bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of temperature on soil organic matter decomposition in three forest biomes of eastern Canada
Authors: Paré D. , Boutin R. , Larocque G. R. , Raulier F.
Published: April 2011

The sensitivity of soil organic matter decomposition to temperature change is critical tothe global carbon balance and to whether soils will respond with positive feedback to climate change. Forest cover determines litter composition, which controls to a large extent soil organic matter quality and its sensitivity to temperature. The effect of temperature on soil organic matter decomposition was studied along a latitudinal gradient encompassing sugar maple, balsam fir and black spruce forest types. Long-term laboratory soil incubations conducted at four different temperatures were used to discriminate the effect of temperature from that of organic matter quality on decomposition rates. The specific C mineralization rate of the humus layer was highest for balsam fir sites, intermediate for one sugar maple site and lowest for black spruce sites and the other sugar maple site. However, considering the total C pools of the FH layer and of the top 20 cm of mineral soil, it was estimated that coniferous sites exhibit a higher C efflux than sugar maple soils at any given temperature. Estimated C mineralization rates in the field using the temperature records for each individual site showed the same trends despite cooler temperature regimes for the coniferous sites. The Q10 respiration rates of the humus layer of all sites increased as the temperature got warmer. A significant effect of temperature on the pool size of labile C in the mineral soil was detected for some sites suggesting a potential long-term loss of C upon warming. The low estimated C evolution rates of sugar maple soils were perhaps due to the greater decomposition activity within the L layer, before the litter C enters underlying soil pools. These observations suggest that coniferous soils are not more resistant than deciduous forests to increasing their specific rates of soil heterotrophic respiration upon warming. Key words: Soil organic carbon, forest type, forest composition, warming, long-term incubation, labile carbon
Potential impacts of climate change on water availability for crops in the Okanagan Basin, British Columbia
Authors: Neilsen D. , Smith C. A. S. , Frank G. , Koch W. , Alila Y. , Merritt W S , Taylor W G , Barton M. , Hall J W , Cohen S J
Published: April 2011

Crop water demand in the Okanagan Basin was determined for 1961 to 1990, 2010 to 2039, 2040 to 2069, and 2070 to 2099. Daily station temperature data were spatially interpolated to a 1 × 1 km grid and adjusted for elevation. Daily precipitation data were estimated across four climatic regions. Output from three global climate models (GCM), CGCM2, CSIROMk2 and HadCM3 was used to create future daily climate. Daily potential evapo-transpiration (grass reference) was estimated from an empirical relationship between Bellani- plate atmometer readings, temperature and extra-terrestrial solar radiation, and then modified by crop coefficients for all crops except pasture. Depending on GCM, projected water demand increased by 12–20% (2010 to 2039), 24–38% (2040 to 2069) and 40–61% (2070 to 2099). Possible elevated CO2 effects on stomatal conductance, which may reduce water demand, were not accounted for. Comparisons with modeled Okanagan Lake inflows indicated that, on average, high water demand and low supply scenarios coincided. In one sub-basin, supply and demand thresholds were exceeded 1 yr in 6 (HadCM3) in the 2050s and at least 1 yr in 4 for all GCMs by the 2080s, and existing water supply infrastructure may be inadequate. Crop growing seasons were defined empirically from growing degree days or threshold temperatures. The growing season lengthened up to 30–35% leading to higher demand in fall and shortages due to low stream flows. Key words: Evapotranspiration, growing degree days, growing season, GIS, PRISM
Quantifying carbon sequestration in a conventionally tilled crop rotation study in southwestern Saskatchewan
Authors: Campbell C A , VandenBygaart A J , Grant B. , Zentner R P , McConkey B G , Lemke R. , Gregorich E G , Fernandez M.
Published: April 2011

In this study we used results from 10 cropping systems in a 37-yr field experiment being conducted on a medium-textured Orthic Brown Chernozem in semiarid southwestern Saskatchewan, in which soil organic carbon (SOC) had been sampled in 7 different years, to quantify trends and changes in SOC in the 0- to 15-cm depth. We tested the effectiveness of three models: Century, the Introductory Carbon Balance Model (ICBM), and the Campbell model to predict the measured values. The 10 cropping systems allowed us to assess the influence of cropping frequency, fertilization and crop type on SOC and, because growing season weather was distinctly more humid in the final 12 yr of the study, we were able to assess the impact of weather. In this soil on which a fallow-wheat (Triticum aestivum L.) (F-W) rotation was maintained for the previous 60 yr, SOC remained fairly constant under normal weather for the first 20 yr of the study for the systems that were frequently fallowed, except for fallow-fall rye (Secale cereale L.)- wheat (F-Rye-W). In contrast, in the final 12 yr, SOC increased in all systems in response to increased C inputs from crop residues associated with improved precipitation. SOC gains were greater for well-fertilized extended crop rotations such as continuous wheat (Cont W) and wheat-lentil (Lens culinaris Medikus) (W-Lent) and the F-Rye-W systems receiving N and P than for the F-W, F-W-W, F-Flax (Linum usitatissimum L.)-W (F-Flx-W) receiving N and P, and Cont W receiving only P. SOC was also greater for well- fertilized than for poorly fertilized systems. The ICBM and Campbell models performed well in simulating SOC trends, partly because they used measured grain yields to estimate C inputs. However, the Century model was less effective in its simulation of SOC especially for the fallow-containing systems due to its difficulty in estimating spring soil water and crop yields. We showed how grain yields can be used, together with coefficients of conversion of C inputs from crop residues to SOC, to estimate SOC changes. Using these relationships, and assuming the coefficient of conversion of C inputs to SOC sequestered is 15% for well-fertilized extended rotations, or 10% for well-fertilized frequently fallowed spring-seeded systems, one can make reasonable first estimates of the impact of management on C sequestration in degraded soils of the semiarid prairies. Key words: ICBM model, Century model, Campbell model, soil organic C, N and P fertilizer, cropping frequency
Tillage and root heat stress in wheat in central Alberta
Authors: Wang H. , Lemke R. , Goddard T. , Sprout C.
Published: April 2011

