bluuebunny/crossref_metadata_2025 huggingface dataset:
Physical properties of the mor layer in a Scots pine stand I. Hydraulic conductivity
Authors: Laurén A. , Heiskanen J.
Published: April 2011

Hydraulic conductivity in the mor layer of a Scots pine (Pinus sylvestris L.) stand was measured in undisturbed samples using the constant-head permeameter and instantaneous-profile method. Saturated hydraulic conductivity (Ks) averaged 2.9 × 102 m d−1. With a decrease in matric potential (ψ) from −4 kPa to −70 kPa the unsaturated hydraulic conductivity (K(ψ)) decreased from 3.1 × 10−3 to 1.1 × 10−8 m d−1. Ks and K(ψ) were similar to those reported in the literature for low-humified peat. The variation in hydraulic conductivity within a stand of Scots pine at a given matric potential was large, ranging from one to two orders of magnitude. Key words: F horizon, humus, hydraulic properties of soil
An analysis of soil organic matter dynamics in relation to management, erosion and yield of wheat in long-term crop rotation plots
Authors: Monreal C. M. , Zentner R. P. , Robertson J. A.
Published: April 2011

We examined the influence of management on soil organic matter (SOM) dynamics and yield of wheat grain in semiarid Chernozemic and humid Gray Luvisolic soils. The Century model was tested with data obtained from long-term research plots cropped to wheat (Triticum aestivum L.) monoculture and cereal-hay (CH). Century simulated changes in soil organic-C (OC) and organic-N (ON) within 10% of actual measurements taken over decades. Our analysis indicated that management and soil erosion affected the time required for SOM to achieve new steady-state level (Tst). Tst ranged between 12 yr under wheat and 46 yr under CH cropping. Increasing the SOM content of degraded soils to new steady-state level appears to increase grain yield between 86 kg ha−1 and 840 kg ha−1.Wheat-fallow (WF) rotation plots receiving <10 kg N ha−1 yr−1, and with erosion >13.6 t ha−1 yr−1 degraded SOM. The average long-term yield of wheat grain (including new high yielding varieties) was maintained at <910 kg ha−1 yr−1 under degraded SOM content. Well-fertilized continuous wheat (CW) and CH rotation plots with erosion <4 t ha−1 yr−1 aggraded SOM content, and maintained the long-term average grain yield at >1290 kg ha−1 yr−1. Sustained OC levels were attained by returning 1030 kg C ha−1 yr−1 as plant residue (roots + aboveground) and keeping soil erosion ≤12.8 t ha−1 yr−1. Sustainable crop production systems need to consider SOM dynamics and erosion as factors limiting grain yield even after introducing genetically improved wheat varieties. Key words: Management, organic matter, erosion, dynamics, yield, manure, nitrogen, tillage, steady-state
Kinetic formulation of oxygen consumption and denitrification processes in soil
Authors: Cho C. M. , Burton D. L. , Chang C.
Published: April 2011

A kinetic expression for oxygen, nitrate, nitrite and nitrous oxide reduction in soil was developed. The formulation was based on competitive Michaelis-Menten kinetics for a steady microbial population whose respiratory activity was assumed to be constant so that the number of electrons produced per unit of time was constant. Competition among the electron acceptors was characterized by their affinity toward the electron and by their concentration. Several different values for the affinity coefficients were used to simulate the concentration of O2, NO3−, NO2−, N2O and N2 at various times. When relative magnitudes of affinity coefficients were chosen to be 100 000, 1, 100 and 0.1, for O2, NO3−, NO2− and N2O, respectively, the temporal plot of concentration showed that the disappearance of O2 and NO3− was zero order. The accumulation of NO2− was very small and it was rapidly reduced to N2O. The production rate of N2O was nearly zero order but the magnitude of the rate was rather small as opposed to the rate of disappearance of NO3−. The reduction of N2O to N2 took place only after NO3− had almost disappeared. With these competition parameters NO3− was stable in the presence of O2. The reduction of N2O was also very much retarded in the presence of NO3−. NO2− was relatively unstable, even in the presence of O2, and it was further reduced to N2O. With the relative magnitude of the chosen affinity coefficients, the kinetic formulation effectively simulated the "inhibitory" effect of O2 upon the denitrification process, and the "inhibitory" effect of NO3− and NO2− upon the reduction of N2O to N2.

Key words: Oxygen consumption, denitrification, kinetics, competition
Measurement of microbial biomass N:C by chloroform fumigation-incubation
Authors: Harris D. , Voroney R. P. , Paul E. A.
Published: April 2011

We present a calculation for soil microbial biomass N:C ratio determined from a 10-d incubation following chloroform fumigation. The calculation is based on a mathematical model of the N content of the pre- and post-fumigation soil microbial biomass and the growth yield of the biomass that develops after fumigation. Biomass N is calculated from the N:C ratio and biomass C. The mineralization of bacteria and fungi, with different N contents, added to fumigated soils was used to establish the model parameters. The model was tested against an independent set of measurements and considers two assumptions: 1) The ratio of N:C mineralized from killed biomass is equal to the ratio of N:C mineralized from soil non-biomass constituents. 2) More realistically, the N and C mineralization in the fumigated soil, from sources other than killed biomass, is a residual fraction of the N and C mineralization in the unfumigated soil. Biomass C:N ratios calculated without a control correction (assumption 1) were, on average, 20% wider than corrected values (assumption 2). Biomass N calculated as the product of N:C and biomass C was compared with published values for several data sets. The new calculation method was robust even when net immobilization of N followed fumigation. Key words: Soil microbial biomass, nitrogen, chloroform fumigation, C:N ratio
Estimates of water deficits and surpluses during the growing season in Ontario using the SWATRE model
Authors: Jong R. De , Bootsma A.
Published: April 2011

