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The measurement of aggregate stability is an important indicator of soil quality and is widely used for monitoring soil condition. The SLAKES mobile app is an alternative tool to laboratory-based methods to measure soil aggregate stability. It provides aggregate stability measurements through Slaking Index (SI) with SI close to 0 suggesting high stability and values above 7 suggesting minimum stability. As the duration of this low-cost experiment is only 10 minutes, SLAKES is very attractive for scientists and no-scientists. SLAKES was implemented in Australia and has proven its efficiency in several studies.This study was conducted to determine whether the SLAKES mobile app could be adapted to French soils and then could be an alternative to the Mean Weight Diameter (MWD) method, normalized in France (ISO 10390). More specifically, the three main objectives were: (i) determining whether the aggregate stability measurements depend on the phones used for the experiment, (ii) estimating the number of measurements necessary to get reliable results, (iii) determining whether the app has the ability to detect the effect of contrasting soil managements previously shown using the MWD method.The study was performed on silty loam soils from EFELE (Effluents d’Elevage et Environnement) experimental site at le Rheu (Brittany, France) which is part of the French “Organic Residues” research observatory (SOERE PRO). The experimental design combines two different tillage practices (conventional tillage and shallow tillage) with two fertilizer treatments (mineral and organic (cattle manure)) randomly replicated three times. Soil samples were collected in March 2017 at both 0-15 cm and 15-25 cm depth from the 12 plots. The SI was measured on three aggregates simultaneously and this measurement was repeated 15 times for each sample which provided 45 SI per sample. Outliers above SI=11 were removed before statistical treatments. Four different phones of the same brand and generation were used to measure SI.An analysis of variance showed that the effect of the smartphone on SI measurements was not significant (p-value = 0.73, 0.88, 0.067 for 3 different samples). The SLAKES results showed comparable significant separation of means (p < 0.0001) between each soil management than the MWD method. According to the results of an analysis of variance, SI was significantly lower in reduced tillage than in conventional tillage condition (p-value = 2.10-16). These results indicate a higher soil stability in reduced tillage. Yet, the analysis of variance did not underline any effect of fertilization on the SI (p-value = 0.28), as previously found with the MWD method.This study proved that a relatively simple mobile app can detect the effect of soil management practices on aggregate stability with a similar performance than the MWD method. This conclusion was reinforced by the existing correlation between the SI and the MWD index (p-value = 0.00059, R2 = 0.39). We recommend to perform similar experiments on other sampling campaigns or in other pedological and soil management contexts taking at least 15 measures per sample.

The term Organic Waste Products (OWPs) encompasses a wide range of byproducts such as manure, sewage sludge or green waste compost. The use of OWPs impacts soil quality and functioning, agricultural yields, carbon (C) sequestration, biogeochemical cycles of nutrients like nitrogen (N) or phosphorus, and organic matter (OM) dynamics. These impacts likely depend on the considered OWP.Taking advantage of 3 mid to long-term experimental trials (6 to 20 years) located in the Northern part of France (Paris region; Brittany; Alsace), we investigated the impact of 16 different OWPs on C content and stability. To do so, surface soil samples from replicated plots amended with the different OWPs used either alone or in addition with mineral N fertilization and appropriated control treatments were analyzed using Rock-Eval 6® thermal analyses. Samples taken up at the onset of the experiment and after 6, 18 and 20 years for the 3 sites respectively were analyzed. It resulted in the analyses of 248 different samples whose Rock-Eval 6® (RE6) signature can be used as a proxy for soil organic carbon (SOC) biogeochemical stability. In particular, we determined 2 RE6 parameters that were related to SOC biogeochemical stability in previous studies (e.g. Barré et al., 2016): HI (the amount of hydrogen-rich effluents formed during the pyrolysis phase of RE6; mgCH.g-1 SOC), and T50 CO2 oxidation (the temperature at which 50% of the residual organic C was oxidized to CO2 during the RE6 oxidation phase; °C). We also computed the amount of centennially stable SOC from RE6 parameters using the model developed in Cécillon et al. (2018). Our results showed that no clear effect of OWPs addition can be established for the youngest site (6 years). On the contrary, OWPs amendments had a clear effect on SOC quantity and quality at the sites having experienced 18 and 20 years of OWPs addition. For these sites, OWPs amendments increased SOC content, decreased SOC thermal stability (T50 CO2 oxidation) and increased the Rock-Eval 6® Hydrogen Index (HI) compared to control plots. OWPs amendments tended to increase slightly the amount of centennially stable SOC at the sites having experienced 20 years of repeated OWPs application. Our results suggest that if OWPs addition does increase SOC content, at least in the long run, the majority of this additional SOC is labile and may be quickly lost if OWPs additions are stopped. References:Barré P., Plante A.F., Cécillon L., Lutfalla S., Baudin F., Bernard S., Christensen B.T., Eglin T., Fernandez J.M., Houot S., Kätterer T., Le Guillou C., Macdonald A., van Oort F. & Chenu C. (2016) The energetic and chemical signatures of persistent soil organic matter. Biogeochemistry, 130: 1-12.Cécillon L., Baudin F., Chenu C., Houot S., Jolivet R., Kätterer T., Lutfalla S., Macdonald A.J., van Oort F., Plante A.F., Savignac F., Soucémarianadin L.N. & Barré P. (2018) A model based on Rock-Eval thermal analysis to quantify the size of the centennially persistent organic carbon pool in temperate soils. Biogeosciences, 15, 2835-2849.

Traditionally, soil quality has been assessed through physical, chemical and biological properties without paying attention to soil biota and the different associated ecosystem services provided (Tyler, 2019). To fill that gap, the european BiodivERsA “SoilMan” project (Ecosystem services driven by the diversity of soil biota – understanding and management in agriculture) is focused on the relations among soil management, soil biodiversity, and ecosystem services, at seven different management gradients in agricultural long term observations (LTO’s) trials across Europe (France “SOERE-PROs EFELE” and “SOERE-ACBB Lusigan”, Romania “Turda”, Sweden “Angermanland” and “Säby-Uppland”, Germany “Garte Süd” and Spain “La Hampa”). Management gradients covered different tillage regimes (zero, minimum and conventional) and different crop rotations (crop types and duration).In the present study, we characterised the bacterial and fungal communities of soils from the different countries and agricultural managements in arable land. The samplings were carried out following the same methodology in all the countries during 2017-2018 when wheat was sown in the LTO’s. The soil DNA was extracted and subjected to metabarcoding analysis of 16S and Internal Transcribed Spacer (ITS) ribosomal RNA (rRNA) for bacterial and fungal community analysis, respectively.Different alpha diversity metrics, including number of OTUs, Simpsons and Shannon indexes, as well as beta diversity distances (weighted and unweighted UNIFRAC, Jaccard and Bray-Curtis) were calculated. Multidimensional Scaling ordination plots (PCoA) were used to visualize the existence of community gradients among locations and soil managements. All the statistical data procedure was analysed using the vegan R package (Oksanen, 2011).In general terms, results show that alpha diversity for both bacteria and fungi, clearly differs among countries while soil management effects are less defined among and within countries. Concerning the beta diversity indexes, communities tend to cluster more according to the spatial location than due to the soil management regimen. This is especially true for fungal communities. Further analysis will identify possible correlations of bacterial and fungal communities with environmental variables and other physicochemical and biological soil properties.References:Oksanen, J. (2011). Multivariate Analysis of Ecological Communities in R: vegan tutorial.Tyler, H. L. (2019). Bacterial community composition under long-term reduced tillage and no till management. Journal of Applied Microbiology, 126(6), 1797–1807. https://doi.org/10.1111/jam.14267