Gao, X., Tenuta, M., Nelson, A., Sparling, B., Tomasiewicz, D., Mohr, R. M. and Bizimungu, B. 2013. Effect of nitrogen fertilizer rate on nitrous oxide emission from irrigated potato on a clay loam soil in Manitoba, Canada. Can. J. Soil Sci. 93: 1-11. This study examined the effect of N fertilizer application rate on N₂O emissions for irrigated potato production on a clay loam soil near Carberry, Manitoba, over two growing seasons. Treatments were an unfertilized control, and urea-N fertilizer application rates of 80, 160 and 240 kg N ha^-1, which were applied as split applications. The marketable yield increased at 80 kg N ha^-1 relative to the unfertilized control, but did not respond to higher rates of fertilizer. Peak emission of N₂O followed fertilizer application and rain or irrigation events. Emission rates following fertilizer application and water addition events were greater from hill than from furrow position in 2009, but not in 2010. In the latter, ponding of water in furrows likely resulted in the greater emissions than from the hill positions. Cumulative N₂O emissions and yield based N₂O intensity increased linearly with N application rate. The growing season emission factor (EF_gs) for percent of added N emitted as N₂O was 0.73% and did not increase with N application rate. The adjusted whole-year emission factor (EF_wy) assuming 30% of annual emissions are emitted during winter and thaw was 1.04%, being lower than the Canadian IPCC Tier II protocol value of 1.72% for irrigated cropland in Canada. The lower measured EF_wy may be because the protocol assumes that under irrigation water input (rain plus irrigation) equals potential evapotranspiration (PET) from May to October, implying no restriction of N₂O emissions by water limitation. For the current study, however, the ratio of water input to PET averaged 70%, suggesting water may have restricted N₂O emission, therefore resulting in a lower EF_wy than predicted by the Tier II protocol. The results of the current study also suggest that a reduction in N₂O emissions can be achieved by avoiding fertilizer N applications beyond optimal for marketable yield, limiting irrigation soon after application of N fertilizer, and managing irrigation to prevent ponding of water in furrows.

Zhou, X. and Wu, F. 2013. Artificially applied vanillic acid changed soil microbial communities in the rhizosphere of cucumber (Cucumis sativus L.). Can. J. Soil Sci. 93: 13-21. Phenolic acids (PAs) have been implicated as autotoxins of cucumber (Cucumis sativus L.), but doubts about the importance of these compounds also exist due to their low concentrations in the field. The physiological alterations caused by PAs are concentration dependent, and the range of bioactivity is between 0.1 and 1 mM. Here, vanillic acid (VA) (0.02, 0.05, 0.1, 0.2 µmol g^-1 soil) was applied into the soil every other day for five times. The effects of VA on C. sativus seedling growth and rhizosphere soil microbial communities were evaluated. Soil bacterial and fungal community structures and sizes were analyzed with polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE) and real-time PCR methods, respectively. Vanillic acid significantly inhibited C. sativus seedling growth at concentrations ≥ 0.05 µmol g^-1 soil, and stimulated soil dehydrogenase activity, soil microbial biomass carbon content, and soil bacterial and fungal community sizes at all concentrations tested. Vanillic acid also caused shifts in rhizosphere soil bacterial and fungal community structures. Overall, VA could change rhizosphere soil microbial communities even when the VA concentration was lower than the level that produced a significant phytotoxic effect in cucumber.

Congreves, K. A., Voroney, R. P., O'Halloran, I. P. and Van Eerd, L. L. 2013. Broccoli residue-derived nitrogen immobilization following amendments of organic carbon: An incubation study. Can. J. Soil Sci. 93: 23-31. Cole crops, compared with many other crops, can pose a high risk of N losses after harvest due to substantial quantities of readily mineralizable N in crop residues. Organic C amendments (OCA) may reduce N losses via immobilization; however, the synchrony of OCA decomposition and cole crop residue N mineralization is crucial. A soil incubation study evaluated net N and C mineralization of broccoli residue-derived N or fertilizer-derived N with three OCAs: wheat straw, yard waste, or used cooking oil, to predict N immobilization and the potential to mitigate post-harvest N losses. By the 56th d of incubation, broccoli residue mineralized 67.0 mg N kg^-1. In the broccoli residue-derived N treatments, wheat straw, yard waste, and used cooking oil significantly reduced the quantity of net N mineralization by 16.9, 12.3, and 86.0 mg N kg^-1, respectively. The net N mineralization data were fitted to a first-order exponential model, and the overall trend of OCA was negative, indicating immobilization, whether N was derived from broccoli residue or fertilizer. The order of effect from OCAs on N immobilization corresponded to the order of effect on net C mineralization, where wheat straw and yard waste were lower than used cooking oil. In broccoli residue treatments, compared with fertilizer, higher N immobilization occurred for used cooking oil, and higher net C mineralization occurred for used cooking oil and yard waste. The higher N immobilization and net C mineralization suggest that broccoli residue produced a synergistic effect on the decomposition of used cooking oil. Additionally, both broccoli residue and used cooking oil treatments had synchronous peaks of net C mineralization at 4 d. This study provides evidence to warrant field studies to confirm that the application of organic C, especially used cooking oil, after cole crop harvest may be a beneficial management practice to minimize soil N losses.

