ALBERT

Beschreibung: Mineralized soil N from meadow soils will become an important source of N to following crops in low-input biological cropping systems. The C and N mineralization rates of soils from 34 sites situated on dairy farms recently converted to biological cropping systems were evaluated in a 56-wk incubation at 25° C. Data on C and N mineralization were fitted to first-order kinetic models. Carbon and N generally presented similar patterns of mineralization. Total mineralized N (Nm) ranged between 88 and 235 mg N kg-1 soil, which represented 6.6 to 22% of total N. Carbon mineralization (Cm) rate was between 11 and 17 times greater than N mineralization (1523–2638 mg C kg-1 soil ) and C mineralized represented 9 to 19% of soil organic C. The rate constant was between 0.05 and 0.123 wk-1 for C (kC) and ranged from 0.032 to 0.088 wk-1 for N (kN). The half-life for C (TC0) and for N (TN0) varied, respectively, between 5.6 and 13.3 wk and between 15 and 28 wk. Results show that about 80% of total mineralized C and N were mineralized during the first 25 wk of incubation, corresponding to the mineralizable fraction of soil organic matter (OM). Data on C and N mineralization have been adjusted using a bicompartmental model (active and recalcitrant pools), which corresponded, respectively, to first-order and exponential equations. Total mineralizable C and N (Cm and Nm), and the C and N rate constants (kC and kN) were strongly related, whereas the rate constants of the recalcitrant pools (hc and hN) were negatively related to these parameters. This suggests that C and N mineralizable pools were independent of the humified stable OM (recalcitrant pool). Carbon and N mineralization parameters were positively related to the soil clay and silt contents, but inversely to the sand levels. This study indicates that when ploughed, meadow soils contain large mineralizable N pools, which could sustain following crops with N nutrition in low-input biological cropping systems. Key words: Meadow soils, C and N mineralization rates, low-input systems, dairy farms, soil particles sizes

Beschreibung: The biodiversity of soil-inhabiting nematodes in Canada is incompletely known, as large areas of Canada’s landmass have not been surveyed for nematode fauna. Nematodes considered as indigenous are generally well adapted to a variety of ecological niches and climatic zones. Much of the available information is based on agricultural ecosystems and agricultural species, and thus is biased toward conditions in disturbed ecosystems and away from “primeval” ecology. Introduced nematode species are frequently quite pathogenic, even to exotic host plants from the same geographic point of origin. Estimates of crop loss due to single species infestations of pathogenic nematodes and the costs of nematode control using chemicals are reasonably well known, averaging about 10% of crop value, but ranging to 100% depending on the situation; the cost of damage by multiple-species infestations is less defined. Nematode-suppressive mechanisms are understood in only a few plant species; sulfur appears to be important as a constituent of active compounds in suppressive plants of agricultural origin. Similarly, some native plants are equally adapted with allelopathic chemicals that suppress nematodes. Management of nematode populations in agricultural soils by integrated crop management methods is at an early stage, requiring research to quantify effects of nematode-suppressive plants and soil amendments containing nitrogen. An integrated program could include nematode-suppressive plants, appropriate soil amendments, and the promotion of microbial antagonists. Different mathematical methods may be required to analyze and explain multi-factor nematode control systems. Less-toxic management systems could benefit the soil-inhabiting nematodes that predate arthropod soil pests. Further research on soil-borne nematodes may demonstrate the value of nematodes as indicators of agroecosystem health and environmental pollutants. Key words: Biocontrol, biodiversity, nematode distribution, nematode management, soil ecology

Beschreibung: Organic residues resulting from crop and animal production either become incorporated in the soil or remain on the surface and, thus, provide much of the nutrient and energy sources for many soil organisms. Characterizing the response of soil biota to these organic materials is a challenging undertaking due to the complexity of the soil ecosystem with respect to the magnitude of biodiversity involved, the possibilities for interrelationships with biochemical and biophysical processes, and the immense range of scale of observation from particle, through to aggregate, field, landscape and regional levels. The objectives of this paper were to review the available research pertaining to Canadian agroecosystems, which characterize the response of soil biota to soil organic matter dynamics, and to identify the issues, challenges and knowledge gaps. The response by soil organisms is discussed from two approaches: (1) their state of occurrence in terms of population response to soil organic matter as a nutrient and carbon/energy source, and (2) the extent of their influence in contributing to organic matter dynamics, that is, assessing their functional role. For the most part, Canadian research has emphasized comparative studies based on population responses by broad soil biota groups to soil organic matter additions or losses as an outcome of undertaking various agronomic practices. Studies that evaluate the extent of contributions by soil biota to soil organic matter dynamics are few, and rare at the species level. For Canadian agroecosystems, there is currently a great need for research initiatives that address the immense knowledge gaps that exist in relation to (a) identifying the specific contributions to soil organic matter processes and interactions of soil biota both at species and community level, (b) predicting outcomes of the contributions of soil biota groups in regulating or controlling soil organic matter processes both spatially and temporally across landscapes, and (c) assessing the risk to soil biodiversity in various agroecosystems in being able to sustain these functional roles. Key words: Soil biota, functional role, soil organic matter, agroecosystems, ecosystem services

Beschreibung: The range of soil properties associated with soil taxonomic class results from natural soil formation and soil-changing effects of human activity. My goal was to assess cultivation effects on soil formation and soil organic carbon (SOC) at four cultivated and two native hummocky till sites from the same climatic region of Saskatchewan. A revised landform segmentation procedure was used for comparisons across sites. Neither A horizon thickness nor SOC was related to topographical attributes at the native sites, but both had significant relationships (P = 0.001) with profile curvature (Pearson r= −0.53 and −0.57 for A horizon thickness and SOC, respectively), specific dispersal area (r = −0.40 and −0.54) and plan curvature (r = −0.24 and −0.34) at the cultivated sites. The greatest decreases in A horizon thickness (16 cm) and SOC (56 Mg ha-1) at the cultivated sites occurred in divergent shoulder elements, which have high rates of tillage-induced soil loss. Increases in soil thickness (including depth to calcium carbonate) occurred in concave footslope and depressional elements, but in situ losses of SOC outweighed the effects of SOC deposition. Soil thinning caused increases in the proportion of Orthic Regosols and decreases in the proportion of Calcareous Chernozems, but horizonation changes in the dominant Orthic Chernozems were minor. The self-terminating nature of the horizonation changes and improved conservation measures suggest that the future rate of soil change in these landscapes may be lower than in the past. Key words: organic carbon, topography, landscape-scale, erosion, tillage redistribution, digital elevation model, cesium

