Soil compaction is one of the primary threats to soil degradation in Europe; however, data to guide grassland farmers on how to avoid traffic induced soil compaction is limited. In grassland systems, soil moisture regimes are measured by daily soil moisture deficit (SMD) values and, when coupled with soil physical indicators could help safeguard the soil physical quality (SPQ). The objective of this study is to investigate how soil physical quality changes across different induced traffic compaction events at targeted SMD. A field study at Johnstown Castle Beef Farm (Wexford, Ireland) investigated the severity of soil physical changes caused by machine trafficking across different targeted soil moisture regimes. A tractor and a fully loaded slurry tanker trafficked moderately drained soil plots at SMD targets of 10 (dry (D)), 0 (moist (M)) and – 10 (wet (W)) mm. Compaction events simulated four passes across one year of grassland management: at the time of the first silage cut, in April; after the first cut silage harvest, in June; before the slurry spreading opening season, in October; and at the beginning of the slurry spreading period, in January. Soil bulk density (BD) samples were taken in the middle of the tyre marks at different depths (0-10, 10-20 and 20-30 cm). To examine indirect soil physical quality of various treatments, soil physical data was used to calculate the S value (S_i) using the SawCal model. Initial results showed that the progressive increase in the number of trafficking events occurring above SMD 0 mm  led to major compaction, which significantly increased (P<0.05) compared to trafficking at SMD 10 mm. The cumulative effect of the four passes showed a significant difference from M to D and W, with M’s BD increasing by 22.2% compared to the control. D and W BDs remained similar ranging between 1.10 and 1.11 Mg m^-3. Accordingly, S_i values were indicative of very poor (i.e. degraded; S < .035) SPQ in M only. These early results indicate that the most severe degradation occurred in the 0 – 10 cm depth. Forecasting soil moisture is a valuable tool for the protection of SPQ and to enable farmers to minimise any soil degradation due to trafficking.

Keywords: soil compaction, grasslands, soil moisture, field traffic, soil physical quality indicators

How to cite: Lepore, E., Schmidt, O., Fenton, O., Tracy, S., Bondi, G., and Wall, D.: Moisture limits for grassland soil to avoid structural damage due to machine trafficking, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3137, https://doi.org/10.5194/egusphere-egu23-3137, 2023.

Harvesting operations of perennial forage crops can lead to soil compaction problems, which in turn lead to poorer soil structure, increased erosion, and reduced organic matter. The present study focuses on the evaluation of soil compaction caused by harvesting operations of Phalaris arundinacea (Reed Canary Grass) by measuring soil penetration resistance in two different areas of the farm of the University of Tuscia. The measurements were carried out in two consecutive years following the biomass harvesting operations. These field trials are part of the H2020 project CERESiS (ContaminatEd land Remediation through Energy crops for Soil improvement to liquid biofuels Strategies) (GA 101006717), which started in November 2020 and will continue until the end of the project in 2024. P. arundinacea is a species that lends itself to biomass production and phytoremediation of contaminated soils. The areas with different textures were treated with a minimum tillage system, notably, only a secondary tillage of the field with a disc harrow was carried out in late winter 2021 and sown in spring 2021. Part of each area was allocated for control and was fenced off after sowing, to avoid any trampling. The remaining areas were divided into 3 plots in which the operations were repeated. Measurements were taken in 2021 and 2022 following harvesting operations using a John Deere 5100 GF tractor with disc mower. Penetration resistance and soil moisture measurements followed, to verify the impact of the operations and the effect of soil type on compaction. For penetration resistance, 15 measurements per plot were taken up to a depth of 80 cm using an electronic penetrometer model Penetrologger (Royal Eijkelkamp Soil &Water; Giesbeek, The Netherlands). The results of the soil analysis indicate different chemical and physical characteristics between the two areas, in particular, one area has a clay texture and the other a sandy loam texture. The data collected from the measurement of penetration resistance pointed out significant differences between the plots subjected to tractor passage for harvesting operations and the control areas. Differences were also observed between the two areas, which was an expected result given the different texture and humidity recorded; thus, confirming the effect that this parameter can have on compaction and giving an indication of when to avoid entering the field.  It was interesting to note that an effect on the soil can already be seen after two years, despite the minimal intervention. Inspection at different depths showed a general tendency for resistance to penetration to increase with increasing depth, a greater difference between treatments (with tractor and control) up to 40 cm and a tendency to overlap beyond this depth. It will now be interesting to see how this will evolve over the next few years and to assess how the increase in penetration resistance can be further reduced. Compaction affects many other soil parameters, in a context of climate change, it is crucial to implement strategies to reduce it in agricultural operations.

