Status quo of soil compaction in Europe

Towards climate-smart sustainable management of agricultural soils SoilCompaC Mapping and alleviating soil compaction in a climate change context Deliverable 1.3 Status quo of soil compaction in Europe Due date of deliverable: M31 (August 2022) Actual submission date: M39 (April 2023) Deliverable 1.3: Status quo of soil compaction in Europe This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement N° 862695 2 GENERAL DATA Grant Agreement: 862695 Project acronym: SoilCompaC Project title: Mapping and alleviating soil compaction in a climate change context Project website: soilcompac Start date of the project: November 1st, 2021 Project duration: 36 months Project coordinator: Mathieu Lamandé DELIVERABLE NUMBER: D1.3 DELIVERABLE TITLE: Status quo of soil compaction in Europe DELIVERABLE TYPE: Report DISSEMINATION LEVEL: Under embargo until publishing, in meantime access allowed within EJP SOIL participants WORK PACKAGE N: WP1 WORK PACKAGE TITLE: Detection and alleviation of soil compaction DELIVERABLE LEADER: vTI AUTHORS: Florian Schneider, Tommy d’Hose SOILCOMPACCONTRIBUTORS: Marine Lacoste, Line Boulonne, Owen Fenton, Giulia Bondi, Reamonn Fealy, Amélie Beucher, Mathieu Lamandé Deliverable 1.3: Status quo of soil compaction in Europe This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement N° 862695 3 1. Introduction Three decades ago, 33 million ha (20 %) of agricultural land in Europe was estimated to be degraded due to anthropogenic soil compaction (Oldeman et al. 1991; Stolte et al. 2016). However, little is known about how Oldeman et al. (1991) came up with their area estimate, which makes it uncertain. Also, in the past three decades the weight of agricultural machinery has increased drastically (Schjønning et al. 2015), hence stresses induced by modern machinery are likely to exceed soil strength (Zink et al. 2010). Today’s extent of compacted agricultural soil should thus be much larger than it was 30 years ago (Keller et al. 2019). However, up till now, most field studies have been targeting soil compaction on plot and field scale and methods for a robust determination on larger scales are still lacking. The objective of the work presented in this report was to update and refine previous area estimates about the extent and severity of soil compaction in European agricultural land based on national soil inventory data. 2. Materials and methods This study refined and updated previous estimates about the area extent and severity of soil compaction in Europe based on representative national soil inventories. We analyzed data which was representative for about 530,000 km2 corresponding to approximately one third (32%) of the European Union’s total agricultural land (see Table 1 and Figure 1). The included datasets were: • France: RMQS1 (Réseau de Mesures de la Qualité des Sols, Institut National de la Recherche Agronomique et al. (2021) • Germany: BZE-LW1 (Bodenzustandserhebung Landwirtschaft, Poeplau et al. (2020) • Ireland: I-SIS (Irish Soil Information System) • Denmark: DSPD (Danish Soil Profile Database) • Belgium: Flanders-CMON (Bodemkoolstofmonitoringnetwerk Cmon) These datasets provided information on current topsoil (0-30 cm) and subsoil (> 30 cm) compaction levels under both grassland and arable land within their respective countries. To capture a broader EU-wide perspective, we also incorporated data from the LUCAS Soil Survey conducted in 2018 (Figure 2). These data were provided by the European Soil Data Centre (https://esdac.jrc.ec.europa.eu/). While the LUCAS Soil Survey dataset only offered topsoil compactness information, it provided the only EU-wide, consistent data available at the time of this report (Orgiazzi et al. 2018). Deliverable 1.3: Status quo of soil compaction in Europe This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement N° 862695 4 Table 1. Regional inventories used for evaluation of the extent of soil compaction in Europe’s agricultural land. Country Agricultural area (km2) Dataset Number of sites Number of soil depth increments EU 1,629,078 LUCAS-Soil 2018 3,743 7,274 France 285,538 RMQS1 1,483 2,814 Germany 165,910 BZE-LW1 3,080 17,187 Ireland 43,370 I-SIS 91 224 Denmark 26,180 DSPD 556 1,793 Belgium/Flanders 6,170 CMON* 168 685 * Campaign still running Figure 1: Map of regional inventories used for evaluating the extent of soil compaction for soil profiles deeper than 30 cm. Agricultural land based on Corine Land Cover 2018 is highlighted in green for regions with detailed regional soil data available for the scope of this study and in grey elsewhere. Black dots illustrate the rough location of inventory sites (only for datasets where this information is public). Deliverable 1.3: Status quo of soil compaction in Europe This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement N° 862695 5 Figure 2: The LUCAS Soil 2018 inventory used for evaluation of the extent of soil compaction for the European agricultural topsoils. Agricultural land based on Corine Land Cover 2018 is shown in grey. Following the recommendation of the ENVASSO-project, the apparent compactness of European agricultural soils was judged on the basis of the packing density indicator (Huber et al. 2008). Packing density can be easily derived from standard bulk density and soil texture data and has been shown to relate the state of soil compactness with crop growth in various pedo-climatic zones (Figure 3) (Daddow 1983; Jones 1983; Kaufmann et al. 2010; Renger et al. 2014; Schneider und Don 2019). For Belgium/Flanders, missing soil texture data in CMON at the time of submission of this report was gap filled with modelled data from SoilGrids (https://soilgrids.org/). In order to ensure the