After 47 yr of no-till and reduced summerfallow at Lethbridge, Alberta, soil organic carbon concentration and stocks increased 2.14 g kg⁻¹ and 2.22 Mg ha⁻¹, respectively, in the surface 7.5 cm layer. These findings confirmed the conservation value of reducing tillage and summerfallow. The annual changes were relatively small.

There is a physical limit to the storage capacity of soil organic carbon (SOC) that is dependent on fine particles in arable soils. Here, it is demonstrated that a ceiling of SOC storage can be identified utilizing a boundary line approach relating SOC to the clay fraction of soils in Ontario. The method can determine the deficit of SOC to establish the potential to regain SOC and ameliorate eroded landscape positions.

Compared with annual crops, dedicated perennial bioenergy crops are ascribed additional benefits in terms of reduced greenhouse gas emissions; these benefits include increased carbon (C) storage in soil. We measured Miscanthus-derived C in rhizomes, roots, and 0–100 cm soil beneath three 16-yr-old stands established on sandy soils at two experimental sites in Denmark. Miscanthus C in soil was estimated from changes in the natural abundance of ¹³C. In the 0–20 cm depth, soil C derived from Miscanthus made up to 15–18% of the soil total C. In the 20–50 cm and 50–100 cm depth, Miscanthus C accounted for less than 7% and 5% of the soil total C, respectively. After 16 yr, the total quantity of Miscanthus C in 0–20 cm ranged from 11.9 to 18.2 Mg C ha⁻¹, of which 23–34% was in rhizomes and roots, substantiating their crucial contribution to soil C storage. Future studies should prioritize the seasonal and annual dynamics of C stored in rhizomes and roots, and the fate of these C pools following termination of Miscanthus stands.

Emissions of nitrous oxide (N₂O-N) from manure applied to annual crop (AC) and perennial forage (PF) are poorly quantified for the Canadian Prairie Region. This study used static chambers over two growing seasons to assess soil N₂O-N emissions from solid pig manure (SPM) and liquid pig manure (LPM) in AC and PF systems on a sandy loam soil. In 2011, when manure application coincided with hot and wet soil conditions, both manure treatments in AC induced N₂O-N emission episodes a week later. In the PF, however, only LPM resulted in an N₂O-N emission peak after 8 d. In 2012, manure application did not coincide with hot and wet soil conditions, and emission rates were smaller. Overall, the effect of manure type was inconsistent. In 2011, cumulative emissions in AC from LPM and SPM were 5.8 and 7.8 kg N₂O-N ha^?1, respectively, and in PF were 10.7 and 0.6 kg N₂O-N ha^?1, respectively. In 2012, cumulative emissions were <1 kg N₂O-N ha^?1, except LPM in PF. In 2011, LPM had significantly higher emission factor (EF ≈ 7%) than SPM (≤0.2%) in both AC and PF, whereas in 2012 manure type had no effect on EF (≈ 0). Over the two growing seasons and across manure types, EF did not differ between AC and PF. These results suggest that SPM would reduce N₂O-N emission relative to LPM when conditions favor intense denitrification.

Spectral analysis is a useful tool for the rapid and accurate prediction of soil properties. Our objective is to select the best model for predicting the three soil cation concentrations ([Na⁺], [Mg²⁺], and [Ca²⁺]) and sodium adsorption ratio (SAR). Three methods were applied, i.e., stepwise multiple linear regression (SMLR), partial least-squares regression (PLSR), and support vector machine (SVM). Estimation models for four soil properties were developed using three different spectral processing and transformation techniques, i.e., reflectance (R_e), logarithm of reciprocal R_e (LR), and standard normal variable of R_e (SNV) were used. A total of 36 models were established. Of these, 27 models for [Na⁺], [Mg²⁺], and [Ca²⁺] were not applicable for subsequent prediction, because the coefficients of determination (R²) were not high (0.224–0.689), and their relative percent deviations (RPD) were all smaller than the 1.4 threshold. However, the models for SAR∼R using PLSR (R²=0.728 for calibration and 0.661 for validation, RPD=1.43), SAR∼LR using SVM (R²=0.791 for calibration and 0.712 for validation, RPD=1.81), and SAR∼SNV using SVM (R²=0.878 for calibration and 0.814 for validation, RPD=2.13) were valid for further prediction. Finally, SAR∼SNV using SVM was selected as the best model. There are intrinsic factors resulting in an unsatisfied model performance.

