0 g pot-1). The P release rate was greater with thin-coated fertilizer than with thick-coated fertilizer during the 0 to 13th days (by 0.199 mg P kg-1d-1) and the 13th to 26th days (by 0.084 mg P kg-1d-1), but the opposite was true during the 26th to 39th days (by 0.112 mg P kg-1d-1) and the 39th to 52th days (by 0.064 mg P kg-1d-1). The polymer-coated, in particular the thin-coated, fertilizers delivered P in a manner that allowed the plants to use it more effectively than the uncoated MAP in several cases, which indicated a potential for improvement of fertilizer P efficiency and crop production. Key words: Barley growth, controlled-release P fertilizer, P uptake, yield

Description: Runoff from manured cropland during the wet fall and winter season, when 70% of the annual rainfall occurs, is a surface water quality concern in the Lower Fraser Valley of British Columbia. This study compares different fall-manure application strategies on runoff and contaminant transport from silage corn (Zea mays) land. The treatments were (i) a control, which did not receive manure in the fall; (ii) manure broadcast in the fall on corn stubble; and (iii) manure broadcast in the fall on corn stubble with an established relay crop. Runoff, solids, and nutrients loads from natural precipitation were measured on replicated experimental plots (0.0125 ha) from 1996 to 1998. Fall-applied manure on 3–5% sloping silage cornland without a relay crop resulted in a high risk to surface water quality, due to high suspended solid loads of between 7 and 14 Mg ha-1 yr-1 and high nutrient transport with mean annual total Kjeldahl N (TKN) P, and K loads of 98, 21, and 63 kg ha-1, respectively. Compared with no relay crop, intercropping silage corn with a relay crop of Italian ryegrass (Lolium multiflorum) reduced the mean annual runoff and suspended solid load by 53 and 74%, respectively, TKN load by 56%, P load by 42%, K load by 31%, and Cu load by 57%. Even though total nutrient loads were lower with the relay crop treatment, all fall manure treatments including the relay crop resulted in nutrient loads above guidelines for the first three runoff events immediately following application. Key words: Runoff, suspended solids, nutrient loads, relay crop, cover crop, silage corn, manure

Description: In corn (Zea mays L.) – soybean [Glycine max (L.) Merr.] – winter wheat (Triticum aestivum L.) rotations cultivated in sandy soil under three tillage systems, with and without cover cropping, the soil wind-erodible fraction ( chisel plow (6.7 and 39%) 〉 conventional plow (5.3 and 35%). Cover cropping had little effect on dry aggregate size distribution or WAS. Key words: Zea mays, Secalecereale, soil structure, aggregate stability, cover crop, tillage

Description: Carrera-Hernández, J. J., Mendoza, C. A., Devito, K. J., Petrone, R. M. and Smerdon, B. D. 2012. Reclamation for aspen revegetation in the Athabasca oil sands: Understanding soil water dynamics through unsaturated flow modelling. Can. J. Soil Sci. 92: 103–116. Reclamation of mined areas in the Athabasca oil sands region is required by law, with the ultimate goal of revegetating to species characteristic of predisturbance native plant communities. To develop adequate reclamation strategies, an analysis of soil water dynamics is of utmost importance, as is understanding the impact of the thickness of the reclamation cover. In this work, soil water dynamics and fluxes at the water table were simulated for three reclamation scenarios and compared with the fluxes obtained for natural conditions assuming that aspen is the target reclamation species. According to the simulations, a reclamation thickness between 0.5 and 1.0 m can be used to provide water for revegetation. The numerical simulations show that the reclaimed landscapes have fluxes at the water table that exhibit less fluctuation than natural conditions. To limit the interaction between the water table and atmospheric fluxes, and to limit upward flux, the water table should be deeper than 2.0 m on reclaimed landscapes that use aspen for revegetation, particularly when reclamation takes place during a dry climatological cycle.

