Traffic-induced Soil Compaction Research Articles

Traffic induced compaction and physical quality of grassland soil under different soil moisture deficits

Soil compaction is widely recognised as one of the key contributors to soil degradation in Europe. Information is needed for farmers and land managers to guide management decisions and prevent traffic-induced soil compaction. Predicted soil moisture deficit (SMD) from the hybrid SMD model may provide information on when soil conditions are suitable for machinery trafficking. The objective of this study was to investigate the relationship between soil water content and traffic induced soil compaction and if a predicted SMD threshold level could be identified, above which soils can be trafficked without significant soil compaction occurring. The study also evaluated the capacity of selected soil physical indicators such as soil bulk density and water stable aggregates to indicate soil physical degradation across a range of soil water contents. The experiment was carried out on grassland with moderately drained soil, located in Wexford, Ireland. Machinery trafficking of the soil with a tractor equipped with a fully loaded slurry tanker, was assessed in the field across the four seasons of the year. Traffic was imposed at target predicted SMD + 10 mm (relatively dry soil), 0 mm (relatively moist soil), and −10 mm (relatively wet soil). After each traffic event, samples were taken in the middle of the wheel track at three depths (0–10, 10–20 and 20–30 cm) to assess soil bulk density. Water aggregate stability was evaluated at the same three depths following the fourth traffic event. Results showed that when planning field machinery operations, especially repeated trafficking events, soil becomes prone to physical degradation when predicted SMD ≤ 0 mm. Traffic on soil at predicted SMD 0 mm (close to field capacity) lead to compaction after two traffic events. However, when predicted SMD was −10 mm, soil bulk density indicated no significant difference from the non-trafficked soil. When water-stable aggregates were measured on the predicted SMD 0 mm and −10 mm trafficked soils, it indicated physical degradation of soil. Hence, bulk density alone did not give an accurate indication of soil structural quality when soils where trafficked under relatively wet or saturated conditions (SMD −10 mm). These results indicate that avoiding machinery trafficking of grassland soils at predicted SMD ≤ 0 mm will help protect soil physical structure. On soils where multiple machinery operations are likely to occur over the year, trafficking when the predicted SMD > 0 mm is recommended to minimise loss of soil physical quality.

Effects of road- vs. field-recommended tyre inflation pressures and small variations in soil moisture content on traffic-induced soil compaction during seedbed preparation

Soil compaction has become one of the most common forms of soil degradation, with associated negative effects on the functioning of agricultural soils. Decades of research have led to publication of several practical measures that mitigate risk of soil compaction, yet adoption among European farmers remains limited. To improve adoption by farmers, experiments under practical conditions using common operations should be performed. A field experiment was set up to evaluate the effects of road- (200 kPa) vs. field- (140 kPa and 100 kPa) recommended tyre inflation pressure and soil moisture content (0.24 g g−1 vs. 0.22 g g−1) on traffic-induced compaction of a silt loam soil during seedbed preparation. The various tyre inflation pressures were tested using two tyre types (standard radial tyre at 200 kPa and 140 kPa; VF tyre at 100 kPa) of similar dimensions mounted onto the same tractor. Variation in experimental soil moisture content was achieved by performing the seedbed preparation on two dates in spring (early, March 30th, vs. late, April 14th). In this one-year study, reducing the standard-tyre inflation pressure from road- (200 kPa) to field-recommended (140 kPa) pressure did not prevent soil compaction. The use of VF tyres at field-recommended (100 kPa) tyre inflation pressure resulted in significant reductions in vertical contact stress and mean normal stress as compared to 200 kPa. Although non-significant, the pressure reduction from 200 kPa to 140 kPa did result in a 4 % increase in in-track dry matter sugar beet yield while a reduction from 200 kPa to 100 kPa resulted in an 11% increase. Lower tyre inflation pressure showed no significant effect on fuel consumption and penetration resistance. Seedbed preparation under slightly drier (0.22 g g−1) soil conditions negatively affected fuel consumption (+11 %) and resulted in an in-track dry matter sugar beet yield increase of 11 %. For both tested prevention strategies, the impact of soil compaction was better observable by sugar beet yield than by most of the measured soil physical parameters.

