Abstract: After attending the 21st Triennial ISTRO Conference in 2018, one of the authors of this letter commented that soil compaction was probably the most common topic aired at the conference. Indeed, soil compaction was mentioned in about 15% of paper and poster titles, with only a small percentage of those addressing issues for its amelioration. Less than 1% of the papers presented at ISTRO 2018 focused on avoiding the problem (e.g., controlling field traffic). ISTRO 2018 is not alone in showing a relative paucity of compaction prevention papers: a very rudimentary Web of Science search shows that publications on the effects of soil compaction outnumber those on controlled traffic by about 13:1 since 1945, and 11:1 in the past five years.

Abstract: Soil compaction in Indian Punjab is an emerging problem affecting crop productivity. Heavy machinery operations or repetitive tillage in fields are main reasons behind this problem. To investigate the direct and residual effect of sub-soiling on soil physical properties and productivity of cotton-wheat cropping system, we conducted a field experiment for three cropping cycles (2014-2017) at two different sites and evaluated a total of five treatments (Control, Sub-soiling at 1.0 m, Sub-soiling at 1.5 m, Cross Sub-soiling at 1.0 m and Cross Sub-soiling at 1.5 m) in complete randomized block design. Results elucidated that any level of sub-soiling if applied once, improved the infiltration rate besides reduction in the bulk density for two years. Consequently, higher root length and increased root mass of cotton under sub-soiled treatments revealed advantages by improvement in yield attributes and seed cotton. Cotton sown after sub-soiling recorded significantly higher seed cotton yield while control exhibited statistically least for two years. Sub-soiling applied prior to cotton sowing in initial year also had beneficial residual effect on succeeding wheat for subsequent two crop cycles. However, during third year, at par yield levels among studied treatments for both the crops indicated that residual effect of sub-soiling persisted no longer beyond two years. Better economic returns and consequently improved benefit: cost ratio clearly revealed that sub-soiling has economic benefits. Our studies concluded that sub-soiling exerted beneficial effect on soil physical properties by reduction in bulk density and improved infiltration rate and any sub-soiling either at 1.0 or 1.5 m once in three years has potential for improving productivity of cotton-wheat cropping system occupying 1.2 million ha in North-Western India.

Abstract: Integrated agricultural production systems with trees, grain crops and forage species are important for land use optimization. However, they can result in non-uniform changes in physical and chemical soil properties. The objective of this work was to evaluate chemical and physical soil properties in a eucalyptus-based agroforestry system. The experiment was conducted in a Red–Yellow Argisol in Southeast Brazil. Eucalyptus (Eucalyptus grandis × E. camoldulensis) seedlings were planted in rows 12.0 m apart, and 2.0 m between plants. For 4 years the inter-row space was cropped to soybeans (Glycine max L. Merrill), Sunn hemp (Crotalaria juncea) and maize (Zea mays L.) in association with palisade grass (Urochloa brizantha). After that, the forage was grazed by beef cattle. Five years after the implementation of the experiment, chemical and physical soil analyses were performed along the profile. Non-uniform changes were observed in fertility and soil physics in the transect between the eucalyptus planting lines, both at the soil surface layers and in depth. Integrated crop/livestock production systems, where eucalyptus is intercropped with annual crops and forage grasses for grazing, results in lower soil fertility near tree lines and up to 100 cm deep over time. Next to the tree line there is an increase in soil compaction and reduced aggregate stability in the uppermost soil layer, while microporosity and soil structuring are increased in the soil deeper layers. These effects are probably due to animal trampling under the trees.

Abstract: The objective of this study was to evaluate the effect of wheeling with two different wheel loads (1.7 and 2.8 Mg) and contrasting wheeling intensities (1x and 10x) on the bearing capacity of a Sta...