Description: The objectives of this study were to evaluate if zero tillage had significantly altered the distribution of certain soil properties formally developed under the shallow cultivation (conventional tillage) soil management systems used on the Canadian prairies. To this end, concentration gradients of available plant nutrients, microbial biomass and mineralizable C and N, were determined in the Ap soil horizon from four locations representing zero and conventional (shallow) tillage systems of 2-, 4-, 12- and 16-yr duration. No significant change coud be detected in total soil organic C and N between tillages systems. Concentrations of plant-available P and K were slightly increased in the surface 0- to 2-cm depth after 16 yr of zero tillage. Except for the 2-yr tillage site, concentration gradients of potential microbial biomass C and N, and potential net mineralizable C and N were significantly greater in the surface soil under zero tillage in comparison to conventional tillage. The reverse situation was observed at the lower depth. The percentage of soil organic C and N that was in the microbial biomass also reflected the above trends. Accumulation of mineral N and calculated N mineralization potentials were closely correlated to both the initial microbial biomass N and the decrease in size of the latter during mineralization. The possible relationships of tillage induced change and redistribution in potential biological activity to N availability were discussed.

Description: The nitrogen (N) cycle is second in importance only to the carbon (C) cycle in natural ecosystems. However, the origin and nature of approximately one-third of total soil N remains poorly understood. We used N-XANES (X-ray absorption near edge structure) spectroscopy, a sensitive, non-destructive synchrotron-based analytical technique, to determine the organic N structures in selected Gleysolic soils of Saskatchewan. Initial results indicate the presence of amide structures and heterocyclic N compounds, which are significant in understanding the transformation of organic N moieties in the soil, both in terms of sources of bio-available N and long-term storage. Key words: Unknown N, amides, heterocyclic N compounds, wetland soils, N-XANES spectroscopy

Description: A study was initiated in 1996 in the Black Soil zone in east-central Saskatchewan to examine soil and crop response to application of feedlot cattle manure at different application rates, frequencies and incorporation timing in a sandy loam and loam soil. Three rates of feedlot cattle manure (approx. 100, 200 and 400 kg total N ha-1) were applied annually and under reduced frequency application regimes. Canola (Brassica napus, L.), spring wheat (Triticum aestivum, L.), hulless barley (Hordeum vulgare, L.) and canola were seeded in spring of 1997, 1998, 1999 and 2000, respectively. Pre-seeding available N (0–60 cm) increased with application rates. Annual application resulted in a linear increase in grain yield with application rates but had no effect on grain N concentration. Cumulative N use efficiency was low (7–10%) with no significant difference among treatments. Single application showed significant residual fertility benefit in the second year but not in the third year except at the high rate. Incorporation timing of feedlot cattle manure had no impact on soil or crop performance. Low availability of N in feedlot cattle manure over the short-term suggests the need for high application rates or addition of supplemental N fertilizer in order to meet crop N requirements. Key words: Feedlot cattle manure, N availability, manure management, N use efficiency

Description: Huang, M., Elshorbagy, A., Barbour, S. L., Zettl, J. D. and Si, B. C. 2011. System dynamics modeling of infiltration and drainage in layered coarse soil. Can. J. Soil Sci. 91: 185–197. A system dynamics (SD) model was developed to simulate transient infiltration and drainage processes in multilayered soils. STELLA Software was used as a stock-flow icon-based simulation environment. The developed SD model combined both physically based formulations and empirical assumptions to describe one-dimensional saturated–unsaturated water flow in the vadose zone. The model was successfully calibrated and validated using measured water contents during the infiltration and drainage phases, respectively, of a double-ring infiltration test. The simulation results were also compared with a finite element model of saturated/unsaturated flow (HYDRUS). The results showed that the SD model was capable of accurately simulating the various hydrological processes in multilayered soils, and could be a useful tool for designing reclamation covers. The simulated and measured results show that the presence of a finer sand layer overlying a coarse sand layer will increase the soil water storage at field capacity.