Lafond, J. et Ziadi, N. 2013. Biodisponibilité de l'azote et du phosphore dans les sols de bleuetières du Québec. Can. J. Soil Sci. 93: 33-44. L'évaluation de la biodisponibilité de l'azote (N) et du phosphore (P) dans les sols de bleuetières est essentielle pour établir des recommandations en fertilisants. Les objectifs de cette étude ont été (i) d'évaluer la biodisponibilité de l'ammonium et du P du sol par différentes méthodes à la suite d'application de fertilisants azotés et phosphatésà la culture de bleuet sauvage (Vaccinium angustifolium Ait.), (ii) de déterminer le meilleur indicateur de la biodisponibilité du N et du P du sol selon la productivité et les analyses foliaires et (iii) d'établir des classes de fertilité des sols pour cette culture. Les traitements ont consisté en quatre doses de N (0, 30, 60 et 90 kg N ha^-1) et quatre doses de P (0, 30, 60 et 90 kg P₂O₅ ha^-1). L'ammonium a été extrait au KCl (N-NH_4KCl), à l'eau (N-NH_4W) et à l'aide de membranes d'échange cationique (N-NH_4MEC). Le phosphore a été extrait au Mehlich 3 (P_M3), à l'eau (P_W) et à l'aide de membranes d'échange anionique (P_MEA). Les teneurs en N et en P du sol ont diminué au cours des saisons avec une accumulation de P dans la couche de sol de surface. Les fractions solubles du N du sol (N-NH4_W) ont été les mieux corrélées à la concentration en N des feuilles (0,28 < r < 0,78) et aux rendements en fruits (0,38 < r < 0,48). Le P_M3 a été le mieux corrélé à la concentration en P des feuilles (r = 0,30) et aux rendements en fruits (r=0,36). Ainsi, le N-NH4_W et le P_M3 sont les meilleurs indicateurs de la disponibilité du N et P du sol au bleuet sauvage. À partir de ces indices, des seuils critiques au-delà desquels la fertilisation n'est plus requise, ont été établis à 3,1 mg kg^-1 pour le N-NH_4W, à 52 mg kg^-1 pour le P_M3 et à 0,028 pour le rapport molaire P_M3/(Fe Al)_M3.

Sheibani, S., Yanni, S. F., Wilhelm, R., Whalen, J. K., Whyte, L. G., Greer, C. W. and Madramootoo, C. A. 2013. Soil bacteria and archaea found in long-term corn (Zea maysL.) agroecosystems in Quebec, Canada. Can. J. Soil Sci. 93: 45-57. The soil microbial community controls all biological processes in soils and is considered a good indicator of general soil health. Assessment of the microbial community in intensively cropped soils that are under reduced tillage management is especially important because the microbes are the primary decomposers of the high residue input in such systems. We investigated the microbial biomass and diversity of bacteria and archaea in a sandy-loam Dystric Gleysol from a long-term (15 yr) corn (Zea mays L.) agroecosystem in Quebec, Canada, under conventional (CT), reduced tillage (RT), and no tillage (NT) and two residue inputs (high level: R and low level: -R). Analysis included microbial biomass C and N (MBC, MBN), catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH) and 5-(4, 6-dichlorotriazinyl) amino fluorescein hydrochloride (DTAF) cell counts, 16S rRNA polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and an archaeal clone library. The PCR-DGGE analysis identified Proteobacteria, Actinobacteria and Firmicutes as dominant groups in all tillage and residue management treatments. The archaeal group was diverse, with most individuals identified as belonging to the Crenarchaeota phylum. We also detected soil archaea belonging to the newly proposed phylum Thaumarchaeota, the chemolithoautotrophic ammonia-oxidizing archaeota, in a corn agroecosystem in Quebec, Canada. Microbial biomass increased in the R treatment according to MBC concentration and direct cell counts. Considering results from the CARD-FISH counts (bacterial and archaeal cell counts without fungal cells) and from MBC results (all microbial biomass including fungi) we concluded the likelihood of greater fungal biomass in the NT plots.

