Abstract: The results of a laboratory study on the influence of standard Proctor and West African standard compactive efforts as well as compaction delays up to 3 h on the compaction and strength characteristics of lateritic soil treated with a maximum of 8% lime (by dry weight of soil) is presented. The results obtained show that the compaction and strength properties of the lime-treated soil decreased with increases in compaction delays. The decreases that were generally greater at higher lime contents were more prominent in specimens compacted at the energy of the West African standard. The determination of properties of lime-treated soil at no compaction delay defines optimum properties of the soil-lime mixtures, while compaction and strength properties determined following compaction delays define the minimum that can be achieved in the field for the specified elapsed times between mixing and compaction.

Abstract: A site-specific farming system for performing work on an agricultural field while soil compaction conditions of the field are being recorded includes a vehicle such as a tractor equipped with an element carrying farming tools for working the field, such as a plow. Sensors, including hitch load pins and/or strain gauge type sensors, detect the load on the tools due to the soil compaction. A location signal generation circuit generates signals relating to the location at which the force signal is sampled. The force data is correlated with the locations at which the force was sampled. The correlated data is stored in a memory. The user interface may include re-definable switches. A display may show a field map including the soil condition values, including soil compaction, and other sensed data.

Abstract: Soil compaction induced by forest harvesting operations can reduce site productivity. Intensity, extent and persistence of soil compaction were assessed on fine- to medium- and coarse-textured soils. Severe compaction took place in the wheel track section of the skid trails. On fine- to medium-textured soils, half of the effects on the 0- to 10-cm and 10- to 20-cm mineral soil bulk densities (+11 and +8%) and half of the changes in the 10-cm depth soil strength (+69%) occurred in the course of the first two skidding cycles (cycle of half impact). On coarse soils, half of the effect on the 0- to 10-cm bulk density (+11%) occurred during the first three passes. Cycles of half impact for soil strength were 9, 14, 7 and 6 for the 2.5-, 5-, 10-, and 20-cm depths and corresponded to increases of 235, 402, 157 and 103% respectively. Compaction was more limited between track sections of trails. Six to twelve years following clearcutting on fine- to medium-textured soils, 0- to 10-cm soil bulk density was less in ...

Abstract: Intensive timber harvesting and site preparation are becoming more common as demand for timber-based products increases. On some harvested sites in the western United Staes of America and Canada, s...

Abstract: The ability of four species of vesicular–arbuscular mycorrhizal (VAM) fungi to increase phosphorus uptake and growth of clover plants (Trifolium subterraneum L.) at different levels of soil compaction and P application was studied in a pot experiment. Dry matter in the shoots and roots of clover plants decreased with increasing soil compaction. Colonization by Glomus intraradices Schenck & Smith and Glomus sp. City Beach WUM16 increased plant growth and P uptake up to a bulk density of 1·60 Mg m−3, although the response was smaller as soil compaction was increased. Glomus etunicatum Becker & Gerdeman and Glomus mosseae (Nicol. & Gerd.) Gerdemann & Trappe had no effect on the shoot d. wt and P uptake when the bulk density of the soil was 1·40 and 1·60 Mg m−3, respectively. Soil compaction to a bulk density of 1·60 Mg m−3 had no effect on the percentage of root length colonized by G. intraradices and Glomus sp. City Beach, but total root length colonized decreased as soil compaction was increased. Decreased P uptake and growth of clover plants colonized by G. intraradices and Glomus sp. City Beach, with increasing soil compaction up to a bulk density of 1·60 Mg m−3, was mainly attributed to a significant reduction in total root length colonized and in the hyphal biomass. Soil compaction, which increased bulk density from 1·20 to 1·75 Mg m−3, reduced the O2 content of the soil atmosphere from 0·16 to 0·05 m3 m−3. The absence of any observable mycorrhizal growth response to any of the four species of VAM fungi in highly compacted soil (bulk density = 1·75 Mg m−3) was attributed to the significant decrease in the O2 content of the soil atmosphere, change in soil pore size distribution and, presumably, to ethylene production.