Beschreibung: The P dynamics in soils should be quantified in agricultural soils to improve fertilizer P (FP) efficiency while limiting the risk of P transfer from soils to water bodies. This study assessed P transformations following FP addition to Gleysolic soils. A pot experiment was conducted with five soils varying in texture from sandy loam to heavy clay, and receiving four FP rates under barley (Hordeum vulgare L.)-soybean (Glycine max L.) rotations. A modified Hedley procedure was used for soil P fractionation. Soil resin-P and NaHCO3-Pi contents were interactively affected by texture and FP. The NaHCO3-Po, NaOH-Po, HCl-P and H2SO4-P were only affected by soil texture. Proportions of 78 and 90% of the variation in labile and total P were, respectively, related to soil clay content. The FP addition increased resin-P, NaHCO3-Pi and NaOH-Pi and -Po contents in coarse-textured soils, but the amount added was not sufficient to mask the initial influence of soil texture on the sizes of soil P pools. Plant P uptake was proportional to FP rate but less closely linked to clay content. The average increase in labile P per unit of total FP added in excess of plant exports was 0.85, 0.8 2 , 0.73, 0.55 and 0.24 for the sandy loam, loam, clay loam, clay and heavy clay soil, respectively. The results of this study stress the important of considering soil texture in Gleysolic soils when assessing P accumulation and transformations in soils, due to commercial fertilizers applied in excess of crop removal. Key words: P fractions, clay content, fertilizer P, plant P uptake, soil texture

Beschreibung: Soil tests for available P may not be accurate because they do not measure the appropriate P fraction in soil. A sequential extraction technique (modified Hedley method) was used to determine if soil test P methods were accurately assessing available pools and if predictions of fertilizer response could be improved by the inclusion of other soil P fractions. A total of 145 soils were analyzed from field P fertilizer experiments conducted across Alberta from 1991 to 1993. Inorganic P (Pi) removed by extraction with an anion-exchange resin (resin P) was highly correlated with the Olsen and Kelowna-type soil test P methods and had a similar relationship with P fertilizer response. No appreciable improvement in the fit of available P with P fertilizer response was achieved by including any of the less available P fractions in the regression of P fertilizer response with available P. Little Pi was extractable in alkaline solutions (bicarbonate and NaOH), particularly in soils from the Brown and Dark Brown soil zones. Alkaline fractions were the most closely related to resin P, but the relationship depended on soil zone. Inorganic P extractable in dilute HCl was most strongly correlated with soil pH, reflecting accumulation in calcareous soils, while Pi extractable in concentrated acids (HCl and H2SO4) was most strongly correlated with clay concentration. A positive but weak relationship as observed between these fractions and resin P. Complete fractionation of soil P confirmed that soil test P methods were assessing exchangeable, plant-available P. Key words: Hedley phosphorus fractionation, resin, Olsen, Kelowna

Beschreibung: Mixed paper mill sludges are an important source of N for crop production. An estimate of direct and residual N recovery is necessary for their efficient management. A 3-yr field study (1997-1999) was conducted in central Quebec, Canada, to evaluate mixed paper mill sludges (PMS) effects on corn (Zea mays L.) yields and N nutrition, N recovery and N efficiency. The effects of PMS on soil NO3-N and total N levels were also determined. The study was situated on a silt loam Baudette soil (Humic Gleysol). The treatments included 3 PMS rates (30, 60 and 90 t ha-1 on wet basis) applied alone or in combination with N fertilizer (90 and 135 kg N ha-1, respectively, for 60 and 30 t ha-1). Treatments also included a control without PMS or N fertilizer, and a complete mineral N fertilizer (180 kg N ha-1) as recommended for corn. The previous plots were split beginning with the second year of the experiment, for annual and biennal PMS applications. Similar treatments as above were made on an adjacent site to evaluate N recovery under climatic conditions in 1999. In all years, PMS applied alone significantly increased corn yields by 1.5–5 t ha-1, compared to the unfertilized control. However, corn yields and N uptake were highest from the application of PMS in combination with N fertilizer. Biennial PMS applications at 60 to 90 ha-1 significantly increased corn yields and N uptake, which suggest high PMS residual effect; however, these increases were lower than those obtained with annual PMS applications. The N efficiency varied in 1997 from 13.0 to 15.4 kg grain kg N-1 for mineral N fertilizer and ranged from 3 to 13.7 kg grain kg N-1 for PMS, decreasing proportionally to increasing PMS rates. Apparent N recovery ranged from 1 3 to 19% in 1997 and from 10 to 14% in the residual year (1998), compared to 30 and 49%, respectively, for mineral N fertilizer. Depending on the PMS rate, N recovery varied from 13 to 21% in 1999. The results indicate high N supplying capacity and high r esidual N effects of PMS, which probably influenced corn yields and N nutrition. Annual PMS applications alone or combined with mineral N fertilizer had no significant effect on soil NO3-N and total N levels. This study demonstrates that application of low PMS rate (30 t ha-1) combined with mineral N fertilizer could achieve high agronomic, economic and environmental benefits on farms. Key words: Mixed paper mill sludges, corn yields, N uptake, N efficiency, residual effects, soil N

Beschreibung: The ability of arbuscular mycorrhizal (AM) fungi to help their host plant absorb soil P is well known, but little attention has been paid to the effect of AM fungi on soil P depletion capacity. A greenhouse experiment was conducted to assess, under different P levels, the effects of mycorrhizae on extractable soil P and P uptake by maize hybrids with contrasting phenotypes. The experiment had three factors, including two mycorrhizal treatments (mycorrhizal and non-mycorrhizal), three P fertilizer rates (0, 40, and 80 mg kg-1) and three maize hybrids [leafy normal stature (LNS), leafy reduced stature (LRS) and a conventional hybrid, Pioneer 3979 (P3979)]. Extractable soil P was determined after 3, 6 and 9 wk of maize growth. Plant biomass, P concentration and total P content were also determined after 9 wk of growth. Fertilization increased soil extractable P, plant biomass, P concentration in plants and total P uptake. In contrast to P3979, the LNS and LRS hybrids had higher biomass and total P content when mycorrhizal. Mycorrhizae had less influence on soil extractable P than on total P uptake by plants. The absence of P fertilization increased the importance of AM fungi for P uptake, which markedly reduced soil extractable P under AM plants during growth. This effect was strongest for LNS, the most mycorrhizae-dependent hybrid, intermediate for LRS, and not significant for the commercial hybrid P3979, which did not respond to AM inoculation. Key words: Arbuscular mycorrhizal fungi, extraradical hyphae, maize hybrid,plant biomass, P uptake, soil extractable P