Reversible strengthening behaviour of subsurface layers in sandy soils – understanding variable response to strategic deep tillage

Deep sandy soils cover more than 10 M ha of Australia's southern dryland cropping lands. Farming these soils is inherently challenging, and yield gaps are often wide due to multiple cropping constraints. Physical constraints that limit rooting depth are commonplace and often attributed to traffic-induced soil compaction. However, recent observations draw attention to a reversible hardsetting behaviour in response to soil water content. This hardsetting phenomenon is poorly understood and it may explain inconsistent crop responses to deep ripping in sandy soils. We examined the dynamic behaviour of soil strength under different soil water contents in deep ripped and unripped sands from four South Australian sites. We analyzed the elemental, mineralogical, chemical and physical compositions to differentiate the nature of hardened subsurface layers. Soil compaction and cementation were ruled out due to the soil's bulk density (<1.6 g cm−3) encountered and the rapid slaking that occurred when a hardened pan was submerged in water. The hardsetting behaviour was confirmed by the abrupt change in soil strength in response to the soil water content, measured using intact samples in a laboratory-based penetrometer. This significant increase in soil strength was also observed for soils collected from the ripped plots and for repacked soil samples, with penetration resistance ranging from 0.4 to 5.7 MPa depending on soil content. In contrast to our hypotheses, the hardsetting layer could not be distinguished from the layers above or below it by any analytical method. Given soil strength is typically measured on field moist soil, and standard chemical analysis did not differentiate hardsetting behaviour, alternative methods of diagnosis are needed to understand where deep tillage is likely to have the desired long-term effect. Identifying the nature of potential binding agents responsible for increased strength upon drying would be valuable. Our results confirmed reversible hardsetting in deep sandy soils is driven by small changes in soil water content, from 0.08 g g−1 to 0.05 g g−1 upon drying. Given that rapid re-consolidation of the soil matrix after expensive deep ripping interventions are reported, there is a strong imperative to improve diagnosis, and to identify if soil ameliorants could improve longevity by disrupting hardsetting behaviour.

Field traffic-induced soil compaction under moderate machine-field conditions affects soil properties and maize yield on sandy loam soil.

Soil compaction due to field trafficking involves a complex interplay of machine-soil properties. In contrast to previous studies simulating worst field scenarios, this two-year field experiment investigated the effects of traffic-induced compaction involving moderate machine operational specifications (axle load, 3.16 Mg; mean ground contact pressure, 77.5 kPa) and lower field moisture contents (< field capacity) at the time of trafficking on soil physical properties, spatial root distribution, and corresponding maize growth and grain yield in sandy loam soil. Two compaction levels, i.e. two (C2) and six (C6) vehicle passes, were compared with a control (C0). Two maize (Zea mays L.) cultivars, i.e. ZD-958 and XY-335, were used. Results showed topsoil (< 30cm) compaction with increases in bulk density (BD) and penetration resistance (PR) up to 16.42% and 127.76%, respectively, in the 10-20cm soil layer in 2017. Field trafficking resulted in a shallower and stronger hardpan. An increased number of traffic passes (C6) aggravated the effects, and the carryover effect was found. Higher BD and PR impaired root proliferation in deeper layers of topsoil (10-30cm) and promoted shallow horizontal root distribution. However, XY-335, compared with ZD-958, showed deeper root distribution under compaction. Compaction-induced reductions in root biomass and length densities were respectively up to 41% and 36% in 10-20cm and 58% and 42% in the 20-30cm soil layer. Consequent yield penalties (7.6%-15.5%) underscore the detriments of compaction, even only in topsoil. In crux, despite their low magnitude, the negative impacts of field trafficking under moderate machine-field conditions after just two years of annual trafficking foreground the challenge of soil compaction.