The spatial and temporal variations in soil water play a key role when considering issues such as irrigation and drainage requirements, crop growth and yield potential and contamination of groundwater by agricultural chemicals. In this study a previously validated deterministic model was used to estimate water (evapotranspiration) deficits and surpluses during the growing season of a perennial forage crop at 14 locations in Ontario. Three different hydraulic soil profile characteristics, representing a clay, clay loam and sandy loam soil, and three different lower boundary conditions (free drainage, fixed and fluctuating water table) were considered. Seasonal deficits ranged from less than 15 mm in abnormally wet years (90% probability of exceedence) in the north, to more than 300 mm in exceptionally dry years (5% probability of exceedence) in the extreme southwest region of the province. With a water table fluctuating between 25 cm depth during the middle of April and 140 cm in early October, 28 to 49% of the evapotranspiration deficit was caused by excess water in all three soils. The flux of water at 100 cm depth, accumulated during the growing season, was used as a measure of the net amount of surplus water moving through the root zone or being extracted from the water table. This flux ranged from significant upward values in dry years in a sandy loam with a fixed water table at 120 cm depth, to downward fluxes of more than 300 mm in abnormally wet years when a fluctuating water table was present. Our simulations show important spatial and temporal interactions among soil and climatic factors and suggest that each one, including the lower boundary condition, should be properly characterized in soil water investigations.

Key words: Soil water, modelling, spatial and temporal variability, forage crop
Changes in soil biochemical and cracking properties induced by "living mulch" systems
Authors: Masciandaro G. , Ceccanti B. , Garcia C.
Published: April 2011

A vermicompost (VC) from biological sludges was incorporated into two soils, or applied on their surfaces as mulch with the addition of worms (Eisenia foetida) or grass seeds (Lepidium sativum) in the experiments of "living mulch". The purpose of this research was to study the influences of different methods of organic matter application on soil chemico-physical and biochemical properties. Two texturally different soils from a Mediterranean climate, a clayey and a sandy soil, were tested in laboratory-scale experiments. Water-soluble C (WSC), NO3-N/NH4-N ratio (nitrification index), and enzyme activities (BAA-protease, dehydrogenase, and β-glucosidase) were taken as indices of soil biochemical fertility as they are related to soil physical properties and microbial activities. Surface cracking area in both soils increased, with the formation of small–medium (<1000 µm) cracks. The positive changes in cracking, the high index of nitrification, and the evolution of WSC provided evidence for high metabolism in mulched soils. Enzyme activity was similar in living mulch and control soils, and was highest when VC was directly incorporated. Significant correlations (P < 0.05) occurred between enzyme activities, organic substrates, and soil cracking area for both soils. The selected parameters were indicators of the different practices of organic matter application. Key words: Vermicompost, mulching, soil enzymes, soil cracking
Estimating storm erosion with a rainfall simulator
Authors: Nolan S. C. , Vliet L. J. P. van , Goddard T. W. , Flesch T. K.
Published: April 2011

Interpreting soil loss from rainfall simulators is complicated by the uncertain relationship between simulated and natural rainstorms. Our objective was to develop and test a method for estimating soil loss from natural rainfall using a portable rainfall simulator (1 m2 plot size). Soil loss from 12 rainstorms was measured on 144-m2 plots with barley residue in conventional tillage (CT), reduced tillage (RT) and zero tillage (ZT) conditions. A corresponding "simulated" soil loss was calculated by matching the simulator erosivity to each storm's erosivity. High (140 mm h−1) and low (60 mm h−1) simulation intensities were examined. The best agreement between simulated and natural soil loss occurred using the low intensity, after making three adjustments. The first was to compensate for the 38% lower kinetic energy of the simulator compared with natural rain. The second was for the smaller slope length of the simulator plot. The third was to begin calculating simulator erosivity only after runoff began. After these adjustments, the simulated soil loss over all storms was 99% of the natural soil loss for CT, 112% for RT and 95% for ZT. Our results show that rainfall simulators can successfully estimate soil loss from natural rainfall events. Key words: Natural rainfall events, simulated rainfall, erosivity, tillage
Bark particle sizes and the modification of the physical properties of peat substrates
Authors: Nkongolo Nsalambi V. , Caron Jean
Published: April 2011

The physical quality of peat mixes is in part related to the capacity of the substrate to store and supply air and water to plant roots. During manufacturing, the mixing of various substrate components modifies the substrate characteristics. The objective of this study was to assess the changes in air storage and supply properties caused by varying the particle size of the substrate components. The substrate was composed of 40% wood bark (WB), 50% peat, and 10% coarse gravel (volume basis). Wood bark particle size was varied in a first (0–2, 2–4, 4–8 and 8–25 mm) and a second (1–2, 2–4, 4–8 and 8–16 mm) experiment. When increasing bark particle sizes to 8–25 mm or 8–16 mm, air supply characteristics, as assessed with gas diffusivity measurements, decreased to 0.78 or 0.45 its value for the 2–4 or 1–2 mm average bark particle size. This occurred despite no significant changes in air storage, as assessed from air-filled porosity measurements. Key words: Gas diffusivity, pore tortuosity, air-filled porosity, peat lite mixes, peat substrates
Long-term tillage and crop residue management in the subarctic: fluxes of methane and nitrous oxide
Authors: Cochran Verlan L. , Sparrow Elena B. , Schlentner Sharon F. , Knight Charles W.
Published: April 2011