Beschreibung: Light fraction of organic matter is a source of nutrients for plants and a substrate for microbes, while total organic matter is critical for optimum physical conditions and retention of nutrients and other chemicals in soil. The objective of this study was to evaluate the effects of cultivation and grassland type on light fraction and total C and N in a Dark Brown Chernozemic soil. Three paired-sets of soil samples, in five replications, were collected from three cultivated field areas under annual crops [mostly wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.)] and from three adjacent grassland areas. The three sets were a 30-yr-old bromegrass (Bromus inermis Leyss.)/alfalfa (Medicago sativa L.) dominated stand cut annually for hay (Lm) and cultivated area 1 (Ct1), an unbroken native grass stand having no vegetation removed (Ng) and cultivated area 2 (Ct2) and a bromegrass/crested wheatgrass (A gropyron cristatum L. Gaertn.) dominated stand on a land reverted to grassland 60 yr ago having no vegetation removed (Og) and cultivated area 3 (Ct3). Soil samples from the 0- to 5-cm, 5- to 10-cm, 10- to 15-cm, 15- to 20-cm and 20- to 30-cm depths were taken using a 4-cm-diameter coring tube sampler. Total organic C (TOC), total N (TN), light fraction organic C (LFOC) and light fraction N (LFN) in soil were determined and the equivalent mass technique was used to calculate their masses in different soil layers. Total mass (for all soil layers) was less in the cultivated areas compared to the grassland areas by 31 to 43% for TOC, by 84 to 85% for LFOC, by 15 to 34% for TN and by 82 to 84% for LFN. The effect of cultivation was much greater in the surface 5-cm depth compared to deeper soil layers. The proportions of LFOC in TOC and LFN in TN as well as the TOC:TN ratios were lower in the cultivated areas than in the grassland areas, whereas the LFOC:LFN ratios were similar in cultivated and grassland areas. The light fractions of C and N were thus more responsive to change from grassland to cultivation of annual crops compared to the total C and N. Within the grassland areas, the mass of TOC and TN in most of the soil layers was greater in the Lm compared to both Ng and Og areas, while the LFOC and LFN did not show the effect of grassland type. The differences in the mass of both total and light fraction C and N in the cultivated areas were small and generally not significant. The findings suggest that including legume in grassland stands can sequester more organic C and N into the soil even when used for hay production. Key words: Cultivated land, light fraction C and N, native grassland, total organic C and N

Beschreibung: Rehabilitation of disturbed native prairie is a challenge facing many in the petroleum industry, with implications for prairie ecology and productivity. The purpose of this research was to examine the relative influence of four rehabilitation strategies on biogeochemical processes (i.e., nitrogen availability, plant uptake of nitrogen, biomass production, carbon allocation, and soil biological activity). Seven petroleum wellsites were selected on Chernozemic and Solonetzic soils in southeastern Alberta. Undisturbed native prairie was compared with four seeding treatments: not seeded, a low diversity seed mix commonly used by industry, a low diversity mix of species more typically dominant in native prairie, and a diverse seed mix. Flux of NO3− and NH4+were measured in situ using ion exchange membranes. Soil total C and N were lower and available N higher as a result of disturbance. In the seeded treatments, biomass production was higher and soil nitrogen flux was lower due to higher plant uptake than in the unseeded treatment. Higher initial N availability favoured species with rapid growth and colonization rates, particularly Agropyron dasystachyum [(Hook.) Scribn.] and Agropyron trachycaulum [(Link) Malte]. Seed mix composition and species attributes were deemed to have greater influence on N cycling and biomass production than seed mix diversity. Key words: Nitrogen cycling, plant competition, secondary succession, wheatgrass, biodiversity, prairie

Beschreibung: The effects of tillage and crop rotations on soil N availability and economy were evaluated over two rotation cycles to address the paucity of such information. From 1993 through 2000, soil was sampled to 120 cm in the autumn from four crop rotations : (i) continuous wheat (Triticum aestivum L.), (ii) field pea (Pisum sativum L.)-wheat-canola (Brassica rapa L.)-wheat, (iii) red clover (Trifolium pratense L.) green manure-wheat-canola-wheat/red clover, (iv) fallow-wheat-canola-wheat, and analysed for KCl-extractable N. The rotations were managed under a conventional tillage (CT) or a no-till (NT) system, and were fertilized based on soil test results. A N budget was constructed for each cropping system comprising N added in seed and fertilizers, and by symbiotic fixation and N exported in the grain. More nitrate accumulated under CT than NT, resulting in lower N fertilizer application rates for CT plots. Soil mineralizable N was higher under NT than CT, and was not influenced by crop rotations. The trend for residual soil nitrate among crop rotations was: fallow rotation 〉 green manure rotation 〉 continuous wheat 〉 field pea rotation, due mostly to residual nitrate following the first phase of the rotations. There was no interaction of tillage with rotation. The continuous wheat and field pea rotation maintained a balanced N budget. The red clover rotation resulted in net N import in each rotation cycle of approximately 25 kg ha-1 under CT and 37 kg ha-1 under NT; net N export from the fallow rotation was 30 kg ha-1 under NT and 46 kg ha-1 under CT. Key words: Field pea, fallow, red clover, N economy, tillage, wheat

