ALBERT

Beschreibung: Soil water storage (0–1.7 m) was measured every 10 m in a 660-m-long transect using a neutron probe and compared to bulk electrical conductivity, ECA, measurements obtained using noncontacting electomagnetic induction meters. Coherency analysis indicated a lack of correlation at scales less than 40 m. At scales greater than 40 m, ECA explained more than 80% of the variation of soil water storage. Measurement of ECA should be a simple and fast method of determining general field patterns of soil water storage. Key words: Spatial variability, soil water, coherency, electromagnetic induction

Beschreibung: Estimation of fertilizer N requirements of crops remains a challenge. Numerous field studies have been carried out to calibrate soil tests against yield response to applied fertilizer N. Synthesis and identification of common crop fertilizer N response across large data sets (years, sites) will allow maximum use of this past work and a framework for comparison of future work. The objective of this paper is to define macro-relationships between the economically optimum fertilizer N rate (EONR) and the yield increase at the EONR defined as the delta yield, ΔYec , for large data sets of 2nd- and 3rd-order estimates of fertilizer N response functions with both 0th and 1st-order rate relationships between fertilizer nitrogen use efficiency and applied fertilizer N. The derived macro-relationships are curvilinear, depend on the price ratio R = the ratio of the (price per kilogram of fertilizer N)/(price per kilogram grain), and are similar to measurements from data sets of corn fertilizer N response functions spanning decades (+20 yr) and representing areas in both the United States and Canada. The macro-relationships appear to be robust and therefore useful for quantifying (post-harvest analysis) soil fertility, crop fertilizer N requirement, and comparison/classification of N response functions.Key words: Response function, prediction, efficiency, economic N rate, corn

Beschreibung: The persistence of 14C-fenoxaprop acid, the major degradation product of the herbicide 14C-fenoxaprop-ethyl, was studied at different controlled temperature and moisture conditions in three Saskatchewan soils. At 85% of field capacity, degradation approximated to first-order kinetics at soil temperatures of 10, 20, and 30 °C, with half-life values ranging from 42 to 5 d. In a clay at 20 °C, there was no effect of moisture, between 50% and 100% field capacity, on the rate of 14C-fenoxaprop acid breakdown. There was no loss of radioactivity after 65-d in air dry soils. In all soils incubated at 85% field capacity and 20 °C with 14C-fenoxaprop-ethyl, uniformly labeled in the chlorophenyl ring, there was evolution of 14CO2 indicating ring fission. Over a 56-d incubation period, 10–15% of the applied radioactivity was released from the treated soils as 14CO2. Extraction with ammoniated acetonitrile recovered 14–19% of the original radioactivity; between 3 and 5% of the initial 14C was incorporated into soil microbial biomass; and 17–25% into the fulvic acid, 7–12% into the humic acid, and 30–34% into the humin soil fractions. Key words: Herbicide, biomass, fenoxaprop-ethyl, fenoxaprop, persistence

Beschreibung: The main objective of this study was to compare the recovery of 15N-labelled fertilizer by different methods of N application and N rates. Field experiments were carried out for 3 yr at Saint-Hyacinthe (Saint-Damase, Du Contour, Sainte-Rosalie soils) and at Saint-Lambert, Lévis (Le Bras soil). Grain corn (cv. Pride K228, 2700 CHU) and silage corn (cv. Hyland 3251, 2300 CHU) were grown at Saint-Hyacinthe and Saint-Lambert, respectively. In 1988 and 1989, field trials were arranged in a randomized complete bloc design consisting of five treatments in three replications: control 0 N and four split application methods of N fertilizer. Labelled 15NH4 15NO3 fertilizer was applied either banded at planting as starter (D), broadcast and incorporated before planting (Vs) or sidedressing between rows at V6 to V8 stages of corn (Bp). In 1990 field trials, treatments consisted of four N rates (0, 60, 120 and 180 kg N ha−1) labelled with 15NH4 15NO3. The effect of N rates on yield and N uptake by corn was significant in all years. However, the effect of application methods was significant only on the soil Du Contour in 1989 where corn grain yield was highest when N fertilizer was split as starter and sidedress band. The CUR of N fertilizer applied broadcast before planting (42 to 48%) was generally lower than sidedressing band application (43 to 54%). N fertilizer recovery in the starter showed also high CUR values (45 to 60%). Consequently, it is recommended to split N fertilizers and apply in band to increase efficiency for grain corn. The CUR values decreased with N rates only in Le Bras soil in 1990. Residual N fertilizer increased from 27 to 103 kg N ha−1 for 60 and 180 kg N ha−1 rates, respectively. Consequently, the environmental impact of N fertilization may increased with high N rate. Key words: Grain corn, silage corn, 15N recovery, fertilizer N split application

Beschreibung: Snow management (tall vs. conventional height stubble) and one-time deep tillage were investigated for increasing water conservation and annual crop production on a rolling soil landscape developed on glacial till in the semiarid Brown soil zone of the Canadian prairies. Tillage depths were 0, 13, 25, and 45 cm. Gleysolic soils had more soil water at time of seeding and greater 3-yr mean durum wheat (Triticum turgidum L.) grain yields than the Chernozemic soils. On the Chernozemic soils, tall (25 cm) stubble increased over-winter soil water at seeding by 15 mm compared with conventional short (14 cm) stubble. Mean 3-yr durum grain yields were 165 kg ha−1 higher with tall than short stubble although yield increases were only significant (P 

Beschreibung: An earlier study indicated that cereal straw may be removed after harvest without affecting crop production, soil organic matter and microbial biomass. Further measurements of early indicators of changes in soil organic matter, viz., the light fraction and mineralizable C and N, confirm that straw removal is superior to straw incorporation with moldboard ploughing, and comparable to straw incorporation by disking, in C and N retention and turnover. Key words: Carbon, light fraction, mineralization, nitrogen, straw management

Beschreibung: Pedotransfer functions (PTFs) were used to assess the sensitivity of the structural characteristics of coarse- and medium-textured calcareous illitic soils at different levels of relative compaction (RC) to changes in the organic carbon (OC) content. The analyses predicted that an increase in the OC content of 0.01 kg kg−1 would:• increase the available water content from 0.02 to 0.04 m3 m−3 with the largest increases occurring in coarser-textured soils and not being strongly influenced by RC;• decrease the air-filled porosity at field capacity from 0.01 to 0.04 m3 m−3 with the largest decreases occurring in the finer-textured soils and not being strongly influenced by RC;• decrease the soil resistance to penetration with the decreases most pronounced at lower water potentials and higher RC; at the permanent wilting point and a RC of 0.95 the decrease would range from 1.2 to 3.8 MPa;• increase the least limiting water range from 0.01 to 0.05 m3 m−3 with the increase varying with clay content.A comparison with predictions based on PTFs derived from data sets from other parts of the world indicated caution should be exercised in applying PTFs to soil and climatic conditions that are different from those from which the PTFs were derived until the impacts of these conditions are better understood. Key words: Bulk density, field capacity, permanent wilting point, available water; aeration, soil resistance, least limiting water range

Beschreibung: Supplementing irrigation water with effluents could reduce the need for potable water for irrigation and promote nutrient recycling, but may require additional amendments to deal with Na. In a growth chamber experiment, winter wheat was seeded into a control soil and to soil amended with either gypsum or wood ash applied at an equivalent rate of 15 dry t ha-1. Wheat was irrigated at a rate of 6 mm d-1 with distilled water (DW), kraft pulp mill effluent (KPME) and waste-activated sludge (WAS), and three KPME/WAS combinations. This included two KPME/WAS combinations diluted with DW to 25 and 50% (KPME/WAS:DW) to evaluate the effect on the nutrient uptake and biomass and the impact on soluble ions in the soil. Effluent applications increased wheat biomass up to 70%, and increases of 97 and 140% were observed in soils amended with gypsum and ash, respectively. Effluent applications increased soluble Na, Ca, and SO4, but only on the gypsum-amended soils, except those irrigated with WAS, had lower sodium adsorption ratio (SAR) than control soils by 0.7 to 3 units. Effluent combinations at the lower dilutions in combination with gypsum could be used to provide supplemental water with moderate increases in electrical conductivity (ECe) and SAR that would still be within tolerable limits of many crops.Key words: Effluent irrigation, electrical conductivity, gypsum, sodium adsorption ratio, wood ash

Beschreibung: Most soil C sequestration research has focused on organic C stabilization, while carbonate precipitation has received little attention. Mineral colloids can accelerate abiotic humification reactions of biomolecules such as amino acids, sugars, and polyphenols, derived from the breakdown of biological residues and metabolites. During these reactions CO2 is produced as a result of the oxidation of biomolecules. However, the biomolecule-induced formation of carbonate during abiotic humification remained to be uncovered. Here we demonstrate using X-ray diffraction, Fourier transform infrared spectroscopy and C K-edge and Mn L-edge near edge X-ray absorption fine structure spectroscopy that the Maillard reaction (glucose and glycine) and the integrated polyphenol-Maillard reaction pathway (catechol, glucose and glycine), in the presence of birnessite (δ-MnO2) produce MnCO3 (rhodochrosite). Increasing the molar ratio of catechol to glucose and glycine dramatically hampered carbonate formation, which is attributed to the enhanced formation of humic polymers, which increased proton generation and perturbed rhodochrosite crystallization through Mn(II)-humic complexation in the reaction systems. Thus, rhodochrosite formation was a competing reaction with humic substance formation. Our findings are of fundamental significance in understanding the vital role of the nature and relative abundance of biomolecules in abiotic carbonate formation, which merits close attention in understanding and regulating C sequestration in natural environments.Key words: Abiotic humification, polyphenol-Maillard reaction, rhodochrosite, birnessite, C K-edge and Mn L-edge NEXAFS

Beschreibung: Leaching of water-soluble contaminants has resulted in degradation of groundwater quality. This research project examined the long-term spatial variability of leaching processes within two hummocky, agricultural landscapes near Bittern Lake, in central Alberta. Analysing the distribution of soil profiles within a landscape, we created a leaching potential index based on a soil profile index (SPI) and plan curvature measurements. The index accurately differentiated locations of very high and high leaching potential from low and very low leaching potential. This index may become a useful tool to determine the variability of leaching within an agricultural landscape, to identify areas of high leaching potential, to determine agricultural best management practices, and to minimize contamination of groundwater. Key words: Soil-landscape, soil horizon, soil classification, sulphate, electrical conductivity, leaching

Beschreibung: Land application of swine manure can result in a loss of nitrogen (N) through ammonia (NH3) volatilization. Accurate NH3 loss assessments are essential to support the development of regional and global emission factors and identify best management strategies for reducing losses. The objectives of this study were to simultaneously assess the reliability and applicability of three simple NH3 flux measurement techniques and their effectiveness and usefulness for the measurement of emissions from surface-applied swine manure. Ammonia losses from two chamber systems were compared: (i) static and (ii) wind tunnel chamber, as well as the (iii) micrometeorological theoretical profile shape (TPS) method. A series of field tests was performed at the Agriculture and Agri-Food Canada (AAFC) Research Farm in Harrington, Prince Edward Island (PE) on a sandy loam, stubble field that was surface applied with 100 kg NH4-N ha-1 of liquid swine manure. After application the three NH3 emission techniques were established and measurements were performed over a 5-d period. Ammonia losses from the wind tunnels were comparable with those from the TPS method. The static chambers were found to underestimate NH3 emissions (by ~95–99%), compared with both the wind tunnel and TPS methods. It is therefore recommended that either the TPS or wind tunnel approaches be used to more accurately quantify NH3 losses for field systems. Key words: Ammonia volatilization, flux measurements, swine manure, micrometeorology, static chambers, wind tunnel

Beschreibung: Tillage influences the retention and storage of organic matter (OM) in soil. We used a sequential density and particle-size fractionation to evaluate the total quantity and distribution of organic carbon (C) and nitrogen (N) in the profile of soils under mouldboard ploughing and no-till. Cores (0-60 cm) from four long-term tillage studies (in Prince Edward Island, Quebec, and two sites in Ontario) on soils of different textures, from sandy loam to clay were collected and divided into six depth increments. Four soil OM fractions were isolated on the basis of size and density from each sample. At two sites the standing stocks of C and N were larger in tilled than in no-till soil profiles at depths slightly greater than plough depth; tillage effects were also evident at a third site, where the mass of C in a layer close to the depth of ploughing was greater in tilled soils. Ploughing also had a substantial and consistent positive effect in all four soils on the quantity of C (and in some cases N) protected within aggregates, particularly at or near the bottom of the plough layer, and sometimes in surface soil layers. We attribute differences observed in whole soil C and N due to tillage mostly to differences in mineral-associated OM, particularly in soils with heavier textures, but the other size and density fractions could, together, account for as much as 25% of the difference. Because the C capacity level was not reached in heavy-textured soils, these soils show greater potential for further accumulation of C in the soil profile than coarse-textured soils, especially near the bottom of the plough layer.Key words: Light fraction, soil organic matter, soil tillage, physically-protected organic matter, no-till, soil texture

Beschreibung: A field study in northern Minnesota was conducted to assess the relative importance of factors that control lateral water movement in peatlands. Hydraulic gradients and groundwater velocities were measured for one mined and three unmined peatlands. Groundwater velocities were measured at shallow depths in the organic soil using the point dilution method. Hydraulic conductivities at different soil depths were estimated by applying the field measurements to Darcy's Law. Hydraulic gradients were persistent from early summer through fall and were generally less than 0.1%, a major factor governing rates of lateral water movement in undisturbed peatlands. Maximum groundwater velocities averaged 0.49 cm h−1 in the upper and least decomposed peat layers and diminished dramatically with depth and increasing decomposition. The von-Post scale of peat decomposition was found to be useful in predicting the hydraulic conductivity of peat layers. The rate of water movement at depths below 35 cm in the natural peatlands averaged less than 0.03 cm h−1. The data contribute to a better understanding of the hydrologic function of peatlands. Key words: Organic soils, peatlands, groundwater velocity, hydraulic conductivity, hydraulic gradient