Description: Wildfire has historically been the major cause of stand initiation in the boreal forest, shaping species diversity, successional and ecosystem processes. Clearcut harvesting may differ from fire in its effects on soil and vegetation processes and thus may cause long-term changes in stand productivity or biodiversity. This study compared the soil properties of mesic black spruce (Picea mariana) stands burned 2, 14, 21 yr prior to sampling, with stands clearcut within ±3 yr of each wildfire and recently undisturbed control stands. The forest floor (FH) and mineral soil (0-10 cm) were sampled volumetrically, air dried and analysed for pH, organic carbon content, available P, Ca, Mg, and K, mineralizable N and nitrification. Forest floors were also digested and analysed for total N, P, K, Ca and Mg. Significant differences between disturbed and control stands were observed in all study areas, with disturbance effects generally decreasing with time since disturbance. Burned stands generally had forest floors with thinner humus layers, lower mass of organic carbon, higher pH, and higher concentrations of total and available nutrients than in either clearcut or control stands. Significant losses in the total mass of N and K in the forest floor were observed in the youngest burned stands as well as a pulse of extractable P that was at least four times higher than cut or control stands in any other treatment or study area. The forest floor of cut stands had greater mass of organic matter and total nutrients, and higher levels of potentially mineralizable N than either fire or control stands. No significant nutrient loss was observed following clearcut harvesting in any study area. Overall, this study suggested that clearcut harvesting can result in changes to the status of soil nutrients that are different from those produced by wildfire. Further study is necessary to determine whether these differences have significant effects on the long-term productivity or biodiversity of the boreal forest. Key words: Fire, clearcutting, boreal forest, nutrients, Quebec

Description: Soil tests for available P may not be accurate because they do not measure the appropriate P fraction in soil. A sequential extraction technique (modified Hedley method) was used to determine if soil test P methods were accurately assessing available pools and if predictions of fertilizer response could be improved by the inclusion of other soil P fractions. A total of 145 soils were analyzed from field P fertilizer experiments conducted across Alberta from 1991 to 1993. Inorganic P (Pi) removed by extraction with an anion-exchange resin (resin P) was highly correlated with the Olsen and Kelowna-type soil test P methods and had a similar relationship with P fertilizer response. No appreciable improvement in the fit of available P with P fertilizer response was achieved by including any of the less available P fractions in the regression of P fertilizer response with available P. Little Pi was extractable in alkaline solutions (bicarbonate and NaOH), particularly in soils from the Brown and Dark Brown soil zones. Alkaline fractions were the most closely related to resin P, but the relationship depended on soil zone. Inorganic P extractable in dilute HCl was most strongly correlated with soil pH, reflecting accumulation in calcareous soils, while Pi extractable in concentrated acids (HCl and H2SO4) was most strongly correlated with clay concentration. A positive but weak relationship as observed between these fractions and resin P. Complete fractionation of soil P confirmed that soil test P methods were assessing exchangeable, plant-available P. Key words: Hedley phosphorus fractionation, resin, Olsen, Kelowna

Description: In 1982, six crop rotation treatments that were initiated in 1967 on a Orthic Brown Chernozemic loam were sampled for soil NO3-N and moisture to a depth of 240 cm. Soil samples were taken on 18 May and 10 June from all treatments, on 2 Sept. on fallow treatments only, and on 14 Oct. from cropped treatments. Precipitation during the sampling period was about 23% above the long-term average. It was estimated that at least 123 kg NO3-N∙ha−1 were leached from the top 240 cm of fallow soils. Leaching appeared to result from a portion of the precipitation moving through macro soil pores. There was evidence that water and NO3-N might also move upwards from below the 240-cm depth. Of the six rotations examined, the 2-yr and 3-yr spring wheat (Triticum aestivum L.) rotations lost the most NO3-N. The presence of fall rye (Secale cereale L.) in a fallow-rye-wheat rotation was very effective in reducing NO3-N losses. Spring wheat, when grown continuously, was also very effective in reducing NO3-N losses but even here there was some evidence of leaching beyond the root zone. Application of fertilizer N and P at amounts based on soil test recommendations reduced NO3-N leached. It was estimated from long-term precipitation data, that over the past 100 yr about 20% of the soil organic N that was present at the time of breaking the land has been lost from the soil via leaching. It was concluded that leaching losses of N from the soils on the Canadian prairies had been greatly underestimated and were partly responsible for losses attributed to the more visible wind erosion. Key words: Nitrate movement, crop rotations, fertilizer and leaching, summerfallow and leaching, bimodal leaching