Abstract: We have simulated the evolution of the accreting Quaternary column at three strategic locations (Venice, Po river delta, Ravenna) along the Upper Adriatic coastline. The analysis is performed by a 1-D nonlinear finite element model of soil compaction driven by groundwater flow in an isothermal sedimentary basin subject to a continuous vertical sedimentation process. The constitutive relationship of the most important parameter controlling the event, i.e. the soil compressibility vs the effective intergranular stress, has been derived from a number of oedometer tests carried out on samples taken from shallow and deep exploratory boreholes scattered through the study area. Dating of the sediments has allowed for the estimate of an average depositional rate at selected time intervals spanning the Middle-Upper Pleistocene, the Holocene and the historical times. The model has been run so as to reproduce the present day sediment thickness with a small excess hydrostatic pressure since the Adriatic Sea basin in known to be normally pressured. It is assumed that sedimentation in the last 0.5 My was substantially in equilibrium with subsidence so that the deposition surface remained at a constant elevation. The results of our analysis indicate a natural land settlement in the next century between 0.5 mm/y at Venice and 4÷5 mm/y in the Po delta, with an intermediate value of 2÷2.5 mm/y at Ravenna.

Abstract: Runoff yield and sediment delivery are compared in three shrub species (Medicago arborea, Atriplex nummularia, and Psoralea bituminosa) with natural (matorral) vegetation in an experimental plot set. The planted species are arranged in discontinuous rows perpendicular to the slope, acting as barriers to the direction of the surface water flow. The study was carried out from 1988 to 1995, in which 56 erosive rain events were monitored in runoff production and in soil losses, together with their intrinsic characteristics (duration, intensity and rainfall). Growth of the three shrub species (height, vegetation cover, and stem diameter) and the influence on soil properties during this period were recorded. Because of certain characteristics of the study area (shallow soils, high levels of carbonates, stoniness) and the climate (an especially intense period of drought since 1990), the growth of these plants was very irregular. M. arborea gave the best protection against water erosion reducing sediment production by more than 58% compared to the bare soil. However, the protection afforded by this species never reached that obtained with natural vegetation, which reduced sediment production by almost 75%.

Abstract: The potential of an intact rye cover crop to reduce machine-induced compaction was the subject of this study. A randomized complete block field experiment was conducted in southwest Virginia in a fine, mixed, mesic, Aquic Agriudolls and in a fine-loamy, mixed, mesic, Typic Hapludults. Three cover-cropped treatments and one fall-tilled fallow treatment were analyzed. The treatments permitted investigation of the effects of a crop, the condition of the crop, and the contribution of root reinforcement to the alteration of soil response to machine traffic. Effects resulting from three levels of traffic—one, three, and five passes—were investigated. Undisturbed soil core samples were analyzed to determine the effects of machine traffic on dry bulk density, pore size distribution, and saturated hydraulic conductivity. Measurable soil response to machine traffic was limited to the uppermost 150 mm of the soil profile. Treatments that included a rye cover produced samples with significantly lower dry bulk densities and higher noncapillary porosities than the bare soil treatment for the soil surface layer (25-75 mm) following multiple machine passes. Soil compaction appeared to be reduced by the reinforcing effect of a network of undisturbed roots within the soil. There was no convincing evidence that above-ground biomass contributed directly to the reduction of machine-induced compaction effects.

Abstract: The influence of moisture content on dynamic compaction efficiency was evaluated at six field test cells, each with a progressively higher average moisture content. The soil profile consisted of collapsible sandy silt, and average test cell moisture contents ranged from 6% to 20%. At each cell, compaction was performed with a 4.54 t weight dropped from a height of 24.3 m. Compaction efficiency was evaluated using (1) crater depth measurements, (2) cone penetration tests before and after compaction, and (3) undisturbed samples before and after compaction. Crater depth increased by a factor of 4 as moisture content increased. The degree of improvement increased up to a moisture content of about 17% and then decreased. The optimum moisture content and the maximum dry unit weight are similar to those predicted by laboratory Proctor testing using energy levels comparable to those employed in the field. Maximum dry unit weight decreased with depth, while optimum moisture content increased before the compactive ...

