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1.
The high strength of some regolith types can limit the growth of rehabilitated jarrah forest following bauxite mining in southwest Australia. Ripping mine floors to a depth of 1.5 m alleviates high strength zones and improves root exploration of substrates. Understanding the variability of regolith strength at the mine pit scale may be useful for improving site-specific ripping and reducing rehabilitation costs. Regolith strength maps were developed based on real-time, field measurement of the hydraulic fluid pressure in the tilt cylinders of Komatsu 475 and Caterpillar D11R bulldozers operating at an average speed of 0.8 ms−1 with standard tip, single shank deep-ripping tines. The strength maps rank regolith into strength classes and show positions of low-, medium-, high- and extreme strength zones in the floors of former opencast bauxite mines. Maps were evaluated using strength measurements on excavated regolith profiles revealing a reliable relationship between bulldozer-mapped regolith strength and actual regolith strength. Weighted unconfined compression strength for mine floor materials within a regolith profile can be grouped as follows: saprolite <4000 kN/m2; quartz-rich, sandy clay (Zm) and silty clay (Zp) 1000–4000 kN/m2; ferruginous/gibbsitic (cemented) material (Zh) 4000–8000 kN/m2; and granite or dolerite rock and hard saprock 5000–14,000 kN/m2. Ripper hydraulic pressure was linearly related to the weighted unconfined compression strength (kN/m2) of classified regolith profiles (r2 = +0.47). The instrumented bulldozer mapping technique can partly distinguish between classified regolith types, particularly granite and granitic saprock (>75 bar) and dolerite and doleritic saprock (25–75 bar). Some regolith types including: quartz-rich, sandy clay; silty clay; and soft saprolite have low bulldozer-measured strength (25 bar) and are indistinguishable by the bulldozer. Regolith strength maps may improve the targeting of secondary contour ripping to parts of a mine floor where it is most-needed. 相似文献
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Prediction of soil depth using environmental variables in an anthropogenic landscape, a case study in the Western Ghats of Kerala, India 总被引：4，自引：0，他引：4
Soil (regolith) depth is a crucial input for modeling earth surface phenomena. However, most studies ignore its spatial variability. Techniques that map the spatial variability of soil depth are of three types: (1) physically-based; (2) empirico-statistical from environmental correlates; and (3) interpolation from point observations. In an anthropogenic landscape, soil depth does not depend primarily on natural processes, making it difficult to apply a physically-based approach. The present study compares empirico-statistical methods with geostatistical methods for predicting soil depth in such a landscape: Aruvikkal catchment (9.5 km2) in the Western Ghats of Kerala, India. Regression kriging applied on blocks of 20 m by 20 m using the environmental covariates elevation, slope, aspect, curvature, wetness index, land use and distance from streams, proved to be the best predictor of soil depth. This model explains 52% of the variability of soil depth in the catchment; with a prediction variance of 0.05 to 0.19. A Gaussian simulation was attempted for a more realistic visualization of the depth, as opposed to the smooth kriging prediction. The most important explanatory variable of soil depth in this landscape is land use, as expected from the strong human intervention. 相似文献
4.
《Communications in Soil Science and Plant Analysis》2012,43(7-8):981-993
Abstract The characteristics and degree of weathering in a deep regolith developed on basalt were investigated. A representative 15m deep regolith of soil‐saprolite‐rock sequence, located in Pahang state, Malaysia, was selected. The intensity of weathering in this deep regolith was assessed by various weathering indices as well as changes in the physicochemical properties and clay mineralogy of the regolith. The values of all weathering indices and other assessments gave strong evidences of intense weathering during saprolite formation. The low CËC and base cation values even in the saprolite layers were accounted By the extreme depletion of major elements such as potassium (K), sodium (Na), calcium (Ca), and magnesium (Mg), and significant enrichment of aluminum (Al), iron (Fe), titanium (Ti), copper (Cu), and niobium (Nb) occurred during saprolitization. The extreme weathering pattern of basalt differed from those described in granite and metamorphic rocks found in Peninsular Malaysia. 相似文献
5.
