Abstract: For many coastal plain soils in the southeastern USA, high soil strength within subsurface horizons requires that deep tillage be performed to provide a suitable rooting environment for row crops such as maize (Zea mays L.), wheat (Triticum aestivum L.), and soybean (Glycine max L. Merr.). We hypothesized that water filtering through the soil was recompacting it and that recompaction could be correlated with cumulative amount of rainfall since tillage. We measured cone indices in a structureless, fine loamy Acrisol near Florence, South Carolina, from 7 days to about 6 years after treatments were deep tilled. Measurements were made to a depth of 0.55 m at the point of maximum disruption of a bent-leg subsoiler (Paratill ® ) that tilled to a depth of 0.35–0.40 m. Regressions of cone indices with cumulative rainfall explained 67–91% of the recompaction and indicated that water filtering through the soil was causing the recompaction. Recompaction was slow, still taking place 6 years after tillage (the end of the experiment) probably because of controlled traffic or excessive disruption by the paratill. Recompaction was also temporarily greater for the 0.1–0.2 m depths when compared with that in the 0.25–0.35 m depths indicating that it was moving down the profile. Recompaction in other climates may be faster or slower depending on their cumulative rainfall relative to an annual amount of 900–1350 mm per year for this study and recompaction for structured soils may be faster or slower depending on whether the structure is stable or not. Though recompaction in this study was slow, tillage may still be necessary annually or seasonally because yield can be reduced even by incomplete recompaction that increases soil strength after a year or less. Published by Elsevier Science B.V.

Abstract: Understanding the problems of grazing land in vertisol areas and seeking long-lasting solutions is the central point where mixed crop livestock is the second stay for the majority of the population. In order to understand this, the current study was conducted at two sites, one with 0-4% slope and the other with 4--8% slope at Ginchi watershed, 80 km west of Addis Ababa, Ethiopia. The specific objectives of the study were to quantify changes in plant species richness, biomass, plant cover, and soil physical and hydrological properties. The grazing regimes were: moderate grazing (regulated), heavy grazing (free grazing), and no grazing (closed to any grazing), which was considered the control treatment. The results showed that the biomass yield in nongrazed plots was higher than in the grazed plots. However, the biomass yield in grazed plots improved over the years. Species richness and percentage of dominant species attributes were better in medium grazed plots than the other treatments. Soil compaction was higher in very heavily grazed plots than in nongrazed and medium-grazed plots. In contrast to that, the soil water content and infiltration rate were better in nongrazed plots than in grazed plots. Soil loss in grazed plots decreased with the increase of biomass yields and as the soil was more compacted by livestock trampling during the wet season. Finally since the medium stocking rate is better in species richness and plant attributes, and lies between nongrazed and heavily grazed plots in the rest of the measured parameters, it could be the appropriate stocking rate to practice by the smallholder farmer.

Abstract: Ploughing is a field operation considered to be associated with severe soil compaction. Two experiments were carried out in Denmark on Eutric Cambisols with a Claas Challenger 2-65 E rubber-tracked tractor with a total weight of 185 kN. In Experiment A, the vertical stress under the track during ploughing was measured by stress sensors at 0.1 m depth in order to study stress distribution. In Experiment B, the vertical soil displacement and vertical normal soil stress during ploughing were measured simultaneously at three different depths. The tracked tractor was compared to a wheeled tractor with a total weight of 97 kN. The rubber-tracked tractor and the wheeled tractor were pulling a plough with 12 and 7 bodies, respectively. The tracked tractor ploughed on-land, whereas the wheeled tractor ploughed both on-land and conventionally (two wheels running in the furrow). In Experiment A, vertical stress was found to be much higher under the rear than under the front part of the tracks. It was caused by unsuitable adjustment of the plough to the tractor for given field conditions. By lowering the point of application of the draught force induced by the plough, maximum vertical stress was reduced from 304 to 158 kPa. However, the vertical stress was concentrated under the supporting rollers and wheels as well as under the centre line of the track, so that maximum stress was 3.8 times higher than average stress. In Experiment B, the vertical stress was higher below the wheeled tractor than below the tracked tractor, which had been adjusted as in Experiment A. No significant difference in maximum vertical soil stress was found between the tracked tractor and the wheeled tractor ploughing on-land at any depth. The vertical stress at 0.3 and 0.5 m depth was significantly higher during conventional ploughing (i.e. under the in-furrow wheels) than during on-land ploughing. The higher vertical stress also resulted in larger vertical soil displacement at 0.3 m depth under the in-furrow wheels when ploughing conventionally than under the on-land ploughing tractor. At 0.5 m depth, no residual vertical soil displacement occurred because the soil strength was very high. The results clearly demonstrated that on-land ploughing may reduce the risk for subsoil compaction compared to conventional ploughing. Using tracks instead of wheels may further reduce this risk. However, this is only the case if the tractor is well balanced. Thus, each particular tillage tool should be adjusted to the tractor, also with respect to the soil type and the field conditions.