Abstract: The possible use of lime-treated acid mine drainage (AMD) for irrigation of agricultural crops was investigated. A field screening trial of 20 agronomic and pasture crop species was established at Landau Colliery Kromdraai Opencast Section (near Witbank, Mpumalanga Province), on a sandy acid soil. The objectives were to monitor crop response to sprinkler irrigation with lime-treated AMD and changes in soil chemical properties due to irrigation with this saline (gypsiferous) water. Considerable increases in yield of irrigated crops were observed, compared with rainfed cropping. Shallow rooting depths were, however, recorded for most crops, possibly due to high soil acidity, soil compaction and P deficiency in deeper layers. No symptoms of foliar injury were noted. Fluctuations in soil salinity levels were recorded depending on rainfall pattern, whilst soil pH(H 2 O) increased after three years of irrigation. Lime-treated AMD could be an additional resource in mining areas, provided that irrigation and fertilisation practices are managed correctly.

Abstract: Subsurface soil compaction is a global problem that causes reduced plant growth and yield. The objective of this study was to evaluate responses of various growth and yield components of smooth bromegrass (Bromis inermis L. cv. Magna) and alfalfa (Medicago sativa L. cv. Rambler) to subsurface compaction of sandy loam and clay loam soils. Regression analysis indicated that all growth variables measured (shoot biomass, root biomass, number of alfalfa branches, number of smooth bromegrass tillers per plant, and leaf blade or leaflet width and length) had a negative relationship with soil bulk density in a linear nature. However, these growth responses varied in their sensitivity to subsurface compaction. For alfalfa, the most sensitive variable was the number of tertiary branches; for smooth bromegrass, shoot biomass was most sensitive. Leaf blade or leaflet length was the least sensitive variable to subsurface compaction. The study is unique in that it provides response curves for various plant growth responses, an assessment of the sensitivity of these parameters to subsurface compaction, and a data base for modeling these relationships. This study also provides plant-based indicators that should be related to soil-based indicators of compaction problems such as bulk density and soil strength, which are often used to determine the extent of compaction.

Abstract: Field experiments were performed in Southern Finland on fine sand and organic soil in 1990 and 1991 to study carrot roots. Fall ploughed land was loosened by rotary harrowing to a depth of 20 cm or compacted under moist conditions to a depth of 25-30 cm by three passes of adjacent wheel tracks with a tractor weighing 3 Mg, in April were contiguously applied across the plot before seed bed preparation. Sprinkler irrigation (30 mm) was applied to fine sand when moisture in the 0-15 cm range of soil depth was 50% of plant-available water capacity. For root sampling, polyvinyl chloride (PVC) cylinders (30 x 60 cm) were installed in the rows of experimental plots after sowing, and removed at harvest. Six carrot plants were grown in each of in these soil columns in situ in the field. Fine root length and width were quantified by image analysis. Root length density (RDL) per plant was 0.2-1.0 cm cm-3 in the 0-30 cm range. The fibrous root system of one carrot had total root lengths of 130-150 m in loose fine sand and 180-200 m in compacted fine sand. More roots were observed in irrigated than non-irrigated soils. In the 0-50 cm range of organic soil, 230-250 m of root length were removed from loosened organic soils and 240-300 m from compacted soils. Specific root surface area (surface area divided by dry root weight) of a carrot fibrous root system averaged 1500-2000 cm2 g-1. Root length to weight ratios of 250-350 m g-1 effectively compare with the ratios of other species. Fibrous root growth was stimulated by soil compaction or irrigation to a depth of 30 cm, in both the fine sand and organic soils, suggesting better soil water supply in compacted than in loosened soils. Soil compaction increased root length in loosened soils (fme sand 90%, organic soil 80%) and compacted soils (fme sand 80%, organic soil 75%) was composed of roots with diameters of approximately 0.15 mm. With respect to dry weight, length, surface area and volume of the fibrous root system, all the measurements gave significant responses to irrigation and soil compaction. Total root volumes in the 0-50 cm of soil were 4.3 cm3 and 9.8 cm3 in loosened fine sand and organic soils, respectively, and 6.7 cm3 and 13.4 cm3 in compacted sand and organic soils, respectively. In fine sand, irrigation increased the volume from 4.8 to 6.3 cm3.