Beschreibung: The purpose of this study was to examine how the treatments ammonium sulfate, drought and irrigation changed chemical characteristics of three soil fractions (bulk soil, rhizosphere and soil root interface (SRI)) from E, Bh and Bs horizons of Podzol in a Norway spruce stand in southwestern Sweden. Regardless of the treatment, the properties of the rhizosphere and SRI nearly always differed from the bulk soil due to the high quantity of organic and root material. Irrigation and ammonium sulfate raised water soluble cations and base saturation in the bulk soil. This was possibly due to leaching from the humus and exchange reactions. In the rhizosphere and SRI, irrigation and ammonium sulfate lowered soluble base cations (BC) and base saturation when compared with control; this is attributed to a combination of leaching and high nutrient demand by trees creating a zone of relative depletion. Drought accumulated more organic matter (OM), acidity and cations in the soil fractions suggesting that the lack of water limited transport and uptake of nutrients. Generally, the magnitude of accumulation/depletion of nutrients in the soil fractions reflected the degree of stress which was in turn linked to root uptake of nutrients or to tree growth. Due to the apparent linkage between tree growth, uptake of nutrients and rhizosphere chemistry, we emphasise that soils must be studied at the rhizospheric rather than the bulk soil scale to further understand the effects of environmental stresses. Key words: Ecosystem manipulation, conceptual model, irrigation, organic matter, relative depletion, soil root interface

Beschreibung: Using a revised Intergovernmental Panel on Climate Change (IPCC) methodology and the process-based model DeNitrification and DeComposition (DNDC), we estimated N2O emissions from agroecosystems in Canada for each census year from 1981 to 2001. Based on the IPCC methodology, direct emissions of N2O ranged from 12.9 to 17.3 with an average of 15.1 Tg CO2 equivalents, while the DNDC model predicted values from 16.0 to 24.3 with an average of 20.8 Tg CO2 equivalents over the same period, and showed a large interannual variation reflecting weather variability. On a provincial basis, emissions estimated by IPCC and DNDC methods were highest in Alberta, Saskatchewan and Ontario, intermediate for Manitoba and Quebec and lowest in British Columbia and the Atlantic provinces. The greatest source of emissions estimated by the IPCC method was from N fertilizer (avg. 6.32 Tg CO2 equiv. in Canada), followed by crop residues (4.24), pasture range and paddocks (PRP) (2.77), and manure (1.65). All sources of emissions, but especially those from fertilizers, increased moderately over time. Monte Carlo Simulation was used to determine the uncertainty associated with the 2001 emission estimates for both IPCC and DNDC methodologies. The simulation generated most likely values of 19.2 and 16.0 Tg CO2 equivalents for IPCC and DNDC, respectively, with uncertainties of 37 and 41%, respectively. Values for the IPCC estimates varied between 28% for PRP and manure and 50% for N fertilizer and crop residues. At the provincial level, uncertainty ranged between 15 and 47% with higher values on the prairies. Sensitivity analyses for IPCC estimates showed crop residues as the most important source of uncertainty followed by synthetic N-fertilizers. Our analysis demonstrated that N2O emissions can be effectively estimated by both the DNDC and IPCC methods and that their uncertainties can be effectively estimated by Monte Carlo Simulation. Key words: Nitrous oxide, IPCC, DNDC model, Uncertainty analysis, Monte Carlo Simulation

Beschreibung: The recent development of low-cost controlled-release urea (CRU) may provide additional options for N fertilization of winter wheat (Triticum aestivum L.). Two field experiments were conducted over 3 yr at three locations in southern Alberta to evaluate different options of applying CRU to winter wheat. In the first experiment, three N fertilizers (20-day CRU, 40-day CRU and urea) were seed-placed and side-banded at the time of seeding at 0, 30, 60, 90 and 120 kg N ha-1. Stand densities were substantially reduced by seedrow application of urea at rates greater than 30 kg N ha-1, but were unaffected by seedrow application of CRU, even at the highest rate of N application. When N fertilizer was sidebanded, stand densities were unaffected by fertilizer type or N rate. Yield gains due to N application were reduced by application of high rates of seed-placed urea, but similar for other treatments. Grain protein concentration and N uptake were also similar for CRU and seed-placed urea. In the second experiment, three N fertilizers (CRU, urea and ammonium nitrate) were broadcast at 30 kg N ha-1 in early spring on plots that had received 0, 30 or 60 kg N ha-1 of CRU at the time of seeding. Inadequate release of spring broadcast CRU was indicated by reduced grain protein concentrations relative to conventional N fertilizers. Under the conditions experienced in our study, CRU substantially increased the maximum safe rate of seed-placed urea, provided minimal benefits to N response relative to side-banded urea, and was less effective than conventional N fertilizers when broadcast in early spring. Key words: N fertilizer use efficiency, slow release, winter survival

Beschreibung: Erosion control practices were evaluated for their ability to reduce soil loss and runoff and for their effects on strawberry (Fragaria × ananassa Duch.) yield on a silt loam soil in the uplands area of the Lower Fraser Valley. Three treatments (underdrainage, winter cover cropping of barley [Hordeum vulgare L.] and cross slope planting) were compared to a control. Soil and runoff losses from natural rainfall were measured on replicated experimental plots (0.01375 ha) from 1991 to 1994. Soil and runoff losses were significantly lower with the winter cover crop and cross-slope planting treatments than the control. Results for the underdrainage treatment were not significantly different from the control and non-representative of proper underdrainage due to too deep an installation under wet conditions. Soil protection by the barley cover crop reduced mean annual soil loss and runoff by 78 and 43%, respectively. Cross slope planting reduced soil and runoff losses by 97 and 84%, respectively, compared with the control. Annual runoff coefficients of up to 21% were observed for the control, while coefficients of 40% were not uncommon for single storm events. Except for the cross slope treatment, strawberry yields were not compromised by the erosion control practices. Winter cover cropping is the preferred erosion control practice for strawberries grown on upland soils, since cross slope planting may cause depressed yields from root rot disease resulting from stagnant water between the rows. Key words: Soil loss, runoff, runoff coefficient, cover crop, across slope, erosion control

Beschreibung: The effect of root exudates on structural stability and the hypothesis that the growing roots of corn (Zea mays L.) can destabilize soil structure by chelating Fe and Al involved in mineral-metal-organic matter linkages were investigated. Exudates were removed from 14C-labelled corn and bromegrass (Bromus inermis Leyss.) plants grown in sand using sequential leaching with water and acetone. The exudates were concentrated by flash evaporation and incubated with 1–2 mm aggregates of a calcareous silt loam soil for up to 240 h. Aggregates to which exudates from bromegrass were added had a higher wet aggregate stability (WAS) and lower dispersible clay content (DC) than aggregates to which exudates from corn were added. The greatest increase in stability occurred on addition of the water-extracted exudates (9.6% for WAS, 27.1% for DC). The increase in stability correlated positively with a release into solution of Ca and Mg from the soil solids. Addition of CaCl2 to the aggregates, to give corresponding amounts of Ca and Mg in solution, had similar effects on stability suggesting that the ions released by the exudates were not in a chelated form. The quantity of carbon added in the exudates and the mineralization of this carbon were positively and negatively correlated with stability, respectively. There was little evidence that corn exudates caused a destabilization of structure. Key words: Wet aggregate stability, dispersible clay, corn, bromegrass, flocculation, calcium

Beschreibung: Core aeration, a management practice originally developed for soil-based putting greens, is still commonly used on sand-based greens. The study objective was to determine the effects of core aeration on soil properties of sand-based putting greens in the Lower Fraser Valley of British Columbia. The experiment was laid out as a randomized complete block design with three replications. The study treatments were regular management practices, including core aeration (CA) carried out in spring and late summer, and regular management practices, but no core aeration (NCA). Each core aeration event impacted 5% of the surface area. Treatments with and without core aeration had similar soil organic matter content, root weight density, and soil bulk density. The CA treatment was generally drier than NCA. Water infiltration was greater on CA than NCA, but only for 1 mo following core aeration. Core aeration generally reduced soil penetration resistance within the mat layer relative to treatment without this practice. On both treatments, soil penetration resistance consistently exceeded 4000 kPa below about 13 cm depth preventing deeper root growth. The limited benefits of the low-surface-area-impact core aeration on the maturing sand-based putting greens in a humid maritime climate suggest that this practice might not be worth doing (at a low surface area impact); however, additional, more detailed studies are needed to confirm this. Key words: Turf management, golf course management, soil penetration resistance, water infiltration

Beschreibung: Two soils derived from glacial deposits and one from alluvium were examined for changes in organic matter (OM) and nitrogen levels between 1943 and 1983 across the international boundary in the Fraser Lowland of western North America. Duplicate samples were collected from the upper 0.2 m from 60 randomly selected sites on the five land clearing periods (1943–1955, 1955–1966, 1966–1976, 1976–1983, uncleared) on each of three parent materials: glacial outwash, alluvium, and glacialmarine deposits in the United States and Canada. The land clearing periods were determined from medium scale aerial photographs taken in 1943, 1955, 1966, 1976, and 1983. Cultivation results in a 20% loss of OM after 35 yr on all soils. The largest loss is in the first 15 yr on all soils. Changes in N levels on the three parent materials is irregular. C:N narrows on all soils from about 15:1 to about 12:1. Key words: Organic matter, nitrogen, Fraser Lowland, land clearing, air photo interpretation, parent material

Beschreibung: New legislation to reduce the amount of fertilizer leached into the environment by horticultural growers and the need to implement water-saving irrigation systems require an understanding of salt build-up and of nutrient cycles in order to develop efficient water-use strategies for growers. Solute transport in growing media is central to this process, but has received little attention thus far. The objectives of this study were to determine how solutes behave in sub-irrigated growing media and to assess a solute transport model for these media. A steady state evaporation (upward water flow) experiment was carried out with three different growing media in packed columns in the laboratory. Bromide, potassium and copper concentrations were determined using in-column pore water solution samplers and by sectioning the columns at the end of the experiment to obtain concentration profiles. The Hydrus-1D model was fitted to the solution sampler data assuming non-linear Freundlich adsorption, and then used to obtain favorable predictions of the measured concentration profiles. Independent adsorption isotherm results from batch experiments were found to be inadequate when used to predict solute movement and the results indicate that the preferred approach is an in-column evaluation of the transport parameters.Key words: Solute transport, sub-irrigation, peat, growing media

Beschreibung: A modular approach is presented to assess terrain-specific soil trafficability in terms of soil resistance to penetration and machine-specific rut depths. These modules address: (1) soil resistance to cone penetration (cone index, or CI) as affected by soil moisture, texture and pore space (Module 1), (2) machine-induced rut depths (single-pass and multi-cycles) as affected by wheel loads, tire specifications and CI (accounting for depth of compactable soil, Module 2), (3) temporal variations in hydrothermal conditions, CI, and potential rut depths due to daily soil moisture and temperature variations (Module 3), and (4) spatial variations in CI and rut depth across terrain due to corresponding changes in soil moisture, depth of compactable soil, bulk density, texture, frost depth, organic matter and coarse fragments (Module 4). The approach is applied to off-road wood-forwarding operations. Modules 1 and 2 were calibrated to apply to a wide range of soil conditions. Modules 3 and 4 were initialized for a wood-forwarding case study at CFB Gagetown, New Brunswick, Canada. Model results should be most applicable for flat to near-flat terrain, with insignificant wheel obstructions, and no organic matter accumulations on top of the mineral soil. Key words: Forest harvesting, soil penetration resistance, cone index, soil rut depth, soil disturbance, soil trafficability, soil compaction, terrain modelling

Beschreibung: 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

Beschreibung: The adsorption of B, in the form of boric acid, was studied on three precipitated humic acids (HA), representing three distinct soil types. B adsorption by HA was strongly pH-dependent, being low and relatively constant in the pH range 3.0–6.5, increasing markedly up to a peak at near pH 9.5, and then decreasing at still higher pH values. Adsorption isotherms for pH values near 6.7 and 8.8 conformed well to the Langmuir equation. The adsorption maxima (b values), as calculated with the Langmuir equation, ranged from 73 to 207 mmol kg−1 HA at a pH near 8.8, and from 10 to 42 mmol kg−1 at a pH near 6.7. The considerable variation in B adsorption by these HA samples was attributed to "Fe + Al" contents present as contaminants in the HA. The role of HA in B adsorption is expected to be minor in most acid and near neutral soils, but may be of greater significance in soils of high pH and above average organic matter content. Key words: Boron adsorption, boric acid, humic acid, Langmuir adsorption isotherm.

