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To reduce environmental impacts of cropping systems, various management strategies are being discussed. Long-term field experiments are particularly suitable to directly compare different management strategies and to perform a comprehensive impact assessment. To identify the key drivers of several environmental impacts, we analysed a six year crop rotation of the Farming System and Tillage Experiment (FAST) by means of the Swiss Agriculture Life Cycle Assessment method (SALCA). The following factors of the FAST experiment were considered: (1) cropping system (stockless conventional farming vs. organic farming), (2) tillage (intensive tillage vs. no or reduced tillage), and (3) cover crop. We analysed the effects of these three factors on the global warming potential (GWP), aquatic and terrestrial eutrophication, and aquatic ecotoxicity for two functional units, i.e. per product and per area. Potential impacts on biodiversity were also analysed. Our analysis revealed that there is not one superior cropping system, as the ranking depended on the environmental impact selected and on the functional unit. The cropping system had the strongest effect on most of the environmental impacts, and this was mainly driven by differences in N-fertilisation (amount and form) and yield. The global warming potential, for instance, was highest in both conventional systems compared to the organic systems, when emissions were calculated per area. In contrast, calculating emissions per product, there were no statistical differences between all four systems. On the other hand, due to higher nitrogen emissions related to the application of cattle slurry in the organic system, the terrestrial eutrophication of the organic systems was higher than the conventional systems, independent of the functional unit. The effects of tillage were much lower compared to the cropping system. No tillage, but not necessarily reduced tillage, and the cultivation of cover crops had the potential to reduce aquatic eutrophication. As N-fertilisation dominated many impact categories, we suggest improving the N-efficiency as a crucial leverage point to improve the environmental performance of arable farming systems.

15 páginas.- 4 figuras.- 3 tablas.- 165 referencias.- Supplementary information accompanies this paper at https://doi.org/10.1038/s41598-019-45702-1, Droughts associated with climate change alter ecosystem functions, especially in systems characterized by low biodiversity, such as agricultural fields. Management strategies aimed at buffering climate change effects include the enhancement of intraspecific crop diversity as well as the diversity of beneficial interactions with soil biota, such as arbuscular mycorrhizal fungi (AMF). However, little is known about reciprocal relations of crop and AMF diversity under drought conditions. To explore the interactive effects of plant genotype richness and AMF richness on plant yield under ambient and drought conditions, we established fully crossed diversity gradients in experimental microcosms. We expected highest crop yield and drought tolerance at both high barley and AMF diversity. While barley richness and AMF richness altered the performance of both barley and AMF, they did not mitigate detrimental drought effects on the plant and AMF. Root biomass increased with mycorrhiza colonization rate at high AMF richness and low barley richness. AMF performance increased under higher richness of both barley and AMF. Our findings indicate that antagonistic interactions between barley and AMF may occur under drought conditions, particularly so at higher AMF richness. These results suggest that unexpected alterations of plant-soil biotic interactions could occur under climate change. © 2019, The Author(s)., This project was supported by the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, funded by the German Research Foundation (DFG; FZT 118). We acknowledge support from the German ResearchFoundation (DFG) and Leipzig University within the program of Open Access Publishing.

Aggravation of weather extremes increases awareness of climate change consequences. Mitigation options are in demand that aim to reduce the atmospheric concentration of greenhouse gases. Amongst others, the conversion from ploughing to reduced tillage is argued to increase soil organic carbon (SOC) stocks as an accumulation of SOC in topsoil layers is commonly reported. Yet, reviews and meta-analyses describe various results from significant increases to just a redistribution of SOC in the soil profile. Reasons can be found in different sampling depths, SOC and bulk density measurement procedure, and stock calculation (equivalent soil mass vs. equal sampling depth). Furthermore, few studies evaluated the impact of organic farming systems. In nine long-term experiments on tillage systems in temperate Europe (France, Germany, Netherlands, and Switzerland), a common soil sampling campaign took place in spring and autumn 2017, and spring 2018. All trials represent common mixed organic farming systems of the respective region and contain plots with conventional and reduced tillage practices. While climatic conditions are similar, soil types vary from sandy to clayey soils. We took three undisturbed soil cores with driving hammer probes (8 cm in diameter) in each plot (minimum 3 plots per treatment) to a maximum depth of 100 cm and divided the cores in the increments 0-30, 30-50, 50-70, and 70-100 cm. The topsoil (0-30 cm) was further divided into the different tillage depths of the respective trial. We determined bulk density and organic carbon concentration as main variables and soil texture and pH as co-variates for each sample and collected C-inputs for each plot in all trails on a yearly basis. Multivariate statistics will enable the comprehensive evaluation of tillage effects on SOC stocks up to a depth of 100 cm in organic long-term trials. Texture, trial age, and the co-variate C-input will be decisive for the development of SOC stocks and enable the evaluation of carbon sequestration potentials of agricultural soils through improved tillage practices.