Abstract: Often as a result of large-scale military maneuvers in the past, many soils in the Mojave Desert are highly vulnerable to soil compaction, particularly when wet. Previous studies indicate that natural recovery of severely compacted desert soils is extremely slow, and some researchers have suggested that subsurface compaction may not recover. Poorly sorted soils, particularly those with a loamy sand texture, are most vulnerable to soil compaction, and these soils are the most common in alluvial fans of the Mojave Desert. Recovery of compacted soil is expected to vary as a function of precipitation amounts, wetting-and-drying cycles, freeze-thaw cycles, and bioturbation, particularly root growth. Compaction recovery, as estimated using penetration depth and bulk density, was measured at 19 sites with 32 site-time combinations, including the former World War II Army sites of Camps Ibis, Granite, Iron Mountain, Clipper, and Essex. Although compaction at these sites was caused by a wide variety of forces, rang...

Abstract: Wheel induced soil compaction is an ongoing concern in mechanized agriculture. This experimental study was performed with the aim to evaluate whether soil compaction is related to stresses induced by towed wheels. Soil bin studies were conducted and soil compaction variables were measured under two towed tires, with different tread patterns, commonly used in Turkey. Tests were carried out at three tire loads (3.5, 5.5 and 7.5 kN) and two forward velocities (0.8 and 1.4 m/s) on a clay loam. To determine soil compaction, surface sinkage, subsurface layer deformation, compaction index, penetration resistance and bulk density were measured. With increasing vertical load, average contact pressure of tires increased from 39.3 to 68.5 kPa. In different trials, surface sinkage, compaction index, penetration resistance and bulk density varied from 46 to 86 mm, 0.18 to 0.48, 1472 to 2530 kPa and 1.31 to 1.70 Mg m −3 , respectively. The soil contact projected area of tire 2 was approximately 10% greater than tire 1. The greater contact surface reduced the compaction at the soil surface and subsurface, but the tire load was still the dominant factor in the 0–20 cm depth range used in this study. According to the experimental results, decreasing contact duration with increasing forward velocity decreased soil compaction. Tire load and type affected soil deformation characteristics stronger than forward velocity.

Abstract: Bacteria from forest surface organic matter and mineral soil horizons were cultivated using four methods and characterized by fatty acid methyl ester (FAME) analysis. Soil samples from a British Columbia Ministry of Forests Long-Term Soil Productivity (LTSP) installation were collected during winter and summer from two disturbance treatments (whole-tree harvesting with no soil compaction (plot N) and whole-tree harvesting plus complete surface organic matter removal with heavy soil compaction (plot S)) and from an unlogged reference plot (REF). Seventy-five percent of 1795 bacterial isolates were affiliated with 42 genera representing β- and γ-Proteobacteria, Actinobacteria, the Bacillus/Clostridium group, and the Cytophaga-Flexibacter-Bacteroides group. Approximately half of the culture collection represented genetic diversity confined to four bacterial genera: Pseudomonas, Bacillus, Paenibacillus, and Arthrobacter. A significantly higher proportion of bacterial isolates belonging to Actinobacteria, and ...

