The influence of soil compaction in explaining spatial heterogeneity of different larch forest types: a preliminary study

Compacted soil has an adverse effect on plant roots and affects water and nutrient availability.However,different degrees of soil compaction may be suitable for growth and development of different understory species.This study determined whether soil compaction could explain characteristics of 10 different Dahurian larch(Larix gmelinii Rupr.)forest types in the Daxing’anling area.The relationship of soil compaction to soil depth was also studied.Forty-five tests were conducted on soil compaction of the 10 forest types with multiple comparisons,of which five showed no significant differences.At different soil depths,there were significant differences in soil compaction among forest types.The correlation between the degree of soil compaction and depth was positive and significant.The Larix gmelinii—shrub forest type,L.gmelinii—herb forest type,and L.gmelinii—swamp forest type were significantly different in soil compaction according to soil depth.This research indicates that,as a physical property,soil compaction may.

Analysis of black soil compaction with driver-agricultural machinery-soil system under corn sowing with high-power tractor in Northeast China

Soil compaction leads to crop yield reduction in Northeast of China.The interaction mechanism of driveragricultural machinery-black soil is not clear.A comprehensive field experiment of 4 hm2 of maize seeding was carried out in Baiquan County Cooperative.The results showed that the average increase rates of soil compaction before and after sowing were 118.82%and 71.02%.The SEM showed that waist fatigue had the greatest impact on soil compaction,and the unit fatigue of waist caused 1.51 and 1.27 unit compactions to the soil at the depths of 10 cm and 20 cm.The neck,waist,arm and leg fatigue of drivers increased the surface soil compaction by 1.83,1.76,1.78 and 1.55 units,and the deep soil compaction by 1.65,1.58,1.60 and 1.40 units.The results can provide a reference for the integration of human factor efficiency and conservation tillage.

Visualization and quantification of soil laboratory impact compaction

As important methods to guide the field soil compaction,the standard and modified Proctor tests for laboratory compaction have remained unchanged for decades,which should be improved to better understand the compaction process and the properties of soils.In this study,an accelerometer was installed on a Marshall impact compactor to capture the dynamic response of three types of soils during compaction.The experimental test results indicated that the acceleration curve for each blow gradually evolved to a stable pattern following the progress of compaction,and the impact and gyratory locking points were linearly related with coefficient of determination R2equal to 0.59.The impact compaction curve could be further constructed by filtering the structural resonance,which can be used to quantify the compactability of soil materials.Although each type of soil had a unique set of compaction curves,the slope and value of compaction curve altered accordingly as the moisture content changed for the same soil.In addition,the average acceleration value at the final compaction stage could serve as the target value of soil stiffness.

Infiltration characteristics of non-aqueous phase liquids in undisturbed loessal soil cores

The widespread contamination of soils and aquifers by non-aqueous phase liquids （NAPL）, such as crude oil, poses serious environmental and health hazards globally. Understanding the infiltration characteristics of NAPL in soil is crucial in mitigating or remediating soil contamination. The infiltration characteristics of crude and diesel oils into undisturbed loessal soil cores, collected in polymethyl methacrylate cylindrical columns, were investigated under a constant fluid head （3 era） of either crude oil or diesel oil. The infiltration rate of both crude and diesel oils decreased exponentially as wetting depth increased with time. Soil core size and bulk density both had significant effects on NAPL infiltration through the undisturbed soil cores; a smaller core size or a greater bulk density could reduce oil penetration to depth. Compacting soil in areas susceptible to oil spills may be an effective stratage to reduce contamination. The infiltration of NAPL into soil cores was spatially anisotropic and heterogeneous, thus recording the data at four points on the soil core is a good stratage to improve the accuracy of experimental results. Our results revealed that crude and diesel oils, rather than their components, have a practical value for remediation of contaminated loessal soils.

How does organic matter affect the physical and mechanical properties of forest soil?