Josef Troxler Miroslav Svercel Andreas Natsch Marcello Zala Christoph Keel Yvan Moënne-Loccoz Geneviève Défago 《Soil biology & biochemistry》2012,44(1):122-129
Little is known about the ecology of soil inoculants used for pathogen biocontrol, biofertilization and bioremediation under field conditions. We investigated the persistence and the physiological states of soil-inoculated Pseudomonas protegens (previously Pseudomonas fluorescens) CHA0 (108 CFU g?1 surface soil) in different soil microbial habitats in a planted ley (Medicago sativa L.) and an uncovered field plot. At 72 days, colony counts of the inoculant were low in surface soil (uncovered plot) and earthworm guts (ley plot), whereas soil above the plow pan (uncovered plot), and the rhizosphere and worm burrows present until 1.2 m depth (ley plot) were survival hot spots (105–106 CFU g?1 soil). Interestingly, strain CHA0 was also detected in the subsoil of both plots, at 102–105 CFU g?1 soil between 1.8 and 2 m depth. However, non-cultured CHA0 cells were also evidenced based on immunofluorescence microscopy. Kogure's direct viable counts of nutrient-responsive cells showed that many more CHA0 cells were in a viable but non-culturable (VBNC) or a non-responsive (dormant) state than in a culturable state, and the proportion of cells in those non-cultured states depended on soil microbial habitat. At the most, cells in a VBNC state amounted to 34% (above the plow pan) and those in a dormant state to 89% (in bulk soil between 0.6 and 2 m) of all CHA0 cells. The results indicate that field-released Pseudomonas inoculants may persist at high cell numbers, even in deeper soil layers, and display a combination of different physiological states whose prevalence fluctuates according to soil microbial habitats. 相似文献
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Coral reefs throughout the world have been damaged by storms, diseases, coral predators, temperature anomalies, and human activities. During the past three decades, recovery has been limited and patchy. Although a damaged coral reef cannot be restored to its original condition, interest in reef restoration is increasing. In a pilot project in the Caribbean (US Virgin Islands), storm-produced fragments of Acroporapalmata, A. cervicornis, and Porites porites were collected from donor reefs and transplanted to nearby degraded reefs. Sixty coral fragments were attached to dead-coral substrate (usually A. palmata skeletons), at similar depths from which they had been collected (1-3.5 m), using nylon cable ties. Seventy-five intact colonies were designated as controls. Study colonies were assessed at 6-month intervals for 2 years (1999-2001) and annually thereafter (through 2004). One-fourth of the 135 colonies and fragments monitored were alive at the conclusion of the 5-year study. Survival of control and transplanted A.cervicornis and P. porites was very low (median survival 2.4 and 1.8 years, respectively), with no significant differences between transplant and control colonies. Site and depth did not contribute significantly to A. palmata colony survival, but colony size and transplant/control status did. Probability of survival increased with colony size. Median survival for A. palmata was 1.3 years for transplant and 4.3 years for natural colonies when not controlled for size. A. palmata was the only viable candidate for reef rehabilitation. Storm swells were the primary cause of mortality. 相似文献
7.