Abstract: Often as a result of large-scale military maneuvers in the past, many soils in the Mojave Desert are highly vulnerable to soil compaction, particularly when wet. Previous studies indicate that natural recovery of severely compacted desert soils is extremely slow, and some researchers have suggested that subsurface compaction may not recover. Poorly sorted soils, particularly those with a loamy sand texture, are most vulnerable to soil compaction, and these soils are the most common in alluvial fans of the Mojave Desert. Recovery of compacted soil is expected to vary as a function of precipitation amounts, wetting-and-drying cycles, freeze-thaw cycles, and bioturbation, particularly root growth. Compaction recovery, as estimated using penetration depth and bulk density, was measured at 19 sites with 32 site-time combinations, including the former World War II Army sites of Camps Ibis, Granite, Iron Mountain, Clipper, and Essex. Although compaction at these sites was caused by a wide variety of forces, ranging from human trampling to tank traf®c, the data do not allow segregation of differences in recovery rates for different compaction forces. The recovery rate appears to be logarithmic, with the highest rate of change occurring in the ®rst few decades following abandonment. Some higherelevation sites have completely recovered from soil compaction after 70 years. Using a linear model of recovery, the full recovery time ranges from 92 to 100 years; using a logarithmic model, which asymptotically approaches full recovery, the time required for 85% recovery ranges from 105±124 years.

Abstract: This study aimed at evaluating root growth and shoot dry matter production of soybean (Glycine max (L.) Merrill) cropped after different vegetal species, in a soil with different compaction levels. The experiment was conducted in pots containing a Dark-Red Latosol (Acrortox, loamy sand), and the pots had a layer 3.5 cm (15 to 18.5 cm) thick and 15 cm deep compacted to 1.12, 1.36 and 1.60 Mg m-3. Before soybean, the pots were cropped with black oat, pigeon pea, pearl millet, black mucuna, soybean, grain sorghum and lupin, plus a treatment without plants. These species were grown for 37 to 39 days, when they were cut at soil level, prick in particles of approximately 3 cm length, and left on the soil surface for 40 days. After this, soybean was planted in the pots and was allowed to grow for 28 days after plant emergence. The soybean shoot dry matter weight, root length, diameter and dry matter were evaluated. The previous crop with black oat, pigeon pea and pearl millet favored the soybean root growth below compacted layer soil. Regardless soil compaction, the soybean shoot dry matter was favored by the previous crop.

Abstract: Research was conducted to develop a knowledge-based decision support system to assess the degree of compaction in agricultural soils. The experiments were conducted in a laboratory soil bin at the Asian Institute of Technology in three soils, namely, clay, silty clay loam, and silty loam. The research was likewise aimed to quantify the effect of tire variables (section width, diameter, inflation pressure); soil variables (soil moisture content, initial cone index, initial bulk density); and external variables (travel speed, axle load, number of tire passes) on soil compaction and to develop compaction models for soil compaction assessment. Dimensional analysis technique was used in the development of the compaction models. The soil compaction models were found to provide good predictions of the bulk density and cone index. Using the compaction models and other secondary data, the decision support system was developed to assess the compaction status of the soil in relation to crop yield. The predictions by the decision support system were validated with actual field data from earlier studies and high correlation was observed. Thus, the output of the decision support system may be able to provide useful recommendations for appropriate soil management practices and solutions to site-specific soil compaction problems.

Abstract: Military training exercises in desert areas have resulted in various types of disturbance through time Camp Laguna, located on the US Army Yuma Proving Ground in southwestern Arizona, served as a military base camp during World War II The camp exhibits a variety of historic disturbances, including vehicle traffic (motor pool) and foot traffic (tent rows, commons, and footpaths) The extent of soil and plant recovery that has occurred at Camp Laguna in the 56 years since abandonment was assessed by comparing sites with historic disturbance to an apparently undisturbed control site Vegetative recovery was determined by measuring perennial plant foliar cover and density Soil was characterized by maximum penetration depth measurements and presence of biological soil crusts Soil samples were collected and analyzed for inorganic and organic carbon and total nitrogen content The tent city, disturbed primarily by foot traffic, did not show full recovery of vegetation and biological soil crust to predistur

Abstract: Effects of different soil moisture (soil drought and waterlogging) and soil compaction (1.33 and 1.50 g·cm−3) on the growth and morphological traits of the root system were studied in four breeding forms and seven cultivars of triticale. Morphological changes, including the restriction of root extension, expansion and proliferation of laterals roots, occur in plants grown in different soil moisture and in compact soil. The investigations comprised quantitative and qualitative analyses of a developed plant root system through determining the number, length and dry matter of the particular components of the root system.