Beschreibung: A study was conducted to examine the effect of tillage on soil conditions and crop growth at three long-term (〉 10 yr) no-till sites, one in each of the Brown, Black, and Gray soil zones of Saskatchewan. The four tillage treatments consisted of one cycle of tillage at three levels of intensity: spring cultivation only, fall + spring cultivation, and fall + spring + disc cultivation, all applied to no-till and also a no-till control. Total and particulate soil organic carbon, soil pH, and soil aggregation were not affected by the tillage operations. Tillage decreased the bulk density in the 5- to 10-cm soil depth, but did not affect soil water content (0-10 cm) or spring soil temperature (0-5 cm). Tillage decreased stratification of available phosphorus to some extent, but there appeared to be no associated effect on crop P uptake. Tillage did not effect crop production in any of the 3 yr following its imposition, except at one site where, in the first year, apparent tillage-induced nutrient immobilization resulted in lower yields. Overall, the imposition of one cycle of tillage on long-term no-till soils appears to have little effect on soil properties or crop growth.Key words: No-till, nutrient stratification, soil organic carbon, tillage

Beschreibung: Despite its importance to the degradation of the land resource, few estimates of soil loss or soil erodibility for water erosion from cropland have been made for the semiarid Brown soil zone of western Canada. To estimate these, we calibrated the event-based Modified Universal Soil Loss Equation with measured sediment yield for three 5-ha fields near Swift Current, Saskatchewan. The calibration used predetermined C, LS, P, and warm-season K factors with all erositivities and the K factors for other seasons optimized. Using this calibrated equation with 31 yr of measured runoff data, mean annual sediment yield for a conventional-tillage spring wheat-fallow cropping system on an undulating landscape (0 to 5% slopes) was estimated to be 0.8 Mg ha−1 yr−1. Estimated erosion from fallow land from 16 March to 15 April constituted 86% of the mean annual sediment yield. Erosion occurring during rainfall-runoff were relatively unimportant, accounting for about 4% of the estimated total sediment yield. An exceptionally severe rainstorm was predicted to have caused erosion of many Mg ha−1but the frequency of such events on a given field is too low to greatly affect mean annual erosion. Apparent field-scale soil erodibility was least in the winter (November to 15 March) when the soil would typically be frozen to the surface and was greatest in April when the soil would typically be partially frozen. Apparent erodibility in the summer and in late March was intermediate between those values. Key words: Erosion, runoff, snow, Universal Soil Loss Equation

Beschreibung: An 11-yr study was conducted on a coarse-textured Brown Chernozemic soil in the semiarid prairie of southwestern Saskatchewan. Soil was sampled after 3, 7 and 11 yr, and the results were used to assess the influence of fallow frequency and tillage on selected soil quality attributes [e.g., total soil organic C and N, microbial biomass C (MB-C) and microbial biomass N (MB-N), C mineralization (Cmin) and N mineralization (Nmin), and specific respiratory activity (SRA)] in the 0- to 7.5-cm and 7.5- to 15-cm depths. Although it took 11 yr before we observed significant treatment effects on total organic C or N, effects on Cmin and Nmin were observed in 7 yr in the 0- to 7.5-cm depth and by 11 yr, MB and SRA also showed significant treatment effects in this depth. Generally, soil quality attributes were greater in no-tillage (NT) systems than in conventional mechanical tillage (CT) or minimum tillage (MT), and greater in continuous wheat (Triticum aestivum L.) (Cont W) than in fallow-wheat (F-W) systems. With time, the labile constituents tended to increase under the Cont W cropping, but to decrease when F-W was coupled with MT. After 11 yr there was a strong, direct association between the labile attributes (viz., Cmin, Nmin and MB-C) in the 0- to 7.5-cm depth and the mean annual straw produced (kg ha−1yr−1) in the four cropping systems tested. Of the soil quality attributes tested, Cmin and Nmin were the most sensitive indices to tillage and fallow frequency effects. Key words: Mineralizable C, mineralizable N, microbial biomass, specific respiratory activity, crop residues

Beschreibung: Field studies conducted throughout the calendar year are needed to improve flux estimates for the greenhouse gas nitrous oxide (N2O). In this study, we report monthly N2O emissions measured using micrometeorological techniques and a Tunable Diode Laser Trace Gas Analyzer (TDLTGA). Nitrous oxide fluxes were measured at the Elora Research Station (20 km north of Guelph, Ontario) from July to November 1992, and from March 1993 to February 1995, giving a total of 2445 daily averages obtained during the full length of the experiment. The soil at the experimental site was a Conestogo silt loam (Gleyed melanic brunisol). Several fields were monitored including fallow, manured fallow, Kentucky bluegrass, alfalfa, barley, canola, soybeans and corn plots. Spring thaw emissions from fallow or ploughed plots measured from March to April ranged from 1.5 to 4.3 kg N ha−1, corresponding to approximately 65% of the total annual emission. Similar effects were not observed on the vegetated (alfalfa and grass) plots. The lowest total annual N2O emissions were measured for second year alfalfa (1 kg N ha−1 yr−1) and bluegrass (0 to 0.5 kg N ha−1 yr−1). Higher annual emissions (2.5 to 4.0 kg N ha−1 yr−1) were observed for corn, barley, canola, and fallow plots. Highest annual emissions were measured after addition of nitrogen in the form of animal manure on a fallowed plot (5.7 to 7.4 kg N ha−1 yr−1), and alfalfa residue by fall-ploughing (6.1 kg N ha−1 yr−1). Plot management during the previous year affected N2O emissions, particularly on the soybean plot (5.9 kg N ha−1 yr−1) that followed a manured fallow treatment. The micrometeorological technique used in this study was successful at quasi-continuous monitoring of N2O fluxes from several plots, and therefore, useful for detecting long-term effects of management on emissions. Key words: Nitrous oxide, N2O fluxes, trace gases, agriculture, greenhouse gases

Beschreibung: Losses of total sediment phosphorus, total sediment nitrogen and dissolved nitrite, nitrate and ammonium resulting from natural rainfall erosion were studied in southern Manitoba during the summers of 1988–1990. Soils used were a Gretna clay, Leary sandy loam, Ryerson sandy clay and a Carroll clay loam. "Standard" erosion plots, i.e 22.13 m slope length, 4.6 m wide on a 9% slope were used. Crop management systems were 1) alfalfa, 2) corn, 3) wheat – minimum tillage, 4) wheat – conventional tillage, and 5) fallow. Nutrient losses averaged over the study period were greatest from the corn and fallow treatments, as high as 160 kg ha−1 yr−1 for nitrogen and 70 kg ha−1 yr−1 for phosphorus. Losses from wheat were intermediate. Losses from alfalfa were negligible. Most of the nutrient losses occurred with the sediment fraction, a result consistent with previous studies. Thus, nutrient loss can be estimated from a knowledge of soil loss. The amount of nutrient loss per unit soil varied with soil, and was a function of the inherent nutrient status of the soil. Key words: Nitrogen, phosphorus, rainfall erosion, nutrients

Beschreibung: Regulation of manure application in Manitoba has raised the question of whether or not biosolids application should be regulated in the same way. This study examined the effects of biosolids (BIO) applications on P sorption characteristics of a Vertisol in comparison with dairy cattle (DAIRY) and hog (HOG) manures, and monoammonium phosphate (MAP) fertilizer using the classical sorption isotherm and single point sorption index. Pertinent chemical properties and degree of P saturation (DPS) were also determined. The sorption maximum (Smax) in the control was reduced from 655 mg kg-1, to a range of 536–655 mg kg-1 with BIO, 559–650 mg kg-1 with MAP, 402–568 mg kg-1 with DAIRY, and 350–587 mg kg-1 with HOG depending upon the rate of P added. The lower DPS in the soil amended with BIO suggests a lower risk of P loss with biosolids compared with manures. The higher P sorption capacity of biosolids-amended soils compared with soils amended with manures suggest that Ca added with BIO increased the number of P sorption sites by a similar proportion to the amount of P added. Key words: Biosolids, P sorption isotherm, degree of P saturation, labile P, non-labile P

Beschreibung: The persistence of the herbicidal ester (14C)thiameturon was studied at different temperature and moisture conditions in three Saskatchewan soils. In all soils at 20 °C and 85% field capacity, the (14C)ester underwent rapid hydrolysis to (14C)thiameturon acid. The hydrolysis was over 85% complete in 1 week, and more than 95% complete after 2 wk. The soil degradation of (14C)thiameturon acid was considerably slower than that of the parent ester. Transformation of (14C)thiameturon to acid in all soils at 85% field capacity was temperature dependent, being slowest at 10 °C, and fastest at 30 °C. Conversion to the acid was also moisture dependent. There was no hydrolysis in air-dry soils after 10 wk. At 50% field capacity 22% of the ester remained after 1 wk, and at field capacity less than 2% of the applied ester was recoverable after 1 wk. Soils treated with thiameturon acid at rates up to 500 μg g−1 exhibited no phytotoxicity to canola, lentil, or sugarbeet seedlings. Key words: Herbicide, thiameturon, persistence, phytotoxicity

Beschreibung: 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

Beschreibung: This study was conducted to determine if deep banding of P fertilizer was as efficient as placing P in a band with the seed. Phosphorus fertilizer (MAP) was deep banded at rates of 0, 10, 20, and 30 kg of P ha−1 which was compared with equal rates applied with the seed, and with one-half seed placed, one-half deep banded. The P rates were applied onto the same plots each year in a cropping sequence of canola (Brassica napus L.), four crops of wheat (Triticum aestivum L.) and then canola. Plots were located on a Melfort silty clay soil (Orthic Black Chernozem). In combination with MAP treatments, ammonium nitrate was applied by deep banding and by broadcast-incorporation to bring the total N application rate to 75 kg ha−1. Control treatments of 0–0 and 11–20 kg of N-P, respectively, were also included. In the first year of the experiment, when soil moisture conditions were dry, seed placement of the P fertilizer, on average, resulted in a significantly higher grain yield (1.01 t ha−1) of canola than deep banding (0.88 t ha−1). In the last year of the experiment, canola grain yields for the two placements were not significantly different (1.87 vs. 1.83 t ha−1). Over the 4 yr that wheat was grown there was no significant difference in grain yield between seed placed P and deep banding (2.97 vs. 2.95 t ha−1). Seed placement of P resulted in a higher grain yield (3.05 t ha−1) with N broadcast than with N deep banded (2.90 t ha−1), but with half-seed plus half-deep-banded P the yield was higher with N deep banded (3.08 t ha−1) than with broadcast-incorporated (2.87 t ha−1). The application of N and P over the 6 yr increased the available P in the soil from 7.5 (control) to 12.9 μg of P g−1 soil (N P treatments with 75 kg N ha−1). In general the application of P fertilizer either by deep banding or placement with the seed of the crop gave similar yields with the exception that at the low rates of P, seed placement was better for canola in the first year of the crop sequence. Key words: Deep banding, N, P, canola, wheat, placement

Beschreibung: Water loss from soil minerals has been known to cause errors in the determination of soil organic matter when the loss on ignition (LOI) method is used. Unfortunately, no known published studies reliably quantify the range of structural water in the soil. To do this, 15 common reference minerals were analyzed by LOI to obtain their individual water loss. In addition, 14 upland, loamy soil samples and 3 wetland/hydric soil samples with varied mineral contents were analyzed to collect their X-ray powder diffraction spectra. Based upon X-ray spectra peak intensities, the modal abundance of minerals in each soil sample was determined using the RockJock computer program. The resultant modal weight percentages of all identified minerals in each soil sample were then multiplied by the LOI value for each mineral to obtain the mineral structural water loss (SWL) of that soil sample. For the 17 soil samples analyzed, the range of mineral water loss is 0.56 to 2.45%. Depending on the LOI values of the soil samples, the SWL:LOI ratios range from 0.04 to around 1.00. The SWL:LOI ratios are particularly low for top wetland soil when the LOI value is higher. The ratios are lower for surface soil samples than for subsurface soil samples because of the high LOI values in surface soil samples. Understanding soil mineral water loss and its relation to the LOI patterns from various environments is important for the accurate evaluation of soil organic matter when the LOI method is used. Key words: Mineral, structural water, loss on ignition

Beschreibung: A study was conducted on a 4-m-high ridge in southwestern Saskatchewan to determine the relationship of slope position with the soil water regime and spring wheat (Triticumaestivum L.) production and to determine if those relationships were altered by subsoiling. In all years, available soil water in the spring to 120 cm increased significantly with distance upslope. This pattern was attributed to residual subsoil water in the rooting zone that had not been used by previous crops in a long-term crop-fallow rotation. After 3 yr of annual spring wheat production, soil water to 1.2 m at all slope positions approximately equalled the water content wilting point (4.0 MPa) water content, showing this residual water had been largely consumed. Apparent use of soil water between seeding and harvest at the upper slope positions was equal to or greater than that at the lower slope positions. Over-winter soil water conservation, using tall (≥ 30-cm-high) wheat stubble for snow trapping, at the upper slope positions was equal to or greater than that at the lower slope positions. In the non-drought years of 1987 and 1989, wheat yields and crop water use efficiency increased significantly with distance downslope. Since these slope effects were not related to water use or availability, they were attributed to higher soil productivity, probably related to more historical net erosion with distance upslope. During the drought year of 1988, wheat yields and water use efficiency were greatest at the upslope positions, but these results were confounded by uneven crop emergence. Subsoiling to 35 cm or deeper increased the amount and depth of infiltration of water in years with near-average November–April precipitation. Subsoiling had little effect on wheat yields and no effect on crop water use. Key words: Landscape, wheat, productivity, soil moisture

Beschreibung: Soil acidity is a major problem in agriculture because it limits plant growth and reduces crop productivity. The neutralizing potential of industrial by-products and their impact on soil properties were evaluated in two acidic soils characterized by contrasting textures, and submitted to intensive agriculture practices. Soil pH, microbial (dehydrogenase and alkaline phosphatase) activity, and Mehlich-3 extractable P, K, Ca and Mg were monitored in the year of soil incorporation of eight liming products and in the following 2 yr. In the sandy loam, liming products did not result in significant increases in soil pH in the 0- to 7.5-cm soil layer. Lime mud (LM) significantly increased soil pH by 0.4 units in the 7.5- to 20-cm layer compared with cement kiln dust (CKD). In the silty clay, calcium-phosphate-magnesium (CalPoMag) significantly raised pH by 0.65 units over both natural calcitic lime (NCa) and the magnesium dissolution product (MgD) in the first soil layer, and by 0.5 units over carbide lime (CL) treatment in the second soil layer. Activities of dehydrogenase and alkaline phosphatase were increased to various degrees by all liming materials, especially on the silty clay; LM and CalPoMag were the most beneficial materials. The exception was MgD, which did not result in any impact on microbial activity relative to the control. Both enzymatic activities were related to the increase in soil pH, particularly the alkaline phosphatase. Ion leaching was more pronounced in the sandy loam than in the silty clay soil, where large differences in the Ca and Mg ion levels were still detected in the 20- to 40-cm layer of the sandy loam. In this study, LM and CalPoMag are interesting liming products, particularly in the silty clay soil. Key words: Enzymatic activity, soil pH, lime, soil cations