Soil microbial processes play an important role in relation to pesticide pollution of groundwater, and may be strongly influenced by hydrological and geochemical properties. The consequences of such heterogeneous environments on bacterial biomass, enzymatic activities, carbon utilisation patterns, and pesticide mineralisation potentials in the unsaturated zone of a sandy loam and a coarse sandy soil profile were studied. In sandy loam soil profiles the number of bacteria decreased from 109 cells g-1 in the surface layers to about 107 cells g-1 at 1.5-5 m depth. Simultaneously, the hydrolysis of fluorescein diacetate and arylsulfatase activity decreased to below the detection limit at about 1.5 m depth, and carbon utilisation patterns showed that bacterial populations from surface soil were significantly different from those from 4 m depth. Bacterial biomass and activity in macropore soil tended to be slightly higher than in matrix soil, and the carbon utilisation patterns of bacterial populations extracted from macropore soil and from matrix soil seemed to be different. Maximally 3% of 14C-labelled mecoprop and isoproturon was mineralised in soil from the 1-1.5 m depth, and less than 1.5% was mineralised in soil from the 3.5-4 m depth. The macropore soil tended to have a higher degradation potential than the matrix soil. The total number of bacteria in the coarse sandy soil profile decreased from about 108 in the plough layer to 107 cells g-1 at 0.4-2 m. The enzymatic activities and the degradation potentials of 14C-labelled mecoprop and isoproturon were significantly correlated (r2 >0.79) and showed a distinct decrease at about 0.4 m. In addition to the depth variability, a horizontal heterogeneity in this soil was observed as horizons or compartments that differed in colour, i.e. with different chemical composition and concentrations of Fe and organic matter. Counts of viable bacteria and measurements of fluorescein diacetate hydrolysis and arylsulfatase activity confirmed a high variability of microbial biomass and activity in the sandy soil profile. 相似文献
8.
Geophysical and remote sensing-based approach to model regolith thickness in a data-sparse environment 总被引：1，自引：0，他引：1
Mapping regolith thickness to bedrock is important for environmental modeling in general and for seismic hazard assessment in particular. However, regolith thickness is often ignored in such studies because of its presumed difficulty of mapping in many terrains. To overcome this limitation we developed a generic remote sensing and geophysics based approach to model regolith thickness for areas with limited possibility of direct field observations. The approach was tested in a seismically-active and depositional landscape in northern Pakistan. Regolith thickness was sampled at exposed bedrock outcrops along the river bed and scarps. At unexposed sites the regolith-bedrock interface was identified through electrical resistivity survey, thus providing an indirect measurement of regolith thickness. A geomorphic classification of landforms and topographic attributes were derived from a remote sensing-based (ASTER) digital elevation model and SPOT-5 satellite imagery. Landform was the most important predictor (adjusted R2 = 72.1%), showing the importance of geomorphic interpretation. A multivariate linear model based on landform, elevation and distance to stream was able to predict the regolith thickness (adjusted R2 = 91.7), including field-observed abrupt changes at landform boundaries. 相似文献
9.
模拟氮沉降对杉木人工林土壤可溶性有机碳和微生物量碳的影响 总被引：1，自引：0，他引：1
在杉木人工林中开展模拟氮沉降试验,设计N0(对照)、N1(60kg N/hm2.a)、N2(120kg N/hm2.a)和N3(240kg N/hm2.a)4种氮沉降水平。通过连续7年的处理后,研究外加氮源对土壤可溶性有机碳及微生物量碳的影响及与土壤酶活性的关系。相同N沉降处理下,土壤有机碳、可溶性有机碳和微生物量碳均随土层加深而降低。氮沉降对土壤有机碳具有促进作用,中-低氮沉降(N1、N2)增加幅度大,高氮沉降(N3)增加幅度小。低氮(N1)处理促进土壤微生物生物量C增加,而中、高氮(N2、N3)则抑制;各氮沉降处理土壤可溶性有机碳含量从高到低的顺序为:N3、N2>N1>N0。40-60cm土壤微生物量碳与蔗糖酶、纤维素酶呈极显著正相关关系,与淀粉酶、多酚氧化酶、过氧化物酶呈极显著负相关关系;除40-60cm土层的β-葡糖苷酶外,各层土壤可溶性有机碳与土壤蔗糖酶、纤维素酶和β-葡糖苷酶活性呈极显著正相关关系,与淀粉酶、多酚氧化酶和过氧化物酶呈极显著负相关关系。因此,氮沉降增加将会对土壤碳累积与分解过程产生较大的影响。 相似文献
10.