Information on how soil texture and related soil properties affect corn (Zea mays L.) nitrogen (N) response is needed to improve N management in corn production. We conducted a study at 12-site yr in Quebec to assess the effect of N rate (0–250 kg N ha⁻¹) and soil surface textural groups [clay, loam, sandy belonging to the gleysolic soil order (Sg), and sandy belonging to the podzolic soil order (Sp)] on corn grain yield, stover yield, total N uptake (TNU), nitrogen uptake efficiency (NUE), thousand kernel weight (TKW), test weight, and chlorophyll meter readings (CMR). Corn was more responsive to N rate in the clay soil textural group for most of the parameters due to lower soil N supply, and least responsive in the Sp group, except for test weight and CMR, due to possibly greater leaching in this group. The CMR at flowering accounted for 87%, 87%, 82%, and 25% of the variation in grain yield, TNU, TKW, and test weight, respectively. This study suggests that soil surface texture has a major influence on corn N response, but other soil properties such as drainage may also be important.

A study was conducted to investigate the impact of biochar amendment on chemical properties and corn nutrient uptake in a sandy Podzol soil. Four rates of biochar (0, 5, 10, and 15 g kg⁻¹) and two rates of inorganic fertilizer (0 and local recommendation rate for corn) were randomly applied to a completely randomized design with four replicates. Corn was grown for 45 d in a glasshouse using sandy Podzol. The increase in pH of the soil was concomitant with a decrease of exchangeable Al. The fertilized soil significantly increased total N, with a concomitant decrease in soil pH due to a N nitrification. Positive changes did occur in the soil due to biochar application, leading to a significant increase in dry matter yield and corn height. Corn N and K uptakes were significantly increased by the addition of biochar, but the same was not true for Ca and Mg. However, it was found that the concentrations of N, Ca, and Mg in the corn tissue were still lower than their critical level. Our results demonstrate that application of biochar alone is not able to supply enough nutrients for the healthy growth of corn.

Crop residue decomposition not only is mainly driven by, but also affects, soil microorganisms. However, soil microbial responses to legume crops are usually studied only in one subsequent crop. We compared the soil microbial effects of pea (Pisum sativa L.) and faba bean (Vicia faba L.) pulse crops (grown for seed) with faba green manure (GM) and chickling vetch (Lathyrus sativus L.) GM crops in three subsequent crops. Soil microbial biomass C (MBC), β-glucosidase enzyme activity, and bacterial physiological (C substrate utilization) diversity were measured in the summer (rhizosphere and bulk soil) and fall (bulk soil) in all subsequent crops: wheat (Triticum aestivum L.), canola (Brassica napus L.), and barley (Hordeum vulgare L.). Residues of faba bean (grown for GM, herein called faba GM, or for seed, herein called faba bean) usually resulted in the most soil MBC and β-glucosidase activity relative to the other residues. Faba and vetch GM residues increased bulk soil MBC or β-glucosidase enzyme activity more than pulse crop residues in the first and (or) third subsequent crops. Soil MBC and β-glucosidase activities were often positively correlated with initial crop residue N concentrations and negatively correlated with initial C:N ratios or C concentrations. Bacterial physiological diversity was the least responsive to crop residues and was affected differently by sampling time. β-Glucosidase activity was always greater in the fall after crop harvest than in summer. Therefore, β-glucosidase activity was a more sensitive and consistent biological indicator of crop residue effects, and perhaps soil health, than MBC or bacterial physiological diversity.

Concurrent N mineralization and immobilization in soils receiving poultry litter containing woodchip bedding may reduce synchrony between the short-term N supply and crop N demand. Therefore, we used soil chemical tests, ion exchange membranes, and wheat N uptake to assess N dynamics in a poultry-litter-amended soil. Air-dried soil was thoroughly mixed with five poultry litter rates (50, 100, 150, 200, or 250 mg total N kg⁻¹) and preincubated for 7 d in a controlled environment chamber. After preincubating, soil was placed in 10-cm-diameter pots and planted with spring wheat (Triticum aestivum ‘Wilkin’), or left unplanted and monitored with anion and cation exchange membranes for 45 d. Soil nitrate (NO₃-N) concentration increased with poultry litter application rate at the end of the preincubation period, but subsequent wheat N uptake did not, suggesting that little net N mineralization occurred during the 45 d of wheat growth. The membrane data indicated a shift from net N immobilization during the early part of the wheat growth period to net mineralization during the latter portion of the wheat growth period. We conclude that alternating N mineralization and immobilization in soils receiving poultry litter containing woodchip bedding limited the short-term N supply to wheat.