The Impact of Traffic-Induced Compaction on Soil Bulk Density, Soil Stress Distribution and Key Growth Indicators of Maize in North China Plain

The traffic-induced soil compaction in the field has gradually become an important constraint to sustainable agricultural development. A field experiment was conducted to acquire the stress transmitted caused by multiple passes with different types of tractors and to investigate the impact of these stresses on soil bulk density and crop growth. The experiment applied two tractors with different masses: LOVOL M904 (HC) and John Deer 280 (LC), and six different treatments of 0 (C0), 1 (C1), 3 (C3), 5 (C5), 7 (C7), and 9 (C9) tractor passes for each tractor. The results showed that at each number of passes, tractors with small axle-loads at 0–20 cm depth generated higher soil additional stress, while tractors with large axle-loads at 20–80 cm depth generated higher soil additional stress. In the 0–20 cm soil layer, when the number of continuous passes is less than 7 times, the passes of a small axle-load tractor lead to larger soil bulk density, and when the number of continuous passes is more than 7, the compaction of large axle-load tractor leads to larger soil bulk density. At depths of 20–80 cm, compaction by large axle-load tractors results in larger soil bulk density. In this study, different levels of tractor compaction inhibited key growth indicators of maize, resulting in yield reductions. The effect of different tractor load compaction on maize yield increased significantly with the number of compaction passes, with 1–5 tractor passes having no significant effect on yield and 7–9 passes producing greater yield reductions for HC. This study will provide a theoretical basis and technical support for the selection of agricultural machinery and reasonable tillage technology.

Controlled traffic farming and field traffic management: Perceptions of farmers groups from Northern and Western European countries

As farming machinery size and weight increases, soil compaction continues to threaten mechanized agriculture. Controlled Traffic Farming (CTF) minimizes soil compaction in the crop zone by restricting traffic to permanent tracks. The adoption of CTF in Europe is low. This study enhances the understanding of farmers' needs and perceptions concerning the application of CTF by analyzing survey data from 103 farmers sampled from 8 European countries. The study adopted a descriptive approach to data analysis. Awareness about traffic-induced soil compaction is high among surveyed farmers and there are positive perceptions about the potential of CTF. The major factors limiting adoption of CTF appear to be: lack of compatibility in machinery and Global Navigation Satellite Systems (GNSS) by different manufacturers; expense (equipment purchase, Real-time Kinematic (RTK) signal, machinery modification); lack of demonstrated benefits under local conditions; incomplete knowledge of research findings and decision support tools; and a perception that CTF is not for small farms. The following interventions are suggested for future development and use of CTF: a shift towards lighter, simpler, adaptable, and energy effective machinery; adapted market models for cost-effective provision of basic services; demonstration of costs and benefits under local conditions in tandem with demand-driven decision support tools as well as standardization of equipment and positioning systems.

Study of the steering of a wide span vehicle controlled by a local positioning system

Controlled traffic farming allows to minimize traffic-induced soil compaction by a permanent separation of the crop zone from the traffic lanes used by wide span tractors. The Authors developed an agricultural wide span vehicle equipped with a skid equipment for turning and an automatic driving system prototype based on a laser beam. The aim of this work was to study the kinematic conditions that control the steering of this machine. Furthermore, the accuracy and the maximum delay time of the signal transmission by the automatic driving system of the set-up was also assessed. In comparison with crawler tractors, the turning of the agricultural wide span vehicle needs a smaller difference in the moments applied to its right- and left-side wheels. For the predetermined accuracy of the beam position relative to the plant rows, ±ds = ±0.025 m, the accuracy of the direction of the laser beam at a distance S=200 m should not be more than ±0.07° and ±0.0014°, considering a run length of 1000 m. Furthermore, at a speed V=2.5 m s–1 a trajectory deviation φ≤5° requires a topmost delay time of the control signal of Δtmax=0.11 s is required.