Abstract: Several indicators have been identified for the conservation and maintenance of soil criterion in the Montreal Protocol. The objective of this study was to use soil compaction and disturbance measures to determine harvesting impacts at a landscape scale in the boreal forest of Saskatchewan. Forest harvesting impacts were studied pre and postharvest for five harvested sites by (i) sampling soil bulk density (D b ) at prescribed grid-points, and (ii) measuring soil disturbance regimes on two 30-m transects at each grid-point. Mean soil D b in the harvested area increased significantly (8-11%) from pre to postharvest conditions for the two winter-harvested sites at both the 10- and 20-cm depths, while two of the three summer harvested sites also showed significant D b increases (7-15%) at the 10-cm depth. Combining all five sites, showed that after harvest 32% of all the grid-points had an increased D b of >15%. Mean soil D b at a 10-cm depth for roadways and landings was significantly higher (8-14%) than postharvest D b for postharvest levels at four of the five harvested sites. Surface soil disturbance regimes were higher for the summer-harvested sites than that for the winter-harvested sites. Landscape position showed no significant differences in D b between the shoulder, backslope, and footslope positions; however, within each landscape position, significant differences in D b were found between pre and postharvest conditions. Soil D b and soil disturbance regimes measured on a grid basis provided a simple, but reliable method for monitoring soil compaction and disturbance effects from harvesting at a landscape scale.

Abstract: To better understand the response of eastern deciduous forest herbs to microenvironmental changes associated with logging, the effects of experimental light and soil compaction treatments were exam...

Abstract: Soil compaction is a side effect of forest reestablishment practices resulting from use of heavy equipment and site preparation. Soil compaction often alters soil properties resulting in changes in plant-available water. The use of pressure chamber methods to assess plant water stress has two drawbacks: (1) the measurements are not integrative; and (2) the method is difficult to apply extensively to establish seasonal soil water status. We evaluated leaf carbon isotopic composition (delta13C) as a means of assessing effects of soil compaction on water status and growth of young ponderosa pine (Pinus ponderosa var. ponderosa Dougl. ex Laws) stands across a range of soil textures. Leaf delta13C in cellulose and whole foliar tissue were highly correlated. Leaf delta13C in both whole tissue and cellulose (holocellulose) was up to 1.0 per thousand lower in trees growing in non-compacted (NC) loam or clay soils than in compacted (SC) loam or clay soils. Soil compaction had the opposite effect on leaf delta13C in trees growing on sandy loam soil, indicating that compaction increased water availability in this soil type. Tree growth response to compaction also varied with soil texture, with no effect, a negative effect and a positive effect as a result of compaction of loam, clay and sandy loam soils, respectively. There was a significant correlation between 13C signature and tree growth along the range of soil textures. Leaf delta13C trends were correlated with midday stem water potentials. We conclude that leaf delta13C can be used to measure retrospective water status and to assess the impact of site preparation on tree growth. The advantage of the leaf delta13C approach is that it provides an integrative assessment of past water status in different aged leaves.

