Nitrous oxide (N2O) emissions from different agricultural systems have been studied extensively to understand the mechanisms underlying their formation. While a number of long-term field experiments ...have focused on individual agricultural practices in relation to N2O emissions, studies on the combined effects of multiple practices are lacking. This study evaluated the effect of different tillage no-till (NT) vs. conventional plough tillage (CT) in combination with fertilisation mineral (MIN), compost (ORG), and unfertilised control (CON) on seasonal N2O emissions and the underlying N-cycling microbial community in one maize growing season. Rainfall events after fertilisation, which resulted in increased soil water content, were the main triggers of the observed N2O emission peaks. The highest cumulative emissions were measured in MIN fertilisation, followed by ORG and CON fertilisation. In the period after the first fertilisation CT resulted in higher cumulative emissions than NT, while no significant effect of tillage was observed cumulatively across the entire season. A higher genetic potential for N2O emissions was observed under NT than CT, as indicated by an increased (nirK + nirS)/(nosZI + nosZII) ratio. The mentioned ratio under NT decreased in the order CON > MIN > ORG, indicating a higher N2O consumption potential in the NT-ORG treatment, which was confirmed in terms of cumulative emissions. The AOB/16S ratio was strongly affected by fertilisation and was higher in the MIN than in the ORG and CON treatments, regardless of the tillage system. Multiple regression has revealed that this ratio is one of the most important variables explaining cumulative N2O emissions, possibly reflecting the role of bacterial ammonia oxidisers in minerally fertilised soil. Although the AOB/16S ratio aligned well with the measured N2O emissions in our experimental field, the higher genetic potential for denitrification expressed by the (nirK + nirS)/(nosZI + nosZII) ratio in NT than CT was not realized in the form of increased emissions. Our results suggest that organic fertilisation in combination with NT shows a promising combination for mitigating N2O emissions; however, addressing the yield gap is necessary before incorporating it in recommendations for farmers.
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•Rain events were the main triggers for N2O emissions over maize growing season.•Cumulative emissions were highest in mineral, followed by organic and no fertilisation.•Mineral fertilisation increased share of bacterial ammonia oxidizers within the bacterial community.•N2O genetic consumption potential was higher in no-till organic-fertilised than mineral or unfertilized plots.
•Effects of four paired management practices on five soil quality indicators were analysed.•Yield was lower under NT and organic agriculture, but with environmental benefits.•SOM increased under NT, ...organic matter addition, crop rotation and organic farming.•Number of earthworms was the most sensitive indicator for the paired practices.•Soil pH appears to be the least sensitive indicator.
In this paper we present effects of four paired agricultural management practices (organic matter (OM) addition versus no organic matter input, no-tillage (NT) versus conventional tillage, crop rotation versus monoculture, and organic agriculture versus conventional agriculture) on five key soil quality indicators, i.e., soil organic matter (SOM) content, pH, aggregate stability, earthworms (numbers) and crop yield. We have considered organic matter addition, no-tillage, crop rotation and organic agriculture as “promising practices”; no organic matter input, conventional tillage, monoculture and conventional farming were taken as the respective references or “standard practice” (baseline). Relative effects were analysed through indicator response ratio (RR) under each paired practice. For this we considered data of 30 long-term experiments collected from 13 case study sites in Europe and China as collated in the framework of the EU-China funded iSQAPER project. These were complemented with data from 42 long-term experiments across China and 402 observations of long-term trials published in the literature. Out of these, we only considered experiments covering at least five years. The results show that OM addition favourably affected all the indicators under consideration. The most favourable effect was reported on earthworm numbers, followed by yield, SOM content and soil aggregate stability. For pH, effects depended on soil type; OM input favourably affected the pH of acidic soils, whereas no clear trend was observed under NT. NT generally led to increased aggregate stability and greater SOM content in upper soil horizons. However, the magnitude of the relative effects varied, e.g. with soil texture. No-tillage practices enhanced earthworm populations, but not where herbicides or pesticides were applied to combat weeds and pests. Overall, in this review, yield slightly decreased under NT. Crop rotation had a positive effect on SOM content and yield; rotation with ley very positively influenced earthworms’ numbers. Overall, crop rotation had little impact on soil pH and aggregate stability − depending on the type of intercrop; alternatively, rotation of arable crops only resulted in adverse effects. A clear positive trend was observed for earthworm abundance under organic agriculture. Further, organic agriculture generally resulted in increased aggregate stability and greater SOM content. Overall, no clear trend was found for pH; a decrease in yield was observed under organic agriculture in this review.