Heat stress occurs often in wheat on the Canadian Prairies especially during reproductive growth, which has markedly negative impacts on yield. As previous studies reported that wheat growth was affected more by heat stress in roots than in shoot, we suspected that the cooling effect of no-till (NT) on soil may reduce the risk of root heat stress and benefit the yield compared with conventional tillage (CT). Data were collected between 2000 and 2003 from a tillage study using a continuous wheat cropping system on a Thin Black Chernozemic clay loam in central Alberta. Consistently lower soil temperatures at 5 and 10 cm in NT than CT were observed in the whole growing season every year. At the grain growth stage, NT mitigated heat shock (>32°C at 5 cm) which occurred in 2001 and 2002 under CT and considerably reduced root heat stress index (HSI), calculated as accumulations of hourly soil temperatures greater than 20°C, every year compared with CT. By reducing root heat stress especially during the grain growth stage and slightly increasing pre-seeding soil moisture, no-till increased above-ground biomass (33–160%) and grain yield (18–147%) every year except 2003 when heat and water stress were relatively mild. Key words: Heat stress, soil temperature, no-till, conventional tillage, wheat, root
Windrow temperatures and chemical properties during active and passive aeration composting of beef cattle feedlot manure
Authors: Larney Francis J , Olson Andrew F
Published: April 2011

Windrow composting emerged in the mid-1990s as an alternative manure-handling practice in Alberta’s cattle feedlot industry. This study compared two composting methods: active (turning) and passive aeration. Temperatures were monitored over the first 90 d and chemical properties over 188 d of composting. Pre- vs. post-turning sampling of the active treatment was also compared. Mean daily temperature was warmest at the bottom windrow location (53.6ºC) and coolest at the top (46.4ºC) in the active treatment, but warmest at the top (44.1ºC) and coolest at the bottom (33.9ºC) in the passive treatment. Final compost from the passive treatment had significantly higher total N (TN), total C (TC), electrical conductivity (EC), Na, and Cl than the active treatment. There were no significant treatment effects on C:N ratio, NH4-N, NO3-N, total P (TP), Kelowna-extractable P (KEP), pH, Ca, Mg or K. Both treatments showed substantial and non-significantly different C (71–80%) and N (44–58%) losses. Pre- versus post-turning sampling showed significant differences for some compost parameters, notably soluble salts. After the thermophilic phase, the passive treatment appeared only partially composted. Additional disadvantages of the passive treatment included lower windrow temperatures, which may fail to reduce pathogens, and higher EC, which could potentially limit the end use of passively aerated compost. Key words: Cattle manure, composting, active aeration, passive aeration, nutrients
Nutrient budgets of Ontario organic dairy farms
Authors: Roberts C J , Lynch D H , Voroney R P , Martin R C , Juurlink S D
Published: April 2011

The sustainability of organic dairying in Canada, with respect to nutrients, remains unexamined. To assess how management affects nutrient status, we documented whole farm nutrient (NPK) budgets over 2 yr (2003 to 2005) and soil (0 to 15 cm) P and K status on 15 long-term Ontario organic dairy farms. Farm size, livestock density and herd productivity averaged 110 ha, 1.00 livestock units ha-1 and 5656 kg milk cow-1 yr-1, respectively. Annual farm nutrient surpluses of 75 (N), 1 (P) and 11 (K) kg ha-1 yr-1 were lower than those reported for confinement-based dairy farms in the United States, pointing to possible environmental benefits from reduced off farm impacts on air and water quality. Weighted average soil test P levels were low (< 10 mg kg-1) on approximately 50% of farms, while exchangeable K levels were moderate to high (76 to 160 mg kg-1) on all farms. Four farms adopting a "self-sufficient" approach, producing most feed on-farm, imported little P as feed (1.37 to 1.90 kg P ha-1 yr-1) and had negative average farm P balances (avg. -1.54 kg P ha-1 yr-1). An integrated nutrient management approach, along with a flexible feed import strategy, fosters the sustainability of organic dairying systems. Key words: Organic dairying, nutrient budget, nitrogen, potassium, phosphorus, soil fertility
The indicator of risk of water contamination by nitrate-nitrogen
Authors: De Jong R. , Yang J Y , Drury C F , Huffman E C , Kirkwood V. , Yang X M
Published: April 2011

Drriven by changes in agricultural production practices, nitrogen (N) inputs have increased steadily on Canadian farms. An agro-environmental indicator was developed to monitor potential water pollution by N: indicator risk of water contamination by nitrate-nitrogen (IROWC-N). The indicator links the residual soil nitrogen (RSN) indicator to climate and soil conditions to assess the likelihood of N moving through the soil and out of the agricultural system. The results are assessed in terms of Nlost via leached water (Nlost) and its concentration in the leached water (Nconc), with the IROWC-N risk classes based on Nlost and Nconc criteria.

