Li, Y., Zhao, X., Chen, Y., Luo, Y. and Wang, S. 2012. Effects of grazing exclusion on carbon sequestration and the associated vegetation and soil characteristics at a semi-arid desertified sandy site in Inner Mongolia, northern China. Can. J. Soil Sci. 92: 807-819. China's Horqin Sandy Land is a region vulnerable to disturbance that has been subjected to serious desertification, mainly because of overgrazing. We investigated whether the establishment of grazing exclosures in areas with active sand dunes would benefit vegetation recovery and improve soil quality. The results showed that along the age sequence of grazing exclosure for 8, 13, and 26 yr, plant cover, species number, and above-ground biomass increased, the soil's water-holding capacity, fine particle content, organic C, total N, total P, available N and K, and electrical conductivity also increased, and the soil coarse sand content, pH, and bulk density in the top 20 cm of the soil decreased. However, the greatest improvements compared with the continuous grazing sites occurred in the 13- and 26-yr exclosures. Based on the area of heavily and severely desertified land in the study region and the results of the present study, the amount of C sequestered in the top 20 cm of the soil could reach 7.8 Mt after 26 yr of grazing exclusion. Our results confirm that grazing exclusion is a positive way to restore desertified ecosystems and has a high potential for sequestering soil C and improving soil quality in the semi-arid Horqin Sandy Land.

Bolinder, M. A., Kätterer, T., Andrén, O. and Parent, L. E. 2012. Estimating carbon inputs to soil in forage-based crop rotations and modeling the effects on soil carbon dynamics in a Swedish long-term field experiment. Can. J. Soil Sci. 92: 821-833. There is a need to improve the understanding of soil organic C (SOC) dynamics for forage-based rotations. A key requisite is accurate estimates of the below-ground (BG) C inputs to soil. We used the Introductory Carbon Balance Model (ICBM) to investigate the effects of C input assumptions on C balances with data from a 52-yr field experiment in northern Sweden. The main objective was to validate an approach for estimating annual crop residue C inputs to soil using the data from a continuous forage-based rotation (A). A rotation with only annual crops and more frequent tillage events (D) was used to obtain a rough estimate of the effect of tillage on SOC dynamics. The methodology used to estimate annual crop residue C inputs to soil gave a good fit to data from four out of the six large plots for rotation A. The approximate effects of more frequent tillage in rotation D increased SOC decomposition rate by about 20%. These results allow us to have more confidence in predicting SOC balances for forage-based crop rotations. Root biomass measurements used for calculating BG C inputs were also reviewed, and we show that they have not changed significantly during the past 150 yr.

Zhang, B., Yang, X., Drury, C. F., Reynolds, W. D., He, H. and Zhang, X. 2012. Effects of 49 years of fertilization on the distribution and accumulation of soil carbon under corn cultivation. Can. J. Soil Sci. 92: 835-839. The effects of 49 yr of monoculture corn (Zea mays L.) production with/without chemical fertilizer addition on the origin and distribution of soil organic carbon (C) among the sand (53-2000 µm), silt (2-53 µm), and clay (<2 µm) particle size fractions in the top 20 cm of a clay loam soil were evaluated using the carbon-13 isotope abundance technique. The C derived from corn (newly formed C4-plant C) was greater under chemical fertilization relative to no fertilization in all three size fractions. However, the resident (old) C derived from C3-plants grown prior to corn was similar between the fertilized and unfertilized treatments for each size fraction. Fertilization of monoculture corn had little impact on the amount of native-formed C3-plant C, particularly in the silt and clay fractions, but did increase the amount of newly formed C4-plant C.

Hao, X., Indraratne, S. P. and Blackshaw, R. E. 2012. Will genetically engineered crop production affect soil carbon? Can. J. Soil Sci. 92: 841-844. We investigated the responses to soil carbon after 8 yr of genetically engineered (GE) crop production. Soil organic carbon contents were similar, but d¹³C levels in SOC were lower in corn-canola rotation than in monoculture corn, whether GE or conventional crops were grown. GE crop production had no effect on soil carbon content and d¹³C level.