Determining the physical and mechanical properties of soil and its behavior for engineering projects is essential for road construction operations. One of the most important principles in forest road construction, which is usually neglected, is to avoid mixing organic matter with road materials during excavation and embankment construction. The current study aimed to assess the influence of organic matter on the physical properties and mechanical behaviors of forest soil and to analyze the relation between the amount of organic matter and the behavior of forest soil as road material. A typical soil sample from the study area was collected beside a newly constructed roadbed. The soil was mixed with different percentages of organic matter（control treatment, 5, 10, and 15% by mass） and different tests including Atterberg limits, standard compaction, and California bearing ratio（CBR） tests were conducted on these different soil mixtures. The results showed that soil plasticity increased linearly with increasing organic matter.Increasing the organic matter from 0%（control） to 15%resulted in an increase of 11.64% of the plastic limit and 15.22% of the liquid limit after drying at 110 ℃. Also,increasing the organic matter content reduced the soil maximum dry density and increased the optimum moisture content. Increasing the organic matter from 0 to 15% resulted in an increase of 11.0% of the optimum moisture content and a decrease of 0.29 g/cm;of the maximum dry density. Organic matter decreased the CBR, which is used as the index of road strength. Adding 15% organic matter to the soil resulted in a decrease of the CBR from 15.72 to 4.75%. There was a significant difference between the two drying temperatures（60 and 110 ℃） for the same organic matter mixtures with lower water content values after drying at 60 ℃. The results revealed the adverse influence of organic matter on soil engineering properties and showed the importance of organic matter removal before excavation and fill construction.

Influence of Tillage and Deep Rooted Cool Season Cover Crops on Soil Properties, Pests, and Yield Responses in Cotton

Soil compaction is a significant problem in the Southeastern USA. This compacted zone or hardpan limits root penetration below this layer and reduces potential yield and makes plants more susceptible to drought induced stresses. Soil compaction in this region is managed using costly annual deep tillage at or before planting and there is a great interest in reducing and/or eliminating annual tillage operations to lower production costs. Deep rooted cool season cover crops can penetrate this compacted soil zone and create channels, which cash crop roots, such as cotton, could follow to capture moisture and nutrients stored in the subsoil. The cool season cover crop roots would reduce the need for annual deep tillage prior to planting, increases soil organic matter, which provides greater water infiltration and available water holding capacity. Field studies were conducted for two years with three different soil series to determine the effects of tillage systems and cool season cover crops on the soil chemical and physical properties, yield responses, and pest pressure. Results showed that cool season cover crops significantly reduced soil compaction, increased cotton lint yield and soil moisture content, reduced nematode population densities, and increased soil available P, K, Mn, and organic matter content compared to the conventional no-cover crop.

Soil Physical Properties and Grain Yield Influenced by Cover Crops and Crop Rotation

The crop yield is related to several factors, among these, soil tillage, soil compaction and crop rotation. This study aimed to evaluate the winter cover crops and crop rotation influence on soil physical properties and grain yield of dry beans, maize and soybean for two growing seasons. Three experiments were conducted, corresponding to dry beans, maize and soybean crops. It was used the randomized block design with three treatments and four replications consisted by 3 × 10 m plots. The treatments were: two cover crops systems and crop rotation in no-till, and the control, consisting of winter fallow and conventional tillage. The cover crop dry matter, soil physical properties and grain yield for dry beans, maize and soybean in the two growing seasons were evaluated. Crop rotation systems and cover crops showed a trend to increase maize and soybean yields. Crop rotation in no-till increases soil compaction in the superficial layer compared to conventional tillage, but does not reduce the dry beans, maize and soybean yields.

The inf luence of soil drying- and tillage-induced penetration resistance on maize root growth in a clayey soil

Soil drying may induce a number of stresses on crops. This paper investigated maize（Zea mays L.） root growth as affected by drought and soil penetration resistance（PR）, which was caused by soil drying and tillage in a clayey red soil. Compared with conventional tillage（C） and deep tillage（D）, soil compaction（P） and no-till（N） significantly increased soil PR in the 0-15 cm layer. The PR increased dramatically as the soil drying increased, particularly in soil with a high bulk density. Increased soil PR reduced the maize root mass density distribution not only in the vertical profile（0-20 cm） but also in the horizontal layer at the same distance（0-5, 5-10, 10-15 cm） from the maize plant. With an increase in soil PR in pots, the maize root length, root surface area and root volume significantly decreased. Specifically, the maize root length declined exponentially from 309 to 64 cm per plant with an increase in soil PR from 491 to 3 370 k Pa; the roots almost stopped elongating when the soil PR was larger than 2 200 k Pa. It appeared that fine roots（〈2.5 mm in diameter） thickened when the soil PR increased, resulting in a larger average root diameter. The average root diameter increased linearly with soil PR, regardless of soil irrigation or drought. The results suggest that differences in soil PR caused by soil drying is most likely responsible for inconsistent root responses to water stress in different soils.