Methane and nitrous oxide are important radiatively active gases that are influenced by agricultural practices. This study assesses long-term tillage, crop residue management, and N fertilization rates on the flux of these two gases at a high latitude site representing the northern fringe of large-scale agriculture. Cumulative methane uptake for the summer was higher from no-tillage plots than tilled plots. This was associated with lower soil water contents with tillage. Thus, the reduction in CH4 uptake was attributed to water stress on methane oxidizers. At planting, soil water contents were near field capacity, and the no-till plots had the lowest uptake which was attributed to restricted diffusion of methane to active sites. A similar pattern of methane uptake to soil water content was found with the residue management treatments. Removing the straw lowered the soil water content and for most of the season methane uptake was also lower than where the straw had been left on the plots. Nitrogen fertilizer rate had little effect on methane uptake over the summer, but high N rates lowered consumption during the time of active nitrification early in the season. This corresponded to the time of maximum efflux of nitrous oxide. Nitrous oxide efflux was greatest at the high N rate where straw was retained on the plots. Key words: Methane, nitrous oxide, nitrification, denitrification, barley
Soybean nitrogen contribution to corn and residual nitrate under conventional tillage and no-till
Authors: Rembon F. S. , MacKenzie A. F.
Published: April 2011

Soybean (Glycine max L. Merill) can produce high-N residues that may benefit subsequent corn (Zea mays L.) production, but the degree of benefit is often unpredictable and may be related to tillage methods. This study investigated the effects of conventional-tillage (CT) and no-tillage (NT) on fertilizer replacement values for corn in a corn-soybean rotation. Field experiments were conducted for two growing seasons on two soils, a Ste. Rosalie clay (Humic Gleysol), and an Ormstown silty clay (Humic Gleysol). Continuous corn, corn following soybean, soybean following corn, continuous soybean, and three levels of fertilizer N (0, 90, 180 and 0, 20, and 40 kg N ha−1 for corn and soybean, respectively) were compared. Tillage did not effect yield or N uptake consistently. Corn grain yields and N uptake were greater following soybean than following corn. Soybean provided N fertilizer credits ranging from 40 to 150 kg N ha−1, which was greater than the residual NO3 in the soil prior to planting. Credits were greater in the year with higher corn yields and lower previous winter precipitation resulting in greater NO3 carryover. Tillage effects on N credits from soybean differed between the sites. Consequently, N contributions of soybean to corn could not be related to tillage method or soil type. Key words:Zea mays L., Glycine max L. Merill, rotations, grain yield, N uptake, tillage, fertilizer N
Fine root biomass and nutrient content in a black spruce peat soil with and without alder
Authors: Bhatti J. S. , Foster N. W. , Hazlett P. W.
Published: April 2011

Vertical distribution of fine root biomass and nutrient content was examined within a black spruce (Picea mariana) stand growing on a boreal peat soil in northeastern Ontario. The influence of site physical and chemical properties on fine root biomass production was assessed. More then 80% of the fine roots were present in moss plus the top 10 cm of peat where nutrients and aeration are most favourable. The fine root biomass (W/V) was significantly higher with alder (5.9 kg m−3) (Alnus rugosa) as understory vegetation compared to non-alder locations (2.9 kg m−3). Total nutrient content in fine roots was 54, 3.2, 5.4, 63 and 5.7 kg ha−1 on the alder site and 20, 1.4, 2.3, 28 and 4.2 kg ha−1 of N, P, K, Ca, and Mg on the non-alder site, respectively. The mass (W/V) of nutrients in fine roots was strongly dependent upon the availability of nutrients in the peat. Fine root content had a strong positive relationship with peat available P and exchangeable K contents suggesting that P and K may be limiting nutrients for black spruce in this peat soil. Key words: Nitrogen, phosphorus, potassium, boreal peatlands, aeration, water table
Nitrous oxide emission as affected by tillage, corn-soybean-alfalfa rotations and nitrogen fertilization
Authors: MacKenzie A. F. , Fan M. X. , Cadrin F.
Published: April 2011

Nitrous oxide (N2O) produced from agricultural activities represents a threat to the ozone layer and economic losses. Rates and magnitudes of N2O emissions of cropping systems must be determined to establish corrective management procedures. In 1994, N2O emissions were determined with corn (ZeaMays L.) and corn-legume rotations. Continuous corn was studied on four soils, two from a long-term experiment, a Ste. Rosalie heavy clay (Humic Gleysol) and a Chicot sandy loam (Grey-Brown Podzol), at 0, 170, 285 or 400 kg N ha−1, and two from a corn rotation study, a Ste. Rosalie clay (Humic Gleysol) and an Ormstown silty clay loam (Humic Gleysol). Treatments included no-till (NT) and conventional tillage (CT), monoculture corn (CCCC), monoculture soybean; corn-soybean; and soybean-corn-alfalfa phased rotations. Nitrogen rates of 0, 90, or 180 kg N ha−1 for corn and 0, 20, or 40 kg N ha−1 for continuous soybean were used, and soybean/alfalfa following corn no fertilizer N. Rates of N2O emission were measured from closed chambers through the growing season. About 0.99 to 2.1% of N added was lost as N2O. Nitrous oxide emission increased with increased soil water content, NO3 concentration and fertilizer N rates. Emission of N2O was higher with NT than with CT, and with corn than with soybean or alfalfa. A corn system using CT, legumes in rotation and moderate fertilizer N would reduce N2O emission.