Abstract: Changes in the soil quality of urban areas is a critical issue emerging from urban expansion, soil compaction, and other anthropogenic exercises. The evaluation of urban soil quality (USQ) is helpful in landscape and urban planning projects. The present study employed the following USQ models—Cornell Soil Health Test (CSHT) and the Improved Soil Environmental Quality Evaluation (ISEQE) for urban management and planning—to assess USQ in the forest, local, and riverside parks of Ahvaz situated in a saline groundwater area of Iran. The ISEQE model was developed in light of the improvement of the Soil Environmental Quality Evaluation (SEQE) model under the environmental conditions of this area. In this manner, salinity, sodium absorption ratio, compaction, soil structure, and water quality factors were added to SEQE. The parameters of these models were determined on the basis of lab experiments or pedotransfer functions. As indicated by CSHT, average overall quality scores among indicator types in all parks were physical riverside parks > forest parks, which is believed to be connected with lower aggregate stability, lower water storage capacity, and higher soil hardness due to foot traffic, compaction, and lower organic matter. On the other hand, USQ determined by ISEQE models was in various orders: forest parks > local parks > riverside parks. Differences in the assessment of USQ between CSHT and ISEQE models refer to the selected indices in relation to urban environmental pollution factors for assessing USQ in the ISEQE model. Therefore, soils receiving pollutants will be of a lower quality. In this study, the USQ of the local parks with higher vegetation cover was less than that of the forest park as a result of high concentrations of heavy metals in the local parks. In light of field observation, the ISEQE model was the most effective model to assess USQ. Consequently, the ISEQE model can be helpful in determining USQ for green space management in Ahvaz.

Abstract: Abstract The intelligent compaction (IC) technology has been demonstrated as a powerful tool for soil compaction. However, the correlation between IC measurement values (ICMV) and in-situ tests has not been always consistent due to the influence of moisture content. The same density can be obtained at two different moisture contents on either side of the optimum moisture content, whereas without the same modulus. In this study, the influence of moisture contents on ICMV and in-situ point measurement values were examined by both in-situ and laboratory tests. By using the compaction curves from the gyratory compactor and field compaction, the impact of different moisture contents on soil modulus was identified, and the sensitivity of ICMV on the soil density and deflection due to varying moisture contents was explained. Another laboratory test, the vibratory compaction, could offer the target ICMV value from a modulus versus water content curve. Based on the test results in this study, an improved IC soil compaction system including laboratory test validations was suggested to identify the soil compactability and the target value at varying moisture contents.

Abstract: Soil mechanical resistance, aeration, and water availability directly affect plant root growth. The objective of this work was to identify the contribution of mechanical and hydric stresses on maize root elongation, by modeling root growth while taking the dynamics of these stresses in an Oxisol into consideration. The maize crop was cultivated under four compaction levels (soil chiseling, no-tillage system, areas trafficked by a tractor, and trafficked by a harvester), and we present a new model, which allows to distinguish between mechanical and hydric stresses. Root length density profiles, soil bulk density, and soil water retention curves were determined for four compaction levels up to 50 cm in depth. Furthermore, grain yield and shoot biomass of maize were quantified. The new model described the mechanical and hydric stresses during maize growth with field data for the first time in maize crop. Simulations of root length density in 1D and 2D showed adequate agreement with the values measured under field conditions. Simulation makes it possible to identify the interaction between the soil physical conditions and maize root growth. Compared to the no-tillage system, grain yield was reduced due to compaction caused by harvester traffic and by soil chiseling. The root growth was reduced by the occurrence of mechanical and hydric stresses during the crop cycle, the principal stresses were mechanical in origin for areas with agricultural traffic, and water based in areas with soil chiseling. Including mechanical and hydric stresses in root growth models can help to predict future scenarios, and coupling soil biophysical models with weather, soil, and crop responses will help to improve agricultural management.

