Abstract: In Swedish forestry, final felling is usually done by a harvester and a forwarder. These machines are heavy and the risk for rutting and soil compaction can be considerable under unfavourable soil conditions. The aim of this study was to evaluate effects of forwarder tyre inflation pressure on rutting and soil compaction after final felling. Three levels of forwarder tyre pressure were studied, 300, 450 and 600 kPa, after 2 and 5 machine passages. The first passage was driven with a 19.7 Mg harvester, and the second to fifth passages with a fully loaded forwarder totalling 37.8 Mg. Rut depths were not significant affected by tyre pressures but increased significantly with the number of machine passages. Soil density was significantly increased by 0.075 Mg m(-3) by the harvester passage. Soil density increased significantly with increasing number of forwarder passages, and tyre pressure did not significantly influence this increase but the interaction between number of forwarder passages and tyre pressure was almost significant. Data suggest that density increases occur earlier in the 600 kPa treatment than in the other treatments. Only parts of an area harvested are trafficked in a normal harvesting operation. Outside the research area approximately 12.5 per cent of the area harvested was covered with ruts. On primary strip roads, which are heavily trafficked, soil compaction cannot be avoided by reducing the tyre pressure. On secondary strip roads, not passed more than once by the forwarder, a low forwarder tyre pressure may reduce soil compaction. Language: en

Abstract: This 2-year study investigated the effects of winter brassica forage crop grazing treatments on soil physical properties on a Fragic Pallic soil, susceptible to compaction, in South Otago, New Zealand. Soil physical measurements including bulk density, percentage of pores >300 μm, macroporosity (air-filled porosity; percentage of pores >30 μm), total porosity, air permeability, and saturated hydraulic conductivity (Ksat) were taken 1.5 and 4 months after completion of winter grazing in year 1, and 2.5 months after grazing in year 2. Treatment main effects in year 1 for macroporosity were ungrazed crop (P < 0.05, 15.5%), established pasture (12.2%), crop on-off grazing (12.8%), crop grazed with back fence (9.6%), and current practice (strip grazing without a back-fence, 8.6%). During both winters the soil was generally more compact at 0.05–0.10 m depth than at 0.15–0.20 m, particularly for the current practice treatment, which may increase the risk of overland flow. Micro-topography differences between hump and hoof-hollow areas for the current practice treatment were also investigated during one sampling, with very low values of Ksat at 0–0.05 m in hoof-hollow areas (P < 0.05, 5 mm/h), compared with hump areas (129 mm/h). Overall, the crop on-off grazing treatment and, with some exceptions, the grazed with back fence treatment have some merit for reducing damage to soil physical properties compared with current practice.

Abstract: One of the limitations for reaching sustainable forest development is related to the traffic of machines and vehicles during harvest operations and wood transport, which may cause soil structure degradation. Seeking a way to analyze this problem, the objective of this study was to determine the traffic effects due to harvest operations and wood transport, on the preconsolidation pressure (sp) in a Typic Acrustox cultivated with eucalyptus. This study was conducted using undisturbed soil samples collected at the 0.1-0.125 m depth. Undisturbed soil samples were used in the uniaxial compression tests. Soil sampling consisted of two stages, before and after the mechanized harvest operations. The traffic effects on the sp in the dry season indicated that the soil compaction process was neither evident nor important. However, in the rainy season the traffic effects on the sp indicated that the operations performed with Harvester and Forwarder caused greater soil compaction than those with Motorized Saw and Manual, which caused less soil compaction.

Abstract: Questions: How does recreational disturbance (human trampling) affect soil characteristics, the performance of the understorey vegetation, and the density and species composition of the soil seed bank in Fagus sylvatica forests? Location: Suburban forests near Basel, northwestern Switzerland. Methods: We compared various soil characteristics and the performance of the understorey vegetation in six beech forest areas frequently disturbed by recreational activities with those in six undisturbed control areas, in spring 2003. In the same forest areas, the soil seed bank was investigated using the seedling emergence method. Samples were obtained from soil cores in January 2003. Results: We found substantial changes in soil compaction, above-ground vegetation and in the soil seed bank due to recreational activities. In frequently visited areas, soil compaction was enhanced which caused a decrease in cover, height and species richness of both herb and shrub layers. Compared with control areas, the numb...