Key words: Greenhouse gases, soil nitrate, tillage methods, water-filled pore space, denitrification, rotations
The rate of carbon change in agricultural soils in Canada at the landscape level
Authors: Smith W. N. , Rochette P. , Monreal C. , Desjardins R. L. , Pattey E. , Jaques A.
Published: April 2011

The Century model [a computer simulation of the dynamics of soil organic carbon (SOC)] was used to estimate the rate of SOC change in agricultural soil in Canada. The analysis was carried out on 180 Soil Landscapes of Canada (SLC) polygons, representing 15% of the SLC polygons within agricultural regions. The analysis was stratified into soil zones and into soil textural classes. For each sampled polygon, Century was run for 1 to 5 types of crop rotations under conventional-tillage as well as no-tillage, providing that no-till was used on at least 5% of the land. From the Century simulations, it was estimated that the overall rate of SOC loss from agricultural soils in Canada for 1990 was 39.1 kg ha−1 yr−1 This implies that 1.93 Mt of SOC (7.08 Mt of CO2) was lost from agricultural soils in Canada. Compared to 1990, the SOC loss was estimated to have been greater by 11.9 kg ha−1 yr−1 in 1980 and 9.1 kg ha−1 yr−1 in 1985. The lower loss in 1990 was primarily due to the incorporation of no-till practices and reduction of summer fallow in the mid 1980s. In 1990, at the provincial level, Alberta had the highest rate of SOC loss at 74.5 kg ha−1 yr−1 followed by Manitoba with 66.1 kg ha−1 yr−1 In Ontario, Quebec, and the Atlantic Provinces the average provincial rate of SOC loss was less than 35 kg ha−1 yr−1 Higher SOC loss rates were typically found in soils with coarser texture and greater native SOC content.

Key words: Carbon dioxide, greenhouse gas, Century model
Seasonal and spatial variations in soil nitrogen and phosphorus supply rates in a boreal aspen forest
Authors: Huang Wei Z. , Schoenau Jeff J.
Published: April 2011

Soil nitrogen (N) and phosphorus (P) supply is one of the growth limiting factors in many forest ecosystems. Seasonal patterns in soil N and P supply rate were examined during a 2-yr period (1994–1995) for forest floor (L, F and H) and upper mineral (Ae) horizons in an 80-yr-old aspen forest in Saskatchewan, Canada. Accumulation of plant nutrient ions on ion exchange resins incubated in the field can provide an estimate of nutrient supply rate in soils because ion exchange resins have the potential ability to simulate nutrient flux to plant roots. Nutrient supply rates and the effect of plant uptake on nutrient supply rate was assessed using ion exchange membranes buried inside and outside polyvinyl chloride (PVC) cylinders. The difference between ion flux to the membranes inside (root uptake excluded) versus outside the cylinders was used as an index of plant nutrient uptake. From May to October, nutrient uptake (µg 10 cm−2 2 wk−2) by plants ranged from 1.6 to 31.7 (NO3−-N), from 2.7 to 13.7 (NH4+-N) and from 2.6 to 12.7 (P), with maximum N and P uptake in summer. Nutrient uptake by plants also varied among horizons. In general, plant uptake of NO3−-N, NH4+-N and P was highest in the H horizon, followed by the F and Ae horizons, with lowest uptake apparent in the L horizon. The results are consistent with the distribution of plant fine roots: most were found in the H horizon (68%), followed by the Ae and F horizons (15%), and the L (2%) horizon. Autumn litterfall represented a nutrient return of 28–40 kg N ha–1 and 4–7 kg P ha–1 to the forest floor which coincided with an increase in ion supply rates in the forest floor. During the growing season, atmospheric inputs via bulk deposition and throughfall contributed small amounts of N (1.8 kg NH4+-N ha–1 and 0.23 kg NO3–-N ha–1) and P (1.38 kg ha−1 inorganic P) to the forest floor. Recycling of nutrients by litterfall and subsequent mineralization and re-assimilation by plant roots in the forest floor is a dynamic and important component of nutrient cycling in boreal aspen forest ecosystems. Key words: Forest floor, ion exchange membranes, nutrient supply
Impacts of soil compaction and tree stump removal on soil properties and outplanted seedlings in northern Idaho, USA
Authors: Page-Dumroese Deborah S. , Harvey Alan E. , Jurgensen Martin F. , Amaranthus Michael P.
Published: April 2011