Abstract: Mechanical resistance caused by soil compaction has significant effect on vegetative and generative plant growth. In this study relation between vegetative and generative growth of sunflower and soil compaction due to wheel traffic was studied. Compaction was applied in the forms of the following treatments: pre-planting in entire plot area (Pre-E), pre-planting intra-rows (Pre-INTRA), post-planting inter-rows (Post-INTER), post-planting intra-rows (Post-INTRA), post-planting in entire plot area (Post-E), and a control (C). During the emergence period, mean emergence dates (MED) and percentage of emerged seedlings (PE) were determined as the characteristics of vegetative growth. During harvesting period, plant height, stem diameter, head diameter and yield were determined as the characteristics of generative growth. MED in Post-E was determined as 10.93 days, which was significantly lower than other treatments, while it was found as 12.93 days for Post-INTER. The lowest PE was found for Post-E with 78% while the highest PE was found for Post-INTER and C treatments with 96%. Compaction caused by Post-E and Pre-E resulted in significantly lower sunflower yields than other treatments. The highest average sunflower yields were 3.2657 Mg ha −1 for treatment C, and 3.2003 Mg ha −1 for treatment Post-INTER, while the lowest average yield was 2.5473 Mg ha −1 for Pre-E treatment, and 2.5440 Mg ha −1 for Post-E treatment.

Abstract: Forest management practices that decrease soil porosity and remove organic matter can reduce site productivity. We evaluated effects of four treatments-merchantable bole harvest (MBH) with three levels of soil compaction (none, light, or heavy), and total woody vegetation harvest plus forest floor removal (FFR)-on fifth-year regeneration and growth of aspen (Populus tremuloides Michx.) growing on soils with similar textures (20-40 cm silt loam over clay loam till) in northern Mimesota (MN) and northeastern British Columbia (BC). Overall mean sucker density was significantly greater in BC than in MN, and mean height was significantly lower. Soil compaction did not affect sucker density in BC, but significantly reduced it in MN, primarily due to late spring treatment. In BC, mean sucker heights generally decreased with level of compaction, but only the differences between non-compacted and the heavy compaction treatments were significant. On the MN plots, sucker heights were reduced significantly by compaction. Treatment responses were similar on both sites: (1) the greatest sucker densities were in the FFR treatment; (2) greatest mean heights were on the non-compacted MBH plots and were significantly greater than those in the FFR treatment; (3) sucker heights generally decreased with level of compaction; and (4) soil compaction decreased the number of suckers that had reached a dbh of 25 mm after five years and will likely delay future stand development and reduce site productivity.

Abstract: A range inventory and condition study was conducted in three altitude zones: lowland (1500-1700m), medium altitude (1700-2000m), and highland (2000-2500m). Each altitude zone was stratified into four or five important grazing areas. One area represented lightly grazed government ranches or parks which were used as benchmarks, another area represented the seasonal grazing areas with an intermediate grazing pressure and the remaining were the heavily grazed roadsides, lakeshores and other communal grazing lands. The range condition assessment was based on the composition of the herbaceous layer, basal cover, litter cover, relative number of seedlings, age distribution of grasses, soil erosion and soil compaction. Dry matter was sampled in the mid-wet season to assess the relationship between available dry matter and range condition. A total of 36 grass species, 3 legume species, 2 sedge species, 15 other herbs and 31 species of trees were identified. The palatable Cenchrus ciliaris was dominant in the bench...

Abstract: Knowledge about soil compaction is increasingly important within agriculture and for environmental protection. The objective of this study is to modify a previous two-parameter model to generalize it to account for preconsolidation effect. A three-parameter model for the relationship between soil bulk density and applied stresses during compaction is presented. It relies on the physical approach of the previous two-parameter model and satisfies the same boundary conditions. The proposed model is applied to compaction data of four silt loam and loam soils. A good fit to data is obtained for a wide range of applied stresses, including stresses less than the preconsolidation stress. The proposed model is compared with the three-parameter version of a recent model. The performances of the two models are similar. The root mean square errors for the four soils ranged between 0.004 to 0.011 for the recent equation and 0.005 to 0.018 for the proposed model. The advantage of the proposed model is that it releases the physically unrealistic constraint in the recent model that the maximal bulk density of a compacted soil is equal to its particle density.