Description: Mixed paper mill sludges are an important source of N for crop production. An estimate of direct and residual N recovery is necessary for their efficient management. A 3-yr field study (1997-1999) was conducted in central Quebec, Canada, to evaluate mixed paper mill sludges (PMS) effects on corn (Zea mays L.) yields and N nutrition, N recovery and N efficiency. The effects of PMS on soil NO3-N and total N levels were also determined. The study was situated on a silt loam Baudette soil (Humic Gleysol). The treatments included 3 PMS rates (30, 60 and 90 t ha-1 on wet basis) applied alone or in combination with N fertilizer (90 and 135 kg N ha-1, respectively, for 60 and 30 t ha-1). Treatments also included a control without PMS or N fertilizer, and a complete mineral N fertilizer (180 kg N ha-1) as recommended for corn. The previous plots were split beginning with the second year of the experiment, for annual and biennal PMS applications. Similar treatments as above were made on an adjacent site to evaluate N recovery under climatic conditions in 1999. In all years, PMS applied alone significantly increased corn yields by 1.5–5 t ha-1, compared to the unfertilized control. However, corn yields and N uptake were highest from the application of PMS in combination with N fertilizer. Biennial PMS applications at 60 to 90 ha-1 significantly increased corn yields and N uptake, which suggest high PMS residual effect; however, these increases were lower than those obtained with annual PMS applications. The N efficiency varied in 1997 from 13.0 to 15.4 kg grain kg N-1 for mineral N fertilizer and ranged from 3 to 13.7 kg grain kg N-1 for PMS, decreasing proportionally to increasing PMS rates. Apparent N recovery ranged from 1 3 to 19% in 1997 and from 10 to 14% in the residual year (1998), compared to 30 and 49%, respectively, for mineral N fertilizer. Depending on the PMS rate, N recovery varied from 13 to 21% in 1999. The results indicate high N supplying capacity and high r esidual N effects of PMS, which probably influenced corn yields and N nutrition. Annual PMS applications alone or combined with mineral N fertilizer had no significant effect on soil NO3-N and total N levels. This study demonstrates that application of low PMS rate (30 t ha-1) combined with mineral N fertilizer could achieve high agronomic, economic and environmental benefits on farms. Key words: Mixed paper mill sludges, corn yields, N uptake, N efficiency, residual effects, soil N

Description: Yang, J. Y., Huffman, E. C., Drury, C. F., Yang, X. M. and De Jong, R. 2011. Estimating the impact of manure nitrogen losses on total nitrogen application on agricultural land in Canada. Can. J. Soil Sci. 91: 107–122. About 1 million tonnes (1 Tg=1012 g) of livestock manure N are applied to farmland in Canada each year. Comprehensive information on manure N production and losses from manure during on-farm storage, handling and field application is scarce, especially at a regional scale. However, manure N losses during storage and land application are of considerable concern with respect to nitrogen use efficiency and environmental pollution of air, soil and water. In this paper, manure N production, manure N losses during storage and land application and manure N mineralization from organic manure and the resultant manure N available for annual crops were estimated using the Census of Agriculture database, Farm Environmental Management Survey data and manure N loss factors obtained from the literature. A database of fertilizer N application rates for field crops was developed at the regional scale based on recommendations provided in agronomic extension bulletins and fertilizer N sales. Fertilizer N and available manure N (i.e., total manure N produced minus N losses plus N mineralized from manure applied in previous years) were allocated to each of 24 crops at the regional scale from 1981 to 2006. The amount of manure N produced in Canada increased by 18.7% from 0.928 Tg in 1981 to 1.102 Tg in 2006. We estimated that 35.6% of the manure N produced was immediately available to crops, 25.6% was lost during storage and land application and 38.8% was carried over to the next year as organic N. The amount of fertilizer N applied to crops increased dramatically from 0.928 Tg in 1981 to a peak level of 1.68 Tg in 2000. There were significant changes in manure N production and application to farmland both on a regional and a temporal basis.

Description: Atmospheric NH3 is potentially toxic to terrestrial plants, and there are other environmental effects such as haze from (NH4)2SO4 aerosols and N enrichment of ecosystems that are normally very low in N. Toxic levels can arise from atmospheric releases from livestock operations. Plants detoxify NH3 by incorporation of the N into the plant, so direct toxic effects are most likely when plants are growing slowly, as in cold weather. Indirect effects include leaching of nitrates and cations, and cation imbalances, and are most likely in N-poor, non-agronomic settings. The concentrations in air that cause direct toxic effects were summarized, and the corresponding "expected no effect value" (ENEV) was established at 35 nmol NH3 mol-1(48 µg m-3). Critical loads, the threshold flux density of NHx-N to the landscape that causes detrimental effects, were also summarized. The critical load was 10 kg N ha-1 yr-1. Using deposition velocity values from the literature (0.3 to 3.6 cm s-1), the ENEV implies a load flux of 24 to 290 kg N ha-1 yr-1. This is above the critical load, suggesting that critical loads to the landscape are more limiting than are direct toxic effects on plants. Another novel approach was to define an ENEV as the mean compensation point (ENEVcp). Compensation point is the atmospheric concentration below which plants emit NH3 and above which they absorb NH3. Compensation point data were summarized and the ENEVcp was established at 3.7 nmol mol-1 (5.1 µg m-3). This coincides with a load flux of 4.8 to 58 kg N ha-1 yr-1, more consistent with the critical loads. Key words: Priority Substance List, compensation point, ammonia toxicity, atmospheric ammonia