In the Alberta oil sands, sand containing less than 8% petroleum hydrocarbon (PHC) is referred to as lean oil sand (LOS) and is used as subsoil in reclamation. The objective of this study was to determine how bulk density and PHC concentration affect the hydraulic properties of LOS. The LOS was packed in soil cores at varying bulk densities and PHC concentrations, representing the range in these parameters that occur in the reclamation setting. The cores were placed on a tension table and pressure plates to measure water retention. The constant head method was used to measure the saturated hydraulic conductivity (K_s) of the LOS. Results show that increasing PHC concentration reduced the water retention of LOS due to the presence of PHCs in soil micropores. PHC concentration also had a significant effect on the van Genuchten curve fitting parameters for the water retention curve, although the shape of the curves remained similar regardless of PHC content. Furthermore, there is a significant reduction in K_s at the high bulk density and high PHC concentrations (3.25%–7.48%), compared with low PHC concentrations (0%–1.63%). Due to the reduced K_s with increased PHCs and bulk density, LOS used as the base material in reclamation will reduce percolation and increase water storage in the reclamation soil cover.

Applications of sulfate and carbonate salts have been shown to improve the solubility of phosphorus (P) in model calcareous soils. It is unclear how these treatments will influence P solubility in real soils. The objective of this study was to determine the effect of sulfate or carbonate salts on P solubility in selected Manitoba soils. We hypothesized that the application of carbonate or sulfate salts in a fertilizer band could enhance the solubility of P in Manitoba soils. Different salt mixtures were prepared by mixing either monopotassium phosphate (MPP) or monoammonium phosphate (MAP) with K₂SO₄, (NH₄)₂SO₄, MgSO₄, or (NH₄)₂CO₃. After the 2 wk of incubation of salt-treated soils, both P sources decreased soil pH significantly. The addition of salts did not significantly affect pH in most of the soils. There was a significant treatment effect (P<0.0001), a significant soil effect (P<0.0001), and a significant soil by treatment interaction (P<0.0001) on water-extractable P. Coapplication of either sulfates or (NH₄)₂CO₃ salt increased soluble P in some soils by 6%–44% or 11%–14%, respectively. Application of carbonate or sulfate salts increased P solubility only in soils with a smaller ratio of HCl-extractable Ca to ammonium acetate-extractable Ca.

The effect of land-use changes on soil carbon stocks has been an increasing concern in the context of global climate change. Through natural reforestation programs, abandoned cropland holds the potential of sequestering soil organic carbon (SOC) if the original forest could be recovered. In this study, we initially delineated the potential distribution of forest species on the north slope of the Tianshan Mountains using species distribution models. We then estimated the corresponding sequestration potential of SOC in the area delineated for reforestation. The deforestated area of a Picea schrenkiana forest converted to cropland (PSC) was defined by the potential and actual distributions of forest and cropland. The SOC contents of the forest and cropland soils were obtained through field sampling and laboratory analysis. We found that the area of the PSC was 26.77×10⁵ ha, and the SOC loss (per unit area) derived from the conversion of forestland to cropland was 171.70±28.20 Mg ha⁻¹. The total SOC loss from the study area was 459.70±75.49 Tg. This result implies that continuing the reforestation programs being implemented in the study area would increase SOC by the same amount. Additionally, we also estimated the total amount of carbon that would be sequestered in the aboveground and underground forest biomass on former cropland.