Efficient resource use is a key factor for sustainable production and a necessity for meeting future global food demands. However, the factors that control resource use efficiency in agro-ecosystems are only partly understood. We investigated the influence of soil biota on nutrient leaching, nutrient-use efficiency and plant performance in outdoor, open-top lysimeters comprising a volume of 230L. The lysimeters were filled with sterilized soil in two horizons and inoculated with a reduced soil-life inoculum (soil biota 11m, microbially dominated) and an enriched soil-life inoculum [soil organisms 2mm, also containing arbuscular mycorrhizal fungi (AMF)]. A crop rotation was planted, and nutrient leaching losses, plant biomass and nutrient contents were assessed over a period of almost 2years. In the first year of the experiment, enriched soil life increased crop yield (+22%), N uptake (+29%) and P uptake (+110%) of maize and strongly reduced leaching losses of N (-51%, corresponding to a reduction of 76kg N ha(-1)). In the second year, wheat biomass (+17%) and P contents (+80%) were significantly increased by enriched soil life, but the differences were lower than in the first year. Enriched soil life also increased P mobilization from soil (+112%) and significantly reduced relative P leaching losses (-25%), defined as g P leached per kg P plant uptake, as well as relative N leaching losses (-36%), defined as kg N leached per kg N plant uptake, demonstrating that nutrient-use efficiency was increased in the enriched soil-life treatment. Synthesis and applications. Soil biota are a key factor determining resource efficiency in agriculture. The results suggest that applying farming practices, which favour a rich and abundant soil life (e.g. reduced tillage, organic farming, crop rotation), can reduce environmental impacts, enhance crop yield and result in a more sustainable agricultural system. However, this needs to be confirmed in field situations. Enhanced nutrient-use efficiency obtained through farming practices which exert positive effects on soil biota could result in reduced amounts of fertilisers needed for agricultural production and reduced nutrient losses to the environment, providing benefits of such practices beyond positive effects on biodiversity. Soil biota are a key factor determining resource efficiency in agriculture. The results suggest that applying farming practices, which favour a rich and abundant soil life (e.g. reduced tillage, organic farming, crop rotation), can reduce environmental impacts, enhance crop yield and result in a more sustainable agricultural system. However, this needs to be confirmed in field situations. Enhanced nutrient-use efficiency obtained through farming practices which exert positive effects on soil biota could result in reduced amounts of fertilisers needed for agricultural production and reduced nutrient losses to the environment, providing benefits of such practices beyond positive effects on biodiversity.

Understanding how communities assemble is a central goal of ecology. This is particularly relevant for communities of arbuscular mycorrhizal fungi (AMF), because the community composition of these beneficial plant symbionts influences important ecosystem processes. Moreover, AMF may be used as sensitive indicators of ecological soil quality if they respond to environmental variation in a predictable way. Here, we use a molecular profiling technique (T-RFLP of 25S rRNA gene fragments) to test which factors determine AM fungal community composition in 40 agricultural soils in the Netherlands. In particular, we test whether species richness, dominance structure and community nestedness are influenced by management type (in pairs of organically and conventionally farmed fields), and we examine the contribution of crop species (maize vs. potato), soil type (sand vs. clay-textured soils) and habitat (plant root vs. bulk soil) on AMF community characteristics. AMF richness varied from 1 to 11 taxa per field. Communities from species-poor fields were found to be subsets of those in richer fields, indicating nestedness and a progressive 'loss' from the species pool. AMF taxa richness and occurrence in soil and plant roots were highly correlated, and richness was related to management intensity (phosphate availability and grass-cropping history together explained 32% and 50% of richness in roots and soils). Soil type together with soil chemical parameters explained only 17% of variance in AMF community structure. We synthesize these results by discussing the potential contribution of a 'bottleneck effect' on AMF communities through increased stochastic effects under environmental stress. © 2012 Blackwell Publishing Ltd.

