Abstract: Soil compaction is generally regarded as negative for crop growth, although many studies show a curvilinear relationship between bulk density and crop yield. In the literature, there are few systematic studies of differences between crop species in their response to compaction. This study used results from short-term Swedish field experiments to analyse the sensitivity of different crops to compaction. The crops included were barley ( Hordeum vulgare L.), horse bean ( Vicia faba L.), oilseed rape ( Brassica napus L.), oilseed turnip rape ( Brassica rapa ssp. oleifera (DC.) Metzg.), oats ( Avena sativa L.), peas ( Pisum sativum L.), potato ( Solanum tuberosum L.), rye ( Secale cereale L.), sugar beet ( Beta vulgaris L.), and wheat ( Triticum aestivum L.). In total 39 experiments were analysed, in two series with spring-sown crops and one with autumn-sown crops, all on soils loosened by mouldboard ploughing. The experiments included different levels of tractor traffic applied track-by-track at the time of seedbed preparation, and a control treatment with no traffic. Bulk density was determined after traffic and expressed as degree of compactness (DC), which is the bulk density in percentage of a reference density. With moderate recompaction, wheat and barley showed a yield increase compared with untrafficked soil, while other crops showed little or no yield increase on average. Oats reacted more negatively to compaction than wheat and barley. Monocots generally had a higher optimum DC than dicots, but the differences were small. Yield losses at high DC values were greater for dicots, especially pea and horse bean crops, although for sugar beet and oilseed rape there was no clear difference compared with cereal crops.

Abstract: Mention of trade names, proprietary products, or specific equipment is intended for reader information only and constitutes neither a guarantee nor warranty by the ARS-USDA, nor does it imply approval of the product named to the exclusion of other products. Soil Sci. Soc. Am. J. 78:737–744 doi:10.2136/sssaj2013.07.0280 Received 12 July 2013. *Corresponding author (jay.jabro@ars.usda.gov). © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher. Repeated Freeze-Thaw Cycle Effects on Soil Compaction in a Clay Loam in Northeastern Montana Soil Physics

Abstract: The rhizosphere, the soil immediately surrounding roots, provides a critical bridge for water and nutrient uptake. The rhizosphere is influenced by various forms of root–soil interactions of which mechanical deformation due to root growth and its effects on the hydraulics of the rhizosphere are the least studied. In this work, we focus on developing new experimental and numerical tools to assess these changes. This study combines X-ray micro-tomography (XMT) with coupled numerical simulation of fluid and soil deformation in the rhizosphere. The study provides a new set of tools to mechanistically investigate root-induced rhizosphere compaction and its effect on root water uptake. The numerical simulator was tested on highly deformable soil to document its ability to handle a large degree of strain. Our experimental results indicate that measured rhizosphere compaction by roots via localized soil compaction increased the simulated water flow to the roots by 27 % as compared to an uncompacted fine-textured soil of low bulk density characteristic of seed beds or forest topsoils. This increased water flow primarily occurred due to local deformation of the soil aggregates as seen in the XMT images, which increased hydraulic conductivity of the soil. Further simulated root growth and deformation beyond that observed in the XMT images led to water uptake enhancement of ~50 % beyond that due to root diameter increase alone and demonstrated the positive benefits of root compaction in low density soils. The development of numerical models to quantify the coupling of root driven compaction and fluid flow provides new tools to improve the understanding of plant water uptake, nutrient availability and agricultural efficiency. This study demonstrated that plants, particularly during early growth in highly deformable low density soils, are involved in active mechanical management of their surroundings. These modeling approaches may now be used to quantify compaction and root growth impacts in a wide range of soils.