为探明地下水埋深与减施氮肥对夏玉米氮素吸收利用及产量的影响,基于大型地中渗透仪,研究了地下水埋深和施氮量对夏玉米氮素利用效率、植株氮素积累量、产量及其形成要素的影响,其中地下水埋深设2 m(G1),3 m(G2)和4 m(G3)3个水平,施氮量设减氮20%处理(240 kg/hm2,N1)、常规施氮处理(300 kg/hm2,N2)2个水平,不控水不施氮处理(G0N0)作为对照,共计7个处理。结果表明:(1)减氮20%条件下,夏玉米产量随地下水埋深增加呈减小趋势,氮素收获指数在埋深2 m下显著高于埋深3,4 m,分别增加5.71%,7.22%;(2)常规施氮条件下,埋深2 m处理茎、叶吸氮量显著高于埋深3~4 m处理,增幅为19.52%~50.31%,但产量、籽粒吸氮量和氮素收获指数埋深2 m处理显著低于埋深3~4 m处理,降幅为17.28%~29.28%;(3)地下水埋深2 m下,产量、氮肥农学效率、氮肥生理利用率、籽粒氮肥吸收利用率和氮素收获指数减氮20%处理均显著高于常规施氮处理,增幅为22.18%~115.35%。地下水埋深2 m条件下,施氮240 kg/hm2显著提升氮肥的增产效果,以及施氮后氮素转化为产量和干物质的效率,同时还增强氮素向籽粒的转移率,从而保持产量不致降低,因此埋深2 m条件下减氮20%有一定可行性。研究结果可为地下水浅埋地区控施氮肥提供理论参考依据。 相似文献
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The acidified Lake Hovvatn have been limed in 1981, 1987, 1989 and 1991. After the first liming the lake reacidified close to the prelimed condition. The reliming, which started in 1987, was planned to maintain the pH at a relatively high level for the lake. A detailed monitoring of pH and temperature was performed at depth 0.5, 1, 1,5 and 5 m since spring 1993. Quantitative samples of benthic invertebrates were taken in spring and fall in 1977 and regularly at the same seasons from 1981 at depth 0.5, 2, 5 and 10 m. A reference lake, Lille Hovvatn have been sampled with the same procedure since 1988. The acid tolerant mayfly Leptophlebia vespertina responded quickly to the first liming with a 20 times increase in density after a few months. However, the densities rapidly decreased during the first years of reacidification. The lime treatments in 1987 and 1989, resulted in a second peak in density in 1990. After this, the densities have been reduced in spite of generally good water quality in Hovvatn. During fall the density increase was significant at 0.5 m depth in 1990, at 2 m depth in 1989, 1990 and 1992 and at 5 m depth in 1988 to 1990. No significant increase was observed in the limed localities during spring. It is concluded that acid surface water, prior to ice break, affect the food resources to L. vespenina and reduce the population at all depths during spring and in the littoral zone in fall. 相似文献
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基于指示Kriging法的土壤盐渍化与地下水埋深关系研究 总被引：10，自引：4，他引：6
在北方干旱、半干旱的地下水浅埋区,土壤盐渍化是土地资源退化的主要原因,防治土壤盐渍化是农业和生态环境可持续发展的重要保障。该文以内蒙古河套灌区解放闸灌域为例,运用指示Kriging法绘制并比较了不同阈值下地下水位埋深和土壤表层含盐量的概率分布图,从概率空间分布的角度分析研究了土壤盐渍化与地下水位埋深之间的关系,从而将这方面的研究从通常的农田尺度扩大到灌域尺度。结果表明:1)土壤盐分和地下水位埋深空间变异强度均为中等,且具有中等的空间自相关性,球状模型拟合变异函数的效果较好;2)在灌域尺度上,解放闸灌域4月底土壤表层发生中度、轻度盐渍化时地下水位临界埋深分别为2.0、2.5m,西南及中东部地下水位埋深小于临界埋深的概率较大,是土壤返盐的高风险区;3)3月底地下水位埋深对土壤返盐的影响比4月底更大一些,这表明地下水位埋深对土壤返盐的影响具有一定滞后效应,只有地下水位埋深小于临界深度的状态维持一段时间,才会造成土壤中度或轻度盐渍化。 相似文献
14.