Abstract: A field study conducted during the 2001 and 2002 growing seasons investigated the integration of fungicide applications and tillage methods for reducing root health problems in dry bean (Phaseolus vulgaris) plants by alleviating soil compaction and its potential exacerbation of root disease. Several cultural practices were combined with applications of the strobilurin fungicide azoxystrobin. Soil compaction was created artificially throughout the entire plot area. Six treatments, consisting of four tillage treatments and two combinations of tillage or applications of azoxystrobin, were tested to alleviate the compaction and enhance root health. Tillage treatments included a compacted control with no additional tillage, formation of beds approximately 10 cm above soil surface, zone tillage with an implement using in-row shanks, and both zone tillage and bedding combined. Fungicide treatments utilized the combination of both zone tillage and bedding with fungicide applications, and a fungicide treatment singly. Effects of compaction on plant vigor and disease development and severity were evaluated 67 and 83 days after planting in 2001 and 2002, respectively, by a visual estimation of plot vigor and by destructively sampling and making root and hypocotyl disease ratings on dry bean plants from nonharvest rows. Soil resistance and moisture were measured in plots 80 and 104 days after planting in 2001 and 2002, respectively, to estimate degree of compaction. In both years, Fusarium root rot, caused by Fusarium solani f. sp. phaseoli, was determined to be the main root disease impacting plant health in studies. All measured variables (root disease index, plant vigor ratings, total seed yield, seed size, and soil resistance) were significantly improved by any treatment that included zone tillage prior to planting. No added advantages were observed for decreasing disease or improving root health and plant performance with the use of azoxystrobin or by planting on raised beds. This is the first study to evaluate zone tillage as a method of reducing plant stress and root disease in dry bean plants.

Abstract: Lodging is the permanent displacement of cereal stems from the vertical. Cereal plants growing in the edge rows next to both wheel tracks (‘tramlines’) and the gaps between experimental plots (‘inter-plot spaces’), which are traversed by farm vehicles during planting operations and agrochemical application, are less prone to lodge than plants growing elsewhere in fields and plots. Previous research has attributed this phenomenon to an increase in the stem strength of edge row plants, and hence their resistance to stem lodging, resulting from reduced competition between edge row plants for resources. However, this explanation gives no consideration to the anchorage strength of edge row plants, and hence their resistance to root lodging. Differences in soil and plant characteristics between the edge and centre rows of plots of winter barley ( Hordeum vulgare L.) were examined on sand, silt and clay dominated soil types. Edge rows next to tramlines were investigated on the silt and clay soil types, whereas edge rows next to inter-plot spaces were investigated on the sand soil type. Edge row plants next to both tramlines and inter-plot spaces had 58.8% greater anchorage strength and hence resistance to root lodging than centre row plants. This was attributed to (1) greater soil compaction in the edge rows resulting from wheel traffic in the tramlines and inter-plot spaces, which increased the strength of the soil matrix surrounding the roots, and (2) greater plant root growth in the edge rows resulting from reduced competition. Bulk density, root plate spread and structural rooting depth were 19, 22, and 12% greater, respectively, in the edge rows of all soil types. The results suggest that in order to reduce lodging risk, energies should be directed towards identifying agricultural practices that optimise soil compaction in the seedbed without causing significant limitations to root growth.