Abstract: Soil compaction is a major environmental problem that affects plant growth and development. In this study, to further our understanding of its negative effects on plant growth, we investigated the effects of soil compaction on the growth, mineral absorption, and activities of key respiratory enzymes in soybean seedlings. We found that moderate-level soil compaction increased the activities of pyruvate kinase and phosphofructokinase in soybean seedling roots, enhancing the accumulation of P, K, Mg, Ca, and other elements. These accumulated elements, particularly Ca, increased the number of fibrous upper roots, but reduced root length and inhibited plant growth. High-level soil compaction inhibited the accumulation of P, K, Mg, Mn, Fe, Cu, and Zn and increased the accumulation of Ca via decreasing the activities of isocitrate dehydrogenase and cytochrome c oxidase. These effects led to a decreased root cell size, blurred root cell boundaries, and the inhibition of plant growth. Taken together, our results provide a new insight into the mechanisms by which soil compaction inhibits plant growth.

Abstract: It is increasingly acknowledged that stresses can resonate across the boundaries between ecosystems. Salt marshes, vast areas shaped by ocean-shore interactions, constitute prime examples of ecosystems where multiple stress factors arising from one ecosystem act on the local community of another ecosystem. Although it is generally recognized that zonation of plant communities on salt marshes is strongly affected by marine stress factors associated with frequent flooding (salinity, anoxia), it is largely unknown what the isolated and interacting effect are of these different stresses. This calls for experiments to disentangle the relative effects of these single and interacting multiple stresses. In this study, we determined the single and interacting effects of two main abiotic stress factors on salt marshes: salinity and anoxia (as a result of flooding) and one biotic stress factor: soil compaction (as a result of livestock grazing) on the growth of the twelve dominant salt marsh plant species, using a full-factorial experiment. To link the experimental work to distributions of natural plant communities along a natural stress gradient, we related our experimental results to observed plant species distributions on a salt marsh that is exposed to all these three stresses. Whereas salinity strongly affected ten species with two high-marsh species not surviving the highest salinity levels whereas anoxia only consistently affected growth of four species. Interestingly, we observed no synergistic effect of anoxia and salinity in salt marsh plants. Moreover, we observed a trade-off between the amount of aerenchyma and mechanical strength, indicating that species vary in their resistance to soil compaction. Overall, our results suggest that salinity is a major determinant of plant species composition on the salt marsh, followed by anoxia. The importance of soil compaction depends on salt marsh elevation: on the low marsh, increased oxygen supply by aerenchyma seems to outweigh resistance against mechanical stress whereas on the anaerobe low marsh, the reverse applies. Using the experimental data to predict cover of plant species in the field, our results suggest that the combination of plant responses to the various stresses may be a powerful predictor for explaining the plant composition on the salt marsh.

Abstract: A single-acting (3 × 3) 510 mm powered disc harrow was developed to achieve timeliness in operation in the extensively followed rice-wheat cropping system by reducing tillage passes with the proper incorporation of residues left after rice cultivation. Experiments were carried out at forward speeds of 3.69, 4.67 and 6.55 km h−1 corresponding to speed ratios of 4.74, 3.75 and 2.67, respectively and at 90, 120 and 140 mm operating depths in sandy clay loam soil having an average moisture content of 12 ± 0.75% (db) and cone index of 930 ± 40 kPa. Its comparison was also made with conventional free rolling disc tilling which generally requires more passes. Optimum performance in terms of tillage performance index was achieved at speed ratio of 3.75 with a reduction in draft, slip, and clod size by 30–36%, 53.47–72.25% and 39.20–60.73%, respectively at the cost of 14.28–18.40% increase in fuel consumption (l ha−1) when operated at depth of 120 mm as compared to free rolling mode indicating better energy utilization. Effect of multiple passes of tilling on soil compaction beneath the tillage depth (100–200 mm) was also studied from separate experiments. Soil compaction was observed to be 4.71–7.17% and 5.21–6.86% lesser as compared to that obtained with rotavator after first and second passes of tillage, respectively. However, it was about 0.38–3.00% and 3.00–5.32% more compared to free rolling disc tilling after first and second passes, respectively. Reduced number of passes required for preparing seedbed with powered disc justifies its use for carrying out the tillage.

