Ai, Y., Chen, Z., Guo, P., Zeng, L., Liu, H., Da, Z. and Li, W. 2012. Fractal characteristics of synthetic soil for cut slope revegetation in the Purple soil area of China. Can. J. Soil Sci. 92: 277-284. Revegetation of the cut slopes formed during railroad construction can reduce potential hazards, improve the quality of the environment, and beautify the landscape along the railways. Artificial backfill soil is required to anchor the plant roots and satisfy the plant's moisture and nutritional demands on the bare rock face. The soil particle size distribution (PSD), fertility and stability of the reconstructed topsoils are affected by the soil type used as a backfill. In this study, a fractal method was used to characterize the PSD. The relationships between the fractal dimension of the PSD and selected soil properties, including soil moisture, bulk density, and organic carbon are discussed. Various soil samples were obtained from four different land-use environments in the purple soil area in southwest, China: a cut slope reconstructed from rock fragments (RF), a cut slope reconstructed with agricultural soil (AS), a naturally developed slope (NS), and a cropland used for growing Vicia faba (CL). Analysis of the soil samples revealed that: (1) from CL to RF, the sand content increased from 59.6 to 83.9%; (2) the fractal dimension of PSD ranged from 2.605 for RF to 2.725 for CL, being the greater the sand content and the lower the fractal dimension; (3) there existed marked linear relationships between the fractal dimensions and selected physicochemical properties of the soils. Therefore, the fractal dimension of PSD can be a useful parameter with which to monitor the structural deterioration and nutrient loss of the synthetic soils used for the revegetation of a cut slope.

Saso, J. K., Parkin, G. W., Drury, C. F., Lauzon, J. D. and Reynolds, W. D. 2012. Chloride leaching in two Ontario soils: Measurement and prediction using HYDRUS-1D. Can. J. Soil Sci. 92: 285-296. Deterministic numerical modelling can often be used to complement and extend field results, and to provide extra insight into the mechanisms of water and solute movement within the profile of agricultural soils. Chloride leaching and near-surface soil water content in a Guelph loam and a Maryhill loam cropped to corn (Zea mays L.) were measured over a 12-mo period (October 2007 to September 2008) and simulated using the HYDRUS-1D numerical model (version 4.12). Field measurements and prediction indicated that over 70% of the applied chloride (Cl) was lost to deep drainage (below 80 cm depth) during the winter months (November 2007 to April 2008) in both soils. Normalized root mean square error (NRMSE) values for HYDRUS-1D estimates of near-surface (0- to 30-cm depth interval) soil water content over the growing season (April to September, 2008) were 28% for Guelph loam and 42% for Maryhill loam. The NRMSE value for estimated versus measured Cl mass remaining in the soil profile (0-80 cm depth interval) over the winter months was 17% for both soils. It was concluded that the HYDRUS-1D model can provide reasonable predictions of near-surface soil water content and profile leaching losses of tracer solutes. Further work is required, however, to determine if the predictive ability of HYDRUS-1D might be improved by incorporating the effects of freeze-thaw cycles on soil hydraulic properties and solute leaching. Further study is also required to establish the model's ability to simulate the leaching behaviour of reactive solutes, such as nitrate, in agricultural soils.

Wang, Z., Coburn, C. A., Ren, X. and Teillet, P. M. 2012. Effect of soil surface roughness and scene components on soil surface BRF. Can. J. Soil Sci. 92: 297-313. Bidirectional Reflectance factor (BRF) data of both rough [surface roughness index (SRI) of 51%] and smooth soil surfaces (SRI of 5%) were acquired in the laboratory under 30° illumination zenith angle using a Specim V10E imaging spectrometer and an Ocean Optics non-imaging spectrometer mounted on the University of Lethbridge Goniometer System version 2.5 (ULGS-2.5) and version 2.0 (ULGS-2.0), respectively. Under controlled laboratory conditions, the rough soil surface exhibited higher spectral reflectance than the smooth surface for most viewing angles. The BRF of the rough surface varied more than the smooth surface as a function of the viewing zenith angle. The shadowing effect was stronger for the rough surface than for the smooth surface and was stronger in the forward-scattering direction than in the backscattering direction. The pattern of the BRF generated with the non-image based data was similar to that generated with the whole region of interest (ROI) of the image-based data, and that of the whole ROI of the image-based data was similar to that of the illuminated scene component. The BRF of the smooth soil surface was dominated by illuminated scene component, i.e., the sunlit pixels, whereas the shaded scene component, i.e., the shaded pixels, was a larger proportion of the BRF of the rough soil surface. The image-based approach allowed the characterization of the contribution of spatial components in the field of view to soil BRF and improved our understanding of soil reflectance.

Kariyapperuma, K. A., Furon, A. and Wagner-Riddle, C. 2012. Non-growing season nitrous oxide fluxes from an agricultural soil as affected by application of liquid and composted swine manure. Can. J. Soil Sci. 92: 315-327. Agricultural soils have been recognized as a significant source of anthropogenic nitrous oxide (N₂O) emissions, an important greenhouse gas and contributor to stratospheric ozone destruction. Application of liquid swine manure (LSM) has been reported to increase direct N₂O emissions from agricultural soils. Composting of LSM with straw under forced aeration has been suggested as a mitigation practice for emissions of N₂O. In cold climates, up to 70% of total annual soil N₂O emissions have been observed during winter and spring thaw. Non-growing season soil N₂O emissions after field application of composted swine manure (CSM) versus LSM have not been directly compared in past studies. A 2-yr field experiment was conducted at the Arkell Research Station, Ontario, Canada, as a part of a larger study to evaluate composting as a mitigation strategy for greenhouse gases (GHGs). The objectives were to quantify and compare non-growing season N₂O fluxes from agricultural soils after fall application of LSM and CSM. Nitrous oxide fluxes were measured using the flux-gradient method. Compared with LSM, CSM resulted in 57% reduction of soil N₂O emissions during February to April in 2005, but emissions during the same period in 2006 were not affected by treatments. This effect was related to fall and winter weather conditions with the significant reduction occurring in the year when soil freezing was more pronounced. Compared with LSM, CSM resulted in a reduction of 37% (CO₂-eq) of estimated N₂O emissions per liter of treated manure and of 50% in the emission factor for the non-growing season.