Roper, J. D., Burton, D. L., Madani, A. and Stratton, G. W. 2013. A simple method for quantifying dissolved nitrous oxide in tile drainage water. Can. J. Soil Sci. 93: 59-64. It is often assumed that the N₂O produced from nitrification and denitrification in soil systems is lost primarily as a gas from the soil surface. However, the dissolution and eventual degassing of N₂O in water leaching through, and draining from, agricultural fields is also a significant loss pathway. The quantification of this pathway of N₂O loss has been limited by available methodologies for measuring dissolved gases in drainage water. Here a simple method is presented, which allows for the collection of tile drainage water samples using standard automated water sampling equipment that maintains the dissolved gases. Tile drainage water was collected in 1 L ISCO™ water sampling bottles outfitted with modified 10 mL volumetric pipettes. The pipettes provide a means of reducing the water:atmosphere interface for water held within the pipette thus reducing the N₂O exchange with the atmosphere. The water samples are removed from the pipette using long slender needles attached to a 20-mL syringe, drawing 5 mL of water from within the bulb of the pipette. The dissolved N₂O in the water samples was measured by headspace analysis using a gas chromatograph. A laboratory trial determined that retaining the water in the pipette bulbs resulted reduced N₂O degassing such that N₂O concentration did not decrease significantly in the first 24 h after filling of the bottle.

Zhao, P., Shao, M-a., Omran, W. and She, D. 2013. A modified model for estimating the full description of soil particle size distribution. Can. J. Soil Sci. 93: 65-72. A full description of the particle size distribution (PSD) curve is widely used as a basis for estimating soil hydraulic properties. However, the incomplete experimental data of PSD sets (i.e., percent clay, silt, and sand) often limit its uses. In this study, an empirical model modified from the Weibull model was used to estimate the complete description PSD from clay, silt and sand fractions. Results show that the estimated distribution agrees reasonably well with the actual distribution for 168 soils samples studied within six different textures. The values of coefficients of determination, the average absolute deviation and the maximum absolute deviation were 98.6%, 3.3% and 12.6%, respectively. The modified model performed best for silt loam samples containing about 70% silt content. The estimation accuracy varied with radii interval. For the estimated PSD curve, a 0.05-0.1 mm size interval was most poorly estimated and had the maximum deviation (28.2%), while the 0.5-1 mm interval was estimated well by the modified model. The model is recommended to estimate complete soil PSD using only clay, silt and sand fractions, which can be well fitted by the Weibull model. Further studies are suggested to validate the PSD estimation by this model when applied to soils with greater variation in texture.

Zhao, Z., Ashraf, M. I. and Meng, F.-R. 2013. Model prediction of soil drainage classes over a large area using a limited number of field samples: A case study in the province of Nova Scotia, Canada. Can. J. Soil Sci. 93: 73-83. Soil drainage maps are frequently required for crop, forest, and environmental management. However, modelling soil drainage over a large area (>1000 km²) is difficult due to complex soil-forming processes, large spatial variations, and the limited number of field samples, which are often insufficient to reflect local variations. In this study, a two-stage approach was used to produce soil drainage maps over a large area (the province of Nova Scotia). In the first stage, an existing soil drainage model developed in a small watershed with a sufficient number of field samples that could represent local topography was adopted. As a comparison, an artificial neural network model was built and calibrated with 1545 field samples across the province of Nova Scotia. Both models were used directly to predict soil drainage maps in the province of Nova Scotia. Results indicate that both models produced poor predictions. In the second stage, after dividing the entire provincial area into sub-areas (landforms) based on different division methods, corresponding linear transformation models were subsequently developed to adapt soil drainage classes produced by a base model (the existing soil drainage model) to fit field samples. Parameters of linear transformation models were estimated with field samples. Results indicate that the best linear transformation model was composed of 12 linear equations corresponding to 12 landforms (combinations of ecoregion and texture), and improved the prediction of rapidly drained (9.6%), well-drained (21.3%), moderately well-drained (14.1%), and imperfectly drained (7.5%) plots compared with the base model. Thus, the two-stage approach can obviously improve the accuracy of predicted soil drainage classes over a large area.