Intensive timber harvesting and site preparation are becoming more common as demand for timber-based products increases. On some harvested sites in the western United Staes of America and Canada, stump removal is used to ameliorate root disease problems. Soil compaction and nutrient loss could become a problem on some sites after harvesting, site preparation, or stump removal. In a non-replicated, randomized block experiment, two levels of soil compaction (none and severe) and a stump extraction treatment were examined on an ash-cap soil in northern Idaho. These treatments were planted with Douglas-fir (Pseudotsuga menziesii var. glauca [Beissn.] Franco) and western white pine (Pinus monticola Dougl. ex D. Don) seedlings. Soil compaction increased post-harvest bulk density 15–20% to a depth of 30 cm. Stump removal decreased surface soil bulk density, but it increased at the 30- to 45-cm depth to levels equal to the soil compaction treatment. One year after outplanting, seedling top weights were similar among treatments, but root volume was significantly reduced in the soil compaction treatment. Soil compaction and stump removal treatments also reduced the numbers and morphological types of ectomycorrhizae and non-ectomycorrhizal short roots on Douglas-fir. Western white pine seedlings had reduced numbers of non-ectomycorrhizal short roots in the same treatments. Three years after outplanting, stump removal resulted in smaller root collar diameters and less total N content for both seedling species. Severe site disturbance, with associated soil compaction and mixing, may decrease productivity of ash-cap sites by reducing pore space and root and ectomycorrhizal activity. Managers must weigh short-term benefits of intensive site disturbance with possible long-term loss of soil productivity. Key words: Bulk density, compaction, ectomycorrhizae, stumping, site preparation, Douglas-fir, western white pine
The effect of fire severity on ash, and plant and soil nutrient levels following experimental burning in a boreal mixedwood stand
Authors: Johnston Mark , Elliott Julie
Published: April 2011

The Boreal Mixedwood Ecosystem Study near Thunder Bay, Ontario is a multi-disciplinary investigation of the impacts of harvesting and fire on the structure and function of a boreal mixed-wood ecosystem. The fire component comprises a set of treatments in which fire severity was manipulated by adjusting fuel loadings through a variety of harvesting techniques, and also included fire in standing timber. Intensive fuel sampling before and after the fire enabled detailed determinations of fuel consumption, heat output and forest floor reduction. Nutrient concentrations in ash, soil, and plant tissue following the fire were compared with fire severity in order to quantify potential nutrient inputs and their relationship to the amount of biomass consumed during the fire. Forest floor and woody fuel consumption varied significantly among treatments, with the most important factor being whether or not the stand had been harvested previous to the fire. The pH was highest and P concentrations among the lowest in the ash of unharvested blocks. Nutrient concentrations of the remaining forest floor and upper mineral soil were weakly related to the treatments. Forest floor P concentrations were highest on whole-tree harvested and lowest on uncut blocks. Whole-tree harvested blocks also had the highest pH values in forest floor and mineral soil. Concentrations of N, P, and Mg in the foliage of Populus tremuloides Michx. and Rubus idaeus L. were higher on unharvested burned than cut and burned plots, and were negatively correlated with the depth of forest floor reduction. These results indicate that fire severity plays a role in determining the extent of nutrient enrichment following fire, and may be important in influencing long-term site productivity. Key words: Fire severity, forest fire, nutrient cycles, soil chemistry, fire ecology
Physical effects of site disturbance on peatlands
Authors: Groot Arthur
Published: April 2011

Forest harvesting on peatland sites during the frost-free season often creates water-filled ruts and transfers more humified layers of peat to the surface. Foresters have generally assumed that such disturbance has negative consequences related to proliferation of graminoid vegetation, disruption of surface drainage leading to raised water tables and, possibly, reduced site productivity. An experiment was established during 1996 near Cochrane, Ontario to examine the physical impacts of site disturbance on peatlands. Summer traffic by forest harvesting equipment was imposed at three intensities on a Black Spruce–Speckled Alder site type. The fractional area of surface disturbance increased with the amount of traffic, but disturbance effects on the thickness of the aerated zone, depth to the water table, and microtopography were not significant. However, the consistency of the effects produced by the most intense disturbance treatment suggests that it reduced average elevations and aerobic layer thicknesses, and increased water levels, by 2 to 6 cm. The hydrological effect of site disturbance in this study was small compared with the typical effect of forest canopy removal on water levels. Key words: Forest harvesting; peat; peatlands; site disturbance; hydrology
Effects of soil compaction and chipped aspen residue on aspen regeneration and soil nutrients
Authors: Corns Ian G. W. , Maynard D. G.
Published: April 2011

The effects of soil compaction and depth of chipped aspen residue on aspen regeneration, plant community development, decomposition, and nutrient cycling were tested on an Orthic Gray Luvisol in the Lower Foothills of Alberta. Twenty-seven 100-m × 15-m plots were established in 1992. Three depths of chipped aspen residue (0, 1–5 cm and >10 cm) and three levels of compaction (no compaction, 6 and 16 skidder passes) were applied following whole-tree harvesting in 1993. Sixteen skidder passes and chip residue depths >10 cm resulted in reduced plant cover and aspen sucker densities for at least 2 yr following treatment. Nutrient concentrations of the chip residue and surface organic horizon (LFH) were similar for the three compaction treatments. The initial total nitrogen (N) concentration of the chipped aspen residue was 3.6 g kg−1. Ammonium (NH4+-N) concentrations in the LFH of the chip residue treatments, particularly at the >10-cm residue depth, were lower compared with the no-residue treatment. However, adequate N apparently was available to the aspen suckers and understory vegetation as the NH4+-N concentration remained higher than in the LFH before harvesting. Compaction and woody residue applications had only short-term (3 yr) effects on soil properties, plant community development and aspen suckering at this site when clear-cut harvesting was done in the fall with low soil moisture content. Key words: Ammonium, aspen regeneration, wood residue, compaction
Silvicultural treatments, microclimatic conditions and seedling response in Southern Interior clearcuts
Authors: Fleming R. L. , Black T. A. , Adams R. S. , Stathers R. J.
Published: April 2011