Abstract: In order to determine whether wheel-induced soil damage affected the subsequent utilization of livestock slurry by grass managed for silage production, dry-matter yield and nitrogen offtake were compared in a replicated field experiment over three years in the presence or absence of soil compaction. Typical and zero compaction were compared in each year, and nominal controlled compaction was included in the two later years. Soil structure, as characterized by porosity and hydraulic conductivity measurements, was of poorest quality in the typical compaction treatment. Averaged over 3 years, typical compaction resulted in an annual yield reduction, relative to non-compaction, of 2·14 t has−1 (20%) and 1·66 t ha−1 (13%) when 198 and 285 kg N ha−1 respectively were provided as ammonium nitrate fertilizer plus slurry-derived ammonium-N. The largest and most consistent yield reductions as a result of compaction occurred at first harvest each year following slower growth on the most compacted soil of the typical treatment. In general, compaction-induced yield penalties increased with increased soil wetness. Offtake of nitrogen from both fertilizer alone and slurry and fertilizer combined was significantly reduced by soil compaction. First-harvest yield response to increasing N rate was larger in the zero compaction treatment than in the typical treatment. Averaged over 3 years, the total annual apparent recovery of applied nitrogen was 55% after typical compaction and 71% after zero compaction. It was likely that the larger proportion of non-recovered N in the former was lost as a consequence of greater surface run-off, denitrification and ammonia volatilization. Over 2 years, the yield and nitrogen offtake trends in the controlled compaction treatment were intermediate between those of the zero and typical treatments, and in general more similar to the former than to the latter. The results indicated that when livestock slurry is recycled as a source of nitrogen, prevention of soil compaction is an important component of efficient and environmentally protective grassland management.

Abstract: Riparian areas are often focal points for recreation on western rangelands. The objective of this study was to assess the impact of recreation on soil compaction, runoff, erosion rates, and vegetation in a central Arizona riparian ecosystem. This study was conducted in a Populus fremontii-Fraxinus pennsylvanica (Fremont Cottonwood-Velvet ash) riparian community type. The dominate recreational use on the study site is camping and the area is accessible by automobile. A rainfall simulator with an application rate of 5 in/hr (12.7 cm/hr) for 30 minutes was used to produce runoff. Initiation of runoff occurred significantly (P

Abstract: Common root rot of pea caused by Aphanomyces euteiches Drechs. is widespread and difficult to control. In many production areas, yearly losses have been estimated at 10% because of the disease. Cultural control is needed even when disease tolerant cultivars are planted. Soil compaction due to traffic is known to aggravate the disease. In a series of research studies in a heavily infested nursery and adjacent farm fields, it was shown that compaction aggravates the disease by decreasing drainage and thus providing more favourable soil water conditions for early infection of pea roots. Traffic compaction has also provided an adverse abiotic environment for plant stress due to poor aeration. A precrop of oat (Avena sativum L.), as a full-season or late-summer crop, suppressed the disease only if the oat residue was incorporated at a shallow depth late in the fall using a chisel. Incorporated oat residue reduced inoculum potential of A. euteiches above 10 cm when incorporated with a chisel and below 10 cm when incorporated with a moldboard plow. A rolled towel bioassay using a susceptible pea cultivar successfully estimated inoculum potential when the test soil was placed near the epicotyl of 7-day-old seedlings. Although A. euteiches is an aggressive disease, all of these findings focus on vulnerability during the infection process. These investigations were required to examine carefully the soil ecology pertaining to the host crop, the pathogen when in the saprophytic mode, and the host crop interaction with the pathogen.

Abstract: The compaction curves of soils are generally expressed in terms of dry density and water content. While this representation serves well to compare the efficiency of compaction of different soils whose specific gravities lie in a narrow range (2.6 to 2.7), it fails for materials of varying specific gravities. It has been shown that for fly ashes with a wide range of specific gravities the degree of compaction of different fly ashes cannot be compared from conventional compaction parameters. Compaction curves expressed on a volume basis, viz., volume of solids per unit volume of compacted sample or porosity or void ratio and volume of water per unit volume of solids, can better serve to explain the compaction. Further, it has been shown that for fly ashes of different specific gravities only compaction parameters expressed on a volume basis can be interrelated.