Beschreibung: The reclamation success of abandoned wellsites in agricultural areas depends on their capacity to sustain levels of biomass production similar to those which existed prior to soil disturbance. We examined the effect of four (0, 50, 100 and 150%) topsoil replacement depths (TRD) and five amendment treatments [compost, manure, alfalfa (Medicago sativa L.) hay, wheat (Triticum aestivum L.) straw, check) in the reclamation of three wellsites in south-central Alberta. The largest incremental effect of TRD on spring wheat response in the 4 yr (1997-2000) study occurred between the 0 and 50% treatments. Increasing TRD from 100 to 150% had little impact on crop response. Of the 20 treatments (four TRD × five amendments), the reclamation capacity of the 100% TRD-compost treatment ranked highest, being 19% higher than the baseline treatment (100% TRD-check). The lowest-ranking treatment overall , was the 0% TRD-straw treatment, which yielded 64% of the baseline treatment. Crop yield responses to organic amendments were larger when the recipient soil was lower in organic matter. Positive responses to one-time applications of organic amendments in the short-term (4 yr), advocate their use in soil reclamation of abandoned wellsites, despite a lingering question about the longevity of their beneficial effects. Key words: Soil reclamation, topsoil, organic amendments, natural gas wellsite

Beschreibung: Subsurface drainage systems can be a significant pathway for P transfer from some soils to surface waters. The objective of the study was to determine P concentration in tile-drainage water and its relationship to P status in surface soils (A horizons) from an intensively cultivated area in the Montreal Lowlands. The profiles of 43 soil units were characterized for their P contents and pedogenic properties. Tile-drainage water P concentrations were monitored over a 3-y r period on a weekly basis on 10 soil units, and four times during each growing season for the other 33 units. The soil units were grouped into lower and higher P sorbing soils using multiple discriminant equations developed in an earlier related study. The A horizons of the lower P sorbing soils had an elevated P saturation degree [mean Mehlich(III) P/Al = 17%] associated with total P concentrations in tile-drainage water consistently greater than the surface water quality standard of 0.03 mg total P L-1. Conversely, low P concentrations in tile-drainage waters (〈 0.03 mg L-1) and a moderate mean Mehlich(III) P/Al ratio of 8% were observed in the higher P sorbing soil group. Total P concentrations in drainage systems were significantly related to soil P status in surface soils. Grouping soils according to their P sorption capacities increased the power of prediction based on only one soil variable. However, accurate predictions in terms of drain P concentration can hardly be obtained unless large dataset and other factors related to field management practices and hydrology of the sites are also considered. Therefore, a better alternative to predict the risk of P leaching is to work in terms of risk classes and rely on a multiple factor index. Key words: Tile-drainage water, phosphorus, P transfer, P loss, degree of soil P saturation, phosphorus index

Beschreibung: Since the ratification of the United Nations Convention on Biological Diversity, there has been increased interest in issues related to biodiversity, particularly with respect to soil biodiversity and the influence of agricultural practices. This paper is one of a series of papers contributing to a state of the art review initiated by Agriculture and Agri-Food Canada on the status of soil biodiversity research in Canada, particularly with respect to agroecosystems. The objectives of this paper are to provide an overview of earthworm species distribution in Canada by province and territory, and to review research that illuminates our understanding of the ecological relationships of earthworms in agricultural systems. Most Canadian earthworm species are considered exotics having generally been dependent on human activity for their introduction and dispersal throughout the Canadian landscape. Twenty-seven earthworm species have been identified so far in Canada; of these, eight species are native to North America. Suggestions for future research on earthworm biodiversity within an agricultural context are discussed including: the need for increased spatial and temporal information on earthworm distributions across Canada, particularly with respect to Canada’s varied agroecosystems and landscapes; information on the ecology of earthworms with respect to their contributions to the soil system and their interactions with other soil fauna; the need for ecosystem process models relating earthworm contributions to soil structure formation and transport of materials and nutrients within the soil system; and the need to determine threshold levels of earthworm species associations in order to optimise effectively their contributions to soil quality and plant growth. To facilitate these studies, expansion of taxonomic expertise and capability across Canada will be required. Key words: Earthworms, agroecosystems, ecology, species distribution, soil biodiversity

Beschreibung: Increasing use of animal manures in Saskatchewan requires information on the fate and distribution of residual manure Cu and Zn in Saskatchewan soils. To address this issue, the amounts of soil Cu and Zn in various inorganic and organic fractions were investigated in a field crop research plot (Cudworth Association soil) with a 5-yr history of annual application of liquid swine manure and solid cattle manure, and in two grassland field research plots (Meota and Oxbow Association soils) that had received annual application of liquid swine manure for 3 yr. The annual rates of manure application were based on N contents in the manures, and were equivalent to approximately 0, 100, 200 and 400 kg total N ha-1 yr-1 in the field crop plots, and 0 and 100 kg total N ha-1 yr-1 in grassland plots. In both the field crop and grassland manured plots there were no substantial increases in total Cu an d Zn in soils associated with manure application. Some increases in the moderately labile Cu and Zn fractions were observed in treatments with large amounts of animal manures applied every year. The liquid swine manure had less effect than cattle manure on increasing labile Cu and Zn fractions. These results indicate that annual addition of animal manures at rates of approximately 100 kg N ha-1 for 3 to 5 yr does not constitute an environmental risk from Cu and Zn loading in these soils. Key words: Cu fraction, Zn fraction, sequential Cu extraction, sequential Zn extraction, urea, swine manure, cattle manure

Beschreibung: Light fraction of soil organic C (LFOC) represents a major portion of labile soil organic C (SOC) and is a key attribute of soil quality. Soil respiration (Cmin) is an important index depicting the potential activity of the labile SOC. Six field experiments, varying in duration (8 to 25 yr), in location (Brown, Dark Brown and Black Chernozemic soil zones of Saskatchewan) and soil texture, were conducted to evaluate the impact of tillage and crop rotations on crop production and soil quality. We sampled the 0-7.5-cm depth of soil in these experiments to determine the treatment effects on LFOC, the proportion of LFOC in the SOC (LFOC/SOC) and Cmin. Increasing the frequency of summer fallow in cropping systems decreased the LFOC in all soil zones; it also decreased the proportion of LFOC in SOC and Cmin. Tillage had little impact on LFOC in the Brown and Dark Brown Chernozemic soil zones, although it significantly decreased LFOC in the Black Chernozemic soil zone. Thus, crop rotation had a greater impact on LFOC than tillage. Tillage did not influence Cmin in any soil zone. Because adoption of no-till management increased SOC in all soil zones, we concluded that LFOC was not a sensitive indicator of the impact of tillage on this soil quality attribute for these Chernozemic soils in Saskatchewan. We also found that LFOC/SOC is directly proportional to sand content. This relationship may assist us in partitioning SOC pools with differing turnover times when modeling SOC dynamics. Key words: Soil organic C, light fraction organic C, tillage, crop rotations, texture, mineralizable C

