Lee, Y. H., Kim, M. K., Lee, J., Heo, J. Y., Kang, T. H., Kim, H. and Yun, H. D. 2013. Organic fertilizer application increases biomass and proportion of fungi in the soil microbial community in a minimum tillage Chinese cabbage field. Can. J. Soil Sci. 93: 271-278. This study evaluated the variations in soil microbial communities in a minimum tillage upland field used for Chinese cabbage (Brassica rapa L.) cultivation by their fatty acid methyl ester (FAME) and chemical properties. Replicated plots received organic fertilizer (OF), chemical fertilizer (CF), and no fertilizer (NF), and microbial communities were analyzed in the early season, mid-season and harvesting stages. The electrical conductivity of the CF soil at mid-season was significantly higher than that of the OF and NF soils (P < 0.05), whereas the NO₃-N content at the harvesting stage was significantly lower in the CF soil than in the OF soil (P < 0.05). The average microbial biomasses in the OF soils during the Chinese cabbage growing period were approximately 1.03~1.27 times higher for fungi, Gram-negative bacteria, total bacteria, total FAMEs, Gram-positive bacteria, and arbuscular mycorrhizal fungi (AMF). Organic fertilizer had a significantly lower ratio of cy19:0 to 18:1ω7c then CF (P < 0.001), which indicates that a decrease in microbial stress was caused by organic matter soil inputs and the lack of chemical amendments. Communities of fungi in OF soils were significantly larger than those in CF soils (P < 0.001) indicating fungi are potentially responsible for the microbial community differentiation between the OF and CF treatments in an upland field. However, the average microbial communities in the OF soils were approximately 0.86 times lower for actinomycetes and 0.95 times lower for AMF. In communities of total bacteria (P < 0.001), Gram-negative (P < 0.001) and Gram-positive bacteria (P < 0.01), the interaction between the growth stage and the fertilizer showed significant differentiation. Further work is needed to relate the seasonal variation and impact of fertilization on microbial communities to productivity of Chinese cabbage in Korea.

Snowdon, E., Zebarth, B. J., Burton, D. L., Goyer, C. and Rochette, P. 2013. Growing season N₂O emissions from two-year potato rotations in a humid environment in New Brunswick, Canada. Can. J. Soil Sci. 93: 279-294. Few studies have examined the effects of crop rotation on N₂O emissions. This study quantified N₂O emissions from seven 2-yr potato rotations over a 3-yr period, 2008-2010, where the potato phase was present in 2008 and 2010. In addition, the potential to predict variation in cumulative growing season N₂O emissions was examined using indices of nitrate availability [nitrate exposure (NE), a time integrated measure of soil nitrate concentrations in the surface soil], carbon availability (cumulative growing season CO₂ emissions) and aeration [time-weighted average water-filled pore space (WFPS)]. In the potato phase of the rotations, even for treatments receiving the same fertilizer N rate (193 kg N ha^-1), a wide range in cumulative growing season N₂O emissions was measured in both 2008 and 2010 (0.39-1.49 and 0.81-2.03 kg N ha^-1, respectively). The NE explained 52 and 70% of the variation in growing season N₂O emissions under potato production in 2008 and 2010, respectively. Carbon availability also had a significant effect on N₂O emissions, as indicated by increased N₂O emissions in rotations where residues of the preceding crop resulted in increased CO₂ emissions early in the growing season. A large proportion (67%) of the variation in cumulative N₂O emissions among rotation crops was also explained by NE. Choice of rotation crop resulted in an almost twofold difference (0.9-1.7 kg N ha^-1) in N₂O emissions over the 2-yr rotation cycle. Greater N₂O emissions over the 2-yr rotation cycle were measured for rotation crops of soybean, Italian ryegrass, red clover and potato than for rotation crops of corn, canola and barley. However, the fertilizer N management in both the potato and rotation crop phases may be as or more important than the choice of rotation crop in influencing the risk of N₂O emissions.

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.

