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Mechanical soil disturbance is one among the key factors influencing soil biodiversity in agriculture. Although many soil organisms are sensitive to soil disturbance, fungi could be highly impacted due to their sessile lifestyle, relatively slow growth and filamentous body structure. Arbuscular mycorrhizal (AM) fungi are of particular interest in arable lands, providing crop plants with numerous vital services such as nutrient acquisition and protection against abiotic and biotic stressors. Considering this, tillage practices that aim to reduce soil disturbance are often seen as a fungal‐friendly alternative to conventional inversion tillage. Although local studies exist on the impacts of minimal tillage practices on AM fungi, the universality of this approach has been debated. Our objective was to assess the effects of reduced tillage intensity on AM fungi in comparison with conventional tillage. Using high‐throughput sequencing techniques in long‐term field experiments in five European countries, we show that the effects of reduced tillage intensity may not necessarily be positive on soil AM fungal diversity. Plots which were tilled using reduced tillage techniques had lower AM fungal richness in three countries, whereas in one of them, no significant differences were found. We also observed a shift in AM fungal communities where prevalence of taxa preferring root colonisation rather than soil exploration increased under reduced tillage regimes. Here, we argue that more detailed and long‐term studies are needed to understand the factors that could make the reduction of soil disturbance more beneficial to AM fungi if agricultural sustainability goals are to be met. [ABSTRACT FROM AUTHOR]

Rapid estimation of the amount and stability of soil organic carbon (SOC) by infraredspectroscopy has been proposed as a means to inform land use decision-making for theoptimization of environmental services provided by soils. Our research tests theviability of this strategy by determining the accuracy and robustness of modelspredicting total and labile SOC content using near (NIRS) and middle (MIRS) infraredspectroscopy. Soil samples were collected from the 0-20 cm depth of arable fields inGermany with variable texture and SOC contents. Seven treatments were applied to20 soils, including application of 2, 4 or 8 g C per kg soil in the form of straw orclover residues, as well as a control treatment without residues. Samples were thenincubated for 56 days at 20˚ C and cumulative CO2 emissions were determined.Additionally, SOC, total nitrogen (Nt), NIRS and MIRS were measured on dried, milledsamples before and after incubation, as well as microbial biomass (Cmic) afterincubation. Partial least square regression (PLSR) and support vector machine regression,both with and without mathematical pretreatments, were compared as a means toestimate SOC, Nt, Cmic and labile C, quantified as the residue application rate,cumulative CO2 loss during incubation, or the difference in bulk SOC before and afterincubation. Separate models for straw and clover were created, both calibrated andcross-validated using control and 8 g C kg−1 soil residue treatments (n=40), and validatedusing 2 and 4 g C kg−1 soil residue treatments (n=40). While PLSR validationestimations of bulk SOC and Nt by both MIRS and NIRS can be categorized as good toexcellent according to the ratio of performance to interquartile distance, estimations oflabile C ranged from not usable to approximately quantitative. Neither spectralregion consistently outperformed the other, suggesting there is value in utilizingboth NIRS and MIRS when possible. As a measure of model robustness, modelscalibrated with samples prior to incubation were also used to predict SOC and Ntafter incubation, when substantially less labile SOC was present. Compared tomathematically pretreated models optimized in cross-validation, models using untreateddata for all wavelengths were a more robust means to accurately predict total SOCand Nt when the amount of labile C differed greatly from the calibration dataset. [ABSTRACT FROM AUTHOR]