Beschreibung: The most sensitive input parameter in many herbicide fate and transport models is the sorption-partitioning coefficient (Kd), a measure of herbicide sorption by soil. Spatial analyses of Kd are traditionally performed using geostatistics, but this approach requires intensive soil sampling and herbicide analysis. This study examined the use of digital terrain modelling as an alternative tool for quantifying the distribution of herbicide sorption within agricultural fields. Soil samples from a conventional-till (CT) and zero-till (ZT) field were analysed for soil organic carbon (SOC), soil pH, clay content, and the 2,4-D ([(2,4-dichlorophenoxy)acetic acid]) soil-water partitioning coefficient. Digital terrain models were used to calculate topographical variables (elevation, slope gradient, slope aspect, horizontal curvature, vertical curvature, mean curvature, specific catchment area, topographic index and stream power index) for each sampling point. Results indicated that topographic variables were adequate predictors of all soil properties in ZT (R2 ranging from 0.64 to 0.76), and of SOC in CT (R2= 0.65, P 〈 0.001). For CT, 2,4-D sorption by soil was very well predicted with soil properties alone (R2= 0.82, P 〈 0.001) and with soil properties in combination with topographic variables (R2= 0.85, P 〈 0.001), but was less predicted by topographic variables alone (R2= 0.50, P 〈 0.001). For ZT, the level of prediction of 2,4-D sorption by soil was weak with soil properties alone (R2= 0.53, P 〈 0.001) or when topographical variables alone (R2= 0.56, P 〈 0.001) were used, but a substantial increase in the level of prediction was achieved when both soil properties and topographic variables were used (R2= 0.73, P 〈 0.001). We conclude that digital terrain modelling, in combination with soil properties data, is an appropriate approach for predicting the spatial distribution of 2,4-D sorption within undulating-to-hummocky glacial till landscapes in western Canada. Key words: herbicide sorption, topography, zero-tillage, conventional-tillage, digital terrain modelling.

Beschreibung: Over-fertilization of agricultural soils with P has been linked to water pollution, and it is becoming apparent that subsurface P losses can be substantial. The silty-loam Gleysol chosen for this study contained 146 mg Mehlich-3 P kg-1, which exceeds the critical limit (66 mg Mehlich-3 P kg-1) for Québec. Equal quantities of fertilizer P (45 kg P ha-1) were applied from inorganic (triple superphosphate) and organic (composted cattle manure) sources to corn-corn and corn-soybean rotations. We evaluated crop production, the Mehlich-3 P and degree of soil P saturation levels, and the P concentration in subsurface water. Crop yields were unaffected by the fertilizer source, and only 31 to 67% of the P applied over a 2-yr period was exported, suggesting that the P fertilizer rate, chosen to match the P requirements of the corn crop, was excessive. After 2 yr, surface (0 to 15 cm) soils contained 149 to 199 mg Mehlich-3 P kg-1 and the Mehlich-3 (P/Al) saturation ratio (DSPSM3) ranged from 0.10 to 0.14. Subsurface water from piezometers installed to a 60-cm depth contained between 0.3 and 1.7 mg total P L-1, and particulate P was the dominant P form at most sampling dates. Mehlich-3 P was positively correlated with dissolved reactive P, whereas the DSPSM3 was positively correlated with the total P and particulate P concentrations in subsurface water. We conclude that these soil test parameters could be useful indicators of subsurface P losses from Québec soils. Key words: Soil test P, degree of soil P saturation, composted cattle manure, triple superphosphate, P leaching

Beschreibung: Pulp fibre, a primary type of sludge of pulp and paper mills containing approximately 40% organic C, is usually disposed of in landfills causing a potential environmental problem. This material may be used as a soil amendment to restore the productivity of organic-matter-depleted potato-producing soils in Atlantic Canada. The effect of incorporating this material at rates equivalent to 0.5, 1.0, 2.0, and 4.0% organic matter in the plow layer of a gravelly loam soil on selected soil physical properties and soil erosion was evaluated. The objectives were to determine the effect of pulp fibre additions on selected soil properties, which are pertinent to water retention and movement and to evaluate its effectiveness in reducing runoff and soil loss, major contributing processes to soil degradation . Chemical analysis of pulp fibre revealed that all heavy metal concentrations were well below allowable concentrations for Category A compost. One year after incorporation, bulk density of the Ap horizon had decreased with increasing rates of organic matter addition. On the other hand, the saturated hydraulic conductivity and specific moisture content increased with increasing rates of treatments. Results on water-stable aggregates revealed that the organic matter in the pulp fibre combined smaller aggregates to form larger aggregates, resulting in a larger proportion of macropores as compared to micropores. In the 4% organic matter treatment, a 27% increase was found in the 1.0 to 5.0 mm-diameter aggregates whereas a 23% reduction was found in aggregates smaller than 1.0 mm diameter. In spite of the higher specific moisture content of the organic-matter-treated soils, soil moisture content measured immediately prior to the erosion test indicated that field soil moisture contents were lower than those of the control. Time of runoff initiation, rates of runoff and soil loss were greatly improved with the amendments. The beneficial effects of the 4% organic matter treatment include 2.1 times delay in runoff initiation, and 23 and 71% reduction in runoff and soil loss, respectively. Although the beneficial effects in soil and water conservation are apparent, a minor drawback appears to be lower field soil moisture content. Large-scale implementation of the addition of this material in potato fields should proceed only with caution. Key words: Saturated hydraulic conductivity, moisture retention, water stable aggregate, mean weight diameter, sediment yield, soil amendment