The estimated amount of Nlost in Canada ranged from 5.1 kg N ha-1 in 1991 to 6.4 kg N ha-1 in 2001. Nconc values remained fairly constant during the 1981 to 1996 census years (ranging from 3.7 to 4.5 mg N L-1), but increased sharply (27%) to 5.7 mg N L-1 in 2001 as compared with 1996. During the 1981 to 2001 period, close to 80% of the Canadian farmland area remained in the very low and low IROWC-N risk classes, but over the years 18% shifted to a higher risk class. In 2001, large areas (> 1 million ha) in the high risk IROWC-N class were found in Manitoba, southern and eastern Ontario and in Quebec.

Provincial averages of Nlost over 5 census years (1981, 1986, 1991, 1996 and 2001) varied from less than 5 kg N ha-1 in Alberta and Saskatchewan to more than 20 kg N ha-1 in Ontario, Quebec and the Atlantic provinces. With the exception of Manitoba, provincial Nconc values did not exceed the Canadian drinking water guideline of 10 mg NO3-N L-1. In each of the census years, British Columbia, Alberta and Saskatchewan had more than 70% of the farmland area in the very low and low risk classes for IROWC-N. In Ontario and Quebec, most of the farmland area was either in the low or in the high risk class. More than 50% of the farmland area in New Brunswick, Nova Scotia and Newfoundland was in the very low, low and moderate risk classes, whereas in Manitoba and Prince Edward Island, more than 60% of the farmland was in the moderate and higher level risk classes for IROWC-N. Overall, the 20-yr trend in risk of water contamination by N was worsening. Key words: Water contamination by nitrogen, nitrate, water quality, Soil Landscapes of Canada, Census of Agriculture
Physical properties of the mor layer in a Scots pine stand III. Thermal conductivity
Authors: Laurén A.
Published: April 2011

Thermal conductivity was measured with thermal probes in undisturbed mor samples subjected to water desorption and sorption. The volumetric water content was determined simultaneously with time domain reflectometry. The thermal conductivity increased from 0.06 to 0.24 W m−1 K−1, when the water content increased from 0.10 to 0.40 m3 m−3. There was little spatial variation in the mor layer. The results were similar to those found in the literature for peat and humus materials. The thermal conductivity of the mor layer could be predicted with the de Vries model with good accuracy if the humus and air particles were assumed to be of lamellae shape and latent heat transport in air-filled pores was neglected. Key words: humus, thermal probe, thermal properties, time domain reflectometry
Yield and N uptake of barley on two artificially eroded soils in north-central Alberta
Authors: Pradhan R. , Izaurralde R. C. , Nyborg M. , Malhi S. S.
Published: April 2011

Topsoil depth is an indirect indicator of soil quality and crop productivity. A 2-yr field study was conducted in north-central Alberta with the following objectives: (1) to determine aboveground barley dry matter yield, N uptake, and fertilizer-use efficiency (FUE) in two artificially eroded soils of contrasting properties, and (2) to assess the effectiveness of KNO3 and urea in compensating for lost productivity. Field experiments were conducted on an Orthic Gray Luvisol (Site 1) and on an Eluviated Black Chernozem (Site 2) in 1991 and 1992. The treatments consisted of three depths of topsoil removal (0, 10 and 20 cm) and three N fertilizers (KNO3 and urea at 150 kg N ha−1, and the control). The plots were sown to barley (Hordeum vulgare L.). Yields and N uptake of aboveground barley dry matter decreased with each increment of topsoil removal and were lowest in the 20-cm topsoil removal. Fertilizer N improved yields and N uptake at each depth of erosion. In most of the erosion treatments barley yields and N uptake tended to be greater with KNO3 than with urea. The effectiveness of each N source, however, varied with site. At the 20-cm depth of erosion, KNO3 was more effective than urea. The trend in fertilizer-use efficiency increased with depth of erosion at Site 1 but decreased at Site 2.

Key words: Artificial erosion, barley, fertilizer-use efficiency, potassium nitrate, urea
Chemical characterization of dissolved organic matter released by limed and unlimed forest soil horizons
Authors: Erich M. Susan , Trusty Georgette M.
Published: April 2011

Liming of forest soils, currently practiced in Europe, may be necessary in the future in North America to counteract calcium (Ca) depletion due to whole tree harvesting. With current concerns over increasing carbon dioxide (CO2) levels in the atmosphere, the effects of forest practices such as liming on carbon (C) cycling in forest ecosystems has been receiving increasing attention. This laboratory study investigated the effect of an increase in pH on dissolved organic matter (DOM) in water extracts of organic horizons. Organic horizons were collected from nine forested sites, some predominantly hardwood and some predominantly softwood stand types. The soils were chemically characterized. Water extracts of limed and unlimed treatments of nine organic horizons were analyzed for pH, Al, Fe, Ca, C, and DOM negative charge density. Total luminescence fluorescence spectra were also obtained for each extract. The addition of lime (CaCO3) to organic horizons caused an average of 55% more C to be released than in unamended samples. Liming caused no significant changes in negative charge density of the DOM. Liming decreased organically-complexed aluminum (Al) and increased organically-complexed Ca. There was a negative correlation between Al concentration of extracts and fluorescence intensity. Chemical changes in the DOM released by liming were suggested by decreased fluorescence emission and excitation wavelengths due to liming. Hardwood samples did not respond differently than softwood samples with respect to DOM concentration, functional group concentration, or spectroscopic characteristics. However, there was a suggestion that particular tree species, such as cedar, may have unique effects on C concentrations and DOM chemistry.