Hahn, A. S. and Quideau, S. A. 2013. Shifts in soil microbial community biomass and resource utilization along a Canadian glacier chronosequence. Can. J. Soil Sci. 93: 305-318. We aimed to describe soil microbial community composition and functional diversity as well as determine the influence of Engelmann spruce (Picea engelmannii Parry) and yellow mountain avens (Dryas drummondii Rich.) on soil microbial community succession along a Canadian glacier chronosequence. Soil microbial composition and functional activity were assessed using phospholipid fatty acid (PLFA) analysis, substrate-induced respiration and enzyme activity analysis. To the best of our knowledge, this is the first study investigating peroxidase and phenol oxidase activities, indicators of fungal activity, along any glacial chronosequence. While no difference in soil microbial community composition along the chronosequence was detected from the PLFA analysis, both total microbial biomass and fungal activity increased with time since deglaciation. Yellow mountain avens, a plant known to support microbial nitrogen fixation in mid- and late successional stages, increased soil microbial biomass, although this effect took 40 yr after deglaciation to emerge. Additionally, significant correlations between microbial respiration of N-acetyl-glucosamine, protocatechuic acid, glucose and percent soil N were found along the chronosequence, indicating that the soil microbial community was influencing changes in the soil environment.

Ziadi, N., Gagnon, B. and Nyiraneza, J. 2013. Crop yield and soil fertility as affected by papermill biosolids and liming by-products. Can. J. Soil Sci. 93: 319-328. Papermill biosolids (PB) in combination with alkaline industrial residuals could benefit agricultural soils while diverting these biosolids from landfill. A greenhouse study was conducted to evaluate the effect of three types of PB at rates of 0, 30, and 60 wet Mg ha^-1, as well as five liming by-products at 3 wet Mg ha^-1 along with 30 Mg PB ha^-1 on crop yield, nutrient accumulation, and soil properties. De-inking paper biosolids (DB, C/N of 65) were applied to soybean [Glycine max (L.) Merr.], and two combined PB (PB₁, C/N of 31; and PB₂, C/N of 14) were applied to dry bean (Phaseolus vulgaris L.) and barley (Hordeum vulgare L.), respectively. The liming by-products included lime mud (LM), wood ash (WA) from paper mills, commercial calcitic lime (CL), Mg dissolution by-product (MgD), and Mg smelting and electrolysis work (MgSE). Compared with the control, PB₂ increased barley yield and total Mg and Na accumulation, and both PB increased plant N, P, and Ca accumulation in barley and dry bean. The impact of DB on soybean was limited. The addition of liming by-products to PB or DB did not affect crop attributes except the combination with MgSE, which severely reduced the growth of dry bean and, to a lesser extent, soybean. Soil NO₃-N was immobilized following DB application, whereas there was a net release with both PB. Combining PB and liming by-products produced the greatest changes in soil properties at harvest. Generally, LM and CL raised pH and Mehlich-3 Ca, and MgSE caused a strong increase in Mehlich-3 Mg and Na and water-soluble Cl. When used with appropriate crops, biosolids from paper mills and alkaline residuals other than MgSE can efficiently enhance soil fertility by providing organic C and macronutrients for balanced crop fertilization.

Zhao, Z., MacLean, D. A., Bourque, C. P.-A., Swift, D. E. and Meng, F.-R. 2013. Generation of soil drainage equations from an artificial neural network-analysis approach. Can. J. Soil Sci. 93: 329-342. Soil properties, especially soil drainage, are known to be related to topo-hydrologic variables derived from digital elevation models (DEM), such as vertical slope position, slope steepness, sediment delivery ratio, and topographic wetness index. Such relationships typically are strongly non-linear and thus difficult to define with conventional statistical methods. In this study, we used artificial neural network (ANN) models to establish relationships between soil drainage classes and DEM-generated topo-hydrologic variables and subsequently formulated the relationships to generate soil drainage equations for soil mapping. A high-resolution field soil map of the Black Brook Watershed in northwest New Brunswick, Canada, was used to calibrate/validate the ANN models, and the obtained equations. Independent data from an experimental farm, about 180 km away, were also used for validation. Results indicated that vertical slope position was the best predictor of soil drainage classes (r=0.55), followed by slope steepness (r=0.44), sediment delivery ratio (r=0.39), and topographic wetness index (r=0.38). The obtained soil drainage equations fitted well to the ANN model predictions (r²=0.78-0.99; root mean squared error=0.39-4.55). Analyses indicated that soil drainage equations clearly reflected the actual relationships between soil drainage classes and DEM-generated topo-hydrologic variables, and have the potential to minimize bias originated from over-training the ANN models when applied outside the area of calibration, especially when the ranges of input variables were outside of the range of calibration data.

