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Organic wastes (OW) are rich in nutrients, and their recycling into agriculture can substitute chemical fertilizers. The level of substitution (partial with mineral fertilizer or exclusive with only OW), along with the method, amount, and timing of OW application, as well as the crop type, can impact crop productivity. The temporal dynamics of crop productivity after repeated applications of OW remain uncertain. Thus, two French long‐term field experiments (QualiAgro and PROspective, started in 1998 and 2000, respectively) were used to evaluate the effect of repeated OW applications on crop yield dynamics and investigate the potential driving factors affecting crop yields. Six different OW were applied: urban sewage sludge (SLU), green waste and SLU compost (GWS), biowaste compost (BIO), municipal solid waste compost (MSW), farmyard manure (FYM), and composted FYM (FYMC). The OW were applied every 2 years in QualiAgro (~4 t C ha−1) and PROspective (~1.7 t C ha−1). QualiAgro was studied under high and low mineral N conditions, while PROspective was examined with and without mineral N fertilization. The results indicated that at the QualiAgro site, a combination of OW and high mineral N treatments resulted in higher maize and wheat yields compared to the mineral N control, while the combination of OW and low mineral N reached the same maize and wheat yield as the mineral N control after 3 and 6 applications of OW, respectively. At the PROspective site, partially substituting mineral fertilizer with OW maintained maize yields but decreased wheat yields, while full substitution led to a decrease in both maize and wheat yields compared to the mineral N control. Results from the gradient boosting model (GBM) showed that soil total N rather than mineral N input was the primary driver of the relative maize yield, while mineral N fertilizer input was more critical for wheat during the second year. We conclude that the joined use of OW and mineral fertilizers is superior to using OW or mineral fertilizer alone for maintaining high yields and soil fertility. We further suggest that OW full substitution of mineral fertilizer may need to apply OW more frequently to meet the crop demands, and/or to use OW with higher N availability like digestates. [ABSTRACT FROM AUTHOR]

Mid-term (MTEs, 5-20 years) and long-term (LTEs, 20+ years) field experiments are key sources of information to design future climate-smart agriculture. Within the European Joint Program SOIL (EJP SOIL), we built the EJP SOIL-MTE/LTE metadataset that contains metadata from 240 MTEs/LTEs across Europe. Metadata collected included precise descriptions of the treatments (combination of factors such as tillage, crop type/rotation, amendments/fertilizers, grazing and pest/weed management), soil and crop measurements and pedo-climatic information. Using different figures and dashboards, an overview of those MTEs/LTEs is presented and specific research themes (tillage systems, residue management, amendment type and cover crops) are further analysed within their pedo-climatic context. An interactive web portal developed in collaboration with the BonaRes project (https://lte.bonares.de), enables users to explore the metadataset and find relevant MTEs/LTEs for specific combinations of practices (e.g. all MTEs/LTEs that investigate cover crops on a Cambisol in no-tillage system). Finally, a SWOT (Strengths, Weaknesses, Opportunities, Threats) analysis of the metadataset was carried out to highlight the potential contribution of MTEs/LTEs to a harmonized European soil observation and monitoring approach. We propose that the metadataset could be elaborated with metadata from other existing MTEs/LTEs in Europe or even worldwide. [ABSTRACT FROM AUTHOR]

The fertilization with organic amendments and digestates from biogas plants is increasingly used to increase carbon stock and to improve the soil quality, but little is still known about their long‐term effects. A common method to analyse organic amendments and their mineralization is incubation experiments, where amendments get incubated with soil while CO2 release is measured over time. In a previous study, carbon models have been applied to model the carbon dynamics of incubation experiments. The derived parameters describing the carbon turnover of the CCB model (CANDY Carbon Balance) are used to simulate the SOC and SON dynamics of a long‐term field trial. The trial was conducted in Berge (Germany) where organic amendments like slurry, farmyard manure or digestates were systematically applied. To grant a higher model flexibility, the amounts of crop residues were calculated for roots and stubble separately. Furthermore, the mineralization dynamics of roots and stubble are considered by the model parameters for each crop. The model performance is compared when using the dry matter and carbon content received from the field trial and the incubation experiments, to evaluate the transferability. The results show that the incubation parameters are transferable to the field site, with rRMSE < 10% for the modelled SOC and rRMSE between 10% and 15% for the SON dynamics. This approach can help to analyse long‐term effects of unexplored and unusual organic fertilizers under field conditions, whereat the model is used to upscale the C dynamics from incubation experiments, considering environmental conditions. [ABSTRACT FROM AUTHOR]