Traditional mule logging method in Hyrcanian Forest: a study of the impact on forest stand and soil

We inventoried plant regeneration and soil compaction along mule trails to evaluate damage to forest stands and regeneration follow- ing mule hauling before and after operations in Kheyrud Forest in the Hyrcanian Forest in northern Iran. About 22% of regenerating plants on mule trails were damaged following mule logging, and damage to trees was observed. In harvested units after timber extraction, 4.3% of the total area （12 ha） was covered with mule trails. Mule passes and slope gradi- ent, and twofold interactions between mule passes x slope gradient had no significant effect on soil bulk density （p 〈 0,05）. Mule iogging had a statistically significant effect on soil bulk density along the mule trails before and after mule passes. Soil bulk density increased Significantly as mule passes increased in number. The degree and level of compaction did not differ with trail slope. With respect to damage to residual stands and seedlings, soil compaction and disturbance to soil, traditional mule log- ging is the preferred skidding method in the steep terrain conditions in the Hyrcanian Forest in northern Iran.

Influence of Skidding Operation on Forest Soil Respiration for Small Four-wheeled Tractors

The TJSD-750-Ⅱ type compactness measurement instrument and Li-8100 soil carbon flux automatic measurement system are used to measure soil compactness and soil respiration rate at different skidding roads. A regression model is established to analyze the correlation between soil respiration and its influencing factors. The results shows that the soil compaction on the main skidding road and sub skidding roads are larger than the control points, and the soil compaction on the main skidding road is larger than that on sub skidding roads. The higher the soil compactness is, the lower the rate of soil respiration is. This also leads to the lower sensitivity of soil respiration rate influenced by temperature and humidity.

Rangeland Degradation Impacts on Vegetation Cover, Soil Properties and Ecosystem Functioning in an Arid and Semi-Arid Climate, South Africa

The negative effect of soil erosion and soil compaction is well documented for the purpose of optimum rangeland functioning, while the impact of rangeland degradation on effective soil depth is seldom quantified. The aim of this study was to quantify the response of vegetation cover and soil properties, particularly effective soil depth and soil texture to rangeland degradation. Forty-one farms were sampled in the arid and semi-arid climate of South Africa. Within these farms, data was collected over a vegetation degradation gradient. Results showed a significant decline in relative basal cover (94% ± 15% to 39% ± 17%) and soil depth (90% ± 14% to 73% ± 24%) as rangeland degraded. Soil texture changes over the degradation gradients vary for different homogeneous vegetation types. Indications regarding the loss of a functioning rangeland ecosystem were also demonstrated, using objective long-term relations between rangeland conditions and grazing capacity. The study highlights the importance of sustainable rangeland management practices to reduce the loss in effective soil depth and to ensure the sustainable utilization of the rangeland ecosystem. These results can probably extrapolate to other arid and semi-arid rangelands worldwide.

Headwaters Deforestation for Cattle Pastures in the Andes of Colombia and Its Implications for Soils Properties and Hydrological Dynamic

Deforestation of headwater in the Andes of Colombia is a historical process that has its origins in pre-Hispanic communities and in nineteenth and twentieth centuries, intensified by settlers and farmers. These lands have been intended mainly to pasture cattle. Soil compaction, caused by the trampling of cattle, was evaluated in soils derived from volcanic ash (Andisols), with reference to values found for variables in undisturbed natural forests in the same region. The compared parameters were bulk density (Db), total porosity (α), soil resistance to penetration (Rp) and pore size distribution, analyzed by water retention curves (WRC). The grazed soils had significant differences with respect to the natural forest reference values: Db was 53.7% higher, α was reduced by 11.0% and Rp in the first 7.5 cm of the top soil was more than double, with an average increase of 275.2 to 527.2 kPa. The analysis indicated that compacted soils had relatively uniform reduction in distribution of macro, meso and micropores. It was concluded that deforestation followed by pasture land destination in steep headwaters generates significant compaction processes that can affect the infiltration, percolation and soil water storage, which would have important hydrological implications: augmentation of surface runoff and soil erosion, decreased the base flow and increased direct runoff. For this reasons, it is considered that forest restoration of headwaters is important for the maintenance of hydrological functions of large river systems.

Review of collapse triggering mechanism of collapsible soils due towetting

Loess soil deposits are widely distributed in arid and semi-arid regions and constitute about 10% of land area of the world.These soils typically have a loose honeycomb-type meta-stable structure that is susceptible to a large reduction in total volume or collapse upon wetting.Collapse characteristics contribute to various problems to infrastructures that are constructed on loess soils.For this reason,collapse triggering mechanism for loess soils has been of significant interest for researchers and practitioners all over the world.This paper aims at providing a state-of-the-art review on collapse mechanism with special reference to loess soil deposits.The collapse mechanism studies are summarized under three different categories,i.e.traditional approaches,microstructure approach,and soil mechanics-based approaches.The traditional and microstructure approaches for interpreting the collapse behavior are comprehensively summarized and critically reviewed based on the experimental results from the literature.The soil mechanics-based approaches proposed based on the experimental results of both compacted soils and natural loess soils are reviewed highlighting their strengths and limitations for estimating the collapse behavior.Simpler soil mechanics-based approaches with less parameters or parameters that are easy-to-determine from conventional tests are suggested for future research to better understand the collapse behavior of natural loess soils.Such studies would be more valuable for use in conventional geotechnical engineering practice applications.