Abstract: The impact of heterogeneous soil compaction in combination with nutrient availability on root system architecture and root growth dynamics has scarcely been investigated. We quantified changes of barley (Hordeum vulgare L.) root and shoot growth during the first 3 weeks of growth in a controlled-environment chamber. Vertically divided split-root rhizotrons were filled either uniformly with loose or compacted peat, or heterogeneously with loose peat in one compartment and compacted peat in the other. We investigated the following questions. (a) Can growth processes affected by soil compaction be mimicked in our system? (b) Do plants show compensatory growth effects when exposed to heterogeneous soil compaction? (c) Does localised fertiliser application affect root systems' responses to compaction? We observed compensatory effects regarding root system architecture and root growth dynamics due to vertically heterogeneous soil compaction. Roots grew deeper and lateral roots emerged earlier in the loose compartment of the split-root treatment compared with uniform treatments. When fertiliser was applied only via the compacted compartment in the split-root treatment, more lateral roots were initiated in the compacted compartment and lateral root formation started a few days earlier than in the uniform treatments. Consequently, the first days after exposure to heterogeneous soil conditions are critical for the analysis of underlying physiological responses.

Abstract: Reducing the traffic intensity and the mitigation of unnecessary traffic especially with heavy vehicles and high ground contact stress are basic requirements for preventing harmful soil compaction. This study focuses on quantifying traffic intensity and evaluating soil compaction risks during silage maize (Zea mays L.) harvest. Based on GPS data recorded by farm vehicles used on two study fields, wheel track patterns and the corresponding contact stresses have been modeled, using empirical approaches. Modeling the wheel track patterns considers the vehicle characteristics (e. g., axle width, tire type and size, and machine weight), and the changes in wheel load and contact stress during loading. The modeling results reveal that up to 62.8% of the field area had been trafficked during a single harvest. Between 16.4 and 26.8% of the field had been subjected to contact stresses exceeding 100 kPa. The actual vehicle-induced stresses calculated for the wheel track patterns were applied to model the stress distribution inside of the soil according to a method described by Horn and Fleige. The susceptibility of wheeled soil horizons to soil compaction was derived from a ratio between precompression stress and soil stress, which provides a useful measure of effective soil strength. Based on three scenarios, this article discusses how geospatial simulations might contribute to soil sustainability through an improved management of field traffic. Simulation results suggest that the risk of plastic subsoil deformation might be reduced from about 70% (related to the wheel track area) at water saturation to < 5% at a matric potential of pF 2.5.

Abstract: [1] Grassland and pastures are important land uses in subalpine and alpine environments. They are typically subjected to management practices that can change the biophysical structure of the canopy through defoliation and can alter soil hydraulic properties. These modifications have the potential to impact hydrological and energy fluxes as well as the primary productivity of grasslands. We investigate how a series of management practices, such as grass cut, grazing, and the consequent soil compaction due to treading by animals are affecting water resources, flood generation, and grassland productivity in a subalpine region. Results are obtained using a mechanistic ecohydrological model, Tethys-Chloris. The model is first confirmed using energy, water, and carbon fluxes measured at three eddy covariance stations over grasslands in Switzerland and discharge measured in a small experimental catchment. A series of virtual experiments are then designed to elucidate the importance of various management scenarios at the plot and catchment scales. Results show that only severe management actions such as low grass cuts or heavy grazing are able to influence considerably the long-term hydrological behavior. Moderate management practices are typically unable to modify the system response in terms of energy and water fluxes. An important short-term effect is represented by animal-induced soil compaction that can reduce infiltration capacity leading to peak flow considerably higher than in undisturbed conditions. The productivity of vegetation in absence of nutrient limitation is considerably affected by the different management scenarios with tolerable disturbances that lead to higher aboveground net primary production.

Abstract: This article presents a numerical approach for modeling of the compaction-induced stresses on the analyses of geosynthetic reinforced soil (GRS) walls. The modeling of the backfill compaction stresses was described and analyses were performed using this suggested procedure. Two distribution loads at the top and bottom of each soil layer were used to simulate the vertical induced stress due to backfill soil compaction. The suggested procedure was validated with the results of a wrapped-faced full-scale reinforced soil wall performed at the Geotechnical Laboratory of COPPE/UFRJ. The results of the simulation using this procedure were compared with another procedure reported in the literature. Parametric studies were carried out to verify the effect of compaction induced stress and surcharge loads on the behavior of GRS walls. Results show that the compaction procedure suggested in the present paper was able to properly represent the measured values of the summation of the maximum tension in the reinforcement and lateral movements. It was verified that the compaction procedure used in the literature overestimated the measured values, and this discrepancy increases with depth and also with compaction effort.