Zhang, Y., Wu, P., Zhao, X. and Wang, Z. 2013. Simulation of soil water dynamics for uncropped ridges and furrows under irrigation conditions. Can. J. Soil Sci. 93: 85-98. The ridge-furrow planting system combined with furrow irrigation can effectively increase soil moisture storage and improve water use efficiency in the semi-arid region of China. The precise soil water dynamics in ridge-furrow systems must be known in order to properly design ridge-furrow geometry and improve irrigation uniformity while reducing deep water percolation. The objective of this study was to investigate soil water distribution in the cross-sectional ridge-furrow infiltration, through laboratory experiments and numerical simulations. Six experimental treatments with three soil types (silty clay loam, silt loam, and sandy loam) were tested to monitor both soil water movement and cumulative infiltration in rectangular soil chambers. The HYDRUS-2D model was calibrated and experimentally validated to simulate soil water dynamics. The root mean square error (RMSE) and coefficient of determination (R²) provide a satisfactory quantitative comparison of the goodness-of-fit between observed and simulated cumulative infiltration. The optimized parameters were accurate and the observed and simulated values were very close, which demonstrated HYDRUS-2D as a reliable tool for accurately simulating soil water movement and applied water volume in ridge-furrow irrigation system. In finer soil, the wetted vertical and horizontal distances were equal and soil water distribution was more uniform than that in coarser soil. A high potential of deep water percolation was produced in sandy loam soil. Cumulative infiltration decreased with the increase of initial soil water content, whereas the volume of wetted soil increased with the increase of initial soil water content. Narrow furrows for crops with deep rooting depth and wide furrows for crops with shallow rooting depth were selected in irrigation design. The 40 cm furrow size and higher furrow water depth (water level) were recommended in a ridge-furrow irrigation system.

Sawut, M., Eziz, M. and Tiyip, T. 2013. The effects of land-use change on ecosystem service value of desert oasis: a case study in Ugan-Kuqa River Delta Oasis, China. Can. J. Soil Sci. 93: 99-108. Ecosystem service valuation has been a hot topic in ecological economic research. The objective of this study was to analyze the changes in ecosystem services in response to oasis land-use change. Landsat images of September 2000 and ALOS images of September 2008 were combined with the published ecosystem service value coefficients about the world and China ecosystem to quantify land-use and ecosystem service changes. A sensitivity analysis was employed to determine the effect of manipulating these coefficients on the estimated values. The results indicate that: (1) the total value of ecosystem services in the Ugan-Kuqa River Delta Oasis increased from 8012 million Yuan in 2000 to 8323 million Yuan in 2008, mainly caused by the increasing areas of wetland and high-cover grassland. Forestland produced most of the ecosystem services value of the study area, about 22% of the total value; (2) the aggregated ecosystem service value of forestland, cropland, medium-cover grassland, wetland, and water body was about 85% of the total value, indicating that these land-use categories play important roles in ecosystem services of the area; (3) waste treatment and soil formation were the top two ecological functions with high service value, contributing about 37% of the total services value; and (4) results of sensitivity analysis showed that the total ecosystem services value estimated in this study area was relatively inelastic with respect to the value coefficients. Therefore, the estimation in this study area was robust in spite of uncertainties on the value coefficients. The study suggests that a reasonable land-use plan should be made with emphasis on protecting wetland and grassland for maintaining stability and sustainable development of oases.

Ashworth, J. and Symonds, C. 2013. Simplified Microtox^®bioassay for drilling waste disposal on lease soils in Alberta. Can. J. Soil Sci. 93: 109-111. The Microtox bioassay is specified in regulations governing drilling waste disposal in western Canada. Traditionally, four serial dilutions of waste-derived fluid are tested, to bracket the regulatory Pass threshold concentration. We find that an equally valid Pass/Fail result can be obtained from one test at the threshold concentration. The simplified method has labour and cost-saving advantages.