Beschreibung: Compositional nutrient diagnosis (CND) provides a plant nutrient imbalance index (CND - r2) with assumed χ2 distribution. The Mahalanobis distance D2, which detects outliers in compositional data sets, has a χ2 distribution. The objective of this paper was to compare D2 and CND – r2 nutrient imbalance indexes in corn (Zea mays L.). We measured grain yield as well as N, P, K, Ca, Mg, Cu, Fe, Mn, and Zn concentrations in the ear leaf at silk stage for 210 calibration sites in the St. Lawrence Lowlands [2300–2700 corn thermal units (CTU)] as well as 30 phosphorus (2300–2700 CTU; 10 sites) and 10 nitrogen (1900–2100 CTU; one site) replicated fertilizer treatments for validation. We derived CND norms as mean, standard deviation, and the inverse covariance matrix of centred log ratios (clr) for high yielding specimens (≥9.0 Mg grain ha–1 at 150 g H2O kg–1 moisture content) in the 2300–2700 CTU zone. Using χ2 = 17 (P 〈 0.05) with nine degrees of freedom (i.e., nine nutrients) as a rejection criterion for outliers and a yield threshold of 8.6 Mg ha–1 after Cate-Nelson partitioning between low- and high-yielders in the P validation data set, D2 misclassified two specimens compared with nine for CND –r2. The D2 classification was not significantly different from a χ2 classification (P 〉 0.05), but the CND – r2 classification differed significantly from χ2 or D2 (P 〈 0.001). A threshold value for nutrient imbalance could thus be derived probabilistically for conducting D2 diagnosis, while the CND – r2 nutrient imbalance threshold must be calibrated using fertilizer trials. In the proposed CND –D2 procedure, D2 is first computed to classify the specimen as possible outlier. Thereafter, nutrient indices are ranked in their order of limitation. The D2 norms appeared less effective in the 1900–2100 CTU zone. Key words: Nutrient balance, simplex closure, variance-covariance matrix, χ2 distribution, grain corn, nitrogen and phosphorus fertilization

Beschreibung: Non-irrigated corn (Zea mays L.) produced on coarse-textured soils during droughty years can result in excess NO3 available for leaching. To evaluate the effect of overseeding cereal rye (Secale cereale L.) into corn on yields, NO3 leaching and a pre-sidedress nitrate test (PSNT), we broadcast rye seed (Aug. 1993, 1994 and 1995) into conventional tillage (CT) and no-tillage (NT) corn receiving six fertilizer N rates. There was no corn yield penalty with the cover crop. Corn grain yields and the extent to which NO3 leaching was reduced by the rye cover depended on rainfall. With the rye (compared with no rye) subsoil solution NO3 concentrations were: unchanged (fall 1994) following above normal rainfall and corn yields; reduced by 8 mg NO3N L−1 (fall 1995) following intermediate rainfall and yields; and reduced by 28 mg NO3-N L−1 (fall 1993) and 11 mg NO3-N L−1 (spring 1994) following the driest growing season (average of CT and NT). Improved N availability with the rye was detected by a PSNT under CT, but not under NT. Therefore sidedress N rates can be adjusted for release of rye residue-N under CT, and potential NO3 contamination of groundwater can be reduced by overseeding winter rye into both CT and NT corn systems. Key words:Zea mays, Secale cereale, pre-sidedress nitrate test, tillage, nitrogen fertilization

Beschreibung: Cultivation is known to reduce the number and diversity of microarthropod (Acarina and Collembola) populations from levels observed under natural forest or grassland vegetation. Under no-tillage crop production, the soil remains relatively undisturbed and plant litter decomposes at the soil surface, much like in natural soil ecosystems. The objective of this study was to investigate whether microarthropod populations under long-term (19 yr) continuous corn (Zea mays L.) production were increased by no-tillage (NT) vs. conventional tillage (CT; moldboard plow and harrowing) management. Numbers of microarthropods were also obtained from a soil managed as the CT treatment for 15 yr until seeding to bromegrass (Bromus inermus L.) hay for the last 4 yr. During the growing seasons over 2 yr, soil cores were taken every 2–3 wk and extracted for microarthropods using a high gradient extractor. The surface 5 cm of soil was sampled during the first year. All three treatments were different (P 

Beschreibung: Previous field research in Alberta has suggested that denitrification occurs mostly when soil thaws in the spring, with associated soil water saturation. Our objective was to determine if denitrification and N2O emission in fact take place in cold, thawing soil in the field. Denitrification and N2O flux were measured in two springs and the intervening summer. Cylinders were placed in soil in November, 1988, and 57 kg N ha−1 of 15Nlabeled KNO3 was added. Soil 15N mass balance technique showed 23 kg N ha−1 of added-N was lost by 15 May 1989. Gas trappings were made (28 March to 29 April) and nearly all of the N2O emission (3.5 kg N2O-N ha−1) occurred during an 11-d period of thaw. The accumulated N2O flux from 20 June to 31 August was small (0.5 kg N2O-N ha−1, or less); during that time there were no rainfall events intense enough to produce water saturated soil. In 1990, 15N-labeled KNO3 (100 kg N ha−1) was applied on 26 March (outset of the thaw) and mass balance showed 32.7 kg N ha−1of added-N was lost by 7 May. A flux of 16.3 kg N2O-N ha−1 occurred largely in a 10-d period during and immediately after soil thaw. The N2O emitted from soil left a considerable fraction of the lost N unaccounted for. This unaccounted N was most likely lost as gaseous N other than N2O (e.g., N2). We conclude that large amounts of soil nitrate may be denitrified, with smaller amounts emitted as N2O, as the soil thaws and soon thereafter. Key words: Denitrification, frozen soil, thawing soil, nitrogen, nitrous oxide

Beschreibung: The development of sound management approaches to reduce soil organic carbon (SOC) losses presupposes that we thoroughly understand the sources of these losses. We used a landscape-scale research design to estimate human-induced SOC losses by comparing SOC storage in undisturbed landscapes with comparable landscapes disturbed by clear-cutting of forests in the Mixedwood/Gray Luvisolic zone of central Saskatchewan and by agricultural activity in the Black soil zone. A 14.0% decrease in soil organic carbon storage in the upper 45 cm of the soil (from 57.1 Mg ha−1 in mature Mixedwood sites to 49.1 Mg ha−1 in clear-cut landscapes) occurred due to clear cutting at the research sites in the Mixedwood forest. The dominant soil type at these sites, Gray Luvisolic soils developed in glacial till, experienced a 11% loss in SOC storage; higher losses (36% loss) occurred from sandy Brunisolic inclusions in the sites. Changes in SOC storage at the research sites in the Black soil zone landscapes varied with texture and parent material: sandy glacio-fluvial landscapes experienced slight gains of SOC (from 54.1 to 60.1 Mg ha−1); silt and clay glacio-lacustrine landscapes experienced a 15.3% decrease in SOC (from 145.2 to 122.9 Mg ha−1); and loamy glacial till landscapes underwent a major decrease in SOC storage (from 116.2 to 75.2 Mg ha−1) Our results indicate that attempts to increase SOC storage in Saskatchewan soils should concentrate on agricultural landscapes, especially those dominated by glacial till. Key words: Landscape, soil organic carbon, Chernozemic, Mollisol

Beschreibung: Mixing non-phosphate salts with phosphate fertilizer modifies the chemical environment of the soil-phosphorus (P) fertilizer reaction zone due to induced changes in soil pH and the interactions of P with soil components and other ions. The objective of this study was to examine the effects of cation and anion interactions on the solubility and diffusive transport of P in columns packed with a mixture of inert quartz sand and Ca2+-saturated cation exchange resin, buffered with CaCO3. The background pH of the resin-sand mixture was 9.4. Three types of cations (K+, NH4+, and Mg2+) were combined with four anions (NO3-, Cl-, SO42-, and CO32-) to produce 12 non-phosphate salts. Each of these salts was mixed with 0.4 g of KH2PO4 to provide 408.9 mg P kg-1 soil. The experiment was carried out in three replicates. Following 2 wk of incubation, columns were sectioned at 3-mm intervals and the pH of each section was measured. The samples were extracted with deionized water and subsequently with 1 mol L-1 HCl. Addition of KH2PO4 alone reduced the pH at the surface (first 3-mm section) of the resin-sand column to 7.1, while pH remained unchanged at 9.1 on addition of K2CO3 and KH2PO4. Addition of MgCl2 and KH2PO4 resulted in the lowest pH in the column and the greatest depth of H+ penetration compared with other treatments. None of the treatments containing NO3- or Cl- salts enhanced the solubility and movement of P. Addition of (NH4)2SO4 or (NH4)2CO3 to KH2PO4 produced the greatest amount of water-extractable P, followed by K2SO4. The lowest solubility of P occurred on addition of K2CO3 (P 〈 0.05). We attributed the enhanced solubility of P by SO42- and CO32- associated with NH4+ to competition between these anions and HPO42- for precipitation with solution Ca2+. Phosphate ion moved to depths of 5.0, 6.0 and 7.5 cm on addition of K2SO4, (NH4)2SO4, and MgSO4 to the column, respectively. These results suggested that salts such as K2SO4, (NH4)2CO3, (NH4)2SO4 and MgSO4 would enhance the lability of fertilizer P in a calcareous soil system. Key words: Solubility, precipitation, diffusive transport, resin, cation exchange, anion competition, dual banding

Beschreibung: 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

Beschreibung: An Acadia silty clay and a Pugwash sandy loam were each fertilized with three rates of either composted chicken manure, fresh chicken manure, or synthetic fertilizer. The effects of these amendments on soil microbial activity (dehydrogenase enzyme activity, DHA), organic C and pH were monitored. The sandy loam soil, which was relatively high in organic C, did not experience increases in DHA due to organic amendments while compost produced higher DHA than manure or fertilizer treatments to the silty clay soil. There was no treatment effect on soil organic C in the sandy loam, while organic treatments increased organic C in the silty clay soil. Soil pH was affected by treatments to both soils with compost amendments producing the greatest increases in this parameter. The results emphasize the importance of considering initial soil organic C and soil texture when planning studies of the effect of organic amendments on soil microbial activity. Key words: Dehydrogenase, compost, chicken manure, pH, soil organic carbon

Beschreibung: 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

Beschreibung: Plant availability of phosphorus (P) in calcareous soil can be improved by modifying the chemical environment of the soil-P fertilizer reaction zone through the banding of non-phosphate fertilizer with P. We investigated the solubility and diffusive transport of P as influenced by addition of two sulphate salts [(NH4)2SO4 and K2SO4] to NH4H2PO4 and KH2PO4. The salts were applied to a series of wax columns packed with approximately 223 g of Ca2+-saturated cation exchange resin-sand mixture buffered with CaCO3. The background pH of the mixture was 8.8. Each treatment contained approximately 204.5 mg P kg-1 soil, while 632.3 mg SO42- kg-1 soil was added to each P source for treatments containing the dual bands to provide a molar concentration of P and SO42- of 6.6 mmol kg-1 soil. After 2 wk of incubation, column segmentation and extraction showed that H+ moved deeper into the columns on addition of the sulphate salts compared with adding NH4H2PO4 or KH2PO4 alone. The maximum depth of P penetration in the columns containing NH4H2PO4 was 4.2 cm, while P transport in the columns treated with KH2PO4 was restricted to the top 4.0 cm depth. Addition of (NH4)2SO4 or K2SO4 to NH4H2PO4 increased the concentration of water-extractable P by 43 and 21%, respectively, above that in NH4H2PO4 alone. Similarly, addition of (NH4)2SO4 or K2SO4 increased the concentration of water-soluble P by 48 and 41%, respectively, above the amount in KH2PO4 alone. The increased water solubility of P on addition of the sulphate salts was attributed to anion competition between HPO42- and SO42- for precipitation with Ca2+. We also observed ionic competition between NH4+ and K+ when both cations were added together, causing K+ to travel farther into the column and with increased solubility than when applied alone. Our results showed that anion and cation competition can be used to modify the transport and solution concentration of ions through dual banding. These results also suggested that the combination of anion competition by SO42- and pH reduction due to salt effect could have a positive influence on the availability of P in calcareous soils. Key words: Phosphate, sulphate, columns, solubility, diffusive transport, resin

Beschreibung: The design for a sleeve-type, quick-mount soil core sampler for bulk density and soil water content determination and for collection of undisturbed soil samples is described and its performance discussed. This core sampler has been used to collect undisturbed soil core samples 47.5 mm in diameter and 300 mm long in tillage and seeding studies. Less than 2 min is required to retrieve, seal and store each soil core sample. The soil samples are contained in 50.8-mm-diameter aluminum liners which are easily sealed with plastic caps and stored for later laboratory analysis. This sampler resulted in very good measurement repeatability and provided subsamples suitable for water retention curve determinations. Key words: Soil sampler, coring device, bulk density, soil moisture, undisturbed cores

Beschreibung: This study examines three methods of evaluating N2O flux and accumulation in soil profile over a growing season under three soil management regimes (fallow, fallow with manure addition and cropped to alfalfa). Estimates of N2O flux were made based on measured soil atmosphere concentration gradients in the top 15 cm and compared to flux estimates based on ex situ cores and micro-meteorological measurements made in parallel studies. All methods indicated strong seasonal trends relating to precipitation events. The amounts of N2O accumulating the profile decreased in the order alfalfa 〈 fallow 〈 fallow/manure. The amounts of N2O accumulating in the profile ranged from ambient (0.35 µL L−1) to 490 µL L−1. Diffusion of N2O to the lower profile was shown to provide temporary storage of N2O and thereby provide the opportunity for further reduction to N2 prior to efflux from the surface. In comparing the estimates of surface flux, all three methods were of the same order of magnitude for the fallow site but profile-based estimates were much lower and much higher for fallow/manure and alfalfa sites, respectively. Differences were attributed to the location and timing of carbon addition in each system. Key words: Nitrous oxide, N2O, flux, measurement, soil, management