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.

Baugé, S. M. Y., Lavkulich, L. M. and Schreier, H. E. 2013. Phosphorus and trace metals in serpentine-affected soils of the Sumas Basin, British Columbia. Can. J. Soil Sci. 93: 359-367. Soils of the Sumas watershed in the Lower Fraser Valley of British Columbia have contrasting P, Mg and trace elements contents arising from two major sources, periodic deposition of serpentine-rich sediments and intensive agricultural activities. Four study sites were examined for soil P by several extractants commonly used for P availability assessments. The results were compared with aqua regia to determine best estimates of extractable P. In addition, these extractants were evaluated as indices of associated trace metal amounts. Aqua regia, acid ammonium oxalate and 1 M HCl extracted similar amounts of P and trace metals. Acid ammonium oxalate was found to be closely related to the estimates of total P and recoverable elements, followed by 1 M HCl. There was clear separation of the sites by both P values and trace elements associated with serpentine (Cr and Ni) and those from agricultural activities (Cu and Zn). Results suggest that a single extraction, 1 M HCl, can be an effective measure of both available P and trace elements in serpentinitic soils.

Bork, E. W., Lambert, B. D., Banerjee, S. and Blonski, L. J. 2013. Soil mineral nitrogen responses following liquid hog manure application to semiarid forage lands. Can. J. Soil Sci. 93: 369-378. Expansion of intensive livestock operations into semiarid regions lacking cultivated lands requires consideration of perennial forages for the efficient and sustainable disposal of manure. Little information exists on the nutrient dynamics associated with the application of manure to these areas. We examined soil mineral nitrogen (N) responses in four sites of the mixed-grass prairie, including two native grasslands and two introduced pastures, following different seasons (fall vs. spring), methods (dribble broadcast vs. coulter injected) and rates of liquid hog manure application (9.4, 18.8, 37.5, 75 and 150 kg ha^-1 available N). Soil mineral N, including NO₃-N, NH₄-N and total mineral N, were assessed after application but prior to plant growth in April 1999, and again one growing season later in April 2000. Initial soil N did not vary with season of application. Soil mineral N predictably increased with application rate, but only in the upper soil profile (0-20 cm). Decreases in soil mineral N after one growing season in all treatments highlighted the ability of these perennial forage lands to immobilize large amounts of soil N, a significant portion of which was related to N uptake by vegetation. Compared with broadcast application, manure injection led to 35% greater soil mineral N (both NO₃ and NH₄) prior to plant growth, a response that persisted 1 yr later ( 12%), thus demonstrating the N conserved benefits of manure incorporation. Overall, increases in soil mineral N within these forage lands appeared to be relatively short-term in nature, largely depleting over the course of a single growing season, suggesting one-time liquid hog manure application at low to moderate rates may be sustainable in this region of the mixed-grass prairie.

Fraser, T. J. and Amiro, B. D. 2013. Initial carbon dynamics of perennial grassland conversion for annual cropping in Manitoba. Can. J. Soil Sci. 93: 379-391. Sequestering atmospheric carbon in agricultural soil is an attractive option for mitigation of rising atmospheric carbon dioxide concentrations. Perennial crops are more likely to gain carbon whereas annual crops are more likely to lose carbon. A pair of eddy covariance towers were set up near Winnipeg Manitoba, Canada, to measure the carbon dioxide flux over adjacent paired perennial grass hay fields with high soil organic carbon. A Treatment field was converted to annual cropping by spraying with herbicide, cutting and tilling. A Control field was cut, but allowed to re-grow. Differences in net ecosystem productivity between the fields were mainly caused by a loss of gross primary productivity in the Treatment field; ecosystem respiration was similar for both fields. When biomass removals and manure applications are included in the carbon budget, the Treatment field lost 149 g C m^-2 whereas the Control field sequestered 96 g C m^-2, for a net difference of 245 g C m^-2 over the June to December period (210 d). This suggests that perennial grass converted for annual cropping can lose more carbon than perennial grassland can sequester in a season.