How to cite: Bianchini, L., Alemanno, R., Lord, R., Nunn, B., and Colantoni, A.: Assessing penetration resistance in Phalaris arundinacea harvest operations under minimum tillage conditions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5907, https://doi.org/10.5194/egusphere-egu23-5907, 2023.

Conservation tillage practices, such as reduced tillage, are often considered beneficial regarding soil fertility and sustainability. However, a risk of developing a shallow compact hardpan is associated with these practices that can hinder optimal water and gas transport within the root zone and thus impact soil health and productivity. To explore this risk, we compared conventional mouldboard ploughing (to 30 cm depth; MP) and reduced tillage (5-7 cm; RT) in a long-term experiment (approximately 15 years) on sandy loam soil. The field was uniformly tilled to a depth of 15-20 cm depth after the termination of the experiment. We evaluated the soil water and gas flow variables (saturated hydraulic conductivity, gas diffusion, and effective air-filled porosity), and biological soil properties for the 20-30 cm layer for the MP and RT treatments.

Soil was more compact in the reduced tillage treatment compared to conventional tillage, especially in the 20-30 cm soil layer. Soil bulk densities in the 20-30 cm soil layer were 1.62 and 1.80 g cm^-3 in MP and RT treatments, respectively. There was no difference between the conventional and reduced tillage for effective air-filled porosity or gas diffusivity measured at -100 hPa water potential. Similarly, saturated hydraulic conductivity measured in the field was not different under the two tillage practices. The conventional tillage had 61% more earthworm abundance than the reduced tillage. The results indicated that despite the formation of a compact hardpan at 20-30 cm soil layer, as characterized by a higher bulk density, there were little to no effects of tillage on the soil functions related to water and gas transport. Moreover, the linkages between the soil physical quality indicators and microbial indicators (enzyme activity, microbial biomass carbon and nitrogen) were also explored.

How to cite: Nawaz, M. M., Arthur, E., Peigné, J., Nazari, M., Fouladidorhani, M., and Lamandé, M.: Impact of long-term reduced tillage on water and gas transport in a sandy-loam soil and linkages to biological indicators, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6402, https://doi.org/10.5194/egusphere-egu23-6402, 2023.

Soil compaction is a major threat to global agriculture as it can affect crop production and negatively impact the environment. This can result in increased production costs, additional labor requirements and reduced time windows for field access. Nevertheless, the actual effects of soil compaction on the growth of different crops in different pedo-climatic regions are insufficiently investigated. In this study, possibilities for such assessments by remote sensing are evaluated in three pedo-climatic zones of Europe using a harmonized experimental design. Oceanic climate is subject in Belgium and The Netherlands, while in Austria a location with continental, drier climate and another location in an intermediate continental-hemiboreal climate are included.

By means of unmanned aerial vehicles (UAV) equipped with optical and multispectral cameras, plant-physiological indicators are surveyed frequently throughout the vegetation period. Examples for such indicators are crop height, vegetation cover and density, NDVI, and a set of further indices derived from the reflectance signature of the plants. Fields are monitored that partly underwent a defined and delimited compaction (headlands or wheel tracks from management using heavy machinery) and soil physical standard methods are applied to characterize the compaction state of the soils (e.g. bulk/packing density, soil penetration resistance). Differences in the listed indicators are analyzed between plants in compacted parts and the non-compacted areas closely nearby under the same growing conditions.

Results from the first year of observations revealed distinct differences between plant growth in compacted and non-compacted areas. Several indicators showed interesting patterns throughout the vegetation period, which will be subject of further in-depth analyses. In the continental climate and affected by an exceptionally dry winter, early stage development of winter wheat was even more vital in compacted areas. Further statistical analyses of the gathered datasets from the UAV- and in-field-observations will provide insights on whether information about the state of soil compaction and its effects on plant physiology are supposed to be derived from these surficial indicators.

How to cite: Weninger, T., Konzett, M., D´Hose, T., Teuling, K., and Schmaltz, E.: Remote sensing of vegetation dynamics as an indirect assessment of soil compaction, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8891, https://doi.org/10.5194/egusphere-egu23-8891, 2023.