Abstract: Soil compaction in the form of a hardpan layer restricts root growth and reduces crop yield throughout the Southeastern United States. However, the depth of this compacted soil layer varies significantly over landscapes. A sampling procedure was developed and evaluated to determine the depth of the hardpan layer in upland soils of Grenada silt loam soil type in this region. Cone index profiles taken with a multiple-probe soil cone penetrometer in three fields were used to measure the hardpan depth and to predict their spatial variation. Continuous treatments of these fields for several years included conventional tillage, no-tillage, segregated traffic, and random traffic. Conventional tillage systems were found to bring the hardpan significantly closer to the soil surface as compared to no-till systems; in trafficked row middles by 0.144 m, directly beneath the rows by 0.165 m, and in no-trafficked row middles by 0.094 m. Little difference in depth of hardpan was found between a no-till field subjected to random traffic and a field where traffic was segregated. However, the effect of this random traffic was found to dramatically reduce the predicted range (which is a geo-statistical measure of field variability) from 43.2 m for the no-till field in the trafficked row middle as compared to 12.4 m for the randomly trafficked no-till field. This may indicate that the depth of the hardpan layer in these soils is brought uniformly closer to the soil surface by the effect of traffic, especially when annual tillage is not practiced which could alter this hardpan depth. This information about the variation of the hardpan layer will greatly assist researchers who are interested in developing site-specific tillage technologies to remedy this soil compaction condition.

Abstract: Tree plantations are sometimes the only alternative in restoring forest landscapes, at least in the short term, especially on very badly degraded soils. Low soil fertility, soil compaction after abandonment from cattle grazing, and invasion by grasses and other aggressive vegetation can be serious obstacles to natural forest regeneration. As the area of degraded lands expands, there is a greater need for tree species that can grow in such conditions and yield useful products (timber, fuelwood, and others) as well as environmental benefits (recovery of ecosystem biodiversity, soil conservation, watershed protection, carbon sequestration). Tree species chosen for a plantation in the context of forest restoration can provide benefits from the tree products (timber, fuelwood, leaf mulches, etc.), and from their ecological effects, for example, nutrient recycling, or attracting birds and other wildlife to the landscape. The choice of a tree species depends on whether both productive and ecological advantages can be achieved in the same system, and in some cases one function, either productive or environmental, may be desired. Within a forest landscape, the preferred choice for restoration would be natural regeneration. Planting would only be a secondary option, to be used in cases where natural regeneration cannot proceed due to the obstacles mentioned above (poor soil conditions, long distances to seed sources, isolation, invasion by aggressive grasses). Within a landscape context, there should be a balance of socioeconomic goals (e.g., productivity) and biodiversity objectives for restoration. The following factors influence species’ choice for plantations: 38 Selecting Tree Species for Plantation

Abstract: Seasonal development of soil microbial activity and bacterial biomass in sub-polar regions was investigated to determine the impacts of biotic and abiotic factors, such as organic matter content, temperature and moisture. The study was performed during spring thaw from three cultivated meadows and two non-cultivated forest sites near Alta, in northern Norway. Samples from all five sites showed increasing respiration rates directly after the spring thaw with soil respiration activity best related to soil organic matter content. However, distributions of bacterial biomass showed fewer similarities to these two parameters. This could be explained by variations of litter exploitation through the biomass. Microbial activity started immediately after the thaw while root growth had a longer time lag. An influence of root development on soil microbes was proposed for sites where microorganisms and roots had a tight relationship caused by a more intensive root structure. Also a reduction of microbial activity due to soil compaction in the samples from a wheel track could not be observed under laboratory conditions. New methodological approaches of differential staining for live and dead organisms were applied in order to follow changes within the microbial community. Under laboratory conditions freeze and thaw cycles showed a damaging influence on parts of the soil bacteria. Additionally, different patterns for active vs.non-active bacteria were noticeable after freeze-thaw cycles.

Abstract: Forest disturbances associated with harvesting activities can affect soil properties and soil respiration. A soda-lime technique was used to measure soil carbon dioxide (CO2) efflux rates in clearcut plots of a Missouri oak-hickory (Quercus spp. L.-Carya spp. Nutt.) forest 4 years after being treated with two levels of forest biomass removal and two levels of compaction, both separate and in combinations, and an uncut control. Respiration rates were measured twice a month from mid-April through October. Soil CO2 efflux rates were significantly (p < 0.001) higher in uncut control plots than in clearcut plots, but differences between biomass removal or soil compaction treatments were not significant. Soil CO2 efflux rates were positively correlated with soil temperature. The lack of difference between soil CO2 efflux rates in weed control and no weed control subplots suggests that several more years may be required for regenerating clearcut plots to produce soil respiration rates similar to those in uncut control plots.

