20 research outputs found
Evaluation of the Potential for Soil Organic Carbon Content Monitoring With Farmers
Increasing soil organic carbon (SOC) content is crucial for soil quality and climate changemitigation. SOC monitoring is indispensable to the corresponding policies and shouldprovide results at farm scale to allow for incentives. In Switzerland, farmers performmandatory analyses of the SOC content of the 0â20 cm topsoil of every field, based ona composite sample, at least every 10 years. The corresponding results are stored in adatabase in canton of Geneva. These data may be relevant for topsoil SOC monitoring,in particular for carbon sequestration policies, provided that they show appropriatequality, which is analyzed in this study. The minimum detectable change (MDC) of pastresults calculated based on the observed SOC changes was 0.013% g gâ1at cantonscale (2,700 fields). Based on extended sampling of three representative fields, differentsampling strategies were simulated to determine the best future sampling guidelines forfarmers. Collecting 20 aliquots with a gouge on the field diagonals was considered thebest sampling compromise with field MDC ofâŒ0.1% g gâ1and a sampling durationof 20 min. Compared to this procedure, former farmersâ sampling was not biased inaverage but showed a variance of 0.22% g gâ1due to smaller number of aliquotsand varying sampling depths. Based on the best sampling results and assumptions onfarm-scale SOC variance or SOC differences, the MDCs at farm scale ranged from0.21 to 0.12% g gâ1(5 fields) and 0.09 to 0.05% g gâ1(30 fields), respectively.These MDCs are small compared to published monitoring networks MDCs and allowdetermining SOC change rates at farm scale, thus offering perspectives for inexpensiveand efficient monitoring in the frame of soil quality or climate mitigation incentives. Forthe latter, however, additional information with equivalent soil mass and deeper-layercarbon content would be necessary
Bypass and hyperbole in soil science:A perspective from the next generation of soil scientists
International audienceWe, the coâauthors of this letter, are an international group of soil scientists at early career stages, from PhD students to postdoctoral researchers, lecturers, and research fellows with permanent positions. Here, we present our collective musings on soil research challenges and opportunities and, in particular, the points raised by Philippe Baveye (Baveye, 2020a, 2020b) and Johan Bouma (Bouma, 2020) on bypass and hyperbole in soil science. Raising awareness about these issues is a first and necessary step. To this end, we would like to thank Philippe Baveye and Johan Bouma for initiating this debate.......
Soil organic carbon content and soil structure quality of clayey cropland soils ::a largeâscale study in the Swiss Jura region
Soil organic carbon (SOC) fashions soil structure, which is a key factor of soil fertility. Existing SOC content recommendations are based on SOC:clay ratio thresholds of >1:10. However, the corresponding SOC content might be considered hard to reach in clayey soils, whose structure degradation risk is assumed to be high. Here, we analysed the SOC content and soil structure quality of soils under similar cropping practices with clay contents ranging from 16% to 52%. Five undisturbed soil cores (5â10 cm layer) were collected from 96 fields at 58 farms in the Swiss Jura region. We assessed the soil structure quality visually using the CoreVESS method. Gravimetric air content and water content, and bulk density at â100âhPa were also measured, and the soil structure degradation index was calculated. We found that the relationship between SOC and clay content held over the clay content range, suggesting that reaching an acceptable SOC:clay ratio is not limited by large clay contents. This suggests that the 1:10 SOC:clay ratio may remain useful for clayey soils. In contrast to what was expected, it is not more challenging to reach this ratio in clayey soils even if it implies reaching very large SOC contents. SOC content explained the considered physical properties better than clay content. From a soil management point of view, these findings suggest that the soil texture determines a potential SOC content, while the SOC:clay ratio is determined by farming practices regardless of the clay content
Quantifier lâintensitĂ© du processus de lessivage dans les sols : apport de la micromorphologie couplĂ©e Ă de lâanalyse dâimage
Quantifier lâintensitĂ© du processus de lessivage dans les sols : apport de la micromorphologie couplĂ©e Ă de lâanalyse dâimage. 12Ăšme JournĂ©es Nationales dâEtude des Sols. Le sol en hĂ©ritag
Long-term quantification of the intensity of clay-sized particles transfers due to earthworm bioturbation and eluviation/illuviation in a cultivated Luvisol