Efficient resource use is a key factor for sustainable production and a necessity for meeting future global food demands. However, the factors that control resource use efficiency in agro-ecosystems are only partly understood. We investigated the influence of soil biota on nutrient leaching, nutrient-use efficiency and plant performance in outdoor, open-top lysimeters comprising a volume of 230L. The lysimeters were filled with sterilized soil in two horizons and inoculated with a reduced soil-life inoculum (soil biota 11m, microbially dominated) and an enriched soil-life inoculum [soil organisms 2mm, also containing arbuscular mycorrhizal fungi (AMF)]. A crop rotation was planted, and nutrient leaching losses, plant biomass and nutrient contents were assessed over a period of almost 2years. In the first year of the experiment, enriched soil life increased crop yield (+22%), N uptake (+29%) and P uptake (+110%) of maize and strongly reduced leaching losses of N (-51%, corresponding to a reduction of 76kg N ha(-1)). In the second year, wheat biomass (+17%) and P contents (+80%) were significantly increased by enriched soil life, but the differences were lower than in the first year. Enriched soil life also increased P mobilization from soil (+112%) and significantly reduced relative P leaching losses (-25%), defined as g P leached per kg P plant uptake, as well as relative N leaching losses (-36%), defined as kg N leached per kg N plant uptake, demonstrating that nutrient-use efficiency was increased in the enriched soil-life treatment. Synthesis and applications. Soil biota are a key factor determining resource efficiency in agriculture. The results suggest that applying farming practices, which favour a rich and abundant soil life (e.g. reduced tillage, organic farming, crop rotation), can reduce environmental impacts, enhance crop yield and result in a more sustainable agricultural system. However, this needs to be confirmed in field situations. Enhanced nutrient-use efficiency obtained through farming practices which exert positive effects on soil biota could result in reduced amounts of fertilisers needed for agricultural production and reduced nutrient losses to the environment, providing benefits of such practices beyond positive effects on biodiversity. Soil biota are a key factor determining resource efficiency in agriculture. The results suggest that applying farming practices, which favour a rich and abundant soil life (e.g. reduced tillage, organic farming, crop rotation), can reduce environmental impacts, enhance crop yield and result in a more sustainable agricultural system. However, this needs to be confirmed in field situations. Enhanced nutrient-use efficiency obtained through farming practices which exert positive effects on soil biota could result in reduced amounts of fertilisers needed for agricultural production and reduced nutrient losses to the environment, providing benefits of such practices beyond positive effects on biodiversity.

Arbuscular mycorrhizal fungi (AMF) can enhance plant nutrition and growth. However, their contribution to nutrient cycling in ecosystems is still poorly understood. Using experimental grassland microcosms filled with two different soil types (pasture and heath soil) and fertilized with different N forms (NO3- or NH4+), we tested the AMF contribution to N and P cycling including measurements of organic and inorganic leaching losses and N2O fluxes. We hypothesized that AMF enhance the sustainability of plant-soil systems by reducing nutrient losses and enhancing plant nutrient uptake. AMF reduced reactive and unreactive P leaching by 31%, enhanced plant P contents by 15% and increased P mobilization from soil by 18%. AMF reduced N2O fluxes and NH4+ leaching in both soils. Leaching of dissolved organic N was reduced by 24% in the heath soil only. Plant N contents were increased by 13% in the pasture soil but not affected in the heath soil. The microbial biomass N content was higher with AMF. This is the first comprehensive assessment of the influence of AMF on N and P cycling, including effects on inorganic and organic nutrient leaching losses and N2O emissions in a single study. We conclude that AMF can promote sustainable nutrient cycling but the effects on N cycling are context dependent.