Experimental study of the implement-and-tractor aggregate used for laying tracks of permanent traffic lanes inside controlled traffic farming systems

Traffic-induced soil compaction is a serious drawback of modern agriculture. However, controlled traffic farming (CTF) systems, which have been adopted worldwide, are useful strategies of lessening this problem. In CTF systems, the crop zone is clearly separated from the permanent traffic lanes (PTL), which are used exclusively for the movement of the machine-and-tractor aggregates. The CTF systems are implemented both with and without the use of the GPS systems. When navigation-aid is not used, the first positioning of the PTL tracks is an essential operation, in which the aggregate intended for this task must perform a sufficiently straight movement. This paper reports the assessments concerning the PTL tracks laid by an experimental aggregate, which consisted of a four-wheel drive tractor and a tillage implement operating in the “push” mode. This aggregate formed tracks with a sufficiently small dispersion (10.30 cm2) and a fairly low (not more than 0.09 Hz) frequency of their fluctuations in a horizontal plane. Furthermore, during the tests, a rather close positive correlation between the bearing angle φ of the tractor and the turning angle α of its driven wheels was registered and the maximum value of the related correlation function was 0.9. Moreover, the phase (time) shift between the disturbing torque and the response to it by the tractor operator did not exceed 0.75 s. The use of the proposed aggregate allowed laying tracks with a depth of 21.2 ± 0.3 cm and vibrations in a longitudinal vertical plane, whose dispersion was not more than 2 cm2 and was concentrated in a fairly narrow frequency range from 0 to 1.78 Hz.

Exploring the sensitivity of visual soil evaluation to traffic-induced soil compaction

Visual Soil Evaluation (VSE) techniques are useful for assessing the impact of land management, particularly the identification and remediation of soil compaction. Despite an increasing body of VSE research, comparatively few studies have explored the sensitivity of VSE for capturing experimentally imposed compaction to estimate sensitivity and limit of detection. The aim of this research was to examine the ability of VSE techniques to indicate soil structure at different soil profile depths and to measure the associated soil productive function (yield) response to imposed compaction. A two-year experiment was conducted on sites with loam and sandy soils. Varying levels of wheeled traffic were imposed on plots in a randomised block design, prior to sowing winter barley (Hordeum vulgare L.). Quantitative crop and soil measurements were taken throughout the season in conjunction with VSE techniques, which assessed to 25 cm (VESS), 40 cm (Double Spade) and 80 cm (SubVESS) depth. Graduated changes were observed by soil and some crop quantitative measurements as traffic treatment varied. VESS and Double Spade successfully identified a graduated treatment effect at all sites to 40 cm depth, although diagnosis translated into a yield response for the loam but not the sandy soil. Correlation between VESS Sq scores and crop yield were found. SubVESS gave mixed signals and indicated impacts lower in the profile in certain instances. These impacts were not captured by quantitative soil measurements.This work highlights the capacity for VSE techniques to indicate soil structural damage, which may cause a crop yield response, therefore allowing appropriate soil management strategies to be deployed before yield penalties occur.

Impact of Load and Inflation Pressure on Traffic-Induced Soil Compaction for Two Types of Flotation Tires