Key words: Lime, forest soil, dissolved organic matter, fluorescence
Nitrogen dynamics under growth chamber conditions as influenced by method of alfalfa termination 2. Plant-available N release
Authors: Mohr R. M. , Janzen H. H. , Entz M. H.
Published: April 2011

Herbicide application has been proposed as an alternative to tillage for termination of established alfalfa (Medicago sativa L.) stands but it may alter the pattern and amount of N released from alfalfa residues. A controlled environment study was conducted to investigate the effect of termination technique on the availability of N to four barley (Hordeum vulgare L.) crops. Four treatments consisting of a factorial combination of two termination methods (chemical, mechanical) and two methods of residue placement (surface, incorporated) were established. Nitrogen uptake by the four consecutive crops of barley was measured during a 125-d period after termination. Termination method, particularly residue placement, strongly affected N release from alfalfa residues. Nitrogen accumulation by the initial barley crop accounted for >60% of cumulative N uptake in incorporated treatments compared with 39% and 24% for herbicide and tillage treatments in which alfalfa residue was surface applied. Herbicide application also slightly increased N uptake by the initial barley crop. Nitrogen uptake by subsequent barley crops was not affected by termination method; however, cumulative N uptake remained substantially greater for incorporated treatments throughout the 125 d experiment. Effects of residue particle size on N release from alfalfa residues were small. These results suggest that herbicide termination in which residue is retained on the soil surface may reduce the short-term plant-available N supply. Provided that mineralization is sufficient to meet the N needs of subsequent crops, maintaining a smaller reservoir of soil inorganic N may be beneficial in reducing the potential for leaching or denitrification losses. Key words: Plant-available N, termination method, alfalfa, herbicide, tillage, growth chamber
Denitrification estimates in monoculture and rotation corn as influenced by tillage and nitrogen fertilizer
Authors: Fan Ming X. , MacKenzie Angus F. , Abbott Melissa , Cadrin François
Published: April 2011

Denitrification in agricultural soils results in loss of N for crop growth and production of N2O, a greenhouse gas. Agricultural management must be evaluated for denitrification losses in order to develop minimum N loss systems. Field estimation of denitrification losses is necessary to evaluate crop management effects. Two methods of field denitrification measurements, a soil core (SC) incubation and an in situ closed chamber (CC), were assessed in monoculture corn (Zea mays L.) and corn in rotation with soybean (Glycine max L. Merill) and alfalfa (Medicago sativa L.). Relative estimates of denitrification by the two methods depended on soil texture, with the CC method showing more treatment effects. Denitrification losses were higher with no-till than conventional tillage at one site, and were generally higher with corn than soybean. Nitrogen losses were linear with added N in monoculture corn plots, and ranged from 1.1 to 4.1% of added N. Losses were not related to added N in corn following alfalfa or soybean. Ratios of N2O/(N2O + N2) as measured with the SC method were lower at the Ste. Rosalie (1) site than at the Chicot site (0.95 to 2.84), but ratios of N2O/(N2O + N2) measured with the CC method were similar for the sites, from 0.46 to 1.20. Denitrification losses measured by either method were related to soil moisture and nitrate content in the soils. Corn production should be carried out with conventional tillage and minimum fertilizer N rates for minimum denitrification.

Key words: Rotations, corn, soybean, denitrification, closed chamber, soil core
Soil acidity in 1970 and 1989 in a coniferous forest in southwest Finland
Authors: Westman C. J. , Jauhiainen S.
Published: April 2011

Forest soil pH in southwest Finland was measured with identical sampling and analysing methods in 1970 and 1989. The acidity of the organic humus layer increased significantly as pH values measured on water and on salt suspensions decreased between the two sampling dates. For the mineral soil layers, no unambiguous trend was found. pH values measured on salt suspension tended to be unchanged or lower, while pH on water suspension in some soil layers were even higher in 1989 than in 1970. Key words: pH, repeated sampling
In situ amelioration of sodic minespoil with chemical amendments and crop management: II. Soil physical properties, soil moisture and plant growth
Authors: Sansom J. J. , Chanasyk D. S. , Naeth M. A. , Bateman J. C.
Published: April 2011

The effects of sulfur and gypsum amendments in conjunction with crop management (fallow/barley and forage) on soil physical properties, soil moisture and vegetation characteristics were measured on a sodic and calcareous sandy loam minespoil at the Highvale coal mine, west of Edmonton, Alberta.Amendment and crop management had no significant effect on bulk density, plant species composition, canopy cover, ground cover or annual aboveground biomass. Crop management significantly affected penetration resistance (which was generally higher under forage), while amendment treatments did not. Profile soil moisture was lowest within the gypsum-amended plots at all depths, and was similar for sulfur-amended and control plots. Crop management affected profile soil moisture, with significantly less moisture under continuous forage than fallow/barley. As percolation is critical to the effectiveness of amendments in the amelioration process, cereal/fallow rotations are more effective than continuous forage in facilitating that process. Key words: Reclamation, bulk density, penetration resistance
Litterfall and soil characteristics in canopy gaps occupied by vine maple in a coastal western hemlock forest
Authors: Ogden Aynslie E. , Schmidt Margaret G.
Published: April 2011