Abstract: Several studies investigated soil disturbances caused on skid trails by forest logging. However, there is still a lack of knowledge about the severity and the distance of disturbances along both sides from the trails. The aims of this study were: i) to investigate the changes in physical and chemical properties of soil along the sides of skidding trails; ii) to measure the effects of soil compaction on of maple seedlings growth. Two levels of trail gradient ( 20%), four levels of traffic frequency (3, 8, 15, and 30 passes) and four distance buffer strip zones (0.5 m intervals from 0 to 2 m in distance) on both sides of skid trail edges were analyzed. Each treatment included three replicate plots. In order to investigate the effect of compaction on seedlings emergence and growth, maple seeds were sown after logging. The results highlighted significant changes in physical and chemical properties of soil for each traffic frequency in the closest buffer strip (from 0 to 0.5 m from the skid trail edges). The largest changes in soil properties were identified at 0.5 m distance zones for a slope gradient >20% after 3, 8, 15, and 30 skidding cycles. The highest changes were recorded on slope category >20%. The higher the soil compaction the lower the germination rate, root length, and stem height of seedlings.

Abstract: Soil compaction is a common consequence of forestry traffic traversing unprotected, moist soils; it decreases porosity and affects hydraulic conductivity even in coarse-textured soils. The aim here was to study root-zone hydrology and vegetation in three microsites (in, between, and beside wheel tracks) 4 to 5 yr after forwarder traffic, on stony and sandy till soils in two clearcuts in northern Sweden. Measurements of soil volumetric water content (VWC), vegetation indicators and one-dimensional hydrological modeling (Hydrus-1D) of wheel tracks and undisturbed soil were conducted. Soil VWC was monitored hourly during 2017 and 2018 in three or four plots along a slope on each site. Soil VWC was also measured once with a portable sensor in 117 plots along two slopes at each site, where the vegetation was recorded and analyzed using Ellenberg indicator indexes. Soil VWC was highest in wheel tracks and lowest between tracks; this was corroborated by the species composition in the wheel tracks (Ellenberg indicator for soil moisture). Bare soil was more frequent in wheel tracks and between tracks than in undisturbed soil. The model simulations indicated that the changed soil hydraulic properties influenced the VWC results in the wheel tracks. However, the differences in average pressure heads in the root zone were small between the microsites and only apparent during dry periods. In the wheel tracks, air-filled porosity was <0.10 m³ m⁻³, indicating insufficient soil aeration during 82% (Site T) and 23% (Site R) of the 2017 growing season. Insufficient aeration could be one explanation for the presence of some still unvegetated areas.

Abstract: Factors affecting soil disturbance caused by harvester and forwarder were studied on mid-grained soils in Finland. Sample plots were harvested using a one-grip harvester. The harvester operator processed the trees outside the strip roads, and the remaining residues were removed to exclude the covering effect of residues. Thereafter, a loaded forwarder made up to 5 passes over the sample plots. The average rut depth after four machine passes was positively correlated to the volumetric water content at a depth of 0–10 cm in mineral soil, as well as the thickness of the organic layer and the harvester rut depth, and negatively correlated with penetration resistance at depths of both 0–20 cm and 5–40 cm. We present 5 models to predict forwarder rut depth. Four include the cumulative mass driven over a measurement point and combinations of penetration resistance, water content and the depth of organic layer. The fifth model includes harvester rut depth and the cumulative overpassed mass and provided the best fit. Changes in the penetration resistance (PR) were highest at depths of 20–40 cm. Increase in BD and VWC decreased PR, which increased with total overdriven mass. After four to five machine passes PR values started to stabilize.