The arbuscular mycorrhizal (AM) symbiosis is widespread throughout the plant kingdom and important for plant nutrition and ecosystem functioning. Nonetheless, most terrestrial ecosystems also contain a considerable number of nonmycorrhizal plants. The interaction of such non-host plants with AM fungi (AMF) is still poorly understood. Here, in three complementary experiments, we investigated whether the non-mycorrhizal plant Arabidopsis thaliana, the model organism for plant molecular biology and genetics, interacts with AMF. We grew A. thaliana alone or together with a mycorrhizal host species (either Trifolium pratense or Lolium multiflorum) in the presence or absence of the AMF Rhizophagus irregularis. Plants were grown in a dualcompartment system with a hyphal mesh separating roots of A. thaliana from roots of the host species, avoiding direct root competition. The host plants in the system ensured the presence of an active AM fungal network. AM fungal networks caused growth depressions in A. thaliana of more than 50% which were not observed in the absence of host plants. Microscopy analyses revealed that R. irregularis supported by a host plant was capable of infecting A. thaliana root tissues (up to 43% of root length colonized), but no arbuscules were observed. The results reveal high susceptibility of A. thaliana to R. irregularis, suggesting that A. thaliana is a suitable model plant to study non-host/AMF interactions and the biological basis of AM incompatibility.

Plants use a range of sophisticated strategies to protect themselves against herbivores and pathogens, such as the production of jasmonates, a group of plant hormones that prime the plant's defense system upon attack. However, defense-related mechanisms, such as the jasmonate response, play a more diverse role than previously appreciated. Jasmonates also regulate key mutualist relationships, leading to a suit of potential conflicting selection pressures as a single response is employed to mediate multiple species interactions. Here, we experimentally manipulate the host's jasmonate response and document the impact on two key plant mutualisms: (i) changes to arbuscular mycorrhizal symbionts belowground (ii) modifications to floral traits affecting pollinator mutualists aboveground. By exogenously applying a range of methyl jasmonate solutions to cucumber plant roots grown with and without mycorrhizal fungi, we are able to examine the potential costs of the jasmonate response to both above and belowground mutualists. We demonstrate that the negative effect of jasmonates on floral traits depends on whether the plant is mycorrhizal or nonmycorrhizal. Mycorrhization had a positive effect on floral traits, but benefits were lost with jasmonate application. While low levels of jasmonate decreased floral traits, these same jasmonate levels increased colonization by the mycorrhizal symbiont three-fold, but only under high phosphorus conditions. Our results highlight potential conflicts for the host in the regulation of their mutualists under different conditions and suggest that the overall impact of the jasmonate response depends on the plant mycorrhizal status and its nutrient context. These findings suggest that increasing the jasmonate response may lead to differential costs and benefits for plants and their mutualists, and highlight potential conflict in planta, with mycorrhizal symbionts benefiting from intermediate levels of jasmonates while certain floral traits can be depressed at this same level. © 2009 The Authors. Journal compilation © 2009 British Ecological Society.

Nitrogen (N) inputs to ecosystems have increased worldwide, often leading to large changes in plant community structure and reducing plant diversity. Yet, the interaction of increased N availability with other factors that determine plant community composition, are still poorly understood. Here, we test whether the impact of N addition on plant communities depends on the presence of arbuscular mycorrhizal fungi (AMF). AMF are widespread plant symbionts that facilitate growth of many plant species. We hypothesize that AM fungi reduce the negative impact of N addition on plant communities by supporting growth of species that are sensitive to N enrichment.We established experimental grassland microcosms consisting of 18 plant species. These microcosms were subjected to high and low N supply and were inoculated with AMF or remained nonmycorrhizal. Both N addition and AMF had a big impact on plant community composition, but with opposite effects. N addition induced a 2.8-fold increase in grass biomass and reduced legume biomass. Grasses dominated the microcosms at high N supply, especially when AMF were absent. In contrast, AMF enhanced biomass of all legumes species (on average 6.8-fold) and reduced the relative abundance of grasses. The proportion of legume biomass out of total shoot biomass at high N supply was 19% with AMF and only 3% without AMF. Our results show that responses of plant communities to N enrichment depend on AMF and that AMF can reduce the negative impact of increased N availability on plant community structure by reducing grass dominance. © 2008 The Authors Journal compilation © 2008 Blackwell Publishing.