Beschreibung: Soils used for intensive vegetable production often become depleted in their organic matter content, and consequently low in their microbial activity. Papermill sludge compost may be an efficient way to improve the biological activity of these soils. An experiment was initiated to determine the effects of a co-composted papermill sludge and hog manure (PHC), applied alone or in combination with mineral fertilizers (MF), on several biochemical properties and crop yield of a Bevin loamy sand (Orthic Humo-Ferric Podzol) located at Saint-Ubalde, province of Quebec, Canada. The PHC was applied in the spring of 1997 at rates of 0, 11.5, 23 and 34.5 Mg dry weight ha-1, with and without MF equivalent to 150 N-200 P2O5-200 K2O kg ha-1. Potatoes (Solanum tuberosum L.) were planted the first year and the residual effect of PHC was evaluated on a spring wheat (Triticum aestivum L.) crop in 1998. Enzymatic activity of β-glucosidase, β-galactosidase, acid phosphatase, urease and fluorescein diacetate hydrolysis, microbial biomass C (MBC) and CO2-C release in incubation were measured throughout both growing seasons. Application of 11.5 Mg ha-1 of PHC resulted in the highest enzymatic activities and MBC, representing a mean in crease of respectively 30 and 55% over the control. Addition of MF to PHC resulted in a greater increase in enzyme activities (12–18%) than PHC alone but had little effect on MBC. Generally, enzyme activities and MBC decreased in the second season. The carbon mineralization potential was low, indicating that the composted material was relatively stable. The addition of 11.5 Mg PHC ha-1 produced the highest marketable potato tuber yield with (34 Mg ha-1) or without (27 Mg ha-1) fertilizer supplement, whereas the highest wheat grain yield was obtained with the 23 Mg PHC ha-1 level in the following season. When PHC was added at 11.5 Mg ha-1, it markedly improved soil biochemical properties and potato crop yield whereas the 34.5 Mg ha-1 level was excessive. Key words: Papermill, farm manure, compost, enzyme activity, microbial biomass

Beschreibung: Repeated application of animal manure or mineral P fertilizer can significantly increase soil P content and enhance the risk of water contamination. The objectives of this study were to evaluate the long-term (8 yr) effect of liquid hog manure (LHM) applied at high rates and its timing of application on the soil P status and on the risk index of water contamination by P. Spring (S), fall (F), or spring + fall (SF) applications of LHM on a silt loam (Humo Ferric Podzol) were compared to recommended application rates of mineral fertilizer (MF) in a continuous corn (Zea mays L.) system. Total P applied ranged from 7 to 34 kg P ha-1 yr-1 in the MF treatment and from 106 to 150 kg P haP ha-1 yr-1 in the LHM treatments. Soil samples were collected to 1.0-m depth after one, six and eight annual applications. Applying high rates of LHM for 8 consecutive years resulted in a significant (P ≤ 0.10) enrichment in total soil P content relative to MF at the 0- to 20-cm soil depth. The effects of LHM on labile P forms (water soluble P, Pw and Mehlich-III extractable P, M3P) were also restricted to the 0- to 20-cm depth with values as high as 11 mg kg-1 for Pw and 241 mg kg-1 for M3P in the LHM plots. The degree of soil P saturation, evaluated as Pox/(Alox+Feox), increased to 15% in the 0- to 20-cm depth after 6 to 8 yr of LHM application. Saturation values of 12 to 15% were also found at the 80- to 100-cm depth in some LHM plots. The P index rating was always medium (109 to 216) in soil receiving MF but was high (217 to 432) after 6 to 8 yr of heavy LHM applications, which indicates a high potential risk of soil P transfer to surface water. The results of this study showed that timing of application had little influence on long-term soil P status. Overall, applying LHM at high rates greatly increased total soil P, the degree of soil P saturation, and the labile P forms in the surface horizons but had little effects below 20 cm. Key words: Hog manure, soil P, long-term effects, labile P, P saturation

Beschreibung: Soil and crop management practices and their effects on surface residue levels can modify soil temperature. Our study investigated the effect of rotation, tillage and row spacing on near-surface (0.025 m) soil temperature under winter wheat (Triticum aestivum L.) in 1993-1994 and 1994-1995. The main treatment was winter wheat rotation: continuous winter wheat (WW); winter wheat-canola (Brassica campestris L.) (WC) or winter wheat-fallow (WF)] with tillage sub-treatments of conventional tillage (CT) vs. zero tillage (ZT) and row spacing treatments of uniform row (UR) vs. paired row (PR) spacing. From fall 1993 to spring 1994, ZT was cooler than CT by 1.2°C on the WC rotation, 1.1°C on WW and 0.4°C on the WF rotation. From fall 1994 to spring 1995, the magnitude of tillage differences was lower on all three rotations with ZT being cooler than CT by 0.1–0.9°C. The magnitude of the row spacing effect on soil temperature was less than that of the tillage effect. Extreme differences in soil temperature due to tillage were generally higher (1.0–4.9°C) on the WW and WC than the WF rotation (0.6–2.5°C) due to the presence of more crop residue. Results demonstrate that while ZT promotes overall cooler soils under winter wheat from fall to late spring, especially on continuously cropped (WW, WC) rotations, it also allows moderation of soil temperatures during extremely cold periods. Key words: Soil temperature, winter wheat, rotation, tillage, row spacing

Beschreibung: Cropping practices interactively affect soil P status. Previous studies mostly focused on cropping practices individually and limited assessments within the plow layer. This study assessed the P status of a Labarre silty clay (Humic Gleysol) profile after 10 yr cultivation under contrasting practices. Soils of 0–15, 15–30, 30–60, and 60–90 cm layers were sampled from a split-plot experiment comprising barley (Hordeum vulgare L.) monoculture and a 3-yr barley-red clover-timothy rotation both tilled with either chisel or moldboard plow as main plots, and receiving fertilizer P or liquid dairy manure as subplots. A modified Hedley sequential fractionation was used to characterize soil P status. Labile P pools were more affected than stable ones by cropping practices. The P fractions depended more on nutrient sources than cropping systems in the 0- to 30-cm soil layer, whereas the impacts were predominated by cropping systems in the subsoil. Compared to the manure, fertilizer P resulted in higher contents of Mehlich III extractable P, resin-P, NaHCO3-Pi and NaOH-Pi, and lower contents of NaHCO3-Po, NaOH-Po and H2SO4-P in the 0- to 30-cm layers. The rotation produced larger labile P fractions than the monoculture in the 30- to 60-cm layer. The impacts of the investigated cropping practices on labile P fractions extended deeper in the soil profile than the depth disturbed by primary tillage. Crop sequence, primary tillage and nutrient source had large effects on P status in the soil profile, of this clayey and poorly drained soil. Key words: rotation; primary tillage; liquid dairy manure; P forms, Mehlich III extractable P (M3P)