Abstract: This paper presents the findings of a digital image analysis based study of clay fills, compacted with dynamic compaction for a building foundation in northeast Beijing, People’s Republic of China. Three levels of compaction energy were used at three compaction pits, respectively. Ground settlements and soil density increased with the number of dynamic impact blows. Microstructures of dry clay fill samples from the pits were examined with a scanning electronic microscope (SEM). Their microstructural parameters were further measured and analyzed quantitatively using digital image analysis. The clay SEM images are automatically converted into ternary images representing particles, pores, and contact zones for effective and efficient calculation of the clay microstructural parameters. The effect of dynamic compaction on the clay microstructural properties at different blow numbers and compaction energy levels is examined. Analysis revealed that the changes of the soil microstructural properties have a good c...

Abstract: The effects of intensity of treading by sheep during winter (0, 900, and 1800 sheep ha–1) on soil physical properties and pasture yield were studied for 3 years on a newly sown ryegrass‐white clover pasture in Southland. Intensive winter treading in wet conditions caused considerable visual soil pugging and pasture damage. Macroporosity (percentage of pores > 30 μm) at 0–5 cm was significantly reduced from 11.1% in the control to 10.2% and 9.4% in the 900 and 1800 sheep ha–1 treatments, respectively. Winter treading reduced soil earthworm numbers at 0–5 cm, but not at 0–20 cm. Soil macroporosity showed some improvement between the post‐winter‐treading and summer periods from natural soil rejuvenation processes. Soil macroporosity at 0–5 cm significantly increased from 9.4% after the winter treading periods to 11.3% in the summer periods. Macroporosity at 5–10 cm showed a decreasing trend after sowing, while saturated hydraulic conductivity increased during the 3‐year period.

Abstract: Root traits and growth of spreading orach and common lambsquarters were compared in response to soil compaction, drought, and waterlogging under controlled environment conditions. On the basis of the typical habitats occupied, the hypothesis was that spreading orach would be more tolerant of compaction and waterlogging and common lambsquarters more tolerant of drought. When grown in buckets with two soil bulk densities (1.2 and 1.6 g cm−3) for 8 wk, the two species responded similarly to compaction, with the fraction of fine roots reduced by 10%, total root length by 70%, root and shoot dry weight and leaf area by 50 to 60%, and plant height by 30% at the high compared with the low bulk density. When grown for 6 wk in soil columns 1 m long, which were watered daily or allowed to dry, common lambsquarters was deeper rooted than spreading orach at both moisture levels and better able to sustain growth in the drying columns. The watering regime did not alter the rooting depth of either species. Tota...

Abstract: A study was conducted to examine the impacts of land reclamation and management practices on the saturated infiltration rates (Ks) and bulk densities (BD) of soils in reclaimed surface coal mines of Wyoming. The use of direct- hauled topsoil vs. stockpiled topsoil, hay mulch vs. stubble mulch, grazing vs. no- grazing, and standard seed mixes (grass seeding) vs. shrub mosaic seed mixes as surface coal mineland reclamation practices were studied in five coal mines of the Powder River Basin, the Green River Coal Region and the Hanna Coal Field in Wyoming. Results from the reclaimed sites with the above listed management practices were compared to each other and with representative soils from adjacent native undisturbed sites. In all the study sites, native undisturbed soils had the lowest BD and the highest Ks compared to reclaimed soils. At Jim Bridger mine, results indicated no differences in BD and Ks between stockpiled and directly hauled soils. At the Belle Ayre mine, there was no significant difference in Ks between reclaimed soils and native undisturbed soil. At Seminoe mine, reclaimed stubble mulched soil had greater Ks (9.208 mm/min) than native undisturbed soil Ks (6.042 mm/min). At Jacob's Ranch, ungrazed soils had greater Ks (6.958 mm/min) than grazed soils Ks (3.350 mm/min) and native undisturbed soils (3.833 mm/min). BD at 0-5 cm for grazed soils was also greater (1.462 g/cm 3 ) than for ungrazed soils (1.255 g/cm 3 ) . Native undisturbed soils had the lowest BD (1.116 g/cm 3 ) averaged over all depths. Although native undisturbed BDs were generally lower, their Ks were not always greater. These results suggest that removal and manipulation of soil during mining accompanied by heavy machinery traffic over reapplied topsoil during reclamation may cause some degree of soil compaction relative to undisturbed sites. However, it can be concluded that land reclamation and management measures taken during and after mining may help to improve infiltration rates.