As a result of the limited knowledge on eluviation/illuviation and bioturbation rates, these two processes of soil particles translocation are qualitatively described either as synergic or competing processes. Here we take the opportunity of the recent development of an image analysis procedure to quantify illuvial clay and earthwormâs porosity to quantify the intensity of illuviation and bioturbation cumulated over soil formation in a temperate cultivated Luvisol. The key objectives of the study are i) to quantify the total intensity of illuviation and bioturbation and their depth distributions and ii) to assess the possibility for bioturbation to limit or compensate the depletion of the clay-sized fraction in topsoil horizons due to eluviation. The total quantity of illuvial clay is 1,100 t.haâ1 while the estimated annual amount of clay-sized fraction translocated by eluviation is between 0.08 and 1 t haâ1 yrâ1. This is comparable to the annual loss of land by water erosion (between 1 and 5 t haâ1 yrâ1) or by arable erosion (3.3 t haâ1 yrâ1). Eluviation/illuviation is thus a discrete and active form of soil loss. With approximately 1,900 t.haâ1 of clay-sized fraction, the amount of fine particles displaced at least once by bioturbation is higher than the one related to eluviation/illuviation. At first sight, it therefore seems possible for biological activity to compensate for vertical transfers of the clay-sized fraction by eluviation/illuviation. However, our study shows that a considerable amount of the clay-sized fraction will never be brought up by the bioturbation and will remain definitively lost for the surface horizons as bioturbation decreases non-linearly with depth. Consequently, a preventive management of the depletion of the clay-sized fraction in topsoil horizons by eluviation/illuviation should be preferred to the curative management of its consequences by bioturbation
Quantification by image analysis on soil thin sections of lessivage and bioturbation rates in soils in response to land use change and recycling of organic residues
Quantification by image analysis on soil thin sections of lessivage and bioturbation rates in soils in response to land use change and recycling of organic residues. 20th World Congress of Soil Scienc
Upward mercury transfer by anecic earthworms in a contaminated soil
Mercury (Hg) is a contaminant of global importance but its fate and impact in soils is overlooked. Earthworms are responsible for soil bioturbation but their interaction with Hg is poorly described. This study was conducted on a Hg contaminated site in Switzerland. The objectives were to determine the Hg tolerance of Lumbricus terrestris and Aporrectodea nocturna, and their capability to redistribute Hg from deep contaminated soil layers to remediated topsoil layers. Earthworms were incubated for 30 days in 35âŻcm height soil columns with soil Hg contents ranging from 0.19 to 83âŻmg Hg kgâ1. 100% survival was observed except for the highest soil concentration (67% survival). Corresponding bioaccumulation factors ranged from 1 to 17. In parallel, Hg upward transfer by earthworms from a deep contaminated soil layer to a non-contaminated 40âŻcm thick surface layer was studied in 80âŻcm repacked soil columns. After 70 days, total Hg content of surface casts was 10 times higher than the non-contaminated soil. Furthermore, the 25â30 and 35â40âŻcm layers had a Hg content of 0.537 and 8.54âŻmg Hg kgâ1 respectively, both exceeding the local threshold intervention value of 0.5âŻmg Hg kgâ1. We concluded that (i) earthworms not acclimated to polluted soils can survive Hg levels as high as 85âŻmg Hg kgâ1 in mesocosms, and (ii) a 40âŻcm thick remediated layer would be recontaminated after 6 months of earthworm activity if the underneath layer remained contaminated
Changes in topsoil organic carbon content in the Swiss leman region cropland from 1993 to present. Insights from large scale on-farm study
Increasing cropland topsoil organic carbon (SOC) content is a key goal for soil improving quality and adaptating soils to climate change. Moreover, the short term potential of climate mitigation by carbon sequestration is mostly attributed to increasing topsoil SOC content (Balesdent and Arrouays, 1999, Chambers et al., 2016; Minasny et al., 2017; Balesdent et al., 2018). However, the possibility to increase SOC content is highly disputed in current literature which is mostly based on field experiments.
We quantified the on-farm SOC content deficit and SOC content change rate of cropland topsoil (0â20 cm) from western Switzerland using the data bases of Geneva and Vaud cantons containing more than 30,000 topsoil analyses, performed every ten years on every cultivated field of the region since 1993. SOC deficit was estimated as the amount of SOC necessary to reach the 0.1 SOC:clay ratio considered as the minimum required SOC amount for acceptable soil quality. Cropland topsoils of the Vaud and Geneva cantons displayed a 20% and 70% SOC content deficit, respectively.
In both cantons, the range of observed rates of change in SOC content from 1993 to present was very large, from â30 to +30â° per year, with a median value of 0. However, the time trends showed a highly significant linear increase of rates from â5â° to +6â° per year on average, in 1995 and 2015, respectively, with no change in SOC content reached by 2005â2007.
These trends were attributed to the Swiss agri-environmental schemes applied at the end of 20th century, namely mandatory cover crops and minimum rotations of 4 crops. Further, SOC content increase was accordant with the continuing adoption of minimum tillage, conservation agriculture and multi-species intense cover crops.
These findings oppose to those obtained in Swiss long-term experiments, which emphasizes the need to use on-farm information when adressing agriculture policy, climate mitigation or soil quality management issues