In some low-elevation coastal British Columbia forests, canopy gaps can be occupied by the hardwood tree species, vine maple (Acer circinatum). The objective of this study was to determine how vine maple gaps influence litterfall, litter decomposition, and forest floor and mineral soil properties. Measurements were made on six vine maple gaps paired with six conifer canopy plots. Vine maple gaps had significantly less conifer litterfall during the autumn, higher pH, and higher concentrations of Ca, Mg and K in the forest floor, thinner forest floors, and a weak tendency for lower C/N ratios, higher pH values and higher total N concentrations in the surface mineral soil. Vine maple litter was found to decompose significantly faster than conifer litter and to have higher concentrations of N, P, Ca, Mg, K, Fe and Zn. Decomposition rates of vine maple litter and of conifer litter did not differ significantly between vine maple gap and conifer canopy plots. Larger vine maple clones had significantly thicker forest floors with higher concentrations of Ca, and higher N concentrations and lower C/N ratios in the surface mineral soil than gaps with smaller vine maple clones. The results indicate that vine maple gaps may improve the nutritional status of the sites that they occupy within conifer forests. Key words: Litterfall, litter decomposition, soil-plant interactions, vine maple, canopy openings, canopy gaps
Carbon-13 CP/MAS NMR and DR-FTIR spectroscopic studies of sugarcane distillery waste
Authors: Benke M. B. , Mermut A. R. , Chatson B.
Published: April 2011

The application of a sugarcane distillery waste known as vinasse to agricultural land has become a common practice in Brazil. The vinasse samples used in this study were collected from several sugarcane distilleries in Northeastern Brazil. These samples were fractionated into dissolved organic carbon (DOC) and particulate organic carbon (POC) fractions. Unfractionated and fractionated vinasse were studied using 13C cross-polarization and magic-angle spinning nuclear magnetic resonance (CP/MAS NMR) spectroscopy as well as diffuse reflectance Fourier-transform infrared (DR-FTIR) spectroscopy. Approximately 79 to 92% of the total unfractionated vinasse dry matter was in the form of DOC fraction. O-alkyl C (42–53% of the total C) and carboxyl C (12–25% of the total C) comprised a significant portion of the 13C NMR spectra of the DOC fraction. The presence of carbohydrates and COOH/COO− was suggested by the DR-FTIR as well. Both 13C NMR and DR-FTIR spectra of this fraction were generally similar to the spectra of the fulvic acid (FA) fraction of soil and sewage sludge. The spectra of DOC differed from the FA fraction in that they showed smaller amounts of aromatic C and had an absence of amide group (bands at 1650 cm−1 and 1540 cm−1). In the POC fraction, O-alkyl (17–52% of the total C) and alkyl C (15–41% of the total C) were the major contributors. The peaks at 62 ppm, 72 ppm, 84 ppm and 105 ppm in the O-alkyl region indicate the presence of cellulose and/or hemicellulose. The alkyl group was comprised mainly of long-chain structures. The total N content in this fraction is ~3–7 times as much as in the DOC fraction. The presence of amino acids in the POC fraction was suggested by both 13C NMR and DR-FTIR spectra. Key words:13C cross-polarization and magic-angle spinning nuclear magnetic resonance, dissolved organic carbon, Fourier-transform infrared, particulate organic carbon, vinasse
Carbon dioxide efflux from the floor of a boreal aspen forest. II. Evaluation of methods — verification by infra-red analysis of a dynamic closed chamber
Authors: Russell C. A. , Voroney R. P. , Black T. A. , Blanken P. D. , Yang P. C.
Published: April 2011

Concern over the global exchange of carbon has highlighted the need for reliable estimates of soil CO2 efflux (soil Fc). Appropriate methods to estimate soil Fc must be identified and adopted. In this study we used a dynamic closed chamber and infra-red gas analyzer (DCC-IRGA) to verify the use of three other methods in a boreal aspen (Populus tremuloides) forest. The three methods were: (1) soil CO2 concentration gradients and volumetric soil moisture by both diffusion theory (a) and empirical relationship (b), (2) an automated steady-state chamber and (3) daytime estimates derived from a relationship between soil temperature and nighttime eddy correlation measures of CO2 fluxes above the forest understory (4 m) and overstorey (39 m). We found reasonable agreement between DCC-IRGA and method 1a (R2 = 0.44 to 0.62), and excellent agreement between DCC-IRGA and the other methods (1b, R2 = 0.76 to 0.88; 2, R2 = 0.89 and 3, R2 = 0.64 to 0.80). Each of these methods has advantages beyond the scope of the DCC-IRGA, and these are discussed. Key words: CO2 flux, soil respiration, soil CO2 concentration, eddy correlation
Unsaturated hydraulic conductivity of conventional and conservation tillage soils in southern Alberta
Authors: Miller J. J. , Sweetland N. J. , Larney F. J. , Volkmar K. M.
Published: April 2011