Abstract. An Automatic Air Inflation-Deflation (AAID) control unit was evaluated on a manure tanker equipped with Alliance model 390 30.5LR32 steel belted radial-ply and Michelin 650/75R32 172A8/172B TL MEGAXBIB radial-ply flotation tires. The objective was to validate the effectiveness of the AAID control unit from an engineering perspective and its benefits for field agricultural operations. The contact patch was characterized in terms of rut depth and width, and tire contact length. Soil cone index was used as an indicator of soil compaction caused by the weight of the manure tanker. Cone index and rut depth at the centerline and edge of both the Alliance and the Michelin tires were affected by tire inflation pressure and load. As inflation pressure or load increased, the cone penetration resistance in the contact patch increased, indicating an increase in soil compaction. The adjusted tire inflation pressure for field operation using the AAID control unit reduced the rut depth at a lug imprint at the tire centerline, at a high load of 68 kN per tire, by 18.4% and 15.6% for the Michelin and Alliance tires, respectively, and by 19.1% and 12.0% at a low load of 44 kN per tire for the Michelin and Alliance tires respectively. Keywords: Automatic air inflation deflation, Cone index, Contact patch, Flotation tire, Manure tanker, Rut depth, Rut width, Soil compaction management.

Soil compaction and controlled traffic considerations in Australian cotton-farming systems

A literature review was conducted to collate best practice techniques for soil compaction management within cotton-farming systems in Australia. Universally negative effects of traffic-induced soil compaction on the whole-farm system and the wider environment include: (i) increased gap between attainable and potential yields, (ii) increased costs of energy and labour, (iii) reduced fertiliser-use efficiency, (iv) reduced water use efficiency (irrigation and rainfall), (v) increased tillage intensity. Knowledge gaps that merit research priority, and research strategies, are suggested. These include: (i) identifying wider impacts on farm economics to guide decision-making and development of decision support systems that capture the effects of compaction on fertiliser, water, and energy use efficiency; (ii) predicting risks at the field or subfield scale and implementing precision management of traffic compaction; (iii) canopy management at terminal stages of the crop cycle to manipulate soil-moisture deficits before crop harvest, thereby optimising trafficability for harvesting equipment; (iv) the role of controlled traffic farming (CTF) in mitigating greenhouse gas emissions and loss of soil organic carbon, and in enhancing fertiliser and water-use efficiencies; (v) recent developments in tyre technology, such as low ground-pressure tyres, require investigation to assess their cost-effectiveness compared with other available options; and (vi) catchment-scale modelling incorporating changes in arable land-use, such as increased area under CTF coupled with no- or minimum-tillage, and variable rate technology is suggested. Such modelling should assess the potential of CTF and allied technologies to reduce sediment and nutrient losses, and improve water quality in intensively managed arable catchments. Resources must be efficiently managed within increasingly sophisticated farming systems to enable long-term economic viability of cotton production. Agronomic and environmental performance of cotton farming systems could be improved with a few changes, and possibly, at a reasonable cost. Key to managing soil compaction appears to be encouraging increased adoption of CTF. This process may benefit from financial support to growers, such as agri-environmental stewardships, and it would be assisted by product customisation from machinery manufacturers.

Advances in Cotton Harvesting Technology: a Review and Implications for the John Deere Round Baler Cotton Picker

To address the progressive increase in farmed land and the decline in labor, cotton production in more developed agricultural systems has seen a movement towards larger, heavier machinery with increased capacity. Recent innovation of on-board module building technology for cotton harvesters follows this trend, which has caused concern for the potential impact of the machine on the farming system. This review acknowledges past and present developments within the cotton harvesting system from both the machine- and soil-management perspectives to inform land managers, machinery manufacturers, technical advisors, and the scientific community of the incidence of soil compaction associated with technology uptake in cotton-based systems. Emphasis is made on the need to ensure that the effects of traffic-induced soil compaction are minimized. For this, the feasibility of confining compaction to the least possible area of permanent traffic lanes is examined along with engineering design constraints of commercially available cotton pickers. Fundamental information is elicited, which provided insights as to why this movement has occurred and how associated problems might be addressed. Within the Australia context, these cotton harvesters have undergone rapid adoption. This review uses this case-study to elucidate direct and latent impacts of the machine to help identify risks and develop management strategies as further technology is developed and adopted. Knowledge gaps that merit a research priority within soil compaction work for cotton-based systems are presented and a synthesis of how to proceed conceptualized.