Abstract: Australian cotton growers have rapidly adopted new picking technology of round module balers on dual tyres. These machines weigh twice that of previous basket pickers, usually on single tyres, being replaced. This raises some concern about implications for subsoil compaction (>0.4 m depth) from harvest traffic. The objective of this study was to quantify changes in soil strength due to picker traffic during harvest. Measurements of soil strength were undertaken before and after traffic by new round module baler (32 t) and current basket (16 t) pickers during one cotton picking season. Soil cone resistance, water content and plastic limit (PL) were measured in the upper 0.6 m depth at eight sites during normal picking operations. Results showed that soil strength increased after traffic of either picker compared with before traffic and increases were detected to a depth of 0.6 m. Despite differences in soils and profile water content, the change in strength was similar under the round module baler and the basket pickers. A zone of greater soil strength (3 MPa) occurred closer to the soil surface under the round module baler (0.3 m) compared with the basket picker (0.4 m). Zones of increased soil strength were also detected at 0.6 m depth under both pickers indicating possible subsoil compaction. The OZCOT cotton simulation model was used to determine the frequency at which the soil profile was wetter than the PL for both irrigated and dryland systems. Simulations showed that the soil profile could be expected to be wetter than the PL 75% and 14% of the time under irrigated and dryland systems, respectively, at harvest over the period from 1960 to 2012. This indicates that cotton picking in irrigated systems has a high probability of occurring when the soil is susceptible to compaction, with the risk of subsoil compaction greater with the round module baler.

Abstract: Soil compaction due to the use of heavy machinery for timber harvesting has become a widespread problem in forestry. However, only few studies deal with the regeneration of compacted forest soils. In the present study, we examined the potential of accelerating soil regeneration by planting black alder trees (Alnus glutinosa (L.) Gaertn.) in skid lane tracks. In 2003, seedlings were planted into the rut beds of severely compacted skid lanes in two Swiss forest sites. In addition, some of the ruts were filled with compost. In 2009 and 2010, we assessed the success of these measures by analysing physical parameters of soil structure (bulk density, total and coarse porosity and air permeability), root densities and tree growth. Tree growth was exceptionally strong on the skid lanes. Total and coarse soil porosity and air permeability showed significant increase in planted skid lanes as compared to untreated control subplots, approaching values found for untrafficked soil in the immediate vicinity. All soil physical parameters were closely correlated to root mass density. Compost application enhanced tree growth and soil structure regeneration on one site, but had a retarding effect on the other site. Planting black alders has great potential as an environmentally friendly measure to accelerate the structural regeneration of compacted forest soils in temperate humid climates.

Abstract: With the increasing of population and the reduction of available land, more and more construction of buildings and other civil engineering structures have to be carried out on weak or soft soil. Owing to such soil of poor shear strength and high swelling & shrinkage, a great diversity of ground improvement techniques such as soil stabilization and reinforcement are employed to improve mechanical behavior of soil, thereby enhancing the reliability of construction. Black cotton soil is one of the major soil deposits of India. They exhibit high swelling and shrinking when exposed to changes in moisture content and hence have been found to be most troublesome from engineering considerations. Stabilization occurs when lime is added to black cotton soil and a pozzolanic reaction takes place. The hydrated lime reacts with the clay particles and permanently transforms them into a strong cementations matrix. Black cotton soil showing low to medium swelling potential from Rajkot Gujarat was used for determining the basic properties of the soil. Changes in various soil properties such as Liquid limit, Plastic Limit, Maximum Dry Density, Optimum Moisture Content, and California Bearing Ratio were studied.