Beschreibung: (Brassica napus L . and B. rapa L.) grown on the sandy soils of northeastern Saskatchewan has been observed to exhibit symptoms similar to B deficiency, and soil testing laboratories often recommend B fertilization on these soils. The objective of the present study was to determine if yield, seed quality and diseases of canola are related to different rates, times and methods of B fertilization on some northeastern Saskatchewan soils (Gray Luvisol) expected to be B deficient. Two growth chamber and seven field experiments were conducted in 1997, 1998, 1999 and 2000. In the field experiments, the treatments included application of B fertilizers as broadcast followed by incorporation (1 to 4 kg B ha-1) prior to seeding, seedrow placement at seeding (0.5 to 2 kg B ha-1) and foliar spray at 10–20% bloom stage (0.25 and 0.50 kg B ha-1) plus a zero B control treatment. In the growth chamber experiments, rates of 1 to 3 mg B kg-1 soil were tested. In the field experiments, seed and straw yields tended to increase in very few of the treatments, with significant increases from incorporated B fertilization at one site for seed and at three sites for straw. The protein content in the seed was significantly increased by B fertilization at one site, while oil content in the seed was not influenced by B fertilization in any field experiment. The B fertilization treatments either increased or tended to increase the B concentration and uptake of B in seed and straw in most cases, with significant contrasts for control vs. incorporated B and seedrow B methods of applications in many cases. The increase in B concentration and uptake of B was usually greater in straw than in seed. Among the methods of B application, the effectiveness of B application could be considered as incorporated B 〉 seedrow B 〉 foliar B. Averaged across the sites and two treatments for each application method for example, B uptake in seed increased by 6.7, 3.8 and 1.0 g ha-1 with incorporated, seedrow and foliar B treatments, respectively. Corresponding methods showed an increase of B uptake in straw by 46, 33 and 23 g ha-1. Disease levels were low for sclerotinia stem rot (Sclerotinia sclerotorum) and low to moderate for blackleg (Leptosphaeria maculans) and alternaria pod spot (Alternaria brassica and A. raphani), and B fertilizer treatments had no impact on the amount or severity of infection for these diseases. In the growth chamber experiments, B fertilization tended to increase the yield of seed and straw (up to 13%) in both soils, with significant contrasts for 0 k g B ha-1 vs. 1, 2 and 3 kg B ha-1 in many cases. In conclusion, the findings of this study suggest that canola rarely responds to B fertilization in field conditions on soils suspected to be B deficient, but canola response to B was influenced by the method of B application. Key words: Boron concentration and uptake, boron fertilizer, canola (Brassica napus L. and Brassica rapa L.), oil and proteincontent, yield

Beschreibung: A study was conducted at the Lacombe Research Centre to quantify and simulate the impacts of forage and grazing systems on soil water content. Four forages used in the study were alfalfa (Medicago sativa L.), a mixture of meadow bromegrass (Bromus riparius L.) and alfalfa, an annual pasture and an old grass pasture that was composed of mainly quackgrass (Elytrigia repens L.), smooth bromegrass (Bromus inermis L.) and Kentucky bluegrass (Poa pratensis L .). Within each 1.2-ha paddock were two grazing treatments: rotational grazed and ungrazed. Soil water measurements to a 65-cm depth were conducted between May and October of 1999 and 2000 using a neutron moisture probe. Total soil water was affected by forage species more than grazing. Actual evapotranspiration rates were 3-4 mm d-1 in both years. Simulation of daily volumetric soil water content (%) for each year was conducted using the Versatile Soil Moisture Budget (VB2000) model on grazed alfalfa, ungrazed alfalfa, grazed annual and ungrazed annual treatments. During calibration year of 1999, the overall modeling efficiency (EF) was 0.58 while, during the evaluation year it was 0.43. Further, simulations for alfalfa were better than those for annual treatments. These EF values are relatively low indicating substantial discrepancies between observed and simulated results, which could have been attributed to a combination of input data errors, model errors and propagation errors in output. Key words: Evapotranspiration, forages, model calibration, model evaluation, versatile soil moisture budget model

Beschreibung: The concentrations of metals in soils are spatially heterogeneous and soil sampling carried out when studying metals in forest ecosystems is often inadequate. We examined the spatial variability of Cd, Cu, Mn, Ni, Pb and Zn in northern forest ecosystems on a transect with distance from two point source emitters with the goal of providing basic information about the distribution and variability of metals in these soils. Samples were taken under six sampling points at four depths from three experimental sites on each of the two transects. Soils were analysed for acid digestible metals, pH and organic carbon content. Standard deviation, coefficients of variation, mean and medians were analysed for each horizon of each site. It was observed that Cu and Mn variability is higher in closer proximity to the point source while the variability of Zn increased with decreasing soil pH. In Sudbury, emitted metals Ni and Cu accumulate together in soils, whereas in Rouyn-Noranda, with the exception of Cd and Zn, metal concentrations were not related in forest floors. Observations suggest that physical factors influencing where metals are deposited as well as the inherent variability in soil chemical characteristics, and the distance from the point source can all act together to result in high variability in soil metal concentrations in a single forest site. Sampling in the interest of relating vegetation metal concentrations or response to soil metals should be carried out on an individual plant basis with multiple samples taken for each individual. Soil samples taken at intervals of 1 to 1.7 m will provide relative error in estimating soil concentrations of 10% or 20%, respectively. Key words: Spatial variability, trace metals, podzolic soils, smelter emissions