Effects of soil moisture content and tractor wheeling intensity on traffic-induced soil compaction

Soil compaction causes deleterious effects on physical and mechanical proprieties of agricultural soils. In order to investigate the effect of soil moisture content and tractor wheeling intensity on traffic-induced soil compaction, this study was carried out on a field with clay loam soil. Soil dry bulk density and hydraulic conductivity as well as emergence percentage of corn seedlings and dry mass of the sampled mature plants were considered the dependent variables of the experiment. Independent variables consisted of soil moisture content with five levels (12, 15, 17, 19, and 21%), traffic intensity with three levels (four, two, and zero passes of tractor wheel (tractor model: John Deere 3350) from the entire area of the plot), and soil sampling depth with three levels (0-10, 10-20, and 20-30 cm). According to the results of this study, gradual increase in soil water content generally resulted in an increase in soil bulk density; moreover, increasing the tractor wheeling intensity from 0 to 4 passes increased bulk density by 13%. Furthermore, the driest soil water content had the highest and the wettest soil water content had the lowest emergence percentage of corn seedlings among the treatments; moreover, traffic intensity treatment inversely affected the emergence percentage of corn seedlings and the dry mass of mature plants. To sum up, these results indicate that, for improving water permeability and reducing dry bulk density of the examined clay loam soil, as well as better emergence of corn seedlings and ultimately increasing crop yield, it is recommended to avoid wheeling when soil moisture content is high, reduce the number of machinery wheel passes from the farm as low as possible, and restrict the wheel passes to fixed strips along the field, whenever possible.

Verification of traffic-induced soil compaction after long-term ploughing and 10 years minimum tillage on clay loam soil in South-East Norway

Grain yields are presented from a 10-year field trial with four tillage regimes (annual ploughing, harrowing only, ploughing/harrowing alternate years and minimum tillage) on clay loam. We also present soil physical analyses and use the compaction verification tool (CVT) to assess compaction on plots with annual ploughing and minimum tillage, after using slurry tankers with contrasting wheel loads (4.1 Mg, 6.6 Mg) and wheeling intensities (1×/10×) in the 11th trial year, and yields monitored two years after compaction. Winter wheat yields in the period before compaction were strongly affected by tillage, with annual ploughing giving on average 24% higher yield than direct drilling. Both wheat and oats were far less affected in treatments with harrowing only or ploughing/harrowing alternate years, on average within 6% of annual ploughing. Yields after compaction were affected by both previous tillage and compaction intensity. In the first year, single wheeling after annual ploughing gave 23% yield reduction with 4.1 Mg wheel load and 28% reduction with 6.6 Mg wheel load, whilst multiple wheeling gave 14% reduction at 6.6 Mg wheel load. Yield reductions after minimum tillage ranged from 63% (single wheeling with 4.1 Mg) to 100% (multiple wheeling with 6.6 Mg). Similar trends were found in the second year. The soil physical data indicated that all wheeling led to changes in bulk density, pore sizes and permeability in both topsoil and subsoil on both sampled tillage plots. However, effects in the subsoil were partly masked by the soil's high initial bulk density, partly due to its high clay content. The CVT, which plots air capacity against hydraulic conductivity, suggested some harmful compaction on both plots, with the minimum tillage plot being less affected than the ploughed plot. However, yield results did not support this conclusion, indicating that other factors limited yields on the minimum tilled plot.