Beschreibung: The kinetics of the adsorption of orthophosphate (Pi), inositol hexaphosphate (IHP), inositol monophosphate (IMP) and glucose 6-phosphate (G6P) by short-range ordered precipitate of Al were studied at the initial pH 4.50 and in the temperature range of 278–308 K. This information is essential for understanding the rate and energy relationship of the adsorption of phosphates by short-range ordered Al precipitate. The amounts of Pi and IHP adsorbed by the Al precipitate were much higher than those of IMP and G6P adsorbed in the temperature range and reaction periods studied. The adsorption can be divided into two stages, a fast adsorption before 1 h and a slow adsorption between 1 and 24 h. The adsorption at both stages obeyed the first-order kinetics. Among all the phosphates studied, the adsorption of Pi proceeded most rapidly. The rate constants for the adsorption of IHP were much greater than those of G6P and IMP at the same temperature; this was attributed to the functionality of multiple phosphate groups of IHP. The Arrhenius activation energies for the adsorption of Pi, IHP, IMP and G6P, which were estimated from the slow reaction, were 48 ± 2, 89 ± 4, 100 ± 8 and 108 ± 10 KJ/mol P adsorbed, respectively. Key words: Organic phosphate, precipitate of aluminum, adsorption, rate constant, Arrhenius activation energy

Beschreibung: A method of measuring the structural stability of moist soils using a combination of turbidimetry and wet sieving has been developed and assessed. Aggregates of 1–2 mm in diameter are shaken end-over-end in test tubes and dispersed clay and stable aggregates greater than 0.25 mm diameter measured. Stabilities determined using this method were compared to stabilities determined using a modification of the Yoder wet-sieving method on 20 soils of different textures, organic-matter content, and recent cropping history. Wet aggregate stabilities determined by the two methods were correlated although the two measurements exhibited different sensitivities to clay content, organic-matter content and moisture content at the time of sampling. Dispersible clay was found to be a function of total clay content, organic-matter content and water content at the time of sampling. The new method offers the advantage of stability measurements of structural units of much different size using the same energy input and can be readily adapted to the routine analysis of a large number of samples without a large investment in equipment or space. Key words: Wet aggregate stability, dispersible clay, cropping history, soil structure

Beschreibung: This study was undertaken to quantify the effects on long-term application of solid cattle manure on physical and biological properties of a Neubois silty loam. Rates of 0, 20, 40, 60, 80 and 100 Mg ha−1 manure were applied every 2 yr to the soil cropped to corn. Significant improvements, proportional to application rates, of water-stable aggregation, bulk density, and water content of the soil were measured. These physical properties were highly correlated with the soil microflora (0.83 ≤ r ≤ 0.98). A positive interaction exists between physical and biological properties of soils following long-term manure application. Key words: Solid cattle manure, aggregation, bulk density, biological activity

Beschreibung: The amount and pattern of plant-available nitrogen (N) release from composts are variable and not well-defined. We used a 425-d canola (Brassica napus L.) bioassay to follow the release of N from eight composted cattle manures applied to soil at 20 g kg-1. Two stockpiled manures, one inorganic fertilizer and an unamended control were also included for comparison. Eight consecutive 30-d growth cycles were conducted in a controlled environment chamber (20°C) and plant N uptake was measured. Total N uptake was greatest from the N fertilizer and least from the wood-chip bedded manure. Addition of compost increased N uptake by 27–99% compared with that in the control. Nitrogen uptake from compost was directly proportional to its inorganic N content (r2 = 0.98; P 〈 0.0001) showing that the initial inorganic N content of compost, analyzed prior to its application can be used to predict plant available N. In seven of the eight composts studied, less than 5% of organic N was mineralized over 425 d, suggesting that little of the organic N in compost becomes available in the year of application. Compost is a valuable organic amendment, but co-application of N fertilizer is recommended to supply adequate N and optimize the benefits of compost for crop growth. Key words: Plant-available nitrogen, compost, nitrogen mineralization, beef manure

Beschreibung: Indirect measurements of denitrification to 120 cm depth in a coarse textured soil in October showed higher denitrification rates following a single spring application of dairy cattle slurry than following a spring application of fertilizer. The highest denitrification rates occurred immediately above and below the water table (90 cm depth) and resulted primarily from C applied in the manure moving down through the soil profile. Key words: Dairy cattle slurry, carbon, nitrate, shallow water table

Beschreibung: 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

Beschreibung: Long-term mineral fertilizer applications could reduce organic matter (OM) levels in soil if coupled with crop rotations with low organic residues inputs. The main objective of this study was to evaluate the C and N contents in whole soil, in densimetric OM fractions and in different aggregate size fractions of a Le Bras silt loam (Humic Gleysol). The treatments were arranged in a split-plot design, with dairy cattle manure applied at 0 and 20 Mgha−1 as the main factor. The subplots consisted of six fertilizer treatments (NK, PK, NP, NPK, NPKMg and the unfertilized check). The four year rotation included silage corn, (Zea mays L.) silage corn, wheat (Triticum Aestivum L.) and barley (Hordeum vulgaris L.). Contrary to mineral fertilizer, long-term manure applications significantly increased the C content in whole soil and also in the light and heavy fractions of OM (Fl and Fd). Mineral fertilizer significantly increased the C and N contents only in Fl. Moreover, manure application also increased the weight of the 5–8 mm aggregate size fraction and the C and N content in the 5–8 mm, 2–5 mm, 1–2 mm and 0,25–1 mm aggregate size fractions, compared to mineral fertilizer alone. In manured plots, soil C biomass, microbial respiration (CO2) and N mineralization (NO3) levels increased by 30% compared with mineral fertilizer treatments. Results of this study demonstrate the important effect of manure applications on C and N enrichment in soil and also on soil macroaggregation and biological activity. To maintain optimal C and N levels in soil and to favour soil macroaggregation, long-term mineral fertilizer application should be combined with crops in rotations which ensure high organic residues returns to soils. Key words: Macroaggregation, microbial biomass, N mineralization, long-term, light fraction, heavy fraction

Beschreibung: 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

Beschreibung: Infiltration capacity is generally reduced with increased grazing intensity and reduced range condition, mainly through vegetation and litter removal, soil structure deterioration, and compaction. Only one study has documented the effect of grazing on Canadian rangelands, necessitating further investigation. In this study, impacts of long-term grazing on infiltration were assessed in mixed prairie and fescue grassland ecosystems of southern and central Alberta, Canada. Grazing regimes were of light to very heavy intensities, grazed early, late, and continuously during the growing season. Ungrazed controls were evaluated at each site. Infiltration was measured with double ring infiltrometers. Heavy intensity and/or early season grazing had greater impact on infiltration than light intensity and/or late season grazing. In mixed prairie, initial and steady state infiltration rates in the control were 1.5 and 1.7 times higher, respectively, than those in the early season grazed treatment. In parkland fescue, initial rates were lowest in June grazed treatments and steady state rates were highest in light autumn grazed and control treatments. Initial infiltration rates in foothills fescue control and light grazed treatments were 1.5–2.3 times those in heavy and very heavy grazed treatments. Steady state rates were 1.5–2 times higher in light grazed and control treatments than in moderate, heavy, and very heavy grazed treatments. Key words: Infiltration, infiltration rate, grazing, rangelands

Beschreibung: Quantifying soil organic carbon (SOC) is important to aide in assessing carbon (C) sequestration potential, and as an indicator of soil quality. However, intensive s ampling of SOC for quantification can be expensive and time consuming. The objectives of this study were to identify which topographic index correlated best with SOC and determine if incorporating the index improved interpolation of limited SOC data. A transect with 93 sample points spaced 6 m apart was set up, and four topographical indices (curvature, wetness index, upslope length, and elevation) were evaluated for their potential as secondary variables. Three Kriging-based interpolation methods, ordinary kriging, cokriging, and simple kriging with varying local means were compared to determine if incorporating topographical indices improved interpolation of SOC. The upslope length, which takes into consideration the quantity of water that will be redistributed to a point, was found to have the strongest relationship with SOC (R2 = 0.48, P 〈 0.01) and was used as a secondary variable for kriging. Thirty points from the SOC data were randomly selected and used in the kriging algorithms to estimate the remain ing 63 points. The sum of squared differences (SSD) showed a significant reduction (from 1677 to 1455 for SKlm and from 1677 to 1464 for cokriging) in estimates when upslope length was used as a secondary variable. These results indicate that fewer samples may be taken to estimate SOC accurately and precisely if upslope length is incorporated. On a landscape scale this could facilitate quantification of carbon credits and management decisions in precision farming systems. Key words: Geostatics, kriging, cokriging, organic carbon, landscape processes, wetness index

Beschreibung: The morphology and composition were studied of a pair of soil profiles that had developed in a dike which was constructed 100 yr ago from marine sediments of silty clay loam texture. Both profiles had a weakly expressed A-B-C horizon sequence and strong structural development. They had Bm horizons and their exchange complex was dominated by magnesium ions. Organic carbon had accumulated in the surface mineral horizon at a maximum rate of 26.3 g m−2 yr−1. Adverse climatic conditions, typical for this and similar site locations, appeared to impose a limit on soil development. Key words: Soil formation, marine sediments, maritime climate

Beschreibung: The understanding of the kinetics of K uptake by plants is necessary for the development of predictive models aimed at optimum fertilizer use and crop yields. The objective of this work was to study the kinetics of K uptake by alfalfa, in a long-term growth chamber experiment (366 d), on 30 soils from Quebec. The soils varied in mineralogical composition and by the amounts of available K in soluble, rapidly and slowly exchangeable forms. In 28 of the 30 soils, a minimal, steady-state level of NH4OAc-K was reached after 208 d and six cuts of alfalfa. This minimal level and the K uptakes were qualitatively related to soil texture. Only soils with clay content greater than 35% were still able to supply enough K to maintain alfalfa yields. The kinetics of K uptake was described by two parabolic diffusion equations. In the first 208 d, the rate and amounts of K uptake were better predicted by extracting procedures using a monovalent cation for the exchange. The amount of HNO3-K in the soils was very significantly related to the rate (r = 0.90**) and amount of slowly exchangeable K uptake (r = 0.89**) in the last 158 d of growth. The availability of K was greater in soils rich in feldspar and vermiculite than in soils where illite is a major component. The results of this study indicate that the amounts of HNO3-K and/or the clay content should be integrated into alfalfa fertilizer requirement tables along with amounts of K in soluble and rapidly exchangeable forms for maintenance of alfalfa fields. Key words: Slowly exchangeable K, alfalfa, uptake kinetics, HNO3-K, diffusion, K uptake

Beschreibung: A study was conducted from 1994 to 1996 in a hummocky landscape near Prince Albert, Saskatchewan in the moist Black soil climatic zone to determine the best criterion for defining fertilizer management zones within a field and how much fertilizer to apply in each zone. A uniform rate fertilization (CF) treatment was compared with three variable rate fertilization (VRF) treatments that used management zones based on soil residual nitrate-N (VRFrn), organic carbon (VRFom) and topography (VRFt). For VRFom and VRFt, fertilizer recommendations were based on soil residual N levels within zones and yield potentials that differed between zones. Flax (Linum usitatissimum) was grown in 1994, spring wheat (Triticum aestivum) in 1995, and canola (Brassica rapa) in 1996. Fertilizer use efficiency (FUE), defined as kilograms seed per kilogram fertilizer N, was markedly higher for VRFom and VRFt than CF or VRFrn. This enhanced FUE resulted in net returns, defined as crop revenue minus fertilizer cost, of about $10 ha−1 more than that of CF. Three successive years of VRF in this study suggests that this practice can enhance the efficient use of fertilizer N and has potential to increase profitability of fertilizer use, by more closely matching fertilizer N inputs with crop nutrient requirements. Key words:Brassica rapa, Linum usitatissimum, Triticum aestivum, nitrogen, variable rate fertilization, precision agriculture

Beschreibung: Residue management may affect soil temperature, and consequently soil biological processes, by influencing energy exchange fluxes at the soil surface. Simulation models in which these fluxes are estimated allow the investigation of hypotheses concerning the effect of residue management on soil thermal regimes. The simulation technique used here involves a finite difference approximation to the estimation of hourly water and heat fluxes through a one-dimensional, layered soil medium, with boundary conditions determined at the surface from surface energy exchange processes, and below the profile from source/sink dynamics. Crop and residue cover are considered as they influence radiative fluxes at the soil surface. Estimated soil temperatures were compared to recorded soil temperatures at 0.05- and 0.15-m depths in plots of barley grown under conventional (CT) and minimum (MT) tillage which left 90% and 30% of the soil surface exposed, respectively. Although diurnal trends in soil temperature were consistent with those recorded, the amplitude of diurnal variation was overstimated by the model under CT, and underestimated under MT. Standard differences between recorded and estimated hourly-averaged temperatures were about 2.5 °C at 0.05 m, and half as much at 0.15 m. The model failed to simulate the consistently lower soil temperatures recorded under MT during the early part of the growing season that may have been caused by longer term tillage effects, such as the persistence of ice lower in the soil profile. Examination of early season temperature effects will require longer term simulations in which the hydrologic and thermal implications of snow and ice are considered. Key words: Soil water flux, soil heat flux, surface energy exchange, soil temperature