Conservation tillage is increasing on the Canadian prairies and its long-term effect on soil physical properties warrants investigation. Tension infiltrometer measurements were conducted on conventional tillage (CT), minimum tillage (MT) and no-till (NT) loam to clay loam soils in southern Alberta to determine if 26 yr of conservation tillage (MT, NT) modified the unsaturated hydraulic conductivity, K(ψ), relative to CT. Tillage of CT and MT plots was performed using a wide-blade cultivator. Measurements were performed on tillage treatments that were replicated on two adjacent parcels of land, with readings taken at the west parcel (Site 1) in 1993 and at the east parcel (Site 2) in 1994. Infiltration rates were determined at water potentials (ψ) of −0.3, −0.6 and −1.5 kPa. The K(ψ) values at −0.3, −0.6, −1.0 and −1.5 kPa (equivalent circular pore diameters of 1000, 500, 300 and 200 µm, respectively) were estimated from infiltration data using the nonlinear regression method of Logsdon and Jaynes. Tillage had a significant (P < 0.10) effect on K(ψ). Geometric mean K(ψ) values for NT (12.8 × 10−8 m s−1) were significantly (P < 0.05) lower than for CT (21.9 × 10−8 m s−1), but there was no significant difference between MT (13.6 × 10−8 m s−1) and CT, or between MT and NT. Although there was no significant tillage × site-year interaction (P > 0.10) for K(ψ), there was a trend for higher K(ψ) values at −0.6, −1.0 and −1.5 kPa in CT than MT and NT for Site 1 in 1993 compared to Site 2 in 1994. This trend was consistent with a shorter lag time between the most recent tillage event and subsequent infiltration measurements in CT for Site 1 in 1993 (1–16 d) compared with Site 2 in 1994 (28–45 d). Key words: Tillage, tension infiltrometer, unsaturated hydraulic conductivity
Effect of rotational grazing on selected physical properties of a Gleyed Brunisolic Gray Luvisol loam in Nova Scotia
Authors: Rodd A. V. , Papadopoulos Y. A. , Laflamme L. F. , McRae K. B. , Fillmore S. A. E. , Wilson R. W.
Published: April 2011

Low organic matter content and weak soil structure, combined with high annual precipitation, make the soils of the Maritime Provinces extremely susceptible to compaction. Although many pasture studies have been conducted in the Maritime Provinces, none has investigated the impact of pasturing cattle on soil physical properties. Soil properties such as resistance to penetration, bulk density and hydraulic conductivity were monitored on pasture swards receiving various rotational-grazing intensities. These parameters were measured concomitantly on traffic-free areas that had been harvested as conserved forage. Resistance to penetration measurements indicate that a significant amount of compaction by cattle occurred during the 1990, 1991 and 1992 grazing seasons. Penetration resistance was generally greatest in the top 6 cm of soil, but was alleviated by frost action during the subsequent winter and spring. The other soil parameters measured were either more variable (surface and subsurface saturated hydraulic conductivity) or less sensitive (bulk density) to compaction. Although more variable, surface hydraulic conductivity was significantly higher in the traffic-free conserved forage areas than in the pasture paddocks. Rest intervals between grazings had no significant effect on saturated hydraulic conductivity. Seasonal change in resistance to penetration generally increased as rest interval decreased. The timothy/alfalfa swards (little alfalfa was left in the pastures by 1992) had the least seasonal change in resistance to penetration. Key words: Cattle, compaction, resistance to penetration, bulk density, hydraulic conductivity
Tillage effects on the dynamics of total and corn-residue-derived soil organic matter in two southern Ontario soils
Authors: Wanniarachchi S. D. , Voroney R. P. , Vyn T. J. , Beyaert R. P. , MacKenzie A. F.
Published: April 2011

Agricultural management practices affect the dynamics of soil organic matter (SOM) by influencing the amount of plant residues returned to the soil and rate of residue and SOM decomposition. Total organic C and δ13C of soil were measured in two field experiments involving corn cropping to determine the effect of tillage practices on SOM dynamics. Minimum tillage (MT) and no tillage (NT) had no significant impact on the soil C compared with conventional tillage (CT) in the 0- to 50-cm soil depth sampled at both sites. Continuous corn under MT and CT for 29 yr in a silt loam soil sequestered 61–65 g m−2 yr−1 of corn-derived C (C4-C), and it accounted for 25–26% of the total C in the 0- to 50-cm depth. In a sandy loam soil cropped to corn for 6 yr, SOM contained 10 and 8.4% C4-C under CT and NT, respectively. Reduced tillage practices altered the distribution of C4-C in soil, causing the surface (0–5 cm) soil of reduced tillage (MT and NT) plots to have higher amounts of C4-C compared to CT. Tillage practices did not affect the turnover of C3-C in soil. Key words: Soil organic matter, 13C natural abundance, tillage practices
Effect of tillage and residue management on barley and canola growth and water use efficiency
Authors: Azooz R. H. , Arshad M. A.
Published: April 2011