Abstract: We tested the effect of main soil characteristics and tree species on earthworm community composition and abundance in reclaimed spoil heaps planted with five different tree species. Earthworm and soil macroarthropod abundance and biomass were highest in alder plantations, followed by oak plantations. The numbers of soil macrofauna were positively correlated with the total soil N content, which was highest in alder plantation. The correlation was strongest for endogeic earthworms (genus Aporrectodea and Octolasion). Soil moisture, measured in top 10 cm, affected only endogeic species. Other soil variables (pH, Ca) did not have a strong effect on earthworms. The earthworm community composition was similar in alder and oak, with most species occurring at both types of forest; however, in alder forest the epigeic species Dendrobaena octaedra was more common, whilst in oak forest the epigeic earthworms form genus Lumbricus were more abundant (L. rubellus and L. castaneus). The anecic species Aporrectodea longa was more abundant at alder sites, but L. terrestris was more abundant under oak. The alder forest was characteristic by a thick humus layer (10–15 cm), which at oak and larch sites was thinner (4–7 cm) and at pine and spruce stands was absent. Soil compaction was lower under the deciduous trees (alder, oak, larch), than under spruce and pine. We conclude that the alder plantations have most palatable litter and lowest C/N ratio and therefore support the highest numbers of soil macrofauna, which affects the humus layer thickness and soil compaction in the surface layers.

Abstract: Eucalyptus forests play a major role in the world economy, providing raw materials for different purposes. In planted forests, harvest operations performed by heavy machinery may cause severe soil compaction. This study aimed to evaluate the impact of a full‐tree harvesting system in planted eucalyptus forests from Northeastern Brazil. Different soils were evaluated (two Hapludults and one Haplorthod) in two horizons (BA and Bt). We tested different equipment, namely feller buncher, skidder (with traffic intensities of 3, 6, 12 and 16 passes), flail (at different ground‐contact points), grapple saw and loader. The soil physical attributes reflected not only the impact of equipment traffic but also the intrinsic differences between the soils. Bulk density (ranging from 1.36 to 1.80 t m−3 after trafficking) related well to soil class and horizon. Precompression stress (ranging from 203 to 430 kPa) and degree of compaction (76%–94%) following trafficking were well correlated, while increase in bulk density (reaching a maximum of 20%) related more strongly to soil moisture. A contingency table was constructed with the number of compacted samples and further examined by correspondence analysis. Compaction varied according to soil, horizon and equipment, indicating that machine–soil interactions are very specific and demand detailed research under different conditions. The Haplorthod experienced the greatest amount of compaction, whereas the Hapludult‐2 was more resistant (60% and 25% of compacted samples, respectively). The grapple saw and the skidder at higher traffic intensities (12 and 16 passes) exerted the highest mechanical impacts (81% and 67% of compacted samples, respectively).

Abstract: This study was carried out to determine the effects of seedling types (grafted and non-grafted) and different plantation systems (raised-bed and flat planting) on growth, yield and quality ...

Abstract: An alternative method for sustainable production of natural forage resources is the use of silvopastoral systems. The study evaluated the impact of a seasonal sheep silvopastoral system on soil and vegetation of a pine-oak forest. The experiment was conducted in the municipality of Jilotzingo, in the State of Mexico, Mexico. The study was performed in Sierra de Las Cruces Mountains, part of the Trans-Mexican neo-volcanic belt. Altitudes were between 2756 and 2870 m. Climate is temperate sub-humid C(w) with rainfalls from June through September. Average annual precipitation is 2680 mm. The experimental plot was delimited in the pine-oak forest, and this area was grazed rotationally by Creole sheep (n = 8) during the rainy season. The microclimate was characterized by air temperature and relative humidity. Soil compaction, leaf litter and floristic composition were assessed before and after the silvopastoralism. The microclimate was more homogeneous in mixed forest than in grassland without trees for both temperature (coefficient of variation: 21.5 vs 24.8%) and relative humidity (coefficient of variation: 37.6 vs 39.3%). Soil compaction showed no significant differences between the condition before and after the silvopastoralism (1.05 vs 0.98 kg cm−2, respectively; P > 0.05). Leaf litter cover and depth were similar before than after the silvopastoralism (85 vs 88% and 7.6 vs 7.4 cm, respectively; P > 0.05). Plant types before silvopastoralism were 10.5% trees, 40.0% shrubs, and 49.5% herbaceous, presenting a balanced relative importance index, although higher values for Cornus excelsa (27.7%), Garrya laurifolia (17.5%), Symphoricarpos microphyllum (17.1%), Bromus carinatus (16.5%), and Smilax moranensis (16.5%). Micro-histological analysis confirmed that sheep selected herbaceous (S. moranensis), shrubs (C. excelsa, Viburnum stenocalyx), and trees (G. laurifolia, Prunus serotina, Crataegus mexican). Results indicate that the pine-oak forest favors the establishment of a sheep seasonal silvopastoral system. The plant diversity of the pine-oak forest provides sheep with a daily diet of herbaceous, shrubs and trees of nutrient quality. Sheep defoliation is selective and stimulates regrowth of some species sheep consume. They also favor and accelerate incorporation of organic matter into the soil due to feces deposition and trampling.