It is widely known that annelids have strong soil functional impacts like the decomposition of crop residues, which affects carbon dynamics and nutrient cycling. In this study the objective was to investigate the combined effect of the vertical placement of organic material and soil annelids on carbon pathway and plant available nutrients. We hypothesize that endogeic earthworms, such as anecic earthworms and thus enchytraeids react differently because of their various lifestyles. A microcosm experiment with undisturbed soil columns (30 cm high, 15 cm Ø) was carried out from October 2017 to February 2018 in a dark climate chamber at 10 °C. The soil columns were taken from a long-term experimental field-site at plots with reduced tillage after winter wheat harvest. The soil type is a Haplic Luvisol with a silt loam texture. Soil columns were defaunated by freezing for one week at -20°C before the experiment started. During the experiment they were hermetically sealed, continuously supplied with fresh air and automatically irrigated (3 times day-1 10 ml). Gas fluxes were obtained and analyzed every 4.5 hours utilizing a gas chromatograph. For the organism treatment we used: (i) the endogeic earthworm species Octolasion cyaneum (four individuals each column), (ii) the anecic earthworm species Lumbricus terrestris (two individuals each column) or (iii) a combination of the two enchytraeid species Enchytraeus crypticus and E. christenseni (350 individuals each column). Half of the columns were inverted manually to simulate inverse tillage. For these columns we placed 5 g of maize leaves, which was used as a crop residue, in a depth of 15 cm. For the columns with simulation of no-till systems, the organic material was put on the surface. All annelid treatments were combined with both organic matter location treatments.At the end of the experiment, soil columns were harvested destructively. Carbon-dioxide was measured as an indicator of biological activity [mg CO2-C kg-1 dry soil]. For biotic soil properties mircrobial biomass carbon was measured by Chloroform-Fumigation-Extraction (CFE) and ergosterol concentration was quantified as a proxy for fungal biomass. The path of carbon through the system is investigated by isotope ratio mass spectometry 13C/12C. First results show that earthworms reached a higher biomass in all treatments and numbers of enchytraeid individuals increased ten times. Contrary to the expectation that anecic earthworms only pick up organic matter, which is on the surface, the uptake of maize leaves could be shown by isotopic analysis in both treatments. On the other hand, it could be confirmed that the position of organic material in a depth of 15 cm seems to be of advantage for endogeic earthworms. Analysis of the biological activity shows that soil annelids respond in a different way the location of the organic material, depending on size scales (enchytraids vs. earthworms) and on ecological performance (endogeic vs. anecic earthworms). [ABSTRACT FROM AUTHOR]

It is well known that annelids such as earthworms and enchytraeids provide ecosystem services concerning soil fertility and sustainability, e.g. by structuring the soil and building stable aggregates, which reduces soil erosion. The objective of this study was to quantify the combined effect of soil annelids and organic matter location on water-stable aggregate size class distribution. In a microcosm experiment, undisturbed soil columns (30 cm height, 15 cm diameter) were used, which were taken at the long-term field trial "Garte Süd" near Göttingen, Germany, in reduced tillage plots. The soil type of the field trial is a Haplic Luvisol with a silt loam texture. The soil columns were defaunated by freezing before the start of the experiment. As annelids we used (i) the endogeic earthworm species Octolasion cyaneum (four individuals), (ii) the anecic earthworm species Lumbricus terrestris (two individuals) or (iii) a combination of the two enchytraeid species Enchytraeus crypticus and E. christenseni (350 individuals). As organic material we used maize leaves (5 g per column) and either put them on the soil surface (simulation of organic matter location of no-till systems) or in 15 cm soil depth (simulation of organic matter location of conventional tillage systems). All three annelids were combined with both organic matter location treatments. We also included control columns with and without maize leaves, in both cases without annelids. The columns were incubated for three months at a temperature of 10 °C. First results show that the macroaggregate concentration in the top 10 cm was lowest in the columns without annelids and highest for the soil columns with O. cyaneum. The location of the organic material influenced the aggregate distribution in the soil columns with L. terrestris (more large and less small macroaggregates in the columns with maize leaves at the soil surface in the top soil) and with Enchytraeus (less microaggregates in the columns with maize leaves at the soil surface in the top soil), while having no effect on the columns with O. cyaneum.Further planned analyses include the measurement of the isotopic signature of the carbon contents in the different aggregate size classes to quantify the maize carbon included in each aggregate size class dependent on the soil annelid species and the organic matter location. [ABSTRACT FROM AUTHOR]