Li, Y., Liu, S., Liao, Z. and and He, C. 2012. Comparison of two methods for estimation of soil water content from measured reflectance. Can. J. Soil Sci. 92: 845-857. Remote sensing (RS) technology has increasingly been used in soil water content estimation, but highly accurate estimates of soil water content are still difficult to obtain using this technique. This study aims to determine the wavelengths at which the reflectance is most sensitive to changes in soil water contents (). Four types of soils were selected and light reflectance (λ) was measured at different . Results showed that parabolic functions fit with measured λ very well but only for individual wavelengths. Multivariate linear functions of with measured λ at visually selected characteristic wavelengths led to improved predictions, but the coefficients of determination between the soil water content and measured reflectance (R² ranged from 0.788 to 0.925 for the four soils) were still not high for the studied soils. Stepwise multiple linear regressions between and measured λ showed higher coefficients of determination (R² increased to 0.99 when the number of the statistically selected wavelengths increased) than the multiple regression, but had lower coefficients of determination than the stepwise multiple linear regressions between and the normalized band depths (D_n). The multi-variable linear functions fitted the measured vs. D_n best with much higher R² values, even when a single wavelength was used. Re-sampling wavelengths of less than 20 nm preserved the main features of the original reflectance for the studied soils. Parameters were fitted for the quadratic functions using the re-sampled reflectance data at 20-nm wavelength intervals for further estimation of soil water content, which was considered potentially applicable in RS technology for estimating soil water content provided that soils are relatively homogeneous. In conclusion, stepwise multiple linear regression functions between vs. D_n are statistically precise and are recommended for estimating soil water content from reflectance. Parameters for quadratic functions relating soil water content to the observed reflectance could be potentially used in RS technology for estimating soil water content.

Spagnoli, G. 2012. Comparison between Casagrande and drop-cone methods to calculate liquid limit for pure clay. Can. J. Soil Sci. 92: 859-864. During the construction of international projects off German coasts, it often occurs that clients and contractors work according to different standards. The aim of this experimental research is to compare the results of DIN and BS standards. The liquid limits of 50 pure kaolinitic and illitic clays were tested according to the German (Casagrande cup hard base) and the British (cone penetrometer) standards. Previous works were performed on natural clayey soils, while the research proposed in this work is based on tests carried out on standard pure clays. Illitic and kaolinitic clay types were chosen since they are abundant in the sediments of the Baltic Sea and North Sea where several offshore wind park projects are currently under construction or planned. The results show that the values obtained with the German Casagrande cup are slightly lower than those obtained with the British cone penetrometer. A regression equation was obtained to compare the liquid limit according to DIN and to BS for pure non-swelling clays namely LL_cone=0.99 LL_cup 1.05. The obtained relation agrees very well with other previous works.

Miller, J. J., Beasley, B. W., Drury, C. F. and Zebarth, B. J. 2012. Denitrification during the growing season as influenced by long-term application of composted versus fresh feedlot manure. Can. J. Soil Sci. 92: 865-882. Application of composted (new practice) rather than fresh (current industry standard) feedlot manure to cropland is increasing in Alberta. We hypothesized that fall application of composted feedlot manure to cropland may lower growing season denitrification losses of nitrogen (N) to the atmosphere compared with fresh feedlot manure because of lower carbon (C) availability from labile C (water-soluble C, acetic acid) and total organic C. Treatments included soil amended with either fresh (FM) or composted manure (CM) containing straw bedding applied annually at 77 Mg ha^-1 yr^-1 from 1998 to 2009, as well as an unamended control. Surface soil denitrification was measured every 2 wk (May 20 to Sep. 25) for 4 yr (2007-2010) on undisturbed soil cores (0- to 10-cm depth) that were incubated in the field (24 h) using the acetylene inhibition method. Daily arithmetic mean denitrification rates for the 30 sampling dates ranged between 0.2 and 214 g N₂O-N ha^-1 d^-1 for the unamended control, 0.2 to 281 g N₂O-N ha^-1 d^-1 for CM, and 0.5 to 553 g N₂O-N ha^-1 d^-1 for FM. Cumulative denitrification fluxes were significantly (P≤0.05) lower for CM (0.7-1.4 kg N₂O-N ha^-1) compared with FM (3.2-5.1 kg N₂O-N ha^-1) for 2 (2007, 2008) of 4 yr, suggesting that cumulative denitrification fluxes over the growing season may be lower for CM in certain years. Total organic C, water-soluble C, and acetic acid contents in surface soil were generally similar for CM and FM, and we found no relationship between these organic fractions in the soil with daily denitrification rates during the 2010 growing season. Water-filled pore space had the most influence on soil daily denitrification rate. Although cumulative denitrification losses (0.7-10.5 kg N₂O-N ha^-1) for the amended soils in our study were negligible (<1%) compared with annual total N applied, the environmental consequences of this N loss should be taken into consideration when fresh or composted feedlot manure is applied to cropland.