Beschreibung: We need an easy-to-use chemical index for estimating the amount of N that becomes available during the growing season, to improve N use efficiency. This paper discusses how producers may, in future, use crop growth models that incorporate indices of soil N availability, to make more accurate, risk-sensitive estimates of fertilizer N requirements. In a previous study, we developed an equation, using 42 diverse Saskatchewan soils, that related potentially mineralizable N (N0) to NH4N extracted with hot 2 M KCl (X), (i.e., N0 = 37.7 + 7.7X, r2 = 0.78). We also established that the first order rate constant (k) for N mineralization at 35°C is indeed a constant for arable prairie soils (k = 0.067 wk−1). We modified the N submodel of CERES-wheat to include k and N0 (values of N0 were derived from the hot KCl test). With long-term weather data (precipitation and temperature) as input, this model was used to estimate probable N mineralization during a growing season and yield of wheat (grown on fallow or stubble), in response to fertilizer N rates at Swift Current. The model output indicated that the amount of N mineralized in a growing season for wheat on fallow was similar to that for wheat on stubble, as we hypothesized. Further the model indicated that rate of fertilizer N had only minimal effect on N mineralized. We concluded that, despite the importance of knowing the Nmin capability of a soil, it is available water, initial levels of available N and rate of fertilizer N that are the main determinants of yield in this semiarid environment. The theoretical approach we have proposed must be validated under field conditions before it can be adopted for use. Key words: N mineralization, Hot KCl-NH4-N, potentially mineralizable N, CERES-wheat model

Beschreibung: Spring soil nitrate and ammonium dynamics in south coastal British Columbia soils were examined with respect to the potential to develop a soil nitrate test for silage corn (Zea mays, L.). Soil nitrate and ammonium contents were measured to 90 cm depth in two soils from April to July of two growing seasons. Treatments included a control, spring application of either 300 or 600 kg total N ha−1 as liquid dairy manure, or 200 kg N ha−1 as inorganic fertilizer. Significant amounts of ammonium were present until late May following manure and until mid-June following fertilizer application, requiring simultaneous determination of both nitrate and ammonium concentrations to assess soil inorganic N contents during this period. Most of the changes in soil nitrate over time occurred in the top 30 cm, suggesting that sampling to 30 cm depth would be sufficient in most cases for a soil nitrate test in this region. Most of the increase in soil inorganic N associated with the spring application of manure occurred by 1 June. A soil nitrate test in early to mid-June when the corn is at the six leaf stage appeared to be most suitable for use in south coastal British Columbia to determine if additional fertilizer N is required. A sample taken at this time will measure soil nitrate contents just before the period of rapid corn N uptake, after most of the additional inorganic N associated with spring manure application is already present in the soil as nitrate, and after nitrification of the manure ammonium has occurred. Key words: N recovery, preplant nitrate test, pre-sidedress soil nitrate test

Beschreibung: An insight into sulphate (SO42−) retention by podzolic and brunisolic soils was obtained by examining SO42− sorption by B horizons from forest soils in northeastern Ontario. The amount of water soluble and adsorbed SO42− present in the soils and the ability to adsorb additional SO42− was evaluated. Relationships between soil pH, organic carbon and different iron (Fe) and aluminum (Al) fractions with water soluble and adsorbed SO42− were examined. Using a surface complexation approach, modelling was carried out to predict the soil SO42− sorption capacity at any given pH. The potential SO42– adsorption capacity was also measured by applying adsorption equations. Both the Freundlich and Langmuir sorption isotherms gave comparative fits to the SO42− adsorption data. The soils contained small amounts of water extractable SO42− (0.1 to 0.8 mmole kg–1). There was a significant positive correlation between water extractable SO42− and organic carbon in the podzolic soils but not for the brunisolic soils. Approximately 90% of the sulphate extracted was contained in the insoluble SO42− fraction. Sulphate sorption by both soil types was most closely related to amorphous inorganic Al. In brunisolic soils, total adsorbed SO42– also had a strong positive correlation with the oxalate extractable silica fraction and a negative correlation with pH. Sulphate adsorption simulations were close to the measured values. Key words: Soluble SO42−, adsorbed SO42−, Podzol, Brunisol, amorphous Al oxide, SO42− adsorption model

Beschreibung: Conservation practices in potato (Solanum tuberosum L.) cropping systems can reduce excess tillage, provide crop residue cover, and maintain crop productivity; however, little is known about their long-term influence on soil biota and biological properties. Conservation tillage was evaluated in two potato rotations: a 2-yr barley-potato rotation and 3-yr clover-based (barley-red clover-potato) rotation initiated in 1994 on a fine sandy loam (Orthic Podzol) in Prince Edward Island, eastern Canada. Soil samples were obtained in 2003 from the 0- to 10-cm soil depth of the potato phase of both rotations to evaluate the influence of conservation, compared with conventional tillage, on changes in soil fertility, soil structural properties, soil C and N fractions, soil-borne pathogens, nematode communities, and micro-arthropod (Collembola and Acari) communities. The 3-yr conservation tillage practice improved soil structural stability, increased soil extractable P and K, increased soil organic C and total N and their particulate fractions, compared with the other treatments. Comparisons with earlier studies indicated that soil organic C had reached an equilibrium level at the 0- to 10-cm soil depth. Reduction of potato disease caused by Rhizoctonia solani was evident in the 3-yr rotation, compared with the 2-yr rotation, but was not influenced by tillage practice. Plant parasitic nematodes were not greatly influenced by rotation and tillage treatments; however, densities of the beneficial bacterial-feeding nematodes were increased under the 3-yr conservation tillage treatment. The abundance of micro-arthropods was increased by conservation tillage, while their diversity was mainly influenced by the rotation cycle rather than tillage practice. Overall, the 3-yr conservation tillage treatment provided a more beneficial soil biological condition than the other treatments, especially when compared with the 2-yr conventional tillage practice. Key words: Conservation systems, potato rotation, fine sandy loam, soil fertility, soil organic C and N fractions, soil structure, soil-borne pathogens, nematode, Collembola; Acari

Beschreibung: A new precipitation titration method, employing cetyltrimethylammonium (CTA+), is proposed for analysis of carboxyl groups of humic substances in solution. The method was tested with polyphenol-polycarboxylic acids standard solutions: recovery factors ranged from 0.94 to 1.09. Results obtained by performing precipitation of humic acids samples at pH = 9.8 and at 7.0 are compared with those obtained by the Ca-acetate method. The difference between the number of COOH per unit weight of humic preparation calculated by precipitation with CTA+ at pH = 7.0 and by the Ca-acetate exchange reaction ranged between 1 and 45%. In most samples overestimation of COOH groups by the Ca-acetate method appears to be higher than the mean relative error of the CTA+ precipitation method (5%). Key words: Carboxylic group determination, humic substances, cetyltrimethylammonium

Beschreibung: Seed bed temperature is often the limiting environmental factor affecting corn (Zea mays L.) emergence, particularly in short-season production areas or when conservation tillage practices are employed. In this study, observations of the percentage emergence and seed bed growing degree days (base 10 °C) are used to assess functions which model the emergence response to temperature. Key words: Percentage emergence, growing degree days, log transformation, logistic function

Beschreibung: Controlled fertilizer nitrogen (N) inputs and releases to drainage waters were recorded for 9 yr in orchard-type lysimeters. Irrigations were varied year by year from about 37 to 100% of the maximum for the area. One apple tree per lysimeter was the test crop. Large amounts of drainage resulting from the highest levels of irrigation carried the largest amounts of nitrate [Formula: see text] to groundwater but when irrigation was less than 75% of maximum much smaller annual amounts appeared in drainage, mostly because drainage was small. Year 1 of drainage, although light, carried substantial amounts of [Formula: see text] out of the lysimeters probably reflecting mineralized native organic N plus applied N. The largest single influence on the retention of N was the presence of a cover crop. In 9 yr, 40 – 45% of applied N reappeared in drainage waters under grass while 88 – 115% of applied N reappeared under bare soil. The quantities of applied N (N1 = 162 kg N ha−1; N2 = 324 kg N ha−1) had less influence than the cover crop. The importance of measuring and sampling every drainage event because of wide ranges of [Formula: see text] concentrations is emphasized. Averaging could be misleading. The potential impact of [Formula: see text] releases to the aquatic environment of the watershed is discussed briefly. Key words: Nitrogen losses, lysimeters, irrigation, watershed, nitrate

Beschreibung: The onset of a decline in net N mineralization, primarily due to denitrification, has been related to water contents, θW, or water-filled porosities, fW, but values of these characteristics vary among soils thus limiting their use as diagnostic criteria. An implicit assumption in the use of these characteristics is that water-filled pores of all sizes are habitable by microorganisms participating in denitrification. However, microorganisms are excluded from small pores, and the volume fraction of these pores varies with soil structure. The objective of this study was to determine if variation in the volume fraction of water-filled microbially habitable pores, θMHP, contributes to the variation in denitrification in soils of different structure. Data were used from studies with and without growing maize (Zea maize L.) plants. Variation in soil structure was achieved by using soils of different texture and organic carbon contents that were packed to two different levels of relative compaction. At the onset of a decrease in net N mineralization, values of θMHP exhibited less variability among soils than either θW or fW. The θMHP will be of greatest value as a diagnostic criterion for the decline in net N mineralization in soils exhibiting variation in the volume fraction of pores ≤ 4 µm diameter. Key words: Denitrification, habitable pore space, soil structure

Beschreibung: DDT was applied at Point Pelee, Ontario, Canada, between 1948 and 1970 for mosquito control in recreational areas and pest control in former agricultural areas. Recent soil sampling programs produced 275 analyses enabling a statistical comparison of DDT concentrations with land use areas, soil conditions, and hydrologic characte ristics. Concentrations of ΣDDT ranged over several orders of magnitude, with the highest concentrations (maximum 316 000 ng g-1) in former agricultural areas and the lowest concentrations in the natural sand dunes (maximum of 116 ng g-1). DDT is undergoing degradation at Point Pelee along two pathways. DDT is transformed aerobically to DDE within the sandy soils exhibiting average %DDT, %DDE and %DDD of 40%, 55%, and 5% of ΣDDT, respectively. DDT is transformed anaerobically to DDD and DDE within the marsh and flooded soils averaging 14% DDT, 44% DDE, and 42% DDD, respectively. The half-lives for the transformation of DDT to DDE within the well-drained and aerobic sandy soils at Point Pelee are highly variable and were estimated to range from 20 to 50 yr. Given the high concentrations of ΣDDT at Point Pelee and the long half-life, it is expected that DDT will remain at concentrations of concern for many decades. Key words: DDT, persistence, degradation rates, concentrations, sandy soil, marshy soil

Beschreibung: Applying ultrasound energy to soil-water suspensions (sonication) is an established method of determining the size distributions of soil primary mineral particles and associated organic matter. The size distributions may vary, however, with sonication input energy and soil type. The objective of this study was to determine the effects of sonication input energy on the size distributions of soil mineral particles and organic matter for a range of soil textures and carbon contents typical of agricultural soils in southwestern Ontario. The soils included a Brookston clay loam, a Brookston clay, a Huron silt loam, a Perth silt loam and a Harrow sandy loam. All soils were under no-tillage management. Nine sonication energies ranging from 50 to 1500 J mL–1 were applied to soil-water suspensions (1:4 mass ratio), and the soil particle size distribution results were compared with those obtained using the standard chemical dispersion (pipette) method. The three medium- and coarse-textured soils (Huron, Perth, Harrow) required about 250 J mL–1 for complete dissociation of soil aggregates, while the two fine-textured soils (Brookston) required sonication energies of 600-750 J mL–1. Increasing sonication energy increased the amount of soil organic carbon (SOC) measured in the clay-size fraction and decreased the amounts in the sand and silt fractions. Therefore, accurate determinations of particle size distribution and SOC contents require an initial assessment of the amount of sonication energy required for the complete dispersion of the particle size fractions. For the Brookston clay loam and Brookston clay soils, 40–52% less particulate SOC was found in the sand fraction at 750 J mL–1 sonication energy than that obtained using the standard pipette method, indicating particle size reduction by sonication of particle organic matter. It should be noted that the sand-size SOC typically represents a small fraction. Furthermore, sonication had a minor effect on the SOC content of the clay fraction. It was concluded that sonication is a viable technique for determining the size distribution of soil primary mineral particles, as well as the amount of SOC associated with the silt and clay fractions. Key words: Sonication, ultrasound energy, particle size distribution, organic carbon fractionation, clay soil

Beschreibung: This paper reports sheep camping influences on soil chemical and physical properties, and pasture dry matter (DM) production of an acidic soil on the southwest slopes of New South Wales, Australia. The experiment was conducted in the spring (October-November) of 2005 on a long-term field experimental site after 13 yr of rotational grazing. The factors considered were sheep camping (distance from the camping site), pasture type (perennial vs. annual pastures) and lime application (limed vs. unlimed treatments). Over 13 yr of rotational grazing, significant amounts of carbon (C), nitrogen (N), phosphorus (P) and potassium (K) were deposited near the sheep camping site via the deposition of animal excreta. Total C increased from 32.8 g kg-1 20 m away from the camping site to 41.9 g kg-1 at the camping site in 0-5 cm soil depth. The Colwell P increased from 44.0 to 125.9 mg kg-1 from the non-camping area to the camping site in 0-5 cm soil depth. The most interesting result from the current study is that soil bulk density decreased as the intensity of camping increased. On the perennial pastures, soil bulk density was 0.96 and 1.34 g cm-3 at the camping site in the 0-5 and 5-10 cm soil depths, respectively, whereas soil bulk density was 1.14 and 1.39 g cm-3 at 20 m away from the camping site at the corresponding soil depths. Across pasture types, mean pasture DM was highest at the camping site (7.3 and 6.6 t ha-1 for the limed and unlimed pastures, respectively), and lowest 20 m away from the camping site (5.4 and 4.5 t ha-1 for the limed and unlimed pastures, respectively). The vigorous pasture growth and high organic matter at the camping site may have had a "cushioning effect", thereby reducing soil compaction. However, this camping effect was confined to within 5 m of the camping site. It is concluded that sheep camping can create spatial heterogeneity in soil chemical and physical properties. The non-uniform influence on pasture productivity and composition could be minimised by altering the grazing management strategies, such as periodic relocation of the site of shelter, or further subdivision of the grazing paddock, if necessary. Key words: Soil carbon, nitrogen, phosphorus, bulk density, grazing management