Robertson, S. J., Rutherford, P. M., López-Gutiérrez, J. C. and Massicotte, H. B. 2012. Biochar enhances seedling growth and alters root symbioses and properties of sub-boreal forest soils. Can. J. Soil Sci. 92: 329-340. Biochar application may enhance soil properties, improve plant productivity, and increase long-term carbon storage, but impacts of biochar on plant-microbe symbioses mediating plant nutrient uptake in temperate or boreal soils are not well known. We planted lodgepole pine (Pinus contorta var. latifolia) or sitka alder (Alnus viridis ssp. sinuata) seeds in pots containing field-collected forest soils (from central British Columbia) amended with 0, 5, or 10% (dry mass basis) biochar with and without urea fertilizer (150 mg N kg^-1). Pine seedlings were harvested at 4 mo and roots were assessed for abundance and diversity of ectomycorrhizal (ECM) morphotypes using light microscopy and DNA sequencing. Biochar raised soil pH, exchangeable cations and cation exchange capacity in some treatments in both soils. Pine had greater biomass in biochar fertilizer treatments compared to control and fertilizer-only treatments; this corresponded in part to an increase in abundance of some ECMs. Alder seedlings were harvested at 2, 3 and 4 mo to measure N fixation in root nodules using acetylene reductase assay (ARA). Alder seedlings had greater shoot biomass when grown in biochar-amended soils compared with unamended control. Although mean ARA rates (at 4 mo) were greater in biochar-amended soils compared with controls, the data showed great variation and differences were not statistically significant (P>0.05). This study showed that biochar addition can enhance soil properties and the early growth of pine and alder in some sub-boreal forest soils; small changes in ECM abundances may be expected.

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.

O'Reilly, K. A., Lauzon, J. D., Vyn, R. J. and Van Eerd, L. L. 2012. Nitrogen cycling, profit margins and sweet corn yield under fall cover crop systems. Can. J. Soil Sci. 92: 353-365. In order to improve N best management practices in southwestern Ontario vegetable farming, the effect of cover crops on N dynamics in the fall and spring prior to sweet corn planting and during sweet corn season was assessed. The experiment was a split plot design in a fresh green pea - cover crop - sweet corn rotation that took place over 2 site-years at Bothwell and Ridgetown in 2006-2007 and 2007-2008, respectively. The main plot factor was fall cover crop type with five treatments including oat (Avena sativa L.), cereal rye (Secale cereale L.), oilseed radish (OSR; Raphanus sativus L. var. oleoferus Metzg Stokes), mixture OSR plus cereal rye (OSR&rye) and a no cover crop control. Compared with no cover crop, sweet corn profit margins were higher by $450 ha^-1 for oat at Bothwell and $1300 and $760 ha^-1 for OSR and OSR&rye, respectively, at Ridgetown. By comparing plant available N over the cover crop season, the cover crops tested were more effective at preventing N loss at Bothwell than at Ridgetown likely due to higher precipitation and sandier soil at Bothwell. Despite differences in site characteristics, cover crops did not result in increased plant available N compared with no-cover during the sweet corn season at either site, indicating that these cover crops will not provide an N credit to the following crop and growers should not modify N fertilizer applications based on cover crops.

Ben Hassine, H., Ben Slimane, D. et Sayari, C. 2012. Effet de la pluviométrie sur la variation des réserves hydriques des sols cultivés en zone semi-aride tunisienne. Can. J. Soil Sci. 92: 367-377. Sur deux types de sols n'ayant pas les mêmes propriétés morphologiques et physico-chimiques et se distinguant par leurs situations contrastées dans le paysage, un suivi décadaire des teneurs en eau pondérales a été réalisé au cours de deux campagnes agricoles. Ces sols ont été traités par les mêmes techniques culturales et ont été emblavés en blé dur (Triticum durum) au cours de la campagne 2009 et en féverole (Vicia faba minor) au cours de la campagne 2010. La plus forte pluviométrie de l'année 2009 a bien chargé les réserves en eau du sol de plaine, mais les quantités absorbées par la culture de blé ont dépassé à la fois celles des pluies et de l'ETM calculée sur la base de données de température et de coefficients culturaux. Les horizons inférieurs de ce sol ont participé à l'alimentation en eau de la culture à l'inverse de ceux du sol du monticule où la consommation s'est faite dans l'horizon 0-60 cm uniquement. Cette consommation est inférieure à celle qui s'est produite dans le sol de plaine. La capacité de ce dernier de mieux servir comme réservoir d'eau supplémentaire lui a conféré des potentialités plus productives en fournissant sept quintaux de grains/ha de plus que le sol situé légèrement plus haut. Lorsque la pluviométrie est insuffisante comme celle de 2010, l'eau est retenue à des potentiels matriciels élevés et la culture est soumise à des conditions de difficulté d'alimentation hydrique dans les deux types de sols. Dans ces conditions, les horizons inférieurs du sol de plaine ne cèdent pas l'eau à la culture comme en année pluvieuse, mais profitent d'une faible hauteur reçue par drainage descendant.