Post-harvest levels of soil disturbance and vegetation regrowth strongly influence microclimate conditions, and this has important implications for seedling establishment. We examined the effects of blading (scalping), soil loosening (ripping) and vegetation control (herbicide), as well as no soil disturbance, on growing season microclimates and 3-yr seedling response on two grass-dominated clearcuts at different elevations in the Southern Interior of British Columbia. Warmer soil temperatures were obtained by removing surface organic horizons. Ripping produced somewhat higher soil temperatures than scalping at the drier, lower-elevation site, but slightly reduced soil temperatures at the wetter, higher-elevation site. Near-surface air temperatures were more extreme (higher daily maximums and lower daily minimums) over the control than over exposed mineral soil. Root zone soil moisture deficits largely reflected transpiration by competing vegetation; vegetation removal was effective in improving soil moisture availability at the lower elevation site, but unnecessary from this perspective at the higher elevation site. The exposed mineral surfaces self-mulched and conserved soil moisture after an initial period of high evaporation. Ripping and scalping resulted in somewhat lower near-surface available soil water storage capacities. Seedling establishment on both clearcuts was better following treatments which removed vegetation and surface organic horizons and thus enhanced microclimatic conditions, despite reducing nutrient supply. Such treatments may, however, compromise subsequent stand development through negative impacts on site nutrition. Temporal changes in the relative importance of different physical (microclimate) and chemical (soil nutrition) properties to soil processes and plant growth need to be considered when evaluating site productivity. Key words: Microclimate, soil temperature, air temperature, soil moisture, clearcut, seedling establishment
Nutrient removals with harvesting and by deep percolation from white birch (Betula papyrifera [Marsh.]) sites in central Newfoundland
Authors: Titus Brian D. , Roberts Bruce A. , Deering Keith W.
Published: April 2011

The effects of conventional stem-only and whole-tree harvesting on nutrient losses in biomass removal and in leachate fluxes over a 3-yr period after cutting three white birch stands in central Newfoundland were determined. Losses of nutrients in biomass were proportionately greater with more intensive harvesting as tree components with higher nutrient concentrations (branches, foliage) were removed. Stem-only harvesting removed 126, 9, 51, 126 and 23 kg ha–1 of N, P, K, Ca and Mg in biomass, respectively. Whole-tree harvesting led to a 19% increase in biomass removal as compared to stem-only harvesting, but nutrient removals with whole-tree harvesting increased by 127% for N, 138% for P, 151% for K, 72% for Ca and 90% for Mg. Nutrient losses in deep percolation of soil solution during the first 3 yr after harvesting were generally greater following stem-only than whole-tree harvesting. This may be the result of increased leaching from slash, increased mineralization beneath slash, and retardation by slash of the successional vegetation that could act as a nutrient sink. In the first 3 yr following harvesting, leaching losses after whole-tree harvesting were 4, 0.2, 8, 23 and 7 kg ha–1 of N, P, K, Ca and Mg, respectively, as compared with 9, 0.1, 7, 28 and 9 kg ha–1 of N, P, K, Ca and Mg after stem-only harvesting. Nutrient losses in leachate were generally small compared to losses in biomass removal. Key words: Intensive harvesting; slash; nutrient budget; sustainable site productivity; Betula papyrifera (Marsh.)
Distribution des cations basiques et de l'aluminium dans la solution de sol de l'horizon humifère d'une érablière fertilisée: représentativité des extraits de sol saturé à l'eau
Authors: Marquis François , Camiré Claude , Lachance Marius
Published: April 2011

Soil solution analysis may provide useful information on nutrition status and Al toxicity in soil. Nevertheless, obtaining soil solutions in low-moisture soils causes a problem. Saturated extracts may act as an alternative for getting information on soil solution. Their effectiveness in assessing representative base cations and aluminum distribution in soil solution was demonstrated in this study. Saturated extracts, which were obtained from air drying and fresh soil, were compared with the "true" soil solution for base distribution and base/Al ratio. Molar fraction and equilibrium ratio in the "true" soil solution depended on soil moisture before extraction. Nevertheless, they were less affected by this approach than intrinsic concentrations. The results showed that molar fraction and equilibrium ratio in soil solution can be predicted from the molar fraction or equilibrium ratio in saturated extracts and soil moisture information, however, saturated extracts obtained from fresh soil were better models. Base/Al ratios in saturated extracts were closely dependent on pH extracts but they were not well linked with the same ratio in soil solution. Key words: Soil solution, molar fraction, equilibrium ratio, soil acidity, sugar maple, Acer saccharum
Influence of non-inversion loosening on permanent pasture productivity
Authors: Carter M. R. , Kunelius H. T.
Published: April 2011

Non-inversion tillage can have significant benefits over inversion tillage in loosening soils under permanent pasture. A suite of attributes was used to characterize the degree of compaction at the 0- to 20-cm depth of a Charlottetown fine sandy loam under a 10-yr pasture in Prince Edward Island. Non-inversion tillage, using a paraplow, a slant-legged cultivator loosened the soil at the 10- to 20-cm depth. Penetrometer resistance profiles showed that the loosened soil condition persisted for 3 to 4 yr. Non-inversion soil loosening caused a negative yield response, which was possibly related to root injury. Key words: Podzol, penetration resistance, Kentucky bluegrass, white clover
Potential use of underseeded barley to increase carbon inputs to a loam soil in the New Brunswick potato belt
Authors: Rees H. W. , Chow T. L. , Walker D. F. , Smith A. O. M.
Published: April 2011