Despite recent technological advances in molecular ecology, DNA extraction from soil remains a crucial step when quantifying and characterizing soil microbial communities. Potential biases could hamper fundamental understanding of the dynamic relationships between soil properties and microorganisms under different agricultural practices. In this study, we compared four different DNA extraction methods for their ability to discriminate microbial communities of an arable soil subjected to different fertilization managements for more than 50 years (Ultuna, Sweden). The abundance and the diversity of bacteria, archaea and fungi were studied using qPCR and molecular fingerprints, respectively. Overall, the choice of DNA extraction method had a more pronounced effect on the fungal and archaeal communities in comparison to bacterial ones. The assessment of the microbial diversity was more sensitive to DNA extraction methods in comparison with the quantification of the abundances. The DNA extraction method clearly affects the intensity of the correlations between the abundance and/or diversity of microbial communities and environmental variables (C, N and pH) according to the targeted taxon. This study highlights that long‐term effects can be offset by biases in DNA extraction methods. Highlights: Using different DNA extraction methods may alter soil microbial survey.Average DNA concentrations vary from 1 to 3 μg.g−1 according to the extraction method.Gene copies numbers vary up to 2 orders of magnitude among DNA extraction methods.Fungal communities diversity descriptors were the most affected by DNA extraction [ABSTRACT FROM AUTHOR]

Climate change will alter precipitation patterns with consequences for soil C cycling. An understanding of how fluctuating soil moisture affects microbial processes is therefore critical to predict responses to future global change. We investigated how long‐term experimental field drought influences microbial tolerance to lower moisture levels ("resistance") and ability to recover when rewetted after drought ("resilience"), using soils from a heathland which had been subjected to experimental precipitation reduction during the summer for 18 years. We tested whether drought could induce increased resistance, resilience, and changes in the balance between respiration and bacterial growth during perturbation events, by following a two‐tiered approach. We first evaluated the effects of the long‐term summer drought on microbial community functioning to drought and drying–rewetting (D/RW), and second tested the ability to alter resistance and resilience through additional perturbation cycles. A history of summer drought in the field selected for increased resilience but not resistance, suggesting that rewetting after drought, rather than low moisture levels during drought, was the selective pressure shaping the microbial community functions. Laboratory D/RW cycles also selected for communities with a higher resilience rather than increased resistance. The ratio of respiration to bacterial growth during D/RW perturbation was lower for the field drought‐exposed communities and decreased for both field treatments during the D/RW cycles. This suggests that cycles of D/RW also structure microbial communities to respond quickly and efficiently to rewetting after drought. Our findings imply that microbial communities can adapt to changing climatic conditions and that this might slow the rate of soil C loss predicted to be induced by future cyclic drought. Climate change will increase the intensity of drought and rainfall events. We investigated whether a history of drought affected the ability of soil microorganisms to withstand low moisture availability during drought ("resistance") and recover quickly when soil was rewetted again ("resilience"). Using soils which had been exposed to an experimental summer drought for 18 years, we found that a history of drought did not affect microbial resistance to low moisture, but did lead to a faster recovery upon rewetting. These findings suggest that historical climate will be important in shaping microbial responses to future climate change. [ABSTRACT FROM AUTHOR]