Beschreibung: Agricultural soils are the recipients of trace elements from general atmospheric pollution and from agricultural inputs such as fertilizer, feeds and urban biosolids. These input fluxes are usually small, and there are processes such as leaching and crop off-take to counterbalance the trace element inputs. Thus, it is difficult to evaluate the changes of trace element concentrations in agricultural soils. This paper examined a survey of 59 soil profiles in Southern Ontario, combining analysis of ~50 elements in three soil depths and corresponding measurements of the soil solid/liquid partition coefficient, Kd. The profile data were adjusted for yttrium concentrations to account for vertical particle migration. Increased concentration in the surface profile relative to the subsurface was considered an indication of enrichment, indicating the possible effects of human activity. For most elements, the surface (0–15 cm) and subsoils (30–60 cm) had similar concentrations. The notable exceptions were Cd, Pb, Sb, Se, Nb, U, and Zn, where surface soils had 1.4- to 2.2.fold higher concentrations than subsoils. Most of these increases can be attributed to human activity. Additional interpretation using the Kd data was useful to identify Ba and Mo as potentially among the contaminant elements. Surface soil concentrations of these elements were not markedly elevated compared with the subsoil, but their Kd values indicated that they were sufficiently mobile that depletion would be expected. Thus, perhaps continued input has supported the concentrations of Ba and Mo in the surface soils. Both are noted contaminants in dust from urban sources. Thus, the results show that several elements that are often of concern because of environmental toxicity or health impacts are at elevated concentrations in agricultural soils, and because these are rural locations the implication is that this has resulted from non.point.source pollution.Key words: Kd, partition coefficient, leaching, metals, cadmium

Beschreibung: En régions de climat tempéré, les terres cultivées ont un potentiel de stockage de carbone que l’on peut tenter d’utiliser pour réduire d’autant les émissions de CO2 atmosphérique par des pratiques culturales adaptées et notamment par les techniques culturales sans labour (TCSL). Cette capacité de stockage de carbone dans le sol a été évaluée sur l’essai de longue durée de Boigneville (Bassin de Paris, France) et a été comparée aux données de la littérature internationale. Le suivi du stock de carbone du sol sous une rotation maïs-blé indique une tendance à un stockage modéré tant en système labouré (0,10 t C ha-1 an-1 sur 28 ans) qu’en TCSL (respectivement 0,21 t et 0,19 t C ha-1 an-1 pour le travail superficiel et le semis direct sur cette même période). Avec une absence de différence significative entre le semis direct et le travail superficiel, l’effet spécifique moyen des TCSL évalué à 0,10 t C ha-1 an-1 sur 28 ans apparait sensiblement plus faible que celui mesuré sur les 20 premières années et évalué à 0,20 t C ha-1 an-1. Ces valeurs, inférieures à d’autres valeurs largement diffusées par ailleurs, et cette variation décroissante de la capacité de stockage avec la durée de TCSL sont cohérentes avec la tendance moyenne observée à partir d’un large échantillonnage de données de la littérature internationale. L’évolution de ce stockage de carbone est discutée en lien avec les indications sur l’évolution du stock de carbone des sols de cette même région, les indicateurs de stockage potentiel, et les implications liées à l’évolution du climat.Mots clés: Techniques de culture sans labour, travail superficiel, semis direct, stockage de carbone, séquestration, mitigation, gaz à effet de serre, essai de longue durée, climat tempéré

Beschreibung: Previous results indicated that the activity of Al3+ in soil solution, Al saturation of the CEC, and 0.01 M CaCl2-extractable Al were related to plant growth. Exchangeable Al values determined by 1 M KCl and 1 M NH4Cl, extractable Al values determined by 1 M NH4OAc, pH 4.8, 0.01 M CaCl2, 0.5 M CuCl2, 0.33 M LaCl3, and 0.005 M NTA, were compared with each other and to the activity of Al3+ in soil solution as well as Al in soil fractions. Aluminum in fractions was measured to determine the forms solubilized by the extradants. The fractions extracted were exchangeable [M Mg(NO3)2], organic bound, Mn oxide, amorphous Fe and Al oxide, and crystalline Fe and Al oxide. The order of Al extracted was CuCl2 〉 NH4OAc, [Formula: see text]. One M KCl and NH4Cl, and CuCl2, LaCl3, NTA, and NH4OAc, pH 4.8, gave similar relative Al values, especially for topsoils, and were not correlated with CaCl2-Al values. The exchangeable fraction Al [M Mg(NO3)2] was well correlated with the activity of Al3+ in the soil solution and Al saturation of the CEC. Organic fraction Al was negatively correlated with the activity of Al3+ in the soil solution indicating that organic matter can bind Al lowering its concentration in the soil solution. Aluminum in the crystalline Fe/Al oxide fraction correlated well with that extracted by CuCl2, LaCl3, NTA, and NH4OAc, pH 4.8, leading to the possible conclusion that these extradants solubilize Al from plant-unavailable fractions. Key words: Soil aluminum, aluminum extractants, aluminum fractions, exchangeable aluminum

Beschreibung: Intensive potato cropping has been reported as a major cause of degradation of sandy soils. Wood residues from tree clipping applied to soils can substitute for crop residues to maintain adequate organic matter levels and crop productivity. However, this ligneous material presents a C:N ratio varying from 50 to 175 and, when applied in large quantities, may induce N immobilization at the expense of the crop. The objectives of this study were to quantify the importance of this N immobilization following addition of residues and its effect on yield and quality of potato crops. Fresh or humified residues (50 t ha−1) were applied to the soil and incorporated. The third treatment received no residue. Each treatment was subdivided into subtreatments which received either 0, 150, 200 or 250 kg N ha−1. P, K, Mg and S were applied at the same rate on all treatments. Following the application of wood residues in 1987, 46 kg N ha−1 were immobilized in amended plots. N recovery from fertilizer was 51%. To obtain comparable yields of similar quality to those measured on unamended plots, an additional 1.9 kg N t−1 residues added or 100 kg N ha−1 were required. In 1988, N immobilization was considerably reduced; yield and quality of potato tubers in plots that received wood residues the previous year were comparable to those of the unamended plots with appropriate fertilization. Water retention was significantly improved in plots that received wood residues. Partial decomposition of the residues for 1 yr prior to application on the soil did not significantly improve plant growth compared to fresh residues. Key words: Wood residues, tree clippings, potato yield, dry matter content, nitrogen immobilization, soil water content

Beschreibung: Field chipping operations often disperse chipping residues of bark and branches in layers or piles in cut-overs. We tested the effects of these residues on the root sucker regeneration of aspen (Populus tremuloides Michx.), using root systems established in large pots. After decapitation of the stems, the root systems were covered with a 4 cm thick layer of chipping residues. Other root systems were treated with an extract of the water-soluble compounds leached from a similar amount of residues while others were left untreated as controls; all three treatments were left to sucker for 7 wk. There were no differences in the number of root suckers that were initiated on the aspen root system among the three treatments. There were, however, significantly lower numbers of suckers that emerged through the chipping residue and their emergence was delayed relative to the other treatments. The delay in emergence and the reduction in sucker numbers were likely a result of the residues acting as a physical barrier. After 7 wk, concentrations of water-soluble phenolic compounds, sugars, and carbon from the chipping residues were elevated in the soil; however, they appeared to be below a level that affects sucker emergence and development. Key words: Allelochemistry, leachate, physical barrier, Populus tremuloides, regeneration

Beschreibung: In order to predict the potential of soils to store carbon in response to land use or climate changes, we measured the fluxes and distribution of residence times of C in French cultivated soils. We used the natural abundances in 13C and 14C to measure this distribution in long-term experiments of maize cultivation in France. 75% of the topsoil carbon had a mean residence time of 40 yr. Coarse particle-size fractions contained most of the younger carbon. A compartment of stable C was estimated using radiocarbon dating. Belowground plant material inputs stored as much as C as aboveground inputs. The effect of temperature on soil carbon mineralization affected only rate constants, with a Q10 = 3.1 constant in the range 1–25 °C. The data were summerized in a simple simulation model, which predicted a nil or low effect of climatic change on soil carbon storage in the next 50 yr. In France, land use changes will have more influence than atmospheric changes on C storage. Key words: France, greenhouse gases, mineralization, model, soil carbon, storage, temperature

Beschreibung: 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

Beschreibung: Near-infrared reflectance spectroscopy (NIRS) is a cost-effective and environmentally friendly technique of soil analysis that is particularly advantageous in intensive soil sampling and soil nutrient management as well. This study evaluated the potential of NIRS for predicting P, K, Ca, Mg, Cu, Zn, Mn, Fe, and Al extracted by Mehlich 3. We used 150 air-dried samples collected from a 15-ha site dominated by Orthic Humic Gleysol and Gleyed Dystric Brunisol soils. Calibration equations were developed using modified partial least squares regression. The accuracy of NIRS prediction was evaluated using the coefficient of determination (R2), the ratio of performance deviation (RPD), and the ratio of error range (RER). Reliable calibrations were found for Ca, Cu, and Mg (R2 ≥ 0.7, RPD ≥ 1.75, and RER ≥ 8). Less-reliable calibrations were found for Al, Fe, K, Mn, P, and Zn (R2 〈 0.7, RPD 〈 1.75, and RER 〈 8). In the validation with independent samples, acceptable regression coefficients (i.e., 0.8 ≤ slope ≤ 1.2) were only found for Ca, Mg, and Mn. We presumed that the pH of the Mehlich 3 extractant (2.5 ± 0.1) may affect the solubility of most of these nutrients, regardless the soil texture and, consequently, the potential of NIRS to predict them. The more a nutrient was correlated to clay content, the more it was likely predictable by NIRS. The prediction models obtained for Al, Ca, Cu, Fe, K, Mg, and Mn could still be used for screening purposes in cases where high accuracy is not required. These NIRS prediction models should be validated across larger geographic areas of geological homogeneity. Key words: Soil analysis, Mehlich 3, near-infrared reflectance spectroscopy, calibration

Beschreibung: Water erosion due to snowmelt is a major form of erosion in boreal regions of the Canadian Prairie. Evaluation of erosion models is an essential step before recommending their use in local or regional assessments of erosion rates and control methods. Using inputs from a runoff study conducted at La Glace, Alberta (55°25'N, 119°10'W) from 1984 to 1986, we evaluated the Erosion-Productivity Impact Calculator (EPIC) for its ability to simulate runoff and sediment yield from snowmelt events. The model was initialized with soil profile data acquired at the study site and complemented with data from standard soil databases (Albright series; loam, Dark Gray Chernozem). Daily weather data were acquired from the nearest climatological station (annual precipitation = 475 mm). Management data were as reported and included combinations of conventional and reduced tillage, annual and perennial, and fallow cropping. Mean runoff volume measured in 1985 was 57 mm while in 1986 it was 76 mm. EPIC over-predicted runoff volume by 25% in 1985 but under-predicted it by 7% in 1986. The period in which snowmelt occurred (mid-March – beginning of April) was predicted correctly. Under the conditions of this study, with many cropping inputs obtained from different sources, the model was unable to reproduce the reported management effects on runoff and sediment yield. EPIC simulated springmelt soil temperature trends at 9-cm depth, although the predicted temperatures in 1985 were generally underestimated. Our results suggest that the EPIC model calculates adequate values of runoff volumes and sediment yields during snowmelt. Key words: Runoff, sediment yield, soil erosion, crop rotations

Beschreibung: The real contribution of composts to N availability depends on their characteristics and maturity. A laboratory incubation experiment (140 d) was conducted parallel to a greenhouse study (330 d) in a split-split-plot design, with, respectively, two peat rates (0, 20 gkg−1 soil), five manure composts and four compost rates (0, 250, 500 and 750 gkg−1 soil). Compost N mineralization, orchardgrass (Dactylis Glomerata L.) yield and N uptake were measured. Total amount of mineralized N and yields and N uptake for six cuts of orchardgrass varied significantly with the type of composts and rate. Peat addition temporarily decreased compost N mineralization rate but significantly increased orchardgrass yields and N uptake as compared to peatless treatments. Mineralized N represented

Beschreibung: Complete loss of topsoil resulting from erosion or other causes generally results in reduced crop yield. To determine, under dryland conditions, the effect of loss of various amounts of soil and of various amendment practices suitable for use under a cereal production program on soil properties and crop yields, a field was artificially eroded during cut and fill of land-levelling in 1957. Continuous cropping to barley for 7 yr was followed by a wheat-fallow rotation for 22 yr. A continuous wheat experiment was conducted from 1987 to 1991 to determine the effects of five fertility amendments on restoring the productivity to soil from which 10–20 cm and 46+ cm of soil had been removed. In 1990, a below-average precipitation year, after 33 yr and 23 crops, yields from the unfertilized 46+ cm eroded field were only 44% of the yields from the uneroded field. However, with the increased precipitation in 1991 this value was 66%. A one-time topsoil amendment was beneficial in the earlier stages of the experiment, but lost its effect as cultivation mixed it into the "subsoil" over time. Plot treatments with annual applications of manure and high rates of fertilizer generally out-yielded the yields of the check plots of the uneroded treatment. Amendment with straw + fertilizer was not very effective. Soil, once lost, is non-renewable without amendments within the working lifetime of the producer. Key words: Soil erosion, manure, commercial fertilizer, topsoil soil, productivity

Beschreibung: Emissions of ammonia (NH3) and odor from livestock operations, and particularly from the landspreading of manure, are an issue from many aspects. Regional and national issues include production of inhalable aerosols (PM2.5), where NH3 from agriculture is a critical precursor. This process is episodic. As a result, it is important to characterize the episodic nature of NH3 emissions. This paper addresses the fact that weather and soil conditions can focus manure landspreading into a relatively few days each year. The Versatile Soil Moisture Budget (VSMB) was used with 30 yr of weather data on 2576 soil landscape units in Canada to estimate the number of days in each month when manure spreading would be possible. In addition, a national survey of about 3100 livestock farmers was used to quantify common practice. The stochastic information from the VSMB and the survey were applied to an NH3 emissions model. The base case, invoked by most national NH3 emission inventory calculations, is that emissions are uniformly distributed throughout each month. The result of our study was that daily NH3 emission fluxes could be up to 20-fold higher in the spring and fall months when manure landspreading is common but when weather and soil conditions limit the number of days available for field work. This has direct implications for estimating the role of agricultural NH3 on the episodic production of PM2.5, and this approach also has application to odor management. Key words: Modeling, livestock, emission factor, odor, NH3, field working day