international comparability among inventory sites, only bulk density values derived via volumetric soil sampling, i.e. no PTFderived bulk density values, were used to calculate packing densities. Bulk density in g cm-3 was calculated as 𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵 𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑 = 𝑚𝑚𝑡𝑡𝑡𝑡𝑡𝑡 − 𝑚𝑚𝑐𝑐𝑡𝑡𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐 𝑉𝑉𝑡𝑡𝑡𝑡𝑡𝑡 − 𝑉𝑉 𝑐𝑐𝑡𝑡𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐 where 𝑚𝑚𝑡𝑡𝑡𝑡𝑡𝑡 is the mass of fine soil (< 2mm) dried at 105°C until constant weight in g, 𝑚𝑚𝑐𝑐𝑡𝑡𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐 is the mass of coarse fragments > 2 mm dried at 105°C until constant weight in g, 𝑉𝑉𝑡𝑡𝑡𝑡𝑡𝑡 is the volume of the soil sample taken from the field in cm3, and 𝑉𝑉 𝑐𝑐𝑡𝑡𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐 is the volume of the coarse fragments in cm3. For samples where 𝑉𝑉 𝑐𝑐𝑡𝑡𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐 was not available, it was estimated as follows 𝑉𝑉 𝑐𝑐𝑡𝑡𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐 =𝑚𝑚𝑐𝑐𝑡𝑡𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐 𝛿𝛿𝑐𝑐𝑡𝑡𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐 Deliverable 1.3: Status quo of soil compaction in Europe This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement N° 862695 6 where 𝛿𝛿𝑐𝑐𝑡𝑡𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐 was the density of the coarse fragments in g cm-3. If also the latter was also not available we assumed the density to be constant and resemble the one of quartz (2.65 g cm-3). A given site was classified as compacted if its packing density exceeded 1.75 g cm-3 (Huber et al. 2008; Kaufmann et al. 2010; Schneider und Don 2019). This threshold is arbitrary but has been used in the cited literture before to separate compacted from non-compacted soil. However, to the best of our knowledge, there are no depth-specific threshold values to sparate compacted from non-compacted soil layers yet. In this study, if at a given site packing density was available at multiple depths, we only considered the maximum packing density measured at that site. Figure 3: Method to derive the packing density from the standard bulk density and the soil texture as an indicator of soil compactness. After Renger et al. (2014). Deliverable 1.3: Status quo of soil compaction in Europe This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement N° 862695 7 3. Results and Discussion A rough evaluation of soil compaction was performed using the arbitrary threshold value of 1.75 g cm-3 as described above. According to this threshold, 10 % of the sites were classified as showing a compacted agricultural soil in the total EU as well as France, 20% in Ireland, 40% in Denmark, and 50 % in Belgium and Germany. Although following well established guidelines to assess soil compaction, these numbers are misleading because they are based on packing density data from different depths. In the present study, the maximum soil sampling depth differed significantly between regions. Those regions with soil inventory data available to larger soil depth showed a larger share of densely packed soil layers above the critical threshold and where therefore classified as more compacted. In parts, this was simply because bulk density and packing density tended to increase with depth – a consistent pattern that may be attributed to the increasing overburden pressure (Gao et al. 2016), decreasing organic matter input (Balesdent et al. 2018), and decreasing pedoturbation (Johnson et al. 2014) with increasing soil depth. Future soil health assessments should therefore consider depth-dependent thresholds for soil compactness, which still have to be developed. Apart from soil depth, this study also revealed potential effects of land-use and management on soil compactness. For Europe, Belgium, France and Germany, which had soil data at fixed depths, average packing densities under permanent grassland were consistently lower than under cropland (Figure 5). This difference was most pronounced in the topsoil and decreased with increasing soil depth. Notably, topsoil under cropland was more densely packed than under permanent grassland despite regular tillage, i.e. mechanical loosening, activities on cropland. It was not possible to perform the same analysis for Denmark and Ireland, where soil data was available at various depths (depths delimiting pedological horizons). Deliverable 1.3: Status quo of soil compaction in Europe This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement N° 862695 8 Figure 4: Soil packing density (g cm-3) as a function of soil depth (cm) calculated for the five regional (Belgium, Denmark, France, Germany, Ireland) and the European (EU) soil inventories for agricultural land. Lines represent average reported packing densities per recorded depth increment at a given site. The threshold value used in this study to separate compacted from non-compacted soil is highligted with dashed lines. Deliverable 1.3: Status quo of soil compaction in Europe This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement N° 862695 9 Figure 5: Soil packing density (g cm-3) as a function of soil depth (cm) calculated for the five regional (Belgium, Denmark, France, Germany, Ireland) and the European (EU) soil inventories for grassland (green) and cropland (brown), separately. Lines represents average reported packing densities per recorded depth increment at a given site. The threshold value used in this study to separate compacted from non-compacted soil is highligted with dashed lines. For countries with soil inventory data from fixed depths, circles illustrate median average packing densities by land-use.