Saturated anisotropic hydraulic conductivity of a compacted lateritic soil

This study focuses on the saturated anisotropic hydraulic conductivity of a compacted lateritic clayey sandy soil. The effects of the molding water content and the confining stress on the anisotropic hydraulic conductivity are investigated. The hydraulic conductivity is measured with a flexible-wall permeameter. Samples are dynamically compacted into the three compaction states of a standard Proctor compaction curve： the dry branch, optimum water content and wet branch. Depending on the molding water content and confining stress, the hydraulic conductivity may increase or decrease. In addition, the results indicate that, when the samples are compacted to the optimum water content, lower hydraulic conductivity is obtained, except at a confining stress equal to 50 kPa. The increase of the confining stress decreases the hydraulic conductivity for each of the evaluated compaction states. In the wet branch, horizontal hy- draulic conductivity is about 8 times higher than the vertical value. The anisotropic hydraulic conduc- tivities of the dry and wet branches decrease when the confining stress increases, and the opposite is observed in the optimum water content state.

California Bearing Ratio Test on the Bearing Capacity of a Foundation in Unsaturated Soil

The value of the California bearing ratio (CBR) test is an index making it possible to evaluate the load of the foundation soil and the resistance of the pavement materials. The California Bearing Ratio (CBR) of unsaturated soils is particularly related to their quality. The mechanism affecting the bearing capacity, in the case of California Bearing Ratio (CBR), has been studied as a transformation of red clay for the backfill. In this study, the effect of compaction energy on compaction characteristics and California Bearing Ratio (CBR) values was investigated. The relationship between the CBR value (California Ratio Ratio) and the degree of compaction is characterized by a gradual evolution of unsaturated soils with different water contents. The results show that the compaction degree and California Bearing Ratio (CBR) value of the soil in the cold region are insufficient, but the bearing capacity of the compacted soil after immersion under the maximum dry density can still meet the filling requirements. The red clays tested are considered useful as bedding in areas of unsaturated soils.

Compaction Performance of Biomimetic Press Roller to Soil

The compaction characteristics of biomimetic press roller with ridge structures, inspired from the geometrical features of the ventral surface of dung beetle （Copris ochus Motschulsky）, were investigated in this work. Field tests were carried out at three weights （300 N, 500 N and 700 N） and two forward velocities （0.64 m·s^-1 and 1.04 m·s^-1） for biomimetic press roller and conventional press roller. To determine compaction performance, rolling resistance, soil bulk density, soil moisture content, emergence rate and percent change of plant spacing were measured. Roller weight was proved to be the major contributory factor on soil compaction. Biomimetic press roller decreased rolling resistance by 2.98% -17.69% at the velocity of 0.64 m·s^-1, and by 6.59% -18.57% at the velocity of 1.04 m·s^-1 compared with the conventional press roller. Both biomimetic roller and conventional roller can achieve proper bulk density for corn seeds under the experimental conditions. However, compared with the conventional roller, biomimetic roller helped soil conserve more moisture. The highest emergence rate was found when the biomimetic roller worked with a weight of 700 N and velocity of 0.64 m·s^-1. Percent change of plant spacing was lower using the biomimetic press roller compared with that using the conventional roller, because that adjacent ridge structures of the biomi- metic roller can well constrain the flow of soil during compacting process.

Spatial-Temporal Ground Deformation Study of Baotou Based on the PS-InSAR Method

Ground subsidence is an emerging geological hazard in Baotou,Inner Mongolia.Four areas of Baotou with relatively large subsidence range and rate were selected for analysis.Focusing on investigation of ground subsidence using PS-In SAR technology,a total of 43 frames of ALOS PALSAR images yielded a SAR data span from December 2006 to January 2011,allowing ground subsidence scope,subsidence velocity,time-series deformation to be obtained.Major causes and influencing factors of the ground subsidence are closely related to soft soil consolidation and compaction and the decrease in the level of groundwater caused by increased development and utilization of groundwater.