Description: Yan, Y., He, H., Zhang, X., Chen, Y., Xie, H., Bai, Z., Zhu, P., Ren, J. and Wang, L. 2012. Long-term fertilization effects on carbon and nitrogen in particle-size fractions of a Chinese Mollisol. Can. J. Soil Sci. 92: 509–519. The response of soil organic matter (SOM) dynamics to long-term fertilization may be deduced from changes in the accumulation and distribution of different soil organic carbon (SOC) and nitrogen (N) pools. The SOC and N in particle-size fractions were therefore measured to assess the influences of pig manure and synthetic fertilizer application on the characteristics of these pools. A long-term fertilization experiment, established in 1979 in the Mollisol area (Gongzhuling, China) was used for this study. Composite soil samples (0–20cm) were collected in 2005 from 12 treatment plots that had received annual applications of pig manure, synthetic fertilizers or combinations of both. Soils were fractionated into fine clay (

Description: Time domain reflectometry (TDR) was used to estimate soil water storage dynamics in several uncultivated blanket bogs and poor fens in southeastern Newfoundland during the summer growing season. The purpose of the research was to evaluate links between surface moisture conditions, evapotranspiration, and recharge processes in order to elucidate factors that govern blanket peat formation in the region. Water storage changes in the peat/Sphagnum above the water table (ΔSWS) were found to be important storage terms in daily water balance estimates. Daily mean ΔSWS values for bog and fen approximated −0.3 and −0.45 mm, respectively. It was also found that, i) fairly high peat water-holding capacities, ii) frequent atmospheric recharge, iii) atmospheric controls on evapotranspiration, and, iv) the transport of water into the unsaturated zone from the shallow water table via capillary and external wicking processes helped to preclude significant de-watering over the bulk of the peatland surfaces. Recharge via groundwater appears to be an important factor governing moisture conditions requisite for peat accrual and the growth of Sphagnum spp., especially in the fens. Key words: Time domain reflectometry, blanket peats, soil water, evapotranspiration, water table depth

Description: Accurate in situ determination of soil water content is important in many fields of agricultural, environmental, hydrological, and engineering sciences. As numerous soil water content sensors are available on the market today, the knowledge of their performance will aid users in the selection of appropriate sensors. The objectives of this study were to evaluate five soil water sensors in the laboratory and to determine if laboratory calibration is appropriate for the field. In this study, the performances of five sensors, including the Profile Probe™ (PP), ThetaProbe™ , Watermark™, Aqua-Tel™, and Aquaterr™ were compared in the laboratory. The PP and ThetaProbe™ were more accurate than the other soil water sensors, reproducing soil water content using factory recommended parameters. However, when PP was installed on a loamy sand in the field, the same soil that was used for the laboratory evaluation, it overestimated field soil water, especially at depth. Another laboratory experiment showed that soil water content readings from the PP were strongly influenced by soil bulk density. The higher the soil bulk density, the greater was the overestimation of soil water content. Two regression parameters, a0 and a1, which are used to convert the apparent dielectric constant to volumetric water content, were found to increase linearly with the soil bulk density in the range of 1.2 to 1.6 Mg m-3. Finally, the PP was calibrated in the field and a good calibration function was obtained with an r2 of 0.87 and RMSE of 2.7%. The values of a0 and a1 obtained in the field were different from factory recommended parameters (a0 = 2.4 versus 1.6 while a1 = 12.5 versus 8.4) and were independent of soil depth, bulk density, and texture. As such, individual field calibration will be necessary to obtain precise and accurate measurement of soil water content with this instrument. Key words: Soil water content, Profile Probe, calibration, soil water content sensor