Larney, F. J., Olson, A. F. and DeMaere, P. R. 2012. Residual effects of topsoil replacement depths and one-time application of organic amendments in natural gas wellsite reclamation. Can. J. Soil Sci. 92: 883-891. The success of reclamation on abandoned wellsites depends on their capacity to recover and sustain levels of soil quality similar to those existing prior to soil disturbance. A 1997-2000 study looked at four (0, 50, 100 and 150%) topsoil replacement depths (TRD) and five amendments [compost, manure, alfalfa (Medicagosativa L.) hay, wheat (Triticumaestivum L.) straw, check] in the reclamation of three natural gas wellsites in Alberta. In 2007 (10 yr after establishment) the wellsites were re-sampled to examine residual effects of reclamation treatments on soil properties. In 2007, there was no difference in SOC between the 50, 100 and 150% TRD treatments and all three were significantly higher than the 0% TRD by an average of 18%. Therefore adding half the amount of topsoil (50%) 10 yr previously caused long-term improvement in SOC (vs. 0% TRD), but adding more topsoil (100, 150%) did not produce further gains. Soil organic C (0- to 15-cm depth) on the compost and manure treatments (across all sites and TRD treatments) was significantly higher ( 8%) than straw, alfalfa and check treatments some 10 yr later. Results show that initial investment in organic amendments for wellsite reclamation can have residual effects on soil quality.

Irshad, M., Saleem, A., Faridullah, Hassan, A., Pervez, A. and Egrinya Eneji, A. 2012. Phosphorus solubility and bioavailability from poultry litter supplemented with gypsum and lime. Can. J. Soil Sci. 92: 893-900. Gypsum and lime are often used as amendments for the regulation of soil reaction (pH), which has an immense influence on soil nutrient availability. We determined the release and bioavailability of phosphorus (P) to spinach (Spinacia oleracea L.) from soils amended with gypsum and lime supplemented with poultry litter (PL). Four types of poultry litter (i.e., broiler litter, breeder litter, layer litter and duck litter) were mixed separately with lime and gypsum at the rates of 0, 2.5 and 5% and incubated at room temperature for 8 wk. The incubated materials were sampled at 4 and 8 wk and analyzed for water-extractable P. Prior to incubation, non-supplemented litter samples were also analyzed for total element contents (P, Ca, Mg, K, Mn, Cu, Zn and Fe). Total P varied in the order duck >broiler >layer >breeder. Water soluble P concentration was highly dependent on the type of PL as well as chemical amendment used. With the application of both gypsum and lime, P concentration decreased with increasing rate of application. There was less water-soluble P with lime than gypsum supplementation for all PL. Time of incubation slightly reduced water-soluble P concentration. Non-supplemented PL had greater P concentration after 8 wk, but soluble P was in the order duck >broiler >breeder >layer. At the 8th week of incubation with 5% gypsum, the soluble P decreased by 28% in duck, 22% in broiler, 17% in breeder and 16% in layer. The 5% lime treatment reduced P solubility by 26% in duck, 23% in broiler, 16% in breeder and 20% in layer. The addition of the supplemented PL to soil significantly reduced water-soluble P, especially with the lime treatment. Application of non-supplemented PL produced greater spinach biomass yield than PL supplemented with gypsum or lime, possibly on account of higher soluble P and micro elements (Zn, Cu, Mn and Fe). Although chemical amendments such as gypsum and lime lowered P concentration and even spinach yield, it may help reduce eutrophication of surface waters in areas where large amounts of PL are applied regularly.

Ashworth, J. and Bullecer, I. 2012. A rapid bioassay to screen soils for toxicity of residual petroleum hydrocarbons. Can. J. Soil. Sci. 92: 901-904. The following 2-h procedure is proposed as a screen to indicate how soils contaminated with petroleum hydrocarbons (PHC) might perform in bioassays required for site remediation in Canada. Bio-available PHC in soil is extracted by aqueous cyclodextrin; a centrifuged extract portion is treated with amylase, then subjected to a standard Microtox^® bioassay. Extract toxicity is correlated to available PHC content.