Traffic-induced soil compaction during manure spreading in spring in South-East Norway

The objective of this study was to evaluate long-term effects of two tillage regimes (ploughing and minimum tillage) on the bearing capacity of a clay rich soil, by using two different slurry tankers (4.1 and 6.6 Mg wheel load) and contrasting wheeling frequencies (1 and 10 passes). The soil strength was assessed by laboratory measurements of the precompression stress (Pc) at −6 kPa in topsoil (20 cm) and subsoil (40 and 60 cm) samples. Stress propagation, elastic and plastic deformation during wheeling were measured in the field with combined stress-state-transducer and displacement transducer system. Results presented in this study show that minimum tilled soil had 74% higher Pc than ploughed soil in the upper soil layer, whilst differences were less distinct in subsoil. Wheeling increased Pc at all soil depths. Compared to ploughing, higher strength in the upper layer of minimum tilled soil led on average to 60% and 48% reductions in the major principal stress with the use of the light and heavy slurry tanker, respectively. The extent of the major principal stress was dependent on the ground pressure in the topsoil. The first pass of a wheel caused the greatest damage in some cases, but all wheelings led to accumulative plastic deformation in both vertical and horizontal directions. Wheeling with high intensity would have exceeded Pc in all cases when soil was at a matric potential of −6 kPa. The results show that soil water content is an important factor influencing bearing capacity. Drier soil (−100 kPa), in combination with minimum tillage, limited the occurrence of stresses exceeding Pc in the upper soil layer.

SoilFlex: A model for prediction of soil stresses and soil compaction due to agricultural field traffic including a synthesis of analytical approaches

Soil compaction is one of the most important factors responsible for soil physical degradation. Soil compaction models are important tools for controlling traffic-induced soil compaction in agriculture. A two-dimensional model for calculation of soil stresses and soil compaction due to agricultural field traffic is presented. It is written as a spreadsheet that is easy to use and therefore intended for use not only by experts in soil mechanics, but also by e.g. agricultural advisers. The model allows for a realistic prediction of the contact area and the stress distribution in the contact area from readily available tyre parameters. It is possible to simulate the passage of several machines, including e.g. tractors with dual wheels and trailers with tandem wheels. The model is based on analytical equations for stress propagation in soil. The load is applied incrementally, thus keeping the strains small for each increment. Several stress–strain relationships describing the compressive behaviour of agricultural soils are incorporated. Mechanical properties of soil can be estimated by means of pedo-transfer functions. The model includes two options for calculation of vertical displacement and rut depth, either from volumetric strains only or from both volumetric and shear strains. We show in examples that the model provides satisfactory predictions of stress propagation and changes in bulk density. However, computation results of soil deformation strongly depend on soil mechanical properties that are labour-intensive to measure and difficult to estimate and thus not readily available. Therefore, prediction of deformation might not be easily handled in practice. The model presented is called SoilFlex, because it is a soil compaction model that is flexible in terms of the model inputs, the constitutive equations describing the stress–strain relationships and the model outputs.

Microbial Responses to Wheel-Traffic in Conventional and No-Tillage Systems

Traffic-induced soil compaction and tillage systems can impact the productivity and sustainability of agricultural soils. The objective of this study was to assess the response of soil microbial populations to wheel-traffic in two tillage systems on a Norfolk loamy sand (Typic Kandiudults; FAO classification Luxic Ferralsols). Experimental variables were with and without traffic under conventional tillage (disk harrow twice, chisel plow, field cultivator-planter) vs. no tillage employed in a split-plot design with four replications; main plots were traffic and subplots were tillage. Soil samples were collected from 0–2 and 2–4-cm depths, sieved (2 mm), and used to assess soil-water content, microbial biomass nitrogen (N), dehydrogenase, and microbial characterization using phospholipid ester-linked fatty acid (PLFA) analysis. Traffic increased soil-water content, had little affect on microbial biomass N, and increased microbial activity (no-till plots only) likely due to increased amounts of residue. Soil-water content, microbial biomass N, PLFA estimates of microbial biomass, and microbial activity were all consistently higher in no-till compared to conventional tillage plots. Data from this study suggest that conventional tillage results in a lower, more static, possibly more mature community of microbes while the microbial community under no-till appears to be a younger, more viable growing population. Finally, these data suggest that overall soil quality, at least in the surface soil layer, is improved in agricultural systems employing no-till operations.