Beschreibung: Crusting can have a prominent effect on seedling emergence. Crust formation at the soil surface is a common feature of many soils including the silty loam soil (Aquic Haplocalsids) from the Konya plain examined in this investigation. The effects of different soil amendments on modulus of rupture and aggregate stability in water were measured in a pot experiment in the laboratory. Seedling emergence of wheat (Triticum durum Desf.) and penetration resistance was investigated in a microplot experiment in the greenhouse. Portland cement, barnyard manure (dairy cattle), city waste compost (municipal refuse) and wheat straw were used in the pot experiment, and Portland cement and barnyard manure were investigated in the microplot experiment. Soil amendments were added to the soil samples at rates of 0, 2, 4 and 6% (wt/wt) and the samples including a control were incubated at about field capacity water content for up to 100 d in the laboratory. The moduli of rupture values and water stable aggregates were measured after 25, 50, 75 and 100 d of incubation. All the soil amendments reduced the modulus of rupture compared with the control soil sample. The modulus of rupture of the control and mixes with Portland cement, barnyard manure, city waste compost and wheat straw (6%, wt/wt) after 100 d of incubation were 726, 0, 494, 564 and 113 kPa, respectively. Aggregate stabilities of the control and the soil amended with Portland cement, barnyard manure, city waste compost and wheat straw (6%, wt/wt) after 100 d of incubation were 5.16, 55.02, 10.82, 8.44 and 34.98%, respectively. Seedling emergences of wheat and penetration resistances of the control and the soil amended with Portland cement and barnyard manure (6%, wt/wt) in the microplots were 29, 80 and 36%; 489, 0 and 471 kPa, respectively. Key words: Surface sealing, aggregate stability, seedling emergence, penetration resistance.

Beschreibung: This study compared iron nodules with their matrix materials in a Hapludult from central Taiwan. Mineralogy and 14C ages of the iron nodules were compared with their associated matrix materials. The samples were analyzed by X-ray diffraction (XRD) and accelerated mass spectroscopy (AMS). Hydroxy-interlayered vermiculite (HIV) and illite were the major clay minerals in the soil matrix, but illite and kaolinite were dominant in the iron nodules. Clay mineralogy of iron nodules revealed more intense weathering process than the surrounding soil matrix. 14C dates showed that the age of saprolite and iron nodules were similar, and were both much older than those of the soil matrix. It is suggested that iron nodules developed from residuum of the Tertiary shale (saprolite). During pedogenesis, saprolite acted as a nucleus, where Fe coated on its surface was transferred to form iron nodules. Key words: 14C dates, iron nodules, saprolite, soil matrix, Ultisol

Beschreibung: Soil mesofauna are an important part of soil ecosystems, but little is known about them in grassland ecosystems of southern interior British Columbia. In this s tudy, 12 300 organisms were examined and prostigmatid mites were most abundant, representing 95% of the total collection. Cattle grazing, sample depth and season of sampling influenced prostigmatid mite densities. However, grazing was the most significant factor, explaining 29% of the variation in prostigmatid mite density. Key words: Soil fauna, mesofauna, Prostigmata, Acari, range management

Beschreibung: The effects of a crude oil spill and remediation on the biological quality of an agricultural soil were examined based on three microbiological indices: microbial biomass carbon (MBC), dehydrogenase activity (DHA) and microbial metabolic diversity (MMD). The soils in both contaminated and uncontaminated plots were clay loam Gleyed Rego Black Chernozems developed from lacustrine materials overlying till. The four remedial treatments consisted of: meadow bromegrass (Bromus biebersteinii. Rohman and Schult), alfalfa (Medicago sativa L. ‘Algonquin’), fallow with wheat straw incorporation (SF) and unamended fallow (UFSP). An unamended fallow on adjacent uncontaminated land served as a control (UFCON). The spill had a statistically significant, negative effect on MBC and MMD (P = 0.01 and 0.05, respectively). Although a negative effect on DHA was not significant (P = 0.05), the results show evident trends. The forage treatments were, overall, significantly more effective than the SF treatment in restoring soil biological quality in hydrocarbon contaminated soil to control levels. Based on overall trends only, bromegrass had the greatest effect on soil biological quality relative to the UFSP, followed by alfalfa. The incorporation of wheat straw did not significantly affect any of the examined microbial indices. Key words: Crude oil contamination, soil microbial biomass, dehydrogenase activity, microbial metabolic diversity, soil biological quality

Beschreibung: The term "mycorrhiza" refers to the mutualistic symbiosis between fungi and the roots of a vast majority of vascular plants, distributed over almost any ecosystem. The fungal symbionts, primarily recognized for their beneficial impact on plant growth and plant protection, are integral components of soil ecosystems and as such, play an active role in improving plant productivity and diversity, soil microflora and microfauna diversity, and soil quality. Classified among major groups of true fungi, the study of their biodiversity and distribution has been explored for only a few decades. Major emphasis was first put on the mycorrhizal status of plants, on the evaluation of their benefits to plant growth, on their geographic distribution and soil inventories, and more recently on their relationship to plant diversity and productivity. In the 1950s, Canadian scientists were among world pioneers in the field of mycorrhizae research and they continue to be recognized by the international scientific community. Studies dealing with soil biodiversity of mycorrhizal fungi, including arbuscular, ecto-, ectendo-, ericoid- and orchid mycorrhizae, performed by Canadian researchers are presented here together with strategies and perspectives for a better exploitation of mycorrhizal fungal diversity in ecosystems. Key words: Symbiosis, mycorrhizae, arbuscular mycorrhizal fungi, ectomycorrhizal fungi, biodiversity, plant protection

Beschreibung: The dependency of agriculture on nitrogen fertilizer inputs is associated with adverse effects on the environment and human health. The importance of biological nitrogen fixation by rhizobia in symbiotic association with legumes is underscored by its potential to reduce or replace chemical fertilizer inputs. This paper reviews research on the diversity of the symbiotic rhizobia resident in Canadian soils. Research has focussed on phenotypic and genotypic variation (e.g., nitrogen fixing efficacy, nodulating competitiveness, host range, adaptation to cool climate) within rhizobial species with the objective of selecting efficient strains for use in inoculants for legume crops. The genetic diversity of rhizobia resident in Canadian soils has been reported only for Sinorhizobium meliloti, Rhizobium leguminosarum and Mesorhizobium spp. There is a need for further studies on populations of other rhizobial species, particularly those associated with native legumes. Exploiting the diversity present in natural soil populations via selection and genetic manipulation should permit the development of superior strains for use in legume inoculants. Other rhizobial traits that may be exploited include plant growth-promoting activity and ability to degrade pollutants. Key words: Symbiotic rhizobia, diversity, Canadian soils