Beschreibung: Canadian consumers are demanding a sustainable agricultural industry as well as products delivered under Best Management Practices (BMPs). Trace element accumulation in soils may influence crop productivity, food quality and ecosystem and human health. Canada’s feed and foodstuff export industry has already faced cases of penalties for high trace element content [cadmium (Cd) in durum wheat]. Thus, it is imperative to be able to estimate the accumulation and potential short- and long-term impacts of trace elements in soil. A national-level Trace Element Indicator (TEI) based on present loadings of trace elements to agricultural land is in progress. An Expert Panel including Canadian, American and Australian experts guided the assembly of a proposed methodology for this TEI. The proposed TEI, described briefly here, is a critical load approach with a single expression of the risk of impact from single or multiple trace elements from multiple sources (manures, biosolids, effluents and fertilizers and natural processes), invoked in a stochastic manner. Two key data requirements are the current background levels of trace elements in soil, and the leachability of these trace elements. A survey of total and soluble concentrations of 54 elements in up to 112 soils was completed. Although preliminary in scope, these represent key soil series in Canada. From this, a database of the solid/liquid partition coefficient, Kd, was computed. These Kd values will be used to characterize the leachability of the trace elements. Key words: Cadmium, copper, zinc, lead, nickel, uranium, metals, Kd, distribution coefficient

Beschreibung: Ammonia (NH3) is emitted in vast quantities from exposed livestock manure. The volatilisation of NH3 from livestock manure is a loss in valuable nitrogen in land-applied manure that could otherwise be used for crop production. Ammonia loss to air is also affiliated with environmental problems when it is deposited to the surrounding landscape. The goal o f this study was to quantify the effect of managing beef cattle manure on NH3 emissions of land-applied manure. Three trials were conducted where beef feedlot manure was applied. The NH3 losses were measured from field plots (90 or 160 m2) using acid traps (passive flux samplers). Immediately after applying manure, irrigating with 6 mm of water reduced NH3 loss by 21–52% while tillage (to 15 cm depth) reduced the loss by 76–85% compared with leaving the manure spread on the soil surface. Piled manure that was applied to the land lost 27% less NH3 than did manure taken directly from the pen. There was little NH3 lost from compost that was applied to land since the applied available-N was very low relative to the pen and piled manure. Our study shows that management of livestock manure has a direct impact on NH3 loss to air. It follows that significant reduction in NH3 volatilisation can benefit agriculture and reduce agriculture’s impact on the environment. Key words: Ammonia, manure, tillage, irrigation, compost, feedlot

Beschreibung: Current interest in carbon (C) exchange processes between terrestrial ecosystems and the atmosphere have identified a need to assess soil C stocks or inventories for specific soil types and climates. In this study, the mean store of C and nitrogen (N) was determined in the soil profile of several Gleysolic, Podzolic, Luvisolic, and Brunisolic soils under different agricultural management systems, in the cool, humid region of eastern Canada. Based on a total of 69 management treatments from 16 agroecosystem sites, mean soil C and N densities (to a soil depth of 60 cm) ranged from 3.1 to 13.1 kg C m−2 and from 0.36 to 1.05 kg N m−2 The C:N ratio ranged from 8.3 to 17.1. Distribution of C and N down the soil profile showed a relatively regular pattern of C and N decrease with depth. Estimated C stocks or storage for the 1-m soil depth ranged from 8.3 to 13.3 kg C m−2 for the Gleysolic soils, and 5.4 to 10.5 kg C m−2 for the Podzolic soils, with an overall range and mean for all soils of 3 to 16 kg C m−2 and 9.8 kg C m−2 ± 2.8 This indicates that some agricultural soils in eastern Canada possess a relatively high potential for organic matter storage. Key words: Organic carbon and nitrogen storage, agroecosystem, Gleysol, Podzol, Luvisol, Brunisol, cool-humid climate

Beschreibung: The reactivity of the colloids formed in soil environments results from complex interactions between clay minerals, (oxy)hydroxides and organic matter of soils. The adsorption/desorption equilibria and kinetics of anionic and cationic species on/from natural colloids could substantially differ compared with their interaction with pure minerals. The objective of this study was to investigate the arsenite and arsenate equilibria and the kinetics of arsenite adsorption on ferrihydrite-coated kaolinite as influenced by the presence of humic acid coverage. The Langmuir adsorption maximum and affinity of arsenite and arsenate adsorption on the kaolinite-ferrihydrite system was reduced by the presence of the humic acid. The enthalpy of adsorption on the kaolinite-ferrihydrite system, measured with isothermal titration calorimetry, was –24.4 kJ mol–1 for arsenite and –39.9 kJ mol–1 for arsenate, and was only slightly decreased by the humic acid coating. The kinetics of arsenite adsorption was substantially influenced by the presence of the humic coverage, resulting in the decrease in the rate constant, the Arrhenius heat of activation, and the pre-exponential factor (indicative of the collision frequency of the sorbate and the sorbent). The hampering effect of the humic acid on arsenic adsorption was attributable to the blocking by the organic ligand of the adsorbing sites, coupled with the steric hindrance of the large organic molecules, which restricted the arsenic to approach the surfaces. Key words: Arsenic, adsorption, kinetics, kaolinite, ferrihydrite, humic acid

Beschreibung: In a greenhouse study, deinking sludge was evaluated as a soil amendment supplemented with four nitrogen (N) fertilization levels for the growth of the grasses Agropyron elongatum (Host.) Beauv. (tall wheatgrass), Alopecurus pratensis L. (meadow foxtail), Festuca ovina var. duriuscula (L). Koch (hard fescue), and four levels of phosphorus (P) for the growth of the legumes Galega orientalis Lam. (galega), Medicago lupulina L. (black medic), Melilotus officinalis (L.) Lam (yellow sweet clover). Fertilizers were applied on the basis of sludge level to maintain uniform carbon (C)/N or C/P ratios across sludge treatments. In one experiment, sand was mixed with 0, 10, 20 or 30% sludge while, in a second experiment, mineral soil was mixed with 0, 27, 53 or 80% sludge (vol/vol). In sand mixtures of 30 and 20% sludge, grasses had similar or greater growth than in unamended mineral soil when N was added at about 6.5 and 8.4 g kg−1 deinking sludge, respectively. For all legumes but Medicago lupulina, P at about 0.8 g kg−1 sludge was required for these sand mixtures. In soil mixtures of 53 and 27% sludge, grasses grew well when supplemental N was about 5.3 and 6.9 g kg−1 sludge, respectively. Legumes required P at 0.5 and 1.2 g kg−1 sludge, respectively. In general, growth was closely related to total amount of added N or P in spite of the wide range of C/N or C/P ratios. When growing in media amended with sludge, grasses needed higher tissue N concentration for an equivalent growth than in control soil; legumes had similar tissue P concentration. The grasses Agropyron elongatum and Alopecurus pratensis as well as the legumes Melilotus officinalis and Galega orientalis are promising species for field testing, based on dry matter production. Deinking sludge can be used as soil amendment when adequate N and P supplements are provided. Key words: Soil amendment, papermill sludge, Agropyron elongatum, Alopecurus pratensis, Festuca ovina, Medicago lupulina, Galega orientalis, Melilotus officinalis

Beschreibung: Cation exchange capacity (CEC) data provide information on important chemical attributes of soil (e.g., ability of soil to retain cations against leaching and to buffer pH). Measurements of CEC are expensive to perform. Further, since CEC is dependent on measurement pH, CEC data are difficult to interpret, especially in the case of soils whose field pH is far removed from measurement pH. We analyzed a large data set (n = 1622), collected in support of soil survey activities in Saskatchewan, to develop a method of estimating CEC as a function of pH and to establish relationships between soil buffer capacity and properties such as texture and organic matter content. A regression equation with organic C and clay as independent variables explained 86% of the variability in CEC measured using BaCl2 buffered at pH 8.2. The CECs (at pH 8.2) of organic matter and clay were estimated at 2130 and 510 mmol (+) kg−1, respectively. About 15% of exchange sites were not accounted for by organic matter and clay and were assumed to reside in the fine silt fraction. The CEC at field pH, i.e., effective CEC (ECEC), was described (R2 = 0.86***) by a function based on the assumption that the ECECs of organic matter and clay increase linearly as pH increases to 8.2, where their values are 2130 and 510 mmol (+) kg−1, respectively. This relationship is especially useful because it enables soil CEC to be estimated at any pH based solely on organic matter and texture. Soil buffer capacity values were obtained by estimating the change in soil ECEC (or titratable acidity) needed to produce a unit change in pH. Buffer strength of clay was low [∼30–50 mmol (±) kg−1 (pH unit)−1]. Our estimates of organic matter buffer capacity [∼400 mmol (±) kg−1 (pH unit)−1] were consistent with published values. The results suggest that prairie soils that are low in organic matter may be susceptible to acidification even if clay content is relatively high. Key words: Buffered CEC, effective CEC, pH dependence of CEC, buffer capacity, titratable acidity

Beschreibung: Responses of both soil and stream inorganic nitrogen (N) after operational clearcut harvesting were explored in two high elevation British Columbia Engelmann spruce-Subalpine fir (ESSF) forests. At one study site, net N mineralization was measured between 1 and 11 yr after harvest. At a second site, for 3 yr after harvesting, available soil ammonium and nitrate were measured using ion exchange resins, and drainage losses of N were estimated using tension lysimeters and soil water balance models. Stream water N concentrations were also measured in one unlogged, and two logged watersheds at the second study area for 12 yr, both pre- and post-clearcut harvesting. Growing season as well as over-winter increases in post-harvest soil nitrate were detected after 3 yr, and the increases were apparent for up to 11 yr. Seasonal losses of N in drainage were greater in clearcut soils than in the forest soils in year 2 for ammonium and in years 2 and 3 for nitrate. A high proportion of the N was lost in drainage during snowmelt. Stream water ammonium in all three streams and nitrate in the unlogged and one harvested creek remained at or below the detection level. In the third creek, the frequency of detection and concentrations of nitrate peaked 2 to 3 yr after 30 to 57% of the watershed was harvested. The annual peak in NO3-N concentrations occurred immediately before the snowmelt-driven stream flow peak. Drainage losses and stream N fluxes were both small, relative to the total soil N content. Key words: Nitrogen, N mineralization, nitrate, harvesting, leaching, stream N, snowmelt

Beschreibung: A Canadian Agricultural Nitrogen Budget model was developed to calculate the agro-environmental indicators: Residual soil nitrogen (RSN) and Indicator of Risk of Water Contamination by Nitrogen (IROWC-N) for 3500 polygons of the 1:1 m Soil Landscapes of Canada scale. Residual Soil Nitrogen was calculated for the census years 1981, 1986, 1991, 1996 and 2001. These results were then used in conjunction with climate data to calculate over-winter N loss and its concentration in the drainage water. The main inputs were the acreages, yields and N recommendation rates for major crops, and the types and numbers of livestock. Various coefficients and assumptions were incorporated into the calculations. Validation of the model was carried out using provincial nitrogen sales data, and results showed good agreement between the calculated fertilizer N and the amount of fertilizer N sold in each province in 1996 and 2001. The two indicators were linked to outputs of the economic-based Canadian Regional Agricultural Model in order to assess the impacts of policy scenarios on nitrogen balance. At the national scale, the scenario of improved N fertilization practices reduced the RSN by 13%. RSN was also sensitive to the N2O:N2 ratio resulting from N losses through denitrification. Key words: Landscape nitrogen model, Agri-Environmental Indicator, Soil Landscapes of Canada, Census of Agriculture

Beschreibung: The current study was conducted to quantify and compare dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) fluxes through black-spruce-dominated forests, to compare the source/sink characteristics of sphagnum- versus feathermoss-dominated forest floors, and to identify changes in DOC and DON flow patterns occurring as a result of clearcut harvesting. After 2 yr of pre-harvest monitoring, replicated, experimental harvests of varying intensities of biomass removals were conducted followed by 4 yr of post-harvest sampling. Prior to harvest, the upland site type, dominated by feathermoss, was a significant source of DOC and DON, whereas, the wet-sphagnum-dominated sites exported minor amounts of these solutes. After harvest, DOC and DON fluxes peaked in the second year, but then dropped off significantly to at or below pre-harvest levels. On the upland site type, chipper debris appeared to be a major source of DOC and DON generating fluxes well above the pre-harvest levels. On the wetter site types, it appeared that microclimate differences between harvest treatments had a stronger influence on DOC and DON production than did the amount or type of harvest residue. Full-tree harvesting did not significantly alter the production of DOC and DON when compared with stem-only harvesting on the sites included in this study. Key words: DOC, DON, forest floor leachate, black spruce, harvesting response

Beschreibung: Understanding the source of spatial variability in soil organic carbon (SOC) stocks will contribute to improved sampling strategies to detect changes in stocks. Most of the variability in SOC stocks in cores collected from small (2 × 3 m) level plots on seven soils with similar cropping histories was related to variation in A horizon depth. Increased variability in horizon depth within plots coincided with the development of zones where the A horizon penetrated to greater depths. Consequently, accurate estimates of SOC stocks cannot be made from shallow measurements at the soil surface (e.g., 10 cm) and minimizing the spatial variability in locations of repeated sampling is necessary when characterizing changes in SOC stocks.Key words: Carbon sequestration, soil organic carbon, spatial variability, soil profile, A horizon