Interactions of traffic and tillage applied to cotton on N movement below the root zone of a subsequent wheat crop

Although research has demonstrated the negative impact of traffic-induced soil compaction on crop productivity, knowledge is lacking regarding the interactive effects of equipment traffic and tillage systems, especially in regards to N management in conservationtilled multiple-cropping systems. The objective of this study was to examine the interaction of traffic and tillage systems applied to cotton ( Gossypium hirsutum L.) on N utilization and movement below the root zone of subsequent double-cropped wheat ( Triticum aestivum L.). A field study was initiated in 1987 on a thermic Typic Hapludult soil complex, utilizing a wide-frame tractive vehicle (WFTV) that allows for 6.1-m wide, untrafficked research plots to double-crop cotton with wheat. The experimental design was a split-plot with three replications. Main plots were: (1) conventional traffic (simulated with tractor); (2) no traffic (WFTV only). Subplots were tillage systems for cotton: (1) complete surface tillage without subsoiling (surface); (2) complete surface tillage and annual in-row subsoiling to 40-cm depth (subsoil); (3) complete surface tillage with once-only complete disruption of the tillage pan by subsoiling to a 50-cm depth on 25-cm centers in 1987 (complete); (4) strip-till where cotton was planted with in-row subsoiling into wheat residue. All tillage treatments were applied to the cotton and residual effects were observed in the wheat. In 1990–1991, fertilizer applications were made to wheat as 15N-labeled NH 4NO 3, and soil solution samples were collected (90-cm depth). While previous cotton tillage had no significant effect on wheat yields, traffic reduced wheat yields from 3427 to 2981 kg ha −1 in 1990. With no traffic, total fertilizer N recovery in the plant-soil system was increased by 20 and 10% in 1990 and 1991, respectively. The strip-till tillage treatment increased total fertilizer N recovery in wheat by 20% compared with other tillage systems in 1990. Surface tillage without subsoiling for cotton increased NO 3-N concentration below the root zone of wheat (90-cm depth) in both years. The data indicate that the tillage/traffic management system used for production of one crop in a doublecropping system was a major factor in reducing N losses and increasing fertilizer N recovery in the plant-soil system of the succeeding crop.

Soil Compaction Effect on Corn Rootworm Populations in Maize Artificially Infested with Eggs of Western Corn Rootworm (Coleoptera: Chrysomelidae)

Controlled infestation with eggs of western corn rootworms, Diabrotica virgifera virgifera LeConte, was used in a 2-yr study on the effects of wheel traffic-induced soil compaction on corn rootworm establishment, survival, and larval injury to the roots of maize, Zea mays L. Root injury ratings and cumulative emergence of adults of western corn rootworms, as taken from emergence cages, were lowest in plots where eggs had been infested into compacted interrows. Measurements of soil bulk density, air-filled porosity, and air permeability were taken on core samples to characterize soil physical properties in relation to soil compaction. Lowest rootworm survival and injury coincided with higher bulk density, lower air-filled porosity, and lower air permeability values characteristic of soil from the compacted interrow plots. Survival and establishment of western corn rootworm larvae were associated with greater soil pore continuity in uncompacted plots. Soil compaction induced by controlled wheel traffic may have potential as a management strategy for reducing larval corn rootworm movement into strip intercropped maize adjacent to areas previously planted to maize and rotated into a crop that is not a host for corn rootworms.

Impact of traffic-induced compaction of sandy soils on the yield of silage maize in The Netherlands

The effects of different axle loads on the yields of silage maize were compared on sandy soils at four locations in the Netherlands over the period 1983–1986. The same traffic intensity resulted in changes in bulk density, cone resistance and crop reactions in several types of sandy soil. Depending on the soil profile and weather conditions during the growing season, the heavy axle loads reduced yields by up to 38%. Average yield reductions were 15% with an axle load of 10 Mg and 4% with an axle load of 5 Mg. It is estimated that traffic-induced soil compaction reduces the total production of Dutch silage maize by 7%.