Kasongo, R. K., Van Ranst, E., Kanyankogote, P., Verdoodt, A. et Baert, G. 2012. Réponse du soja (Glycine max) à l'application de phosphate de Kanzi et de dolomie rose de Kimpese sur sol sableux en RD Congo. Can. J. Soil Sci. 92: 905-916. Le sol sableux de l'hinterland de Kinshasa (RD Congo) est caractérisé par une faible fertilité chimique, un pouvoir de rétention en eau très limité, et présente une réaction acide propice à la toxicité aluminique, voire manganique pour les plantes. Cette étude traite de l'effet d'application de phosphate de Kanzi (PK) et de dolomie rose de Kimpese (DK) sur les paramètres de la culture du soja (biomasse, nodulation et rendement en graines) et sur les propriétés chimiques du sol après culture. Quatre doses de chaque roche finement broyée (0 ; 199 ; 397 et 794 mg PK, et 0 ; 437 ; 874 et 1748 mg DK kg sol^-1) ont été appliquées sur des sols pour un essai de culture du soja (Glycine max) réalisé suivant un dispositif complètement randomisé avec trois répétitions. L'apport de PK et de DK au sol stimule sensiblement l'absorption de Ca, Mg, P et K, et augmente significativement la nodulation, la matière sèche (MS) et le rendement en graines du soja (PGS). L'application de 2,48 Mg ha^-1 PK et 5,46 Mg ha^-1 DK augmente respectivement la MS de 111 et 191 %, et le PGS de 86 et 197 %. L'analyse des sols après culture révèle que les sols amendés contiennent, dans certains cas, des nutriments (Ca, Mg, N et P) pouvant produire des effets résiduels bénéfiques à long-terme. De plus, la hausse significative du pH engendre une augmentation substantielle de la CEC avec une neutralisation complète de la phytotoxicité aluminique. L'étude a permis de démontrer que la diminution significative de la solubilité des micronutriments (Cu, Zn, Mn et Fe) dans le sol réduit sensiblement leur absorption par les plantes. Les roches PK et DK ont des potentialités permettant d'accroitre la productivité des sols tropicaux.

Gagnon, B. and Ziadi, N. 2012. Papermill biosolids and alkaline residuals affect crop yield and soil properties over nine years of continuous application. Can. J. Soil Sci. 92: 917-930. Residues from paper and wood mills are a valuable source of nutrients for field crops, but little is known about the effectiveness of repeated applications over many years. A study was initiated at Yamachiche, QC, to assess the effect of continuous applications over 9 yr of combined papermill biosolids (PB), applied alone or with several liming by-products, on grain yield, plant nutrient accumulation, and soil fertility in a loamy soil cropped to grain corn, dry bean, and soybean. The PB treatments (0, 30, and 60 Mg wet ha^-1) and liming by-products [calcitic lime (CL), lime mud (LM), wood ash (WA)], and two magnesium residuals, each at 3 Mg wet ha^-1 along with 30 Mg PB ha^-1) were surface applied annually at post-seeding. In the last 6 yr, the two treatments receiving magnesium residuals were replaced with 90 Mg wet PB ha^-1 and mineral N fertilizer (MIN), respectively. Repeated annual applications of LM followed by CL increased soil pH the most (up to 1.4 unit). Crop yields were not significantly affected by treatments in the first 3 yr but subsequent applications of PB at 90 Mg ha^-1 increased yields in grain corn ( 1.9 Mg ha^-1) and dry bean ( 0.77 Mg ha^-1) relative to the control, while PB with WA increased yield in soybean ( 0.85 Mg ha^-1). The PB at 30 Mg wet ha^-1 with supplemental N (average of 45 kg N ha^-1), or at 60 Mg wet ha^-1 applied alone, achieved yields comparable with MIN treatment under corn. The PB applications increased soil organic matter and all major soil nutrients except K and Mg. The results of this study indicate that PB and alkaline residuals can be effectively applied to agricultural soils over many years although PB exceeding 60 Mg wet ha^-1 yr^-1 induce significant nitrate leaching.