Soil compaction due to field traffic can reduce yields and increase a fields susceptibility to surface runoff and soil erosion. However, detecting and monitoring compacted soils is time and labor intensive. Additionally, most detection methods focus on few points within a field and usually do not provide information on the spatial distribution of soil compaction and its effects on a field scale. 
In this study, we aim to present a method for detecting potentially compacted areas on field scale using an unpiloted aerial vehicle (UAV). Using an UAV enable the non-inversive collection of field vegetation patterns want, which can be linked to differences in soil properties and soil structure.
In two study regions, we monitored six fields for four years. For each field, at least four UAV-flights were carried out per season. The UAV was equipped with a RGB and a multispectral sensor. Spatial corrections and spectral calibrations were performed with ground control points and calibration targets. To analyze the data for patterns in the vegetation, models of plant height and various vegetation indices (NDVI, SAVI, WDRVI, EVI) were calculated and combined with three different clustering algorithms (k-means, fuzzy k-means, CLARA). To validate the identified vegetation patterns, several field campaigns were conducted to analyze soil texture, saturated hydraulic conductivity, air permeability, bulk density, and yield. 
Our study shows that patterns in the vegetation can be distinguished by their geometry and orientation. Linear patterns running parallel to the tramlines and planar patterns in the headland indicate potential compaction, whereas rounded patterns are indicators for topography changes. Soil samples within the detected linear patterns overall showed an increase in bulk density, and a decrease in saturated hydraulic conductivity and air permeability. Yield samples were also reduced in those patterns for all studied crops. Thus, we can conclude that UAV analysis is suitable method for soil compaction detection. However, detected patterns can be overlaid by other causes.

How to cite: Lindenstruth, F., Kuhwald, M., Augstin, K., and Duttmann, R.: Detection of soil compaction by the spatial analysis of vegetation characteristics via UAV and clustering algorithms, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11751, https://doi.org/10.5194/egusphere-egu23-11751, 2023.

Soil compaction caused by modern mechanized agriculture has severe impacts on soil functioning and negative consequences on crop production. In the subsoil, these effects are persistent and difficult to ameliorate. To further clarify the compaction effect on the subsoil, we imposed compaction on 21^st April 2022 on a moist Calcaric Chernozem (silty clay loam) by pulling a full 2-axle slurry tanker (10 m³, pendulum tandem axle, max. wheel load 3 Mg) with a tractor (19.5 Mg total load) through the field. Six months after the compaction event (in autumn (18^th October 2022)), we evaluated the effects on field-measured soil structural quality indicators (SubVESS, bulk density, penetration resistance) and saturated hydraulic conductivity, then compared them to laboratory-measured gas flow-related parameters on intact 100 cm³ soil cores at -100 hPa (air-filled porosity, gas diffusion, and air permeability) at one depth in the subsoil (30-40 cm) and quantified pore geometry and tortuosity and geometry.

Simulation of traffic using TerranimoÒ indicated a risk of compaction down to 30 cm depth. The compacted treatment did not noticeably affect the soil bulk density. However, based on visual evaluation by SubVESS, compaction decreased porosity and aggregate friability. The overall soil structural quality (Ssq) scores were 2.1 and 1.4 for the compacted and control subsoil layers, respectively. Further, compared to the control treatment, a higher penetration resistance for the compacted treatment was observed from 5 cm to 35 cm. Field-measured saturated hydraulic conductivity decreased by 42% after compaction. Soil gas transport by convection (air permeability) and diffusion (gas diffusivity) decreased by 67% and 48%, respectively, after compaction. Furthermore, compaction decreased air-filled porosity and pore organization by 28 and 60%, respectively, and increased pore tortuosity. It can be concluded that although compaction did not increase bulk density in the subsoil, the negative effects of traffic was detectable by SubVESS, and the quantitative parameters related to air and water flow.

How to cite: Fouladidorhani, M., Lamandé, M., Moitzi, G., Nawaz, M. M., Nazari, M., Wagentristl, H., and Arthur, E.: Subsoil compaction impacts soil quality indicators in a Calcaric Chernozem, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9118, https://doi.org/10.5194/egusphere-egu23-9118, 2023.