Description: Gagnon, B., Ziadi, N. and Grant, C. 2012. Urea fertilizer forms affect grain corn yield and nitrogen use efficiency. Can. J. Soil Sci. 92: 341–351. Controlled-release urea may be a good management strategy to increase the efficiency of N fertilizers. In a 3-yr study (2008–2010) conducted on a clay soil near Quebec City, Canada, we compared the effect of polymer-coated urea (PCU), nitrification inhibitor urea (NIU), dry urea and urea ammonium nitrate 32% (UAN) on corn yield, plant N accumulation and soil NO3-N remaining at harvest. Corn was fertilized with urea and PCU at 50, 100 and 150 kg N ha−1 in addition to an unfertilized control (0 N), and NIU and UAN at 150 kg N ha−1. Urea, PCU, and NIU were pre-plant broadcast whereas UAN was side-banded at the six-leaf stage of corn. Response to N fertilization occurred in all years, but the magnitude of the response varied with years. In wet years (2008 and 2009), PCU and NIU resulted in higher grain yield than urea, but the increase was greater for PCU (+0.8 to 1.6 Mg ha−1) than for NIU (+0.3 to 0.6 Mg ha−1). In a dry year (2010), no significant difference was found between urea, PCU and NIU. Yields and apparent N recovery were comparable for PCU and UAN except in the dry year, when plant N accumulation was much higher for the UAN treatment. At harvest, soil NO3-N was increased by PCU in all years. Economic analysis revealed that despite 30% higher cost, PCU gave comparable net returns at equivalent N rate than UAN in wet years. We conclude that controlled-release urea, particularly PCU, would be an additional option to farmers instead of sidedressed UAN application for fertilizing corn grown in eastern Canada.

Description: Experiments were done to characterize the hydrolyzed solutions of aluminum nitrate, aluminum chloride and aluminum sulfate. The hydrolysis of the dilute solutions (10−3M) was accomplished under reflux process at 92 °C. The results showed that anions associated with Al have an effect on hydrolysis of aluminum and the order of ease of hydrolysis for similar concentrations of Al was NO3 〉 Cl 〉 SO4. The average composition of the hydroxyaluminum cation (Aln(OH)m) was calculated as [Formula: see text] and [Formula: see text] for hydrolyzed solutions of Al(NO3)3, AlCl3, and Al2(SO4)3, respectively. The infrared spectra of the hydrolyzed species of aluminum were obtained by a subtraction technique and infrared peaks at 1410 cm−1 and 1085 cm−1 in the AlCl3 system and at 1435 cm−1 and 1070 cm−1 in the Al2(SO4)3 system were assigned to polynuclear hydroxyaluminum species having been formed due to reflux process.

Description: Dhief, A., Abdellaoui, R., Tarhouni, M., Belgacem, A. O., Smiti, S. A. and Neffati, M. 2011. Root and aboveground growth of rhizotron-grown seedlings of three Tunisian Desert Calligonum species under water deficit. Can. J. Soil Sci. 91: 15–27. In southern Tunisia, plants are subjected to severe drought and many human disturbances, causing the degradation of soils and plants. The study of wild plants and their response to water deficit can facilitate their conservation and help in ecosystem rehabilitation. In this context, the adaptive responses to water deficit of three desert Calligonum species (C. comosum L'Herit, C. azel Maire and C. arich Le Houerou), differing in their topographic location, were studied in rhizotrons under two water regimes. The objectives were to correlate the adaptive ability of these species, with several developmental traits, such as root architecture and growth, aerial growth and height, with environmental and soil properties, and to define which of the three Calligonum species is best adapted to water stress. Water deficit was applied when plants formed two green branches, and measurements were carried out over 8 mo. Under water deficit, all species increased their cumulative root length. In deeper soil layers, only treated C. arich plants developed secondary roots. Under drought, C. azel and C. arich increased their biomass production during the experiment. It seems that C. arich has adapted better to water deficit by developing a deep root system and the greatest root and aboveground biomass. Hence, C. arich is suggested as the best species for early dune stabilization and biomass production.