《Soil Science and Plant Nutrition》2013,59(1):122-132
Abstract In the course of a series of studies conducted to investigate the long-term behavior of 129I (which has a half-life of 16 million years) in the environment, seasonal variation in the concentration of stable iodine (127I) in precipitation and soil water to a depth of 2.5 m in a forest plot, an upland field and a paddy field in the upland area of Tsukuba, Japan, were determined. Iodine concentration in precipitation tended to increase during the summer (high air temperature) season and low-rainfall period, and a positive high correlation was observed between annual rainfall and the annual amount of iodine supplied by precipitation. No seasonal variations in iodine concentration in soil water were observed at any depth in the forest plot and upland field unlike at shallow depths (0.2 and 0.5 m) in the paddy field. In the paddy field, from the beginning of summer irrigation, under flooding conditions, iodine concentration in soil water at shallow depths (0.2 and 0.5 m) continuously increased, and immediately before mid-summer (intermittent) drainage and drainage, the maximum iodine concentration (approximately 50 µg L?1) and lowest Eh values (approximately ?150 to ?200 mV) were recorded. These high iodine concentration levels and low Eh values were ascribed to high air temperature (approximately > 25°C on average every 10 days) and the continuation of the groundwater level above the ground surface. As for the temporary winter irrigation period (mean daily air temperature 2?4°C), the iodine concentration was low (1.7–3.7 µg L?1) at all depths, as was the case in the non-irrigation period. After mid-summer drainage, and drainage, the iodine concentration in soil water at depths of 0.2 and 0.5 m decreased drastically as the groundwater level decreased. The mean annual amount of iodine accumulated in the surface soil horizons (0–0.67 m) in the forest plot was estimated to be approximately 2.9 mg m?2 (7.5 µg kg?1 dry soil), which coincided with the mean annual amount of iodine supplied to the earth surface by precipitation. A mildly oxidative subsurface 2Bw horizon (0.60–0.89 m) in the paddy field was estimated to illuviate approximately 3.1 mg m?2 (20 µg kg?1 dry soil) of iodine annually by retaining iodine in the soil water percolated to this horizon. 相似文献
15.
Studies on badland areas in the Vallcebre basin (Pyrenees) suggest that erosion rates are controlled by the weathering rate of mudrocks. To obtain the temporal pattern of physical weathering and its control on the erosive processes, monitoring of regolith temperatures at different aspect, depth and lithology, and periodical determination of regolith moisture and bulk density were carried out. Changes in surface regolith have also been monitored by means of photographic techniques, using an especially designed tripod. Finally, the hydrological and erosive response of the regolith trough the seasons were studied using rainfall simulations. The results obtained support and confirm previous knowledge on the role of frost action in mudrock weathering and the role of subsequent regolith development and wetness status on infiltration and runoff generation. These seasonal changes of behaviour are so important that they raise serious questions about the validity of observations or experiments carried out in only one season.This work confirms that erosion processes are controlled by regolith formation during winter and regolith depletion by storm rainfall erosion during summer, spring and early autumn. It also raises important points about annual trends of infiltration and erodibility, that should be used as guidelines for modelling runoff and sediment production. 相似文献
16.