Methane (CH4) is a powerful greenhouse gas controlled by both biotic and abiotic processes. Few studies have investigated CH4 fluxes in subarctic heath ecosystems, and climate change-induced shifts in CH4 flux and the overall carbon budget are therefore largely unknown. Hence, there is an urgent need for long-term in situ experiments allowing for the study of ecosystem processes over time scales relevant to environmental change. Here we present in situ CH4 and CO2 flux measurements from a wet heath ecosystem in northern Sweden subjected to 16 years of manipulations, including summer warming with open-top chambers, birch leaf litter addition, and the combination thereof. Throughout the snow-free season, the ecosystem was a net sink of CH4 and CO2 (CH4 −0.27 mg C m−2 d−1; net ecosystem exchange −1827 mg C m−2 d−1), with highest CH4 uptake rates (−0.70 mg C m−2 d−1) during fall. Warming enhanced net CO2 flux, while net CH4 flux was governed by soil moisture. Litter addition and the combination with warming significantly increased CH4 uptake rates, explained by a pronounced soil drying effect of up to 32% relative to ambient conditions. Both warming and litter addition also increased the seasonal average concentration of dissolved organic carbon in the soil. The site was a carbon sink with a net uptake of 60 g C m−2 over the snow-free season. However, warming reduced net carbon uptake by 77%, suggesting that this ecosystem type might shift from snow-free season sink to source with increasing summer temperatures. [ABSTRACT FROM AUTHOR]

Soil-quality assessment provides a tool for evaluating the sustainability of alternative soil-management practices. Understanding the effects of the long-term use of chemical fertilizers on soil quality is essential for sustaining soil productivity. The cumulative effect of a 17-y-old chemical-fertilizer application on integrated soil quality was investigated in the surface (0-15 cm) and subsurface (15-30 cm) soils of a soy-broomcorn-millet cropping system with an experiment design of two factors with three levels for each factor. The treatments were N0P0, N0P1, N0P2, N1P0, N1P1 (local farmer' fertilization strategy), N1P2, N2P0, N2P1, N2P2, and a control NF. The objectives were to describe and quantify the effect of continuous applications of chemical fertilizer through soil-quality index (SQI) and attempt to offer an efficient and appropriate nutrient-supply strategy for the local region. Following 17 y of chemical fertilization, the SQI increased markedly in the studied soil layers, and soil chemical indicators changed more significantly than physical properties. The soil-quality indicators in the surface soil layer were more variable and sensitive to fertilizer application than the subsurface layer. The indicators that sensitively responded to long-term fertilization could be classified into three types: soil-fertility indicators (soil organic matter [SOM], total P, and available N), soil-texture indicators (clay, silt), and soil-structure indicators (bulk density, mean weight diameter [MWD]). The simplified indicators (SOM, sand, available N, bulk density, and total P in the surface soil and SOM, MWD, and silt content in the subsurface soil) preferably reflected the status of the integrated soil quality as influenced by continuous fertilization. Among the fertilized treatments, the combined-fertilizer treatments maintained a higher SQI than the single-fertilizer treatments in the surface and subsurface soils. The N1P2 treatment maintained the highest SQI in both soil layers, followed by N1P1 treatment. However, for the slope cropland, given the relative costs, soil resource, and environmental protection, the traditional treatment of N1P1 may be the optimal fertilizer treatment in the local region. [ABSTRACT FROM AUTHOR]

Anthropogenic increases in atmospheric CO2 concentration and the connected deposition of organic matter into the soil influence the occurrence of decomposers who regulate carbon release back into the atmosphere. The effects of increased concentration of atmospheric carbon dioxide, plant species cover quality and nitrogen (N) fertilization on the coenosis composition of soil saprobic microfungi were studied under field conditions (Swiss Free Air Carbon Dioxide Enrichment experiment). In total, 42 species of microfungi were detected in examined soil. The most significant response of soil mycoflora was induced by the species identity of plant cover. Higher N fertilization significantly suppressed the abundance of soil microfungi at ambient CO2. The effect of increased CO2 on colony-forming units was not significant when taken as an independent treatment; however, this factor interacted significantly with N availability. Some species, e.g. theClonostachys rosea, were proven associated with the plant cover components, in this particular case withTrifolium repens. Therefore, we suggest the identity of plant species constituting plant cover as the most important factors affecting soil microfungi in agroecosystems. [ABSTRACT FROM AUTHOR]