Abstract: In the south-central region of Brazil, there is a trend toward reducing the sugarcane inter-harvest period and increasing traffic of heavy harvesting machinery on soil with high water content, which may intensify the compaction process. In this study, we assessed the structural changes of a distroferric Red Latosol (Oxisol) by monitoring soil water content as a function of the Least Limiting Water Range (LLWR) and quantified its effects on the crop yield and industrial quality of the first ratoon crop of sugarcane cultivars with different maturation cycles. Three cultivars (RB 83-5054, RB 84-5210 and RB 86-7515) were subjected to four levels of soil compaction brought about by a differing number of passes of a farm tractor (T0 = soil not trafficked, T2 = 2 passes, T10 = 10 passes, and T20 = 20 passes of the tractor in the same place) in a 3 × 4 factorial arrangement with three replications. The deleterious effects on the soil structure from the farm machinery traffic were limited to the surface layer (0-10 cm) of the inter-row area of the ratoon crop. The LLWR dropped to nearly zero after 20 tractor passes between the cane rows. We detected differences among the cultivars studied; cultivar RB 86-7515 stood out for its industrial processing quality, regardless of the level of soil compaction. Monitoring of soil moisture in the crop showed exposure to water stress conditions, although soil compaction did not affect the production variables of the sugarcane cultivars. We thus conclude that the absence of traffic on the plant row maintained suitable soil conditions for plant development and may have offset the harmful effects of soil compaction shown by the high values for bulk density between the rows of the sugarcane cultivars.

Abstract: Soil physical properties, plant growth, and water availability in the soil are factors that interact in response to changes in soil structure. Knowing how these factors interact in field conditions is of great importance for management of soil compaction for crop yield. In this paper, three levels of soil compaction, with and without irrigation, were assessed in regard to growth and yield of common bean (Phaseolus vulgaris L.). The probability of interaction between soil compaction and irrigation was 88 % for leaf area index (LAI) and 86 % for yield. However, water availability led to distinct responses between growth and grain yield at different levels of soil compaction. From the lowest to the highest level of soil compaction, the increase in soil water availability due to irrigation (120 mm) resulted in decreasing gains in LAI (1.8, 0.8, and 0.3) and increasing gains in grain yield (695, 1042, and 1198 kg ha-1). Thus, with the increase in soil compaction, the soil water content exhibits decreasing control on plant growth, but the yield remains more elastic than growth. Thus, the compensation in common bean growth through the increase in water content declined as the state of compaction increased, but compensation in grain yield was greater than in growth. Consequently, the use of different plant characteristic provides different critical levels to physical indicators of soil compaction. Thus, the choice of irrigating and/or chiseling depends on knowing how the harvested part of a plant responds to compaction and soil water availability in combination.

Abstract: The invention relates to a method of, and system (200) for, obtaining an indication of the soil strength of soil (100) over which a compactor roller (10) travels. The method includes determining the depth to which a drum (14) of the compactor roller (10) penetrates into and depresses the soil (100) when the compactor roller (10) travels over a soil surface. The system (200) includes a compactor roller (10), a measuring arrangement (40) and a processor (50) which is operatively connected to the measuring arrangement (40) and which is configured to process data received from the measuring arrangement (40). The measuring arrangement (40) includes an inertia! measurement unit (70, 72, 74) which is operatively connected to the compactor roller (10), wherein the arrangement (40) is configured to obtain an indication of the soil strength of soil (100) over which the compactor roller (10) travels during operation, by determining the depth to which the drum (14) penetrates into and depresses the soil (100) over which it travels.

Abstract: Soil organic carbon (SOC) stocks and fluxes in forest ecosystems are influenced by natural and human disturbances In the tropical regions the highest impacts on disturbance in forest C cycles are related to human activities such as conversion of natural lands to cropland and pasture areas and to forest plantations The disturbances in the forest C cycles will release CO2 emissions to the atmosphere triggering global warming In this study the focus was set in subtropical soils in Brazil, south extreme region of Bahia The aim of the study was to investigate whether reforestation of Eucalyptus plantations under former pasture areas will help mitigate climate change through carbon sequestration Field measurements were made on the total SOC and nitrogen amount, along with soil physical and chemical attributes, between different land use systems , also to analyze if there will be any positive effect on soil chemical and physical properties with the reforestation The study areas included the intact rainforest Mata Atlântica called Native Forest, as a reference, pasture areas, which have been settled in the past from deforestation of Mata Atlântica, and Eucalyptus plantations recently reforested under former pasture areas aimed for paper and pulp production With the field measurements and simulated amounts of SOC using the CO-Fix V32 programme it could be compared the effects on SOC sequestration in short and long term ( max 50 years) under the Eucalyptus reforestation Our results show significant differences with lower SOC, higher pH and soil compaction under pasture areas after deforestation of the rain forest Meanwhile reforestation with eucalypt plantations on former pasture areas did not lead to any significant total nitrogen and total SOC accumulations in short term However, the simulated results showed that Eucalyptus reforestation will play a role on carbon sequestration in soils with time After 20 years of production the Eucalyptus forests will gain higher SOC accumulations than in pasture systems After 50 years the simulated SOC accumulation showed closer values to the amounts measured on field under the Native Forest areas These results indicate that the Eucalyptus plantations are efficient at sequester carbon in the soil in the long term However, the comparison with the Native Forest field measurements should be carefully interpret since the measurements on field were made within a certain depth while the program shows the total amount with no limited soil depth For a complete comparison it remains to take deeper soil samples in the field measurements