The depletion of hypolimnetic DO and the upper depth boundary of anoxia for four different years (1978, 1979, 1980 and 1981), and the accumulation of sulfide for a single year (1981), are documented for ionically enriched hypereutrophic Onondaga Lake, NY, USA. The depletion rate, represented as the areal hypolimnetic oxygen deficit (AHOD, g m?2 day?1), was extremely high (1.2–2.7 g m?2 day?1), The large differences in the rate within individual years and from year to year were largely a result of differences in attendant vertical mixing (parameterized as the hypolimnetic heating rate). The entire hypolimnion (depth interval from 11 to 20 m) was without O2 by late June of all 4 yr; anoxia was observed above the hypolimnion on some occasions when secondary stratification occurred. Sulfide accumulated progressively in the hypolimnion in 1981 following the onset of anoxia to a volume weighted concentration of I1 mg L?1. The ionic discharge from an adjoining alkali manufacturer exacerbated the problem of limited O2 resources of the hypolimnion by: (1) decreasing vertical mixing, (2) prolonging the duration of stratification, (3) causing abbreviated turnovers, and (4) encouraging increased rates of phytoplankton settling. 相似文献
17.
Soil and soil solution chemical composition at three sites within the Loch Dee catchment, SW Scotland 总被引：2，自引：0，他引：2
I.C. GRIEVE 《European Journal of Soil Science》1990,41(2):269-277
Soil solution chemical composition was monitored over a 2–year period at three plots near the edge of an igneous intrusion in SW Scotland. Soil solutions were all strongly acidic with mean pH of approximately 4.0 at 0.20 m depth and 4.5 at 0.60 m. Chemical composition of the deeper soil solutions varied with geology. Greatest acidity and aluminium concentrations were found over metamorphosed Ordovician sedimentary rocks, with mean pH of 4.3 and A1 concentration of 22 mmol m?3 at 0.60 m. At a site on similar rocks nearer the intrusion, mean pH at 0.60 m was 4.8, with very low A1 (3 mmol m?3) and correspondingly greater Ca. At a peaty site on igneous rocks, increased pH with depth was associated with no change in base cations and A1 but a reduction in mean SO, from 41 mmolm?3 at 0.20m to 10mmol m?3 at 0.60m. Ion-exchange selectivity coefficients calculated from soil and solution chemistry differed slightly from currently used values for peaty upland soils, with larger coefficients for A1/K exchange and smaller coefficients for A1/Ca and A1/Mg exchange. Relations between A1 and H ion concentrations confirmed under-saturation of solutions with respect to gibbsite at 0.20 m. The differences between plots were consistent in different seasons, despite significant seasonal variability in Na, C1, dissolved organic carbon and Fe. 相似文献
18.
《Communications in Soil Science and Plant Analysis》2012,43(13-14):2371-2384
Abstract Spatial variation of soil test phosphorus (P) was studied by measuring soil‐test P for individual soil samples collected from uniform areas in south‐western Australia. The soil samples were collected using standard 10 cm deep by 2.5 cm diameter samplers. The Colwell alkaline bicarbonate soil test, the standard reagent adopted in Western Australia, was used. There were two parts to this study. In Part 1, 36 individual soil samples were collected on 20 m by 20 m grids within a uniform 100 m by 100 m area in paddocks on 16 different lateritic soil types. Superphosphate had been applied each previous year, using normal farmer practices, for either nine years at two sites or >20 years at the other sites. For pastures, fertiliser is usually applied to the surface. For crops, it is drilled with the seed at about 5 cm depth. In Part 2, 10 to 20 individual soil samples were collected at random locations within experimental plots (either 2 or 4.8 m wide by 30 m long) of five long‐term field experiments that were treated once only with different amounts of superphosphate applied from two to eight years previously. The P was applied to the soil surface and either incorporated through the soil with a rotary hoe or when sowing crops at 5 cm depth with tined implements, or the P was placed at 5 cm depth in bands that were 180 mm apart and the soil was not disturbed thereafter. For each site in Part 1, or each plot of each experiment in Part 2, soil‐test P for the individual soil samples varied, often markedly. Coefficient of variation was large. It was up to 56% for Part 1. For Part 2, it was up to 82% when P was incorporated into the topsoil, and up to 210% when P was banded in the soil. Spatial variation of soil‐test P is attributed to natural variation of soil physical, chemical, and mineralogical properties. Some of the variation may also be due to heterogenous mixing through the topsoil of fertiliser P applied in recent years. Soil‐test P is usually larger for recently applied fertiliser P. 相似文献
19.