Abstract: The increase use of Off-Road Vehicles (ORVs) coupled with the absence of control strategies have led to extensive use of natural areas for the creation of recreational trails. We assessed the effects of quad bikes on vegetation and soils in an arid ecosystem subjected to intensive quad bike use. We selected randomly eight traffic sites (disturbed sites) and eight adjacent control sites (undisturbed sites). Plant cover and composition were assessed with the point-intercept method and phytosociological census. In each site, we collected soil samples to assess soil physicochemical properties, including apparent specific weight (ASG), actual specific weight (RSG), porosity, texture, electric conductivity (EC) and pH. Soil compaction was measured at 30 spaces points per site. Plant cover and richness was significant lower in disturbed sites, with only four species present in areas subjected to disturbance. There were also changes in species dominance, with native perennial shrubs and grasses characterizing the undisturbed sites while the disturbed sites were mainly dominated by the invasive exotic herb Salsola kali. ORVs traffic also affected soil physicochemical properties including soil compaction, ASG, EC and soil pH. Soil compaction was more than double in disturbed sites and ASG tended to be higher under this condition. The EC was significantly higher and soil pH was significantly lower in the disturbed sites. Reduced vegetation cover and changes to soils physicochemical properties on quadbike trails highlights the impacts of ORVs in the landscape and the need to develop management strategies to minimize disturbance from ORVs on vegetation and soils.

Abstract: The root surface physicochemical properties affect the ratio and uptake of cations by plants and are influenced by environmental threats. In this study, we examine the effect of soil compaction on the root surface properties and growth of dicotyledonous plants including Fabaceae: lupine, pea, soybean and Brassicaceae: mustard and rape. Undisturbed samples from a Haplic Luvisol derived from loess were taken in cores at 5–15 cm depth from a structurally intact area in the centre of a field (reference R) vs. repeatedly and intensively compacted headland area of the same field (compacted C). The soil dry bulk densities were 1.29 and 1.61 Mg m−3, respectively. Plants were grown in these soil cores for 11 days in a controlled environment chamber. Based on the curves of potentiometric titration, the cation exchange capacity (CEC), the total negative charge (Qtot) and the acid strength of the surface groups responsible for surface charging were determined. The apparent surface area (S) was calculated using the adsorption of water vapour method. Soil compaction resulted in a reduced fraction of strongly acidic groups (pKapp<5.5) in rape and mustard and increased in soybean and pea. The CEC of roots response to soil compaction increased in pea and soybean (by 6.1 and 22.8%, respectively) and decreased in mustard and rape (by 10.5 and 22.9%, respectively). In lupine roots, the number of the surface groups and CEC were not significantly influenced by soil compaction. The S decreased from R to C in lupine and pea (by 32.8 and 20.8%, respectively) and increased in soybean, mustard, and rape (by 10.3, 44.1, and 38.3%, respectively). Fourier-transform infrared (FTIR) spectroscopy was used to describe the chemical composition and structure of plant roots. Soil compaction caused an increase and a decrease of the pectin carboxylic groups in the Fabaceae and Brassicaceae species, respectively. The peaks of lignin and cellulose decreased mostly in the lupine grown under C. Cluster analysis grouped the obtained FTIR spectra in two clusters for the Fabaceae and Brassicaceae species with a higher heterogeneity between the roots from R and C for the former. Among the five dicotyledonous plants used in this study, the lowest relative reduction in root length was recorded for lupine with the thickest roots. Based on results of the surface physicochemical properties and root and shoot growth, incorporating lupine in crop rotation seems to be most reasonable to improve plant growth conditions in compacted headland soil.