Description: Information about the dynamics of soil P fractions is useful to predict their bioavailability and risk of P transfer from soils to surface waters. The objective of this study was to assess the effects of cropping systems and nutrient sources on P fractions in a Labarre silty clay (Humic Gleysol). Soil samples (0-15 cm) were collected in 1989, 1994 and 1997 from a field with four cropping systems, combining two crop rotations, barley (Hordeum vulgare L.) monoculture and 3-yr barley-forage rotation, with two tillage operations (chisel and moldboard plowing) as main plots, and two nutrient sources (mineral fertilizer and liquid dairy manure) as subplots. A modified Hedley sequential fractionation scheme was used. The inorganic P (Pi) fractions (resin-P, NaHCO3-Pi, and NaOH-Pi) increase with time in all cropping system and nutrient source combinations. Organic (Po) fraction (NaHCO3-Po and NaOH-Po) changes were related to C inputs and total soil C contents. The barley monoculture combined with mineral fertilizer slightly reduced NaHCO3-Po and NaOH-Po. The barley-forage rotation increased labile Po fractions. Rotation, chisel plowing and liquid dairy manure addition result in a buildup of labile P. A larger labile P increment per unit of P added, in surplus to plant exports, was observed with dairy manure than for mineral fertilizer, suggesting a higher risk of surface water contamination by P. Cropping systems and nutrient sources have a large influence on the changes in P fractions in this fine-textured Gleysolic soil. Key words: P fractions, crop rotations, liquid dairy manure, chisel plowing, moldboard plowing

Description: The distribution of NO3-N in the soil, and N uptake by the crop during the first 12 yr of a long-term rotation study at Swift Current, Saskatchewan were studied. A considerable amount of NO3-N appeared to be leached beyond the rooting zone of the cereal crop in years of above average precipitation and also in some relatively dry years with heavy spring rains. Thus, leaching of NO3-N seemed to occur even under continuous wheat rotations. At all times there was considerable NO3-N situated at the 60- to 120-cm depth. In wet years N uptake by the plants reduced the amount of NO3-N located in the subsoil, but in dry years the amount of NO3-N in the subsoil remained higher throughout the growing season. The latter could result in groundwater pollution, especially if such a soil was fallowed the next year. Fall rye (Secale cereale L.) made more efficient use of mineral N than spring-sown crops. In dry years more NO3-N persisted in the root zone of N-fertilized wheat than in the root zone of unfertilized wheat, but in wet and average years there was little difference due to N application. The average rate of net NO3-N production in fallow land from spring thaw to freeze-up (166 days) was 107 kg∙ha−1. Values ranged from about 60 to 175 kg∙ha−1 with the lowest values being obtained during very dry or very wet years. The quantity of N mineralized (kg∙ha−1) between spring thaw and freeze-up was related to precipitation (mm) by the equation Nmin = 29.0 + 0.20 precipitation for the 0- to 60-cm depth (R2 = 0.65*). Key words: Nitrate leaching, N uptake, crop rotations, N mineralization rate

Description: Organic matter with high C:N ratios accumulated on mineral soil retards cycling of nutrients in semi-mature jack pine (Pinus banksiana Lamb.) ecosystems. To test whether N as ammonium sulfate or as urea stimulates organic matter decomposition, 200 kg N∙ha−1 were applied to mixed L and F horizon material in Warburg respirometer flasks. Soils were incubated at 13 °C and constant 0.3 bar (340%) moisture; O2 consumption was measured as an index of microbial activity. In urea-treated soil, O2 uptake was much higher than with unamended soil over a 7-wk incubation period, and this indicated a marked effect of urea on microbial activity. The fact that ammonium sulfate depressed respiration rates was evidence that stimulation of microbial respiration by urea was not initially related to added N, but rather to an increase in soil-soluble C resulting from soil pH changes during hydrolysis. In the presence of a C source (ethanol), a 5-fold increase in respiration was noted, whereas C and urea together produced a 15-fold increase in activity. These results suggest that readily available energy for microbial growth, rather than N, limits the initial decomposition of L and F materials in this pine stand. Once microbial demand for C is satisfied, a further increase in microbial activity is produced by N addition.