Laura Alakukku 《Soil & Tillage Research》1996,37(4):211-222
Short-term effects of high axle load traffic on soil total porosity and pore size distribution were examined in field experiments on a clay (Vertic Cambisol) and an organic soil (Mollic Gleysol) for 3 years after the heavy loading. The clay soil had 48 g clay (particle size less than 2 μm) per 100 g in the topsoil and 65 g per 100 g in the subsoil. The organic soil consisted of well-decomposed sedge peat mixed with clay below 0.2 m depth down to 0.4–0.5 m and was underlain by gythia (organic soil with high clay content). The experimental traffic was applied with a tractor-trailer combination in autumn 1981. The trailer tandem axle load was 19 Mg on the clay and 16 Mg on the organic soil. There were three treatments: one pass with the heavy axle vehicle, with wheel tracks completely covering the plot area, four repeated passes in the same direction, and a control treatment without experimental traffic. During loading, the clay was nearly at field capacity below 0.1 m depth. The organic soil was wetter than field capacity.
One and four passes with the high axle load compacted both soils to a depth of 0.4–0.5 m. On the clay soil the total porosity was reduced by the heavy loading nearly as much as macroporosity (diameter over 30 μm) to 0.5 m depth. On the organic soil, macroporosity was reduced and microporosity (under 30 μm) increased in the 0.2–0.5 m layer by the heavy loading. Total porosity did not reveal the effects of compaction on the organic soil. The compaction of the clay below 0.1 m persisted for 3 years following the treatment despite annual ploughing to a depth of 0.2 m, cropping and deep cracking and freezing. Likewise, in the subsoil (below 0.2 m) of the organic soil, differences in pore size distribution persisted for a period of at least 3 years after the heavy loading. 相似文献
20.
Tillage systems can influence weed seed viability and the distribution with depth of weed seeds in soil. To investigate this ‘tillage effect’, weed seed bank composition was determined at two soil depths (0–10 and 10–20 cm) in three tillage systems [mouldboard plough (MP), shallow tillage (ST), and direct drilling (DD)] established for 14 years on a sandy loam (Podzol) in Prince Edward Island, Atlantic Canada. The cropping system was a cool-season soybean (Glycine max L. Merr.) in rotation with barley (Hordeum vulgare L.). The objectives were to evaluate the size and composition of the viable soil seed bank, using the seedling germination method, and to determine if the adoption of non-inversion tillage practices (DD and ST) influence seed bank parameters relative to the conventional full inversion MP. The diversity of weed species was slightly lower for MP (17 species) compared to the ST (21 species) and DD treatments (22 species). The population for most weed species was relatively low with only three common species [low cudweed (Gnaphalium uliginosum L.), creeping buttercup (Ranunculus repens L.), common lambsquarters (Chenopodium album L.)] above 5 m−2. For the total soil depth sampled (0–20 cm), weed seed population was significantly greater under DD (56 weeds m−2) and ST (66 weeds m−2), compared to MP (25 weeds m−2), and mainly related to changes in the number of annual broadleaf weeds, compared to perennial broadleaf and grasses. Comparison of the 0–10 with the 10–20 cm soil depth showed a relatively uniform weed seed distribution for the MP treatment, while a greater proportion of weed seeds was found at the lower soil depth for DD and ST. This distribution tended to be weed species dependent. Soil texture and weed seed characteristics were considered to have a critical impact on the total weed seed bank size, specifically for the 10–20 cm soil depth. Overall, the weed bank size was relatively small indicating that adoption of conservation tillage practices for sandy loams in Atlantic Canada should not cause a major change in weed community and weed populations, or present a need for significant changes in weed control management. 相似文献