Mechanization operations in agriculture have, for the last two decades, involved consistently higher wheel loads with an increased risk of soil compaction, particularly in the subsoil. Subsoil compaction is more persistent compared to the topsoil due to limited mitigation options. There is, however, a potential for the natural recovery of compacted subsoils through processes such as freeze-thaw and wet-dry cycles, and biological activity. The objectives of the present study were to (i) quantify the persistent effects of subsoil compaction on subsoil pore characteristics and water flow, based on visual and quantitative methods, and (b) investigate the potential for natural recovery nine years after the compaction event.

Soil compaction was achieved by tractor-trailer combinations for slurry application with a maximum wheel load of 8 Mg on a loamy Luvisol. The compacted plots were trafficked annually for four years (2010-2013). Nine years later (2022), field measurements (saturated hydraulic conductivity, visual evaluation of subsoil structure [SubVESS], and penetration resistance) were conducted at a depth of 0.3-0.4 m. Additionally, undisturbed samples of 100 cm³ were taken for measurements of gas flow (air permeability [k_a] gas diffusivity [D_p/D_o], and air-filled porosity[ε]) after equilibration at a matric potential of −100 hPa. The negative impact of compaction on the measured variables was compared to previous measurements conducted four years after (2017) the compaction event.

Nine years after compaction, there was still a marked negative effect of compaction on the soil structure assessed by the SubVESS method, with the largest impact observed on soil strength, root growth restriction, and aggregate friability. Saturated hydraulic conductivity was 63% lower in the compacted treatments compared to the control, while penetration resistance increased from 1.91 to 2.65 MPa after compaction. We also observed a strong negative effect of compaction on soil air permeability (−54%), gas diffusion (−30%) and the effective air-filled porosity (−24%). These changes were reflected in decreased pore organization [PO] and tortuosity in the compacted plots. Compared to five years earlier, there was a potential for natural recovery of the gas transport and pore structure variables (k_a, D_p/D_o, ε, PO). In 2017, there was an average compaction-induced reduction of 55% in the mentioned variables, and this changed to 38% in 2022, suggesting an increased recovery with time. Thus, although the effect of compaction on the subsoil was persistent after several years, there is a possibility that natural processes may play a significant role in recovering critical soil functions after compaction in the upper subsoil.

How to cite: Arthur, E., Fouladidorhani, M., Yan, F., Nazari, M., Nawaz, M. M., Munkholm, L., and Lamandé, M.: Persistence of subsoil compaction and potential for natural recovery in a sandy loam soil, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9332, https://doi.org/10.5194/egusphere-egu23-9332, 2023.

Soil erosion by water is one of the main causes of degradation of arable soils worldwide. Through the degradation of soil functionality and the long-distance effect of polluted soil particles, water erosion can severely limit soil fertility and the condition of aquatic ecosystems. Nowadays, a variety of different soil erosion models are used on different spatial and temporal scales to assess soil erosion risk, identify risk areas and support decision makers in adapting soil protection measures. Field studies show that highly compacted field areas such as wheel tracks, can have a major influence on the extent of soil erosion and runoff, but so far, they are not considered in any model-based soil erosion assessment.

The aim of this study is therefore to present an approach for integrating compaction effects of tramlines into process-based soil erosion models. Furthermore, the effects of tramlines on soil erosion and runoff processes within a watershed are to be identified. For this purpose, the soil erosion model EROSION 3D (E3D) was parameterized by accounting for soil conditions of compacted wheel tracks for a watershed in Norther Germany. In a further step, the modelling was conducted for a real heavy rainfall event and calibrated and tested with mapped runoff and soil erosion data. Additionally, a sensitivity analysis of the input parameters was conducted in order to assess soil properties which have a major impact on the model results.

The study shows that small-scale features such as tramlines can be integrated into soil erosion models and that this can significantly improves the spatial prediction of runoff and soil erosion. The model results also show that tramline tracks can have a significant contribution (up to 75 %) to total erosion as well as to sediment input into the water network, while bulk density of the wheel tracks is a major factor influencing modelled runoff and soil loss. The model results indicate that tramlines can play a key role in runoff and erosion processes and that the consideration of highly compacted areas in soil erosion assessments in agricultural landscapes is crucial. The results also indicate, that soil conservation measures may need to foster on tramlines and other compacted field areas such as headlands.

How to cite: Duttmann, R., Saggau, P., and Kuhwald, M.: Compacted wheel tracks as underestimated structures in water erosion events in agricultural landscapes: Results of a first process-based model application at catchment level., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17436, https://doi.org/10.5194/egusphere-egu23-17436, 2023.