Kowalenko, C. G. and Ihnat, M. 2013. Residual effects of combinations of limestone, zinc and manganese applications on soil and plant nutrients under mild and wet climatic conditions. Can. J. Soil Sci. 93: 113-125. A field trial from 1979 through 1993 with three limestone and five zinc (Zn) and manganese (Mn) treatments applied at various intervals on several different crops was used to assess residual treatment effects on crop yields and nutrient contents, and Mehlich-3 soil element extractions. Limestone (0, 9 and 19 Mg ha^-1) was applied in 1979, 1981 and 1986. Micronutrients (Zn at 2.3 kg ha^-1 (Zn), Mn at 2.3 kg ha^-1 (Mn1) and 4.5 kg ha^-1 (Mn2), and Zn Mn1) were applied to the foliage of cauliflower in 1979, 1980, 1982, 1984 and 1985, and incorporated into the soil in 1988, 1989 and 1990 prior to growing oats. From 1991 through 1993, the test crop was orchard grass (Dactylis glomerata L.). The historic limestone treatments that were completed in 1986 continued to affect grass growth with up to 7% increase with high limestone rate in cut #2 in 1993. The historic micronutrient treatments (completed in 1988) also affected grass yield to mid-1993, but the nature of the effects was variable (increases, decreases and no effects depending on limestone treatments and micronutrient rate combinations). Concentrations of Ca extracted from the soil in 1993 increased to 60-cm depth with limestone applications. Soil extractable Zn and Mn decreased in response to increased historic limestone applications. The historic Zn and Mn applications increased extractions of corresponding nutrients in surface 15 cm of soil sampled in fall 1993. Limestone applications decreased total C and N in the soils, which has implications on N management and C sequestration. Limestone decreased the apparent availability of several non-treatment nutrients (K, Mg, Na, S and Fe), which could reduce the intended benefit of applying limestone.

Venkatesh, M. S., Hazra, K. K., Ghosh, P. K., Praharaj, C. S. and Kumar, N. 2013. Long-term effect of pulses and nutrient management on soil carbon sequestration in Indo-Gangetic plains of India. Can. J. Soil Sci. 93: 127-136. As an important component of crop diversification, pulses/legumes are known to improve soil quality through their unique characteristics of biological N₂ fixation, root exudates, leaf litter fall and deep root system. Changes in the soil organic carbon pool due to the inclusion of pulses in an upland maize-based cropping system were evaluated after seven cropping cycles. The results indicate that inclusion of pulses in an upland maize-based cropping system improved the total soil organic carbon content, being greater in surface soil (0-0.2 m) and declining with soil depth. Of the four carbon fractions of total soil organic carbon (C frac₁-C frac₄) measured in the upland maize-based system, the most labile C fraction (C frac₁) was dominant. Distribution of the carbon pool varied with depth and the size of the active carbon pool was larger than that of the passive carbon pool in the surface soil, whereas in the subsurface soil depth, the size of the passive carbon pool was larger than that of the active carbon pool. Maize-wheat-mungbean and pigeonpea-wheat systems resulted in significant increases (P≤0.05), of 11 and 10%, respectively in total soil organic carbon, and 10 and 15% in soil microbial biomass carbon, respectively, as compared with a conventional maize-wheat system. Application of crop residues along with farmyard manure at 5 Mg ha^-1 and biofertilizers resulted in greater amounts of carbon fractions and higher carbon management index than in the control and the recommended inorganic (NPKSZnB) treatment, particularly in the system where pulses were included. In plots receiving organic amendments, the variable cumulative carbon input had higher correlation with total organic carbon (R²=0.997), active pool (R²=0.934), passive pool (R²=0.916) and soil microbial biomass carbon (R²=0.664). Inclusion of pulses in the maize-based system and the organic nutrient management system sequestered more organic carbon and maintained better soil health in Inceptisols of the Indo-Gangetic plains of India.

Shrestha, B. M., McConkey, B. G., Smith, W. N., Desjardins, R. L., Campbell, C. A., Grant, B. B. and Miller, P. R. 2013. Effects of crop rotation, crop type and tillage on soil organic carbon in a semiarid climate. Can. J. Soil Sci. 93: 137-146. There is uncertainty about how crop rotation and tillage affect soil organic C (SOC) on the Canadian prairies. We compared SOC amount and change (ΔSOC) for one continuous crop and four 3-yr fallow-containing crop rotations under no-tillage (NT), and two fallow-containing crop rotations under minimum-tillage (MT), from 1995 to 2005 in semiarid southwestern Saskatchewan. After 11 yr, SOC (0- to 15-cm depth) was 0.2 Mg C ha^-1 higher under continuous crop compared with fallow-containing systems. There were no significant differences in SOC and ΔSOC among fallow-containing rotations or between MT and NT. Total C inputs were weakly (R²=0.18) but significantly (P<0.05) correlated to ΔSOC, which changed by ±0.33 Mg C ha^-1 for each Mg ha^-1 C input above or below 2.4 Mg C ha^-1 yr^-1. Carbon inputs were typically less than this amount and SOC generally decreased over the experiment. Simulations of SOC with the Century model were consistent with our observations regarding ΔSOC per unit of C input. There was slight loss of SOC for the above-average precipitation regime during the study. Simulations also supported our finding that SOC differences between crop mix and tillage systems may require several decades to become distinguishable in this semiarid climate with small and variable C inputs.