Organic carbon depletion as a result of intensive potato production is a serious concern in northwestern New Brunswick, Canada. Underseeding of rotational grain crops with selected grasses and legumes is being used by farmers to increase crop residues in order to maintain soil organic carbon levels. The objectives of this study were to quantify changes in selected soil propertiesm, effects on grain yield, and increases in total biomass production resulting from different underseeding treatments on a Caribou fine-loamy Brunisolic Gray Luvisol. Clovers, ryegrasses and a mixture of timothy, Alsike and red clover were underseeded in Chapais barley plots. Underseeding did little to improve soil bulk density, macroporosity and saturated hydraulic conductivity of the upper plow layer (4–12 cm depth) over one growing season. Averaged over a 3-yr period, underseeding did not significantly affect barley grain yields; however, annual reductions of up to 17% were experienced with some of the more aggressive companion crops, such as Lemtal Italian ryegrass. Underseeding significantly increased total biomass contributions (residues) to the upper 20 cm of the soil by 40 to 90%, making the year in grain production a potential net organic carbon supplier rather than an organic carbon depletor. Key words: Companion crop, roots, soil organic carbon, soil bulk density, soil permeability, crop residue
Limed sewage sludge effects on nutrient status and metal fractions in acidic soils
Authors: Simard R. R. , Beauchemin S. , Laverdière M. R.
Published: April 2011

The potential impacts of limed sludge on nutrient and heavy metal bioavailability must be studied for their safe use on acidic soils. The objective of this study was to assess the impact of limed sludges on six acidic soils from eastern Canada. CaCO3 and raw sewage sludges (RSS) stabilized with either CaO (CaO + S) or cement kiln dust (CKD + S) were added to soils in amount necessary to reach pH 6.5 and the mixtures were then incubated for 64 d. CaO + S treatments were the most efficient to neutralize soil acidity. After 10 d of incubation, the Sr-citrate extractable P was significantly increased by the CaO + S treatment in low P sorption soils. The extractable K, Zn and Cu contents were also slightly increased by CaO + S compared to CaCO3 whereas CKD + S resulted in an excessive soil exchangeable K content. After 64 d, labile Al content was decreased by all liming amendments. RSS and CaO + S tended to increase labile Cu and Mn contents. The RSS increased NaOH-extractable Cu but the treatments had no significant effects on the labile and stable forms of heavy metals. A combination of CaO + CKD to stabilize sewage sludge would be more suitable to provide appropriate levels of P and K without resulting in large increases in extractable heavy metal contents. Key words: pH, extractable P and K, cement kiln dust, Al and Mn toxicity, Cu fractions, water-soluble metals
Glyphosate application and timing of tillage of red clover affects potato response to N, soil N profile, and root and soil nematodes
Authors: Sanderson J. B. , MacLeod J. A. , Kimpinski J.
Published: April 2011

The effects of glyphosate application and time of tillage of red clover on soil NO3-N profiles, the response of the subsequent potato crop to varying rates of N fertilizer application, and root and soil nematodes, were evaluated. The study was conducted over three cropping seasons on a Charlottetown fine sandy loam on Prince Edward Island. Red clover was moldboard ploughed in mid-September (early fall), or moldboard or chisel ploughed in mid-October (late fall), or moldboard ploughed in the spring. Glyphosate was applied in early fall and the dead clover was moldboard or chisel ploughed in mid-October or left undisturbed until spring. A barley control, where barley was harvested and straw incorporated with a tandem disc harrow in early September, was included. Potato were planted with 6 rates of N (0 to 250 kg ha–1 in 50-kg increments) band applied at planting. The barley control treatment produced lower potato yield without fertilizer N in all 3 yr of the study compared to red clover treatments, but potato yields were similar at high rates of applied N. Potato tuber yields after spring moldboard ploughing of red clover were higher at low N rates and lower at high N rates than yields after late fall treatment in one year of the study. Concentrations of nitrate-N in the soil in mid-November were highest following the early fall moldboard ploughing and lowest in the undisturbed clover plots. Fall soil nitrate-N levels were intermediate following the glyphosate application and late fall tillages. Early spring soil nitrate-N levels in the surface 30 cm were generally highest with the spring and late fall tillage and lowest with the early fall tillage. Levels of nitrate-N in potato petioles increased with increased rates of N application and generally increased as tillage of the red clover was delayed from early fall to late fall to spring. In general, cultivation and the application of glyphosate did not affect soil and root nematode populations. In two instances, the moldboard plough tillage treatments were associated with higher levels of the clover-cyst nematode, Heterodera trifolii. One of the tillage treatments was combined with glyphosate, but this was the only case where the herbicide had an impact on nematodes. To maximize the benefits to the subsequent potato crop and to minimize leaching of nitrate, incorporation of legume residue should be delayed until the rate of mineralization and nitrification of the legume N is minimized. It is suggested that incorporation of red clover be delayed until after mid-October for clover–potato systems on PEI. Key words: Glyphosate, nematodes, nitrate leaching, petiole nitrate-N, potato, soil nitrate-N, tillage time
Seasonal trends in soil biochemical attributes: Effects of crop management on a Black Chernozem
Authors: Campbell C. A. , Lafond G. P. , Biederbeck V. O. , Wen G. , Schoenau J. , Hahn D.
Published: April 2011