Residue management and tillage are used to reduce the effect of water deficit or excess on crop production in northwestern Canada. This study was conducted on Donnelly silt loam and sandy loam soils (both Gray Luvisols) to evaluate the effects of conventional tillage (CT), no-tillage (NT) and modified NT (MNT, i.e., NT with 75-mm wide residue-free strip over the planting row) on barley (Hordeum vulgare L.) and canola (Brassica campestris L.) dry matter accumulation and grain production, water depletion and water use efficiency (WUE) in 1992 and 1993. Infiltration rates (Ic), soil water content, plant dry matter and grain yields were measured. The Ic of the two soils was greater than the rainfall rate (Rr) in both years, suggesting that there was no runoff. In 1992, a dry year, barley grain yields were significantly greater by 16% on the silt loam and by 17% on the sandy loam under MNT as compared with CT. The MNT increased barley grain yield by 3% compared with NT on the silt loam and increased canola grain yield by 12% on the sandy loam soil in 1993, which was a wet year. Dry matter accumulation and grain yield of barley in CT were adversely affected by a prolonged early dry period in 1992. Abundant rainfall slowed barley and canola growth and depressed yield in the NT in 1993. From seeding to harvest in 1992, WUE for barley grain production on the silt loam was greater by 21% in the NT and by 18% in the MNT as compared with the CT, which had a WUE of 5.25 kg ha−1 mm−1; it was greater by 19% in the NT and by 10% in the MNT compared with the CT on the sandy loam soil with a WUE of 5.07 kg ha−1 mm−1. In 1993, NT and MNT had lower WUE, which coincided with lower grain yield as compared with CT. Key words: Infiltration, water depletion, drying rate and drainage
Evidence for solum recarbonation following forest invasion of a grassland soil
Authors: Fuller L. G. , Wang D. , Anderson D. W.
Published: April 2011

Calcareous organic-matter-rich Black Chernozemic soils often persist under poplar forests in Saskatchewan, not acquiring the Ae horizons and related properties more characteristic of Gray Luvisol soils. These are Rego Black Chernozems, locally termed "Wooded Calcareous" because of the occurrence of a dark, calcareous horizon (AC) at depths of 10 to 30 cm. We hypothesize that dark, calcareous horizons are former Bm horizons that have been recarbonated because of intense biocycling of Ca by aspen (Populus tremuloides). The comparatively small amounts of carbonate occur mainly in the fine silt and clay fractions, and are dominantly calcite, indicating secondary origin, in comparison to the carbonate minerals of the Ck horizons where both calcite and dolomite occur, the latter more common in coarse fractions. The δ13C values of the carbonate minerals indicate that virtually all the carbonate in fine fractions of the upper horizons of the Wooded Calcareous soil is pedogenic. The dominance of pedogenic carbonate in the Ahk and AC horizons of the Wooded Calcareous soil is consistent with a secondary enrichment, a probable result of increased biocycling of Ca where aspen grows on sites with large amounts of soluble Ca in the subsoil. High concentrations of soluble Ca2+ and SO42− in the LFH of the Wooded Calcareous are consistent with increasing biocycling of these ions, from a gypsum-rich subsoil. Key words: Pedogenic carbonate, prairie-forest transition, stable carbon isotopes, biocycling, δ13C values
Characterization of several on-farm and industrial composted materials
Authors: Gagnon Bernard , Robitaille Robert , Simard Régis R.
Published: April 2011

Manure management and composting methods may greatly affect compost characteristics. An experiment was conducted to characterize 23 on-farm and 6 industrial composts in Québec (Canada). Cluster analysis identified two major groups characterized by their chemical composition, source materials, management intensity and degree of decomposition. Electrical conductivity, total N and K, water-soluble NH4+, PO4, K, Al and organic C, and a cress test were the best chemical and biological parameters for grouping composts. These groups were strongly associated with bedding rate, turning frequency, composting duration, profile windrow appearance, material aggregation and odor. When restricted to dairy manure composts, no clear relationship could be established by cluster analysis between material grouping and their farm management. Statistical analysis on single chemical parameters of dairy manure composts, however, identified five farm management factors: type and amount of bedding, system of manure handling and storage, compost windrow turning, composting length and milk production intensity. These factors affected one or several major parameters: pH, dry matter, electrical conductivity, total and water-soluble C, N, P and K, and humic components characteristics. This study demonstrated the importance of leaching losses in the on-farm composting operations in humid cold regions and the need for more environmentally sustainable composting methods. Key words: Farm manure management, composting, chemical composition
Iron bands, fragipans and duripans in the northeastern plateaus of Brazil — properties and genesis
Authors: Boulet R. , Fritsch E. , Filizola H. F. , Araujo Filho J. C. De , Leprun J. C. , Barretto F. , Balan E. , Tessier D.
Published: April 2011

Iron bands, fragipans and duripans are common in yellow low-activity clay soils developed from the Barreiras Group in coastal plateaus of northeastern Brazil. Such indurated horizons are found in depressions of the plateaus where sugar cane growth is greatly reduced. Little research has being done on the nature of their bonding agents and their genesis. Research carried out in arid zones has frequently attributed duripan consistency to amorphous silica; however, duripans in northeast Brazil occur under higher rainfall (1500–2000 mm). The objective of this work was to study the nature and distribution of soil features in a plateau to better understand the processes associated with soil hardening. Two transects, across a small and a large depression, were investigated using field soil characterisation, micromorphological techniques, and mineralogical and geochemical analyses.The formation of the indurated horizons studied is due to two sequential processes: development of aquic conditions and incipient podzolization. Such processes have affected the upper part of a thin (<0.6 m in small depressions) or thick (>0.6 m in large depressions) compact clay horizon, showing horizontal plans likely inherited from the sediment. Onset of aquatic conditions formed the first fragipans overlying iron bands. Later, aquic conditions are combined with incipient podzolization to produce bleached loose horizons overlying duripans and iron bands. As the bonding agents in the duripans are organo-metallic complexes, these duripans appear to be very different from those described in arid environments. Key words: Low activity clay Ultisols, Barreiras Group, iron bands, fragipans and duripans, organo-metallic complexes
Sorption of ammonia and release of humic substances as related to selected peat properties
Authors: Vaillancourt N. , Parent L. E. , Buteau P. , Parent V. , Karam A.
Published: April 2011