Effects of Tillage Practices and Straw Management on Physical Properties of Mollisols,Root Architecture and Maize Yield in Northeast China

Tillage practices and organic amendment are strategies used worldwide to preserve the properties and fertility of soils.This study aimed to elucidate effects of 3-year field treatments of tillage practice and straw management on physical properties of Mollisols,root architecture and maize yield in northeast China.The experiment was conducted from 2015 to 2018 following a splitplot design of a randomized complete block with tillage practices[rotary tillage(R)and deep tillage(D)]as main plots and straw managements[straw returning(S),straw returning and organic fertilizer(M),straw removal(T)]as subplots.Soil samples at 0-15,15-30,30-50 cm depths and root samples at the seedling stage were collected.The results showed that DM treatment significantly improved soil moisture content at 10-50 cm soil depth and decreased soil compaction(P<0.05),which led to a better root architecture.Rotary tillage had a slower thermal conductivity but better thermal insulation performance,while deep tillage showed a higher daily temperature difference.Bulk density of topsoil was significantly lower in DS(1.16 g·cm^(-3))than in other treatments,but the soil permeability in DS(1.40 mm·min^(-1)in 0-15 soil depth and 1.45 mm·min-1in 15-30 cm soil depth)was the highest.At the maize seedling stage,DM had the highest root dry weight,root-shoot ratio and root length,while RM had the highest root volume,root furcation number and root tip number.The maize yield of three years in DM was 6.19%,5.21%and 15.72%higher than that in DS,DT and RM(P<0.01),respectively.Relative to RT and DT,a slight decrease(2.72%and 0.93%,respectively)in maize yield under RS and DS was observed,which could be alleviated by the addition of organic fertilizer.The correlation matrix indicated that kernel per ear number and 100-kernel weight were the dominant factors that affected maize yield.Redundancy analysis suggested that straw managements and tillage practices were significantly positively correlated with root-shoot ratio,root dry weight,maximum root length,the total root length and maize yield,but significantly negatively correlated with soil compaction,bulk density,soil moisture content and soil temperature.Among all the treatments,deep tillage with straw returning and the addition of organic fertilizer was recommended as a promising strategy in restoring soil productivity,promoting maize growth and increasing maize yield in Mollisols of northeast China and similar regions around the world.

Comparison of Skidding Performance of Small Track-type Experimental Prototype Skidder and J-50 Skidding Tractor

In this paper, field experimental comparison is made between a small track-type experimental prototype skidder and a J-50 skidding tractor. Experimental data, including skidding productivity, soil compaction on skidding trails, and damage rate of the residual trees, are analyzed. The results indicate that with the condition of scattered skidding area and low skidding volume per cycle, small track-type experimental prototype skidder has advantage on working and a higher skidding productivity. It makes lower soil compaction to the skidding trails in the depth of 0-5 cm, 5-10 cm, and 10-15 cm. Under the same work conditions, the damage rate of the residual trees made by small track-type experimental prototype skidder is only 1/5 of those made by J-50 type skidding tractor. The damage rate is reduced by 80%.

Quantification of traffic-induced compaction based on soil and agricultural implement parameters

Vehicle-induced soil compaction occurs when agricultural machinery is working in the fields.The accumulated soil compaction could destroy soil structure and inhibit crop growth.The low degree of visualization of soil compaction has always been an important reason for restricting the development of compaction alleviation technology.Therefore,the main objective of this study was to predict soil compaction based on soil and agricultural implement parameters.The component of soil compaction prediction includes traffic-induced stress transmission evaluation and the quantitative relationship between soil stress and bulk density.The modified FRIDA model was used to elucidate the soil stress propagation,which has been validated by previous studies.The Bailey formula was used to establish the intrinsic relationship between soil stress and bulk density.The soil uniaxial compression test was applied to obtain the parameters of the Bailey formula,and soil samples were prepared with three different levels of water content.After fitting with the Bailey formula,under the condition that the soil moisture contents were 16%,20%,and 24%,the fitting coefficients of soil bulk density were respectively 0.980,0.959,and 0.975,which were close to 1.The results indicated that the Bailey formula could be used to calculate soil bulk density based on the stress conditions of the soil.To verify the practicality of the soil compaction prediction model,a field experiment was carried out in Zhuozhou City,Hebei Province,China.The treatment was set for 1,3,5,7,and 9 times compaction with two different loads of compaction equipment.The results showed that the fit coefficient between the predicted and measured values of soil bulk density was greater than 0.641.The slope of the equation was greater than 0.782,proving that the soil bulk density prediction model based on agricultural implements and soil parameters has a good predictive effect on soil bulk density.The soil compaction evaluation model can provide a theoretical basis to further understand the soil compaction mechanism,allowing rational measures of soil compaction alleviation to be made.