Abstract: The compaction quality of soil embankments is critical to the long-term performance of the pavements placed on them. In current quality assurance (QA) practice, state highway agencies (SHAs) rely o...

Abstract: Background Over 25% of the UK land area is covered by uplands, the bulk of which are comprised of blanket bog. This not only contains most of the UK's terrestrial carbon stocks, but also represents 15% of this globally rare habitat. About 30% of UK blanket bog is managed for red grouse by encouraging ling heather (Calluna vulgaris) with rotational burning, which has been linked to habitat degradation, with reduced carbon storage and negative impacts on water storage and quality. Alternative cutting is currently being pursued as a potential restoration management. However, the often used heavy cutting machinery could cause considerable compaction and damage to the peat surface. Two particular issues are (i) a potential increase in bulk density reducing water storage capacity (i.e., less pore volume and peat depth), and (ii) a possible reduction of the micro-topography due to cutting off the tops of hummocks (i.e., protruding clumps or tussocks of sedges). Methods We set up a fully replicated field experiment assessing cutting versus burn management impacts on peat physical and surface properties. Both managements reflected commonly used grouse moor management practice with cutting using heavy tractors fitted with load distributing double wheel and tracks (lowering ground pressure), whilst burning was done manually (setting heather areas alight with flame torches). We assessed management impacts on peat depth, bulk density and peat surface micro-topography which either included pre-management measurements or plot-level data for uncut plots. Total peat depth and bulk density in four 5 cm sections within the top 50 cm was assessed. Micro-topography was determined as the standard deviation of the height offsets measured over several plot transects in relation to the plot peat surface level at the start and end points of each transect. Results Despite an anticipated compaction from the heavy machinery used for cutting, the peat showed resilience and there was no lasting plot-level impact on either peat depth or bulk density. Notably, bulk density showed differences prior to, and thus unrelated to, management, and an overall increasing bulk density, even in uncut plots. However, cutting did reduce the plot micro-topography by about 2 cm, mostly due to removing the tops of hummocks, whereas burnt plots did not differ from uncut plots. Discussion Cutting is suggested as a suitable alternative to burning on grouse moors, although compaction issues might be site specific, depending on the nature of the peat, the machinery used and impacts at resting and turning points (which were not assessed). However, any observed bulk density differences could reflect natural changes in relation to changes in peat moisture, requiring adequate experimental comparisons. Moreover, where micro-topography is a priority, cutting equipment might need to consider the specific ground conditions, which could involve adjusting cutting height and the type of cutting machinery used.

Abstract: For satisfactory performance of soil structures, it is necessary to properly control soil compaction ensuring the physical properties of compacted soil required in design. Usually the dry density ρd and the water content w are controlled in relation to the maximum dry density (ρd)max and the optimum water content wopt determined by laboratory compaction tests on a chosen representative sample at a certain compaction energy level CEL. Although CEL and soil type affect significantly (ρd)max , wopt and physical properties, they change inevitably, sometimes largely, in a given project while field CEL may not match the value used in the laboratory compaction tests. In comparison, the optimum degree of saturation (Sr )opt (i.e., Sr when (ρd)max is obtained) and the normalized compaction curve (i.e., ρd/(ρd)max vs. Sr - (Sr )opt relation) for given CEL and soil type are insensitive to variations in CEL and soil type and they are essentially fixed in a given project. Besides, the stress-strain and hydraulic properties of compacted soil are controlled by ρd and “Sr at the end of compaction relative to (Sr )opt ”. It is proposed to control w and CEL so that Sr = (Sr )opt while ρd becomes large enough to ensure the physical properties required in design fully taking advantage of available field CEL on site. A case history of earth-fill dam construction in Japan following this soil compaction control method is reported.