Knowledge of the response of soil biochemical attributes to crop management and growing season weather is important for assessing soil quality and fertility. Long-term (38–39 yr) crop rotations on a Black Chernozem at Indian Head, Saskatchewan, were sampled (0- to 7.5-cm depth) between early May and mid-October, 11 times in 1995 and 9 times in 1996. We assessed the effect of cropping frequency [fallow–wheat (Triticum aestivum L.) (F–W) vs. F–W–W, vs. Continuous (Cont) W], fertilizers (unfertilized vs. N + P applied), straw harvesting, legume green-manure (GM) in GM–W–W (unfertilized), and legume-grass hay (H) in F–W–W–H–H–H (unfertilized) systems. Changes in organic C and total N (OC, TN), microbial biomass C (MBC), light fraction C and N (LFC and LFN), mineralizable C and N (Cmin and Nmin), and water-soluble organic C (WSOC) were monitored. Organic C and TN were constant and unaffected by rotation phase during the season, but most of the other more labile soil biochemical attributes varied during the season. Much of this temporal variability was associated with changes in soil moisture, temperature and precipitation, and with rhizodeposition in some cases. Whenever conditions favoured rapid decomposition in situ (e.g., high moisture, temperature and/or precipitation) we obtained lower values for the more labile attributes in subsequent laboratory measurements. Seasonal trends in the more labile attriutes were more pronounced in 1995 (a much wetter year) than in 1996, and the proportion of the variability attributable to weather conditions was greater in 1995 than in 1996 (viz., R2 ranged from 20 to 44% in 1996 and from 37 to 60% in 1995). Seasonal variability was greater in the more fertile treatments [e.g., Cont W (Fert) and F–W–W–H–H–H) than in F–W or Cont W (Unfert). Seasonal variability in LF was unaffected by cropping. Light fraction was lower in 1995 than 1996 because of faster decomposition in 1995 (335 mm of growing season precipitation compared to 157 mm in 1996). Microbial biomass was not influenced by cropping in 1996, but in 1995 it was higher in cropped than in fallow phases of the rotations, suggesting a positive effect of rhizodeposition. Water-soluble organic C was greatest in the more fertile treatments and in cropped than in fallow phases. Mineralizable C and N were greater in cropped than in fallow rotation phases in 1995, but unaffected by cropping in 1996. Further, Cmin and Nmin were higher in 1996 than in 1995, likely due to more rapid decomposition in the wetter 1995. Over the last 10 yr of this experiment LFC and Cmin have increased markedly in the more fertile treatments [e.g., Cont W (Fert), F–W–W–H–H–H], but have hardly changed in the less fertile treatments such as F–W or Cont W (Unfert). In this period the less labile attributes (e.g., OC) have hardly changed in any treatment. Key words: Microbial biomass, carbon, nitrogen, mineralization, water-soluble C, light fraction, weather variables
Chemical and mineral composition of ectomycorrhizosphere soils of subalpine fir (Abieslasiocarpa (Hook.) Nutt.) in the Ae horizon of a Luvisol
Authors: Arocena J. M. , Glowa K. R. , Massicotte H. B. , Lavkulich L.
Published: April 2011

Differences in the properties of bulk forest and rhizosphere soils are often attributed to ectomycorrhizal association, or the symbiosis characterized by a fungal sheath surrounding the root (mantle) and intercellular root colonization (Hartig net). We compared the soil pH, total C, N, cation exchange capacity, and the contents of mica, chlorite, kaolinite, 2:1 expandable clays, feldspars and amorphous materials between two ectomycorrhizosphere soils (or soil environment in the vicinity of ectomycorrhizae (ECM)) and non-ectomycorrhizosphere soils to study the influence of ectomycorrhizae on chemical and mineralogical properties of soils. The two ectomycorrhizosphere soils were characterized by ectomycorrhizal colonization dominated by (1) Piloderma spp., and (2) Mycelium radicis atrovirensand cottony yellow-brown (MRA-CYB) types or where Piloderma spp. colonization was <2%. Our results showed that total C and N were higher in ectomycorrhizosphere than non-ectomycorrhizosphere soils, and the ectomycorrhizosphere soils dominated by Piloderma spp. had almost twice the total C and N as ectomycorrhizosphere soils with MRA-CYB. Soil pH was lower by half a pH unit in ectomycorrhizosphere soils compared to non-ectomycorrhizosphere soils. Cation exchange capacity as well as exchangeable Ca2+, Mg2+ and K+ were lower in non-ectomycorrhizosphere soil compared to ectomycorrhizosphere soils. We also found that cation exchange capacity, exchangeable Ca2+, Mg2+ and K+ values in soils dominated by Piloderma spp. were higher compared to ectomycorrhizosphere soils with insignificant Piloderma spp. Our results suggest that transformation rate of mica and chlorite to 2:1 expandable clays was predominant in ectomycorrhizosphere compared to non-ectomycorrhizosphere soils, likely as a result of high production of organic acids and direct extraction of K+ and Mg2+ by fungal hyphae. In ectomycorrhizoplane samples, it is suggested that K+ and possibly amorphous Al2O3 and Fe2O3 could reconstitute the degraded mica and chlorite through the formation of hydroxy-interlayered 2:1 clays. Key words: Ectomycorrhizosphere soils, subalpine fir, Piloderma spp.