Peat is a hetorogenous material containing humic substances (HS) that increase its fertilizer value, and acid functional groups that react with ammonia. However, polyvalent cations may block some ammonia-sorbing sites. Sixty-seven peat samples were collected in Quebec (i) to relate the colorimetric Kaila pyrophosphate test for extracting HS to the von Post field test and (ii) to correlate ammonia sorption capacity (ASC) to selected peat properties as follows: von Post test, Kaila pyrophosphate test, pH(H2O), pH(CaCl2), pH(KCl), exchangeable acidity as well as ash, Ca, Al and Fe contents. Exchangeable acidity was the most highly correlated with ASC (P < 0.01). Using field-moist material and a 1:4 peat:solution volumetric ratio, the most reliable criteria were pH(CaCl2) < 4.4 and pH(KCl) < 4.5. Using air-dry peat and a 3:50 peat:solution ratio, the corresponding criteria were pH(CaCl2) < 4.3 and pH(KCl) < 4.1. The pH(CaCl2) method provided the most consistent determination of peat acidity, whether taken on a volume or weight basis. A minimum pyrophosphatate test value between 0.1 and 0.2 absorbance unit is apparently required for making peat composts and peat-ammonia-mineral fertilizers enriched in soluble humic substances. The pH(CaCl2) method and the Kaila pyrophosphate test should be combined to routinely control the quality of peat materials for making peat composts and peat-ammonia-mineral fertilizers. Key words: pH, exchangeable acidity, pyrophosphate test, ammonia sorption capacity
Soil microbial biomass and carbon dioxide flux under wheat as influenced by tillage and crop rotation
Authors: Lupwayi N. Z. , Rice W. A. , Clayton G. W.
Published: April 2011

Soil organic matter is important both from an agronomic and an environmental perspective because it affects the capacity of the soil to sustain crop growth, and it is a source and sink of atmospheric CO2-C. Soil microbial biomass comprises a small proportion of total soil organic matter, but it is more dynamic than total soil organic matter. Therefore, measurements of soil microbial biomass may show the effects of soil management on potential changes in soil organic matter before such effects can be detected by measuring total soil organic matter. The effects of tillage and crop rotation on soil microbial biomass and activity were studied in 1995–1997 in the wheat phase of different cropping rotations that had been established in 1992 under zero tillage or conventional tillage in northern Alberta. Soil microbial biomass was often significantly (P < 0.05) higher, but never significantly lower, under zero tillage than under conventional tillage. However, CO2 evolution (basal respiration) was usually higher under conventional tillage than under zero tillage, resulting in higher specific respiration (qCO2) under conventional tillage than under zero tillage. The higher additions but lower losses of labile C under zero tillage mean that more C is sequestered in the soil in the zero-tillage system. Thus, this system contributes less to atmospheric CO2 than conventional tillage, and that soil organic matter accumulates more under zero tillage. Plots preceded by summerfallow, especially under conventional tillage, usually had the lowest microbial biomass and CO2 evolution, and plots preceded by legume crops had higher microbial biomass and lower qCO2 than other treatments. Tillage and rotation had little effect on total soil organic matter 5 yr after the treatments had been imposed, probably because of the cold climate of northern Alberta, but the results confirm that the labile forms of soil C are more sensitive indicators of soil organic C trends than total soil organic C. These effects of tillage and rotation on soil microbial biomass were similar to those on microbial diversity reported previously. These results confirm that zero tillage and legume-based crop rotations are more sustainable crop management systems than conventional tillage and fallowing in the Gray Luvisolic soils of northern Alberta. Key words: Carbon sequestration, carbon mineralization, microbial activity, soil organic matter
Influence of tillage and cropping system on soil organic matter, structure and infiltration in a rolling landscape
Authors: Elliott J. A. , Efetha A. A.
Published: April 2011

The influence of tillage and cropping system on soil organic matter, structure and infiltration was studied in a rolling, glaciolacustrine landscape in Saskatchewan with slopes ranging from 6 to 30%. A field that had been continuously cropped using zero tillage (ZTCC) for 11 yr was compared with conventional tillage in a crop–summerfallow rotation (CTCF) on an adjacent field. Soils in each field were sampled according to their position in the landscape. Soil organic C, aggregrate size and aggregate stability were significantly greater on the ZTCC plot than the CTCF. Infiltration rates averaged 74 and 52 mm h−1 on the ZTCC and CTCF plots, respectively. Differences between treatments were most pronounced at the shoulder positions. Increased soil strength was measured on the CTCF plot at depths corresponding to the action of tillage implements (0.05 m and 0.15 m). On the CTCF plot, infiltration rates correlated with initial moisture, aggregate stability and bulk density but on the ZTCC plot consistent correlations were only found between infiltration and bulk density. When measured infiltration rates were compared with expected storm intensities, the differences in infiltration rates between treatments and their distribution in the landscape resulted in substantially more runoff from the CTCF plot than the ZTCC. Key words: Zero tillage, cropping frequency, infiltration rate, aggregation, organic carbon, landscape