Abstract: The magnitude of yield reduction due to soil compaction is variable and depends on the soil type, fertility status and other soil and environmental factors. The present investigation was carried out at the research farm, Department of Soil Science, Punjab Agricultural University, Ludhiana. The experiment was conducted to evaluate the effect of different levels of subsoil compaction and nitrogen fertilization on maize phenology, yield and heat use efficiency. The C2 (subsoil bulk density (Db)= >1.8 Mg m-3) treatment reduced yield by 15.5 and 24.3 % and heat use efficiency (HUE) by 15.2 and 20.9 % than that in C0 (subsoil Db=1.55-1.65 Mg m-3) treatment during the year 2012 and 2013, respectively. The tasseling and silking stage was delayed, while physiological maturity was advanced under C2 subsoil compaction treatment than that in C0 treatment. The N2 treatment improved the yield by 14.9 and 13.9 % and HUE by 15.2 and 14.3 % than that in N0 treatment during the year 2012 and 2013, respectively. Maize took more days to reach physiological maturity under N2 treatment as compared to N0 treatment. Phenothermal index (PTI) showed that crop reached different stages earlier under C1 and C2 than that of C0. The data emphasized the need to take care of soil strength and soil temperature related parameters along with weather conditions for better yield prediction using thermal time.

Abstract: Expansive soils undergo heave and settlement due to soil moisture changes, causing differential movement to light weight structures built on them. These movements may be significant when extreme weather conditions such as prolonged droughts are encountered. Indeed, there have been major concerns regarding footing movements and cracks in houses in Victoria following the breaking of the last prolonged drought experienced in the late 90s to early 2000s. As part of an ongoing research project at Swinburne University of Technology on damage to residential structures due to ground movements, a field site was established in a western suburb of Melbourne. In situ soil moisture variation and corresponding ground movements are monitored using a neutron moisture probe and magnetic extensometers respectively. In addition, various laboratory experiments including soil classification, suction, swell and shrinkage were carried out on both disturbed and undisturbed soil samples collected from the field site. Suction variations of undisturbed soil along with moisture content have been measured using miniature tensiometers and a Chilled Mirror Hygrometer to develop the Soil Water Characteristic Curve (SWCC). Atterberg limit tests and particle size distribution tests have also been carried out at different depths to classify the soil. This paper discusses results from both the field and the laboratory investigations. In addition, it presents mechanical and hydraulic properties of the field soil that can be used in numerical analyses.

Abstract: Miller, J. J., Curtis, T., Chanasyk, D. S. and Willms, W. D. 2014. Influence of streambank fencing and river access for cattle on riparian zone soils adjacent to the Lower Little Bow River in southern Alberta, Canada. Can. J. Soil Sci. 94: 209–222. Cattle grazing in riparian pastures adjacent to rivers may increase soil compaction and increase soil nutrients, such as N and P. We conducted a 4-yr study with sampling in 3 yr (2009, 2010, 2012) of riparian zone soils adjacent to fenced and unfenced reaches of the Lower Little Bow River in southern Alberta. We examined the effect of grazing, access of cattle to the river (access versus no-access), and distance (0.25, 1, 2, 4, 6, 8, 10 m) from the river on surface soil bulk density, volumetric water content, NH4-N, NO3, and soil test P. Penetration depth was also measured in 2012. The three grazing treatments consisted of one fenced reach (ungrazed treatment), one unfenced and grazed reach with high cattle impact (high-impact grazed treatment), and one unfence...