Fertility enhancement with biochar application is well documented for tropical acidic soils; however, benefits of biochar coapplied with synthetic fertilizers (SFs) on soil fertility are not well documented, particularly for alkaline chernozems. We examined the short-term interactive effects of woodchip biochar amendment with fertilizers on selected soil properties, available phosphorus (P), and P fractions of two alkaline Chernozems from Manitoba. Treatments were (1) urea and monoammonium phosphate fertilizers, (2) biochar at 10 g kg⁻¹, (3) biochar at 20 g kg⁻¹, (4) biochar at 10 g kg⁻¹ with fertilizers, (5) biochar at 20 g kg⁻¹ with fertilizers, and (6) a control. Treated soils were analysed for pH, electrical conductivity (EC), and Olsen P concentration biweekly, and for P fractions, cation exchange capacity (CEC), organic carbon (OC), and wet aggregate stability after 70 d of incubation. Biochar amendment without fertilizers significantly increased soil pH and CEC but had no effect on EC, while coapplication with fertilizers significantly increased Olsen P and labile P concentrations. When coapplied with fertilizers, biochar did not significantly increase soil pH relative to the control. Results suggest that biochar improved soil properties and available P in alkaline Chernozems, and the beneficial effects were enhanced when coapplied with SFs.

The validity of emission factors derived from small-scale measurements of ammonia (NH₃) volatilization has been questioned in the literature because gaseous NH₃ concentration gradients differ at the edge of the measurement plot and may result in higher emissions than at field scale. We studied this “oasis effect” using two very long (22 m) wind tunnels constructed indoors over soil plots fertilized with surface-applied urea (20 g N m^?2). We hypothesized that NH₃ flux would be highest at the start of the tunnel and decrease with distance. Air NH₃ concentration was measured every 2 m along each tunnel for 2 wk after urea application; NH₃ flux did not decrease along the length of the tunnels. Of the 60 measurement periods, when there was significant NH₃ volatilization, only two had a significant nonlinear relationship (P≤0.05) between NH₃ concentration and distance. For the other periods, the NH₃ concentration increased linearly with distance (P≤0.05). The background NH₃ concentration difference between halves of the tunnels was not significantly related to NH₃ flux difference (P>0.1). Our results indicate that wind tunnel measurements of NH₃ volatilization fertilized using urea are not impacted by a measurable oasis effect.

Spills of brine wastewater produced during oil well drilling are occurring more frequently in the Great Plains, resulting in crop production loss on affected soil. Remediation requires removal of salt from the topsoil, which might be accomplished by leaching to subsurface horizons or subsurface drains. A laboratory study determined the effects of brine on saturated hydraulic conductivity (K_s) of four nonimpacted surface soils from western North Dakota, USA. Repacked soil cores were subjected to saturated water flow, followed by one pore volume of brine. Subsequent saturated water flow leached brine from the soil and reduced K_s as much as 97% (0.086–0.003 cm h^?1) within 24 h. Effluent total dissolved solids (TDS) approached 250 000 mg L^?1 then declined (5 mg L^?1) with continued leaching, but K_s did not increase. Removal of soluble salts during leaching increased the relative sodium concentrations (ESP>55), causing clay swelling/dispersion and reduced K_s. Postbrine gypsum application (11.2 Mg ha^?1) to replace exchangeable sodium with calcium did not improve K_s. This evidence suggests that if subsurface drainage is used for reclaiming brine-impacted soils that special attention be given to where dispersion/swelling is occurring, leaching water quality, and closely positioning calcium amendments within the high sodium zones.

Extreme rainfall events are infrequent disturbances that affect urban environments and soil respiration (Rs). Using data measured in an urban forest ecosystem in Beijing, China, we examined the link between gross primary production (GPP) and soil respiration on a diurnal scale during an extreme rainfall event (i.e., the “21 July 2012 event”), and we examined diel and seasonal environmental controls on Rs. Over the seasonal cycle, Rs increased exponentially with soil temperature (Ts). In addition, Rs was hyperbolically related to soil volumetric water content (VWC), increasing with VWC below a threshold of 0.17 m³ m^?3, and then decreasing with further increases in VWC. Following the extreme rainfall event (177 mm), Rs showed an abrupt decrease and then maintained a low value of ~0.3 μmol m^?2 s^?1 for about 8 h as soil VWC reached the field capacity (0.34 m³ m^?3). Rs became decoupled from Ts and increased very slowly, while GPP showed a greater increase. A bivariate Q₁₀-hyperbolical model, which incorporates both Ts and VWC effects, better fits Rs than the Q₁₀ model in summer but not for whole year.