Background: Agricultural soils represent a potential sink for increasing amounts of different nanomaterials that nowadays inevitably enter the environment. Knowledge on the relation between their actual exposure concentrations and biological effects on crops and symbiotic organisms is therefore of high importance. In this part of a joint companion study we describe the vertical translocation as well as plant uptake of three different titanium dioxide (nano )particles (TiO2 NPs) and multi walled carbon nanotubes (MWCNTs) within a pot experiment with homogenously spiked natural agricultural soil and two plant species (red clover and wheat). Results: TiO2 NPs exhibited limited mobility from soil to leachates and did not induce significant titanium uptake into both plant species although average concentrations were doubled from 4 to 8 mg/kg Ti at the highest exposures. While the mobility of MWCNTs in soil was limited as well microwave induced heating suggested MWCNT plant uptake independent of the exposure concentration. Conclusions: Quantification of actual exposure concentrations with a series of analytical methods confirmed nominal ones in soil mesocosms with red clover and wheat and pointed to low mobility and limited plant uptake of titanium dioxide nanoparticles and carbon nanotubes.

Background: Nanoparticles are produced and used worldwide and are released to the environment e.g. into soil systems. Titanium dioxide (TiO2) nanoparticles (NPs) carbon nanotubes (CNTs) and cerium dioxide (CeO2) NPs are among the ten most produced NPs and it is therefore important to test whether these NPs affect plants and symbiotic microorganisms that help plants to acquire nutrients. In this part of a joint companion study we spiked an agricultural soil with TiO2 NPs multi walled CNTs (MWCNTs) and CeO2 NPs and we examined effects of these NP on red clover biological nitrogen fixation by rhizobia and on root colonization of arbuscular mycorrhizal fungi (AMF). We also tested whether effects depended on the concentrations of the applied NPs. Results: Plant biomass and AMF root colonization were not negatively affected by NP exposure. The number of flowers was statistically lower in pots treated with 3 mg kg-1 MWCNT and nitrogen fixation slightly increased at 3000 mg kg-1 MWCNT. Conclusions: This study revealed that red clover was more sensitive to MWCNTs than TiO2 and CeO2 NPs. Further studies are necessary for finding general patterns and investigating mechanisms behind the effects of NPs on plants and plant symbionts.

Symbiotic interactions are thought to play a key role in ecosystems. Empirical evidence for the impact of symbiotic bacteria on plant communities is, however, extremely scarce because of experimental constraints. Here, in three complementary experiments, we show that nitrogen-fixing rhizobia bacteria act as a determinant of plant community structure and diversity. Grassland microcosms inoculated with a mixture of rhizobia had a higher above-ground plant productivity (+35%), contained more nitrogen (+85%) and had significant higher community evenness (+34%) than control microcosms without rhizobia. Moreover, three of the four studied legume species required rhizobia to successfully coexist with other plant species. In contrast, the growth and survival of three grass and five forb species were not affected by the presence or absence of rhizobia. Finally, our results also showed that the legume species largely relied on symbiotically fixed nitrogen, both in the field and in the microcosms. This indicates that results in the microcosms are indicative for processes occurring in the field. It is concluded that symbiotic interactions between plants and prokaryotes can contribute to plant productivity, plant community structure and acquisition of limiting resources in legume-rich grassland communities. © 2006 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

Recruitment of new seedlings into the vegetation is essential for maintaining species rich plant communities. Hence it is of pivotal importance to understand factors determining seedling recruitment. Here it is tested whether arbuscular mycorrhizal fungi (AMF) promote seedling recruitment in perennial grassland communities. Seeds of four plant species (two grasses and two forbs) were added to patches within 1-year old grassland microcosms that were inoculated with different AMF taxa or to control microcosms that were not inoculated. The seedlings grew larger and obtained more phosphorus when AMF were present. Moreover, the seedlings obtained different amounts of phosphorus in microcosms inoculated with different AMF taxa. The results indicate that AMF promote seedling establishment by integrating emerging seedlings into extensive hyphal networks and by supplying nutrients to the seedlings. AMF, thus, act as a symbiotic support system that promotes seedling establishment and reduces recruitment limitation in grassland.