Abstract: The establishment of cover crops, in relay, to minimise soil erosion, improve soil physical condition and provide a main-season crop in rotation with potatoes ( Solanum tuberosum L.) is a recommended agronomic practice in Atlantic Canada. This is usually achieved by seeding winter rye ( Secale cereale L.) or winter wheat ( Triticum aestivum L.) immediately after potato harvest for ground cover followed, the next spring, by inter-seeding an annual or biennial forage crop by drilling. Spring drill seeding can, however, be delayed or prevented by wet ground conditions, thus, making broadcast seeding a considered alternative. This study examined, therefore, the comparative merits of spring broadcast seeding and drill seeding of two adapted forages, Italian ryegrass ( Lolium multiflorum Lam.) and red clover ( Trifolium pratense L.), into a standing crop of fall-seeded winter rye or winter wheat. Crop performance was evaluated, using meter-square quadrats, as ground coverage and grain yield (of cereals). Soil compaction, evaluated as shear strength in the 0–15 cm layer (avoiding wheel tracks) of a fine sandy loam (Orthic Podzol), was greater after drill seeding than after broadcast seeding by a factor of 7.2% and was attributed to the greater ground-contact mass of the drill seeder. The forage crops provided 5.5% more ground coverage with drill seeding than with broadcast seeding. However, seeding method had no effect on the cereal host crops' ground coverage or grain yield. Ryegrass coverage was 123% of red clover coverage and winter rye coverage was 176% of winter wheat coverage. Forage coverage, in this study, suffered no setback because of the greater soil compaction associated with drill seeding. However, soils are subject to greater compaction under wetter conditions, thus, broadcast seeding is expected to be a better option, the wetter the spring.

Abstract: Revised November 1990. Reprinted March 1998. Facts and recommendations in this publication may no longer be valid. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalog

Abstract: Soil compaction has been considered as one of the agent that affects the sugar cane roots productivity. In this work, the effects of soil compaction were studied on the structural aspects of sugar cane roots (Saccharum officinarum L. 'SP 701143', Poaceae), developed in culture conditions, in a clayed "latossolo roxo" soil. Root samples were colleted in ten areas, at two soil depth, 0-20 and 20-40 cm. The soil bulk density varied from 0.94 to 1.21 g/cm3 at 0-20 cm depth and from 1.02 to 1.23 g/cm3 at 20-40 cm depth in all areas. It was observed a tendency to develop a larger ratio cortex/vascular cylinder in compacted soils.

Abstract: Multipurpose woody species can play an important role in the improvement and maintenance of soil productivity in traditional and planted fallow systems This study examined the longterm effects of woody species grown in hedgerows in alley cropping and of soil tillage, on soil properties, runoff and erosion, and crop performance Observations conducted from 1988 to 1993 on a trial established in 1982 on a sloping land is reported in this paper Six land use systems were compared: Leucaena leucocephala and Gliricidia sepium hedgerows planted at 2 and 4 m interhedgerow spacings and tilled, and no-till and tilled controls without hedgerows

Abstract: In this project, researchers used extensive laboratory, greenhouse, and field studies to determine the relative salt tolerance of select native grasses and forbs used to revegetate right-of-ways within four meters of the pavement edge. The studies found that grasses prove relatively tolerant to salt, but show poor survivability in the field during over-wintering. In contrast, forbs generally are sensitive to salt in their environment. Planting success of monocultures and mixtures of grasses near the pavement edge was poor. Observed percent coverage after two years ranged from about 10% to 20% over all tested species. Monitoring of longer established sites also shows that native species do not increase as a stand ages. Soil amendments including gypsum, potash, and potassium nitrate were only minimally effective in alleviating salt stress in sodic soils, although gypsum may have some promise in further field testing. The application of salt during winter salting operations also permanently and negatively impacts soil chemistry, which in concert with other plant stress factors such as soil compaction and infertile roadside soils, will continue to limit the success of establishing desirable vegetation on the inslopes of heavily salted roadways in Minnesota.