Abstract: The effects of machinery traffic on soil attributes following the adoption of no-till systems in tropical environments are still poorly documented. Numerous questions persist about the dynamic variation of soil structure and its interaction with machinery and equipments. The present study had the objective to evaluate the effect of time of adoption of no-tillage system and compare them to a conventionally tilled soil and a soil under a native forest using soil compressibility models. The evaluated systems were: PD1 (one year of adoption of no-tillage), PD4 (no-tillage for four years), PD5 (no-tillage for five years), PD12 (no-tillage for 12 years), one system under conventional tillage (PC for 18 years ) and another without use or intervention (native forest-MN) on a Dystroferric Red Nitosol. The time since adoption of the no-tillage system altered the soil compression performance at both depths (0-5 and 10-15 cm) through changes in the compression index and pre-consolidation pressure. The smallest capacity of load support was observed at the 0-5 cm depth and the highest at the 10-15 cm depth. Soils of all systems proved more susceptible to soil compaction at the 0-5 cm depth than at the 10-15 cm depth. The load support capacity of soils under no-tillage and conventional tillage systems presented the following sequence: PD5 < PD12 < PD1 < PD4 @ PC for the 0-5 cm depth and MN @ PD12 < PC @ PD4 < PD5 for the 10-15 cm depth. The PD1 system presented a distinct behavior.

Abstract: Excessive settlements occur in granular soils where specified field compaction is based on Standard Proctor (ASTM D 698, AASHTO T 99) maximum dry unit weights. A laboratory test program evaluated alternative test methods for granular soil compaction control and showed that a Vibrating Hammer method (similar to British Standard BS 1377:1975, Test 14) has great promise for laboratory compaction of these soils. A One-Point Vibrating Hammer test on an oven-dried soil sample provides the maximum dry unit weight and water content range for effective field compaction of granular soils. The maximum dry unit weight obtained is comparable to that from other current methods such as the Vibrating Table test (ASTM D 4253) and the Modified Proctor test (D 1557), and is greater than that from the Standard Proctor test (ASTM D 698). This test method is applicable to a broader range of soils than current vibratory table compaction tests (up to 35 percent nonplastic fines and up to 15 percent plastic fines). The equ ipment is relatively inexpensive and is portable enough to be taken into the field. The test is easier and quicker to perform than the other methods mentioned above and provides reproducible and consistent results. The paper also introduces a simple cali bration procedure to check that the vibrating hammer is supplying sufficient energy to the soil.

Abstract: The agricultural use of soils usually relies on the use of heavy machinery that cause soil compaction, affecting the amount of air and water available for plants. The present study was carried out in the year 2000 and aimed at studying the performance of aggregates of an Amazon Oxisol under mechanical compression and that were subjected to varying degrees of matric potential. Humid and undisturbed tropical forest soil samples were collected from the A horizon (10 cm deep) and B horizon (150 cm deep). In the laboratory, the samples were broken into fragments and sieved to obtain 2 to 3 mm aggregates, which were placed in equilibrium under four matric potentials. Thereafter, they were exposed to uni-dimensional compression with pressures varying from 32 to 1.000 kPa. The highest compressibility of the aggregates for horizon A as well as for horizon B was observed for a matric potential of -32 kPa (soil moisture of 0.38 kg kg-1), and the lowest for the potentials of -1 kPa and -1.000 kPa (soil moistures of 0.32 and 0.30 kg kg-1, respectively), indicating that the soil should not be managed when moisture approximates 0.38 kg kg-1. The largest reduction in aggregate volume occurred under a mechanical pressure below 400 kPa. This indicates that these soils are quite prone to compaction, specially the aggregates of the A horizon (10 cm), possibly because of better structural conditions owing to the higher organic matter content.