Description: Limitation of tree growth due to inadequate P supply has been found for young plantations following harvesting of old-growth in high rainfall areas of coastal British Columbia. To understand the reasons for P limitation, we investigated P chemistry in mineral soil to 50 cm depth in sites from the Coastal Forest Chronosequence project on Vancouver Island. This allowed comparison of biogeoclimatic subzone (higher rainfall on west than east coast sites) and of time from harvesting disturbance (seral stage). Available (Bray 1) P was significantly higher (P 

Description: From the solubility equilibrium data of basic aluminite at three temperatures, the standard free energy change (ΔG°), enthalpy change (ΔH°), and entropy change (ΔS°) were determined as 160.02 kcal∙mole−1, 65.48 kcal∙mole−1 and 317.1 cal∙deg−1]mole−1, respectively. From these values the free energy of formation (ΔGf°) and the heat of formation (ΔHf°) of basic aluminite was also computed and was 1465.25 kcal∙mole−1 and 1682.08 kcal∙mole−1, respectively.

Description: Selles, F., Campbell, C. A., Zentner, R. P., Curtin, D., James, D. C. and Basnyat, P. 2011. Phosphorus use efficiency and long-term trends in soil available phosphorus in wheat production systems with and without nitrogen fertilizer. Can. J. Soil Sci. 91: 39–52. Efficient use of phosphorus (P) in crop production is important for economic and environmental reasons, and to prolong the life of a limited resource. Short-term studies often show low recovery of fertilizer P, but P use efficiency may be underestimated because the value of residual P in the soil is ignored. Our objective was to determine fertilizer P use efficiency in two wheat production systems [continuous wheat (CW) and a 3-yr rotation of summer fallow-wheat-wheat (FWW)] using data from a 39-yr study (1967–2005) at Swift Current, SK. Each rotation received either P only (P) or nitrogen plus P (NP) fertilizer. Annual grain P removal was monitored (all straw was returned to the soil) and changes in soil available P (0- to 15-cm layer) were measured by the Olsen bicarbonate method. In 1993, subplots which received no additional P were established to evaluate the residual effect of P fertilizer applied in the preceding 27 yr. Where P was applied each year, grain P removal averaged 54 to 78% of fertilizer P, with values as high as 65 to 109% in 1994 to 2005, the period of lowest water deficit. The P-only treatments removed 13% less P in grain, on average, than NP treatments. In the P-nly systems, Olsen P content increased linearly with time, but in the NP systems it reached a maximum after 20–22 yr and then stabilized. The cumulative P balance (fertilizer P minus P removed in grain) accounted for 60% of the variability in Olsen P accumulation over the course of the experiment. In CW, Olsen P content increased by 0.15 kg ha−1 for each kg ha−1 of P added in excess of crop removal. The rate of Olsen P accumulation was greater (0.20 kg ha−1 for each kg ha−1 of excess fertilizer P) in the FWW rotation possibly due to P mineralization during the summer fallow year. When P was withheld between 1994 and 2005, total grain production in the CW rotation was reduced slightly (by 10%), but there was no significant effect on FWW. Crop P removal (1967–2005) where P was withheld in the final 12 yr was equivalent to 105 and 90% of fertilizer P added to the NP and P-only systems, respectively. We concluded that residual P in prairie soils is retained in forms that are available to plants; wheat crops may therefore recover close to 100% of applied fertilizer P given sufficient time.

Description: Wang, E., Cruse, R. M., Chen, X. and Daigh, A. 2012. Effects of moisture condition and freeze/thaw cycles on surface soil aggregate size distribution and stability. Can. J. Soil Sci. 92: 529–536. Freeze/thaw cycles can affect soil aggregate stability, which in turn impacts wind and water erosion. The objectives of this laboratory study were: (1) to determine the effect of variable freeze/thaw cycles and soil water conditions on aggregate size distribution and stability; and (2) to evaluate differences in aggregate size distribution and stability between disturbed soil and undisturbed soil cores as affected by freeze/thaw cycles and soil water conditions. Surface soil was collected before freezing in late fall of 2009. Aggregates isolated from disturbed soil or intact soil cores were subjected to a factorial combination of 3 gravimetric water content treatments: 0.15 m3 m−3, 0.23 m3 m−3 or 0.30 m3 m−3, and 3 freeze/thaw treatments: 0, 3, or 9 cycles. A freeze/thaw cycle involved soil freezing at –10∘C for 24 h, followed by thawing at 5∘C for 24 h. Most aggregate size classes were affected significantly (P5 mm. Dry-sieved aggregates were relatively more sensitive to the freeze/thaw treatment than wet-sieved aggregates. The mean weight diameter (MWD) of dry-sieved aggregates was significantly (P