Abstract: As a result of the development of much heavier earth-moving and vibratory roller compaction equipment, soil compaction densities in the field are reaching levels that are not attainable in the laboratory. Higher compaction efforts, routinely seen in the field, not only result in higher unit weights but also lower optimum moisture contents than those found by the modified Proctor test. An experimental study was undertaken to evaluate field and laboratory compaction characteristics and to study laboratory compaction techniques further, such as gyratory compaction, in addition to impact and vibratory compaction, for the laboratory simulation of field compaction of A-3 sandy soils. Field test sections were constructed using typical field compaction techniques of today. Earth pressure cells were installed at the base of each lift to monitor total vertical stresses. A series of laboratory gyratory compaction tests for A-3 soils were conducted. Factors including vertical pressure, gyration angle, and gyration nu...

Abstract: Equipment was developed and tested for injection and broadcast application of municipal solid waste (MSW) compost at selected rates to agricultural land for cotton production. Replicated tests were conducted to determine the effects of injected versus broadcast applied compost on soil parameters (organic matter, soil compaction, and soil fertility) and plant growth. All broadcast application rates of compost significantly reduced hardpan formation in the top 15 cm of soil compared to no compost application. In addition, all rates of injected material significantly reduced soil compaction in the E– and B–horizons (15 to 45 cm). Broadcast application of compost significantly increased soil organic matter content 6 and 12 weeks after planting proportional to the compost application rate. In addition, soil nitrogen content was significantly higher in the broadcast application plots 6 weeks after planting. MSW compost (broadcast or injected) significantly increased plant N, P, and K contents compared to no compost application. Increases in plant nitrogen were proportional to application rates. In addition, injected application increased plant sulfur compared to no compost application. All rates of compost (injected or broadcast applications) significantly increased cotton lint yield compared to no compost application. Yield increase was proportional to application rates. For the 26.9–Mg/ha injected application treatment, yield increases were 23, 24, and 44% in 1997, 1998, and 1999, respectively, compared to no compost application. Vitazyme increased plant N, P, and K contents with no effects on Ca, Mg, and S. Vitazyme increased cotton lint yield 35 kg/ha or 3%. In addition, soil nitrogen content 6 weeks after planting in plots treated with Vitazyme was 12% higher than no–Vitazyme plots.

Abstract: Extensive field tests were conducted on the UC Davis campus in three different types of soil, two operating speeds, and three distinct moisture regimes to determine the effect of soil properties on the soil cutting force measured by the UC Davis soil compaction profile sensor. The results indicated the speed of operation of the profile sensor did not affect the soil cutting force. Although the regression coefficients for the force prediction equations tended to depend on the soil type, they were similar in all three soils tested (clay, sand, and loam). Furthermore, the profile sensor output was well correlated to soil cone index values obtained using a standard cone penetrometer.

Abstract: Equipment was modified and/or developed for broadcast and banded applications of municipal solid waste (MSW) compost at selected rates to agricultural land for cotton production. Replicated tests were conducted for four years to determine the effects of compost on soil properties, crop yield, and nematode populations. Soil type in the test field was Faceville loamy sand. Broadcast application of compost significantly reduced soil compaction in the top 30 cm of soil in cotton rows and row-middles compared to no compost application. Banded application did not affect compaction in the row middles. Columbia lance nematode densities decreased in all compost-treated plots during all four years of study. Several plots treated with compost had nematode densities comparable to those found in the plots treated with Temik 15G nematicide. Compost application significantly increased the soil organic matter content and soil nitrogen content at six and 14 weeks after planting. However, the compost did not affect the lea...

Abstract: These proceedings address engineering issues related to vibratory pile driving and deep soil compaction. Also included are keynote lectures and the documentation of an international vibratory class-A prediction event.

Abstract: The fragile ecological environment of the Gurbantunggut Desert is damaged/disturbed by human activities relating to the development of oil-gas resources and the constructions of desert road and great engineering in the Jungger Basin It was mainly represented: soil compaction, vegetation cleaning, burial of vegetation, oil polluting, and soil disturbance With investigation and experiment, we found that when the way and intensity of engineering activities disturbing the eco-environment does not make its ecological stability disintegrated, the desert vegetation has a capacity of natural recovery To speed and strengthen the process of vegetation recovery efficient assistant measurements, including stabilizing mobile sands promptly and sowing seeds of shrub and herb plants in good time will be needed