Abstract: Little is known of the effects of mechanized harvesting on ground conditions during the harvesting of short-rotation coppice. An investigation was therefore carried out in which different vehicles were used to simulate the effects of wheeling from heavy and light harvesters and crop removal equipment. The experiments were carried out on sites containing Bowles hybrid willow ( Salix viminalis ) and poplars ( Populas rap ) and on clay and sandy loam soils. The effect of different vehicles was assessed in terms of rut damage and direct measurements of soil stress using buried sensors. Maximum stresses measured 0.3 m below tractor wheels ranged from 50 to 200 kPa, but the greatest stresses, 350 kPa, were recorded under laden trailer wheels. Maximum stresses measured beneath crawler tracks were only 25 kPa. Similarly, substantial ruts were caused by vehicles simulating wheeled harvesters, the deepest ruts were caused by laden trailers but crawler tracks created least disturbance. Wheeling was carried out at soil water contents above the plastic limit and the deepest ruts were created on clay rather than sandy loam soil. The effects of the stresses generated in the soil could impede future root growth, and the deeper ruts formed could damage existing root systems of coppice.

Abstract: Compaction of soils is known to reduce crop yield. The impacts on crop yield may be imparted through effects on plant nutrition. Thus, interactive effects of different levels of soil compaction (bulk densities of 1.4, 1.65, and 1.8 Mg m−3), organic matter (0, 20, and 40 Mg ha−1), and phosphorus (P) (0, 25, and 50 mg kg−1 P) on growth and P accumulation of Berseem or Egyptian clover (Trifolium alexandrimum L.) were investigated in a factorial experiment with a randomized block design. Results indicated that as soil compaction increased, the dry mass of shoots and roots, root length, and P accumulation in shoots and roots decreased. Application of organic matter reduced soil compactability. Organic matter and P additions significantly increased the dry mass of shoots and roots, root length, P accumulation in roots and shoots, and total P accumulation by clover. The highest dry mass of shoots and P accumulation by the crop were obtained with the lowest soil compaction level that received 50 mg kg−1 ...

Abstract: Strength and deformation parameters of a compacted soil are known to be related to soil type and moisture. However, little attention has been directed towards understanding the influence of compaction energy on soil type and moisture. This paper describes a laboratory study conducted to evaluate the relationship between soil type, soil moisture content, and compaction energy on five cohesive soil types. Specimens were compacted with impact energy at levels of 355, 592 (standard Proctor), 987, 1643, and 2693 kJ/m3 (modified Proctor) over a wide range of moisture contents to determine dry unit weight, unconfined compressive strength, and the secant (50% strain) stiffness. In total, 125 Proctor tests and 95 unconfined compression tests were performed. At each energy level, a soil specimen was tested at four to five moisture contents with respect to its standard Proctor moisture range. In addition, 48 consolidated undrained triaxial tests were performed at the five energy levels and four moisture content levels for a silt to evaluate changes in effective stress shear strength parameters. This paper summarizes the results of statistical analyses performed on all tests conducted. The models that best explain variability in dry unit weight, strength, and stiffness are presented. Models are presented for each individual soil type and for all soils grouped together. Independent variables used in the modeling include compaction energy, moisture content, Atterberg limits, material passing the No. 200 sieve, and clay fraction. Results show that compaction energy is a key factor in determining soil strength and stiffness parameters and should be considered during the planning phase of any earthwork construction operation.