Reduced tillage intensity is known to increase soil organic carbon (SOC) in the topsoil, but can also lead to increased microbially derived nitrous oxide (N2O) emissions. Although the trade-offs ...between C sequestration and N2O emissions under different agricultural practices have been extensively investigated, the reported results are conflicting and, thus remain unclear. In this study, the effects of different types of tillage no-till (NT) and conventional mouldboard tillage (CT) in combination with four fertilisation regimes unfertilised control (CON), mineral NPK (MIN), organic (compost) (ORG), and mixed (NPK + compost) (MIX) on SOC and microbial biomass (Cmic) were examined two decades after the experiment was initiated. The abundance of the microbial community and N-functional guilds within the soil profile (up to a depth of 60 cm) was also determined. SOC content was significantly higher in NT than in CT at 0–10 cm depth, with an average difference of 0.6–1.3 % SOC, depending on fertilisation. Organic fertilisation increased the SOC content in both tillage systems up to a depth of 20 cm. Microbial biomass, abundance of total bacterial and archaeal 16S rRNA, and fungal ITS genes decreased with depth, corresponding to the decrease in SOC, and, consequently, were higher in NT than in CT, in the top 20 cm soil for microbial biomass and bacterial abundance and top 10 cm for fungi and archaea. Denitrifiers and ammonium oxidising archaea (AOA) were affected by soil depth and tillage, whereas the distribution of ammonium oxidising bacteria (AOB) was affected by fertilisation and depth. The ratios between (i) the two nitrite-reducing communities (nirS/nirK), (ii) the two N2O-reducing communities (nosZI/nosZII), and (iii) the nitrite- and N2O-reducing communities (nirK + nirS)/(nosZ + nosZII) increased significantly with soil depth, indicating niche differentiation caused by differences in nutrients contents and environmental conditions. Overall, stratification of SOC and nutrients in the soil by tillage and fertilisation was the main driver of the differences in the total microbial and N cycling communities. The findings of our study provide novel insights that can aid in development of effective strategies for steering soil microbiome responsible for N2O emissions.
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•SOC content increased the most as a combination of no-till and compost fertilisation.•Bacterial amoA abundance increased with increasing amounts of mineral fertilisation.•Ratios (nirK + nirS)/(nosZI + nosZII) and nosZI/nosZII increased with depth.•Higher ratio nosZI/nosZII observed in no till as compared to conventional tillage.
The combination of conservation tillage (non-inversion and no-till) with organic farming is rare due to weed problems. However, both practices have the potential to improve soil quality and increase ...soil organic C (SOC). This study investigated the changes in SOC, microbial biomass, and microbial composition during the transition from conventional to organic farming (from 2014 to 2020) in a long-term tillage trial established in 1999. Non-inversion minimum tillage to a depth of 10 cm (MT) resulted in SOC stratification, whilst conventional soil tillage with 25-cm-deep mouldboard ploughing (CT) maintained an even SOC distribution in the plough layer. After 12 years of contrasting tillage in 2011, the uppermost soil layer under MT had a 10% higher SOC content (1.6% w/w) than CT (1.45% w/w). This difference became even more pronounced after introducing organic farming in 2014. By the fall of 2020, the SOC content under MT increased to 1.94%, whilst it decreased slightly to 1.36% under CT, resulting in a 43% difference between the two systems. Conversion to organic farming increased microbial biomass under both tillage systems, whilst SOC remained unchanged in CT. Abundances of total bacterial and Crenarchaeal 16S rRNA and fungal ITS genes indicated shifts in the microbial community in response to tillage and depth. Fungal communities under MT were more responsive to organic farming than bacterial communities. The improved soil quality observed under MT supports its adoption in both organic and conventional systems, but potentially large yield losses due to increased weed cover discourage farmers from combining MT and organic farming.
Soil plays a central role in most aspects of human societies, and there is a large body of literature about sustainable soil management. Nevertheless, soil is currently facing degradation arising ...from different threats, which undermines sustainable development globally. In order to design effective research and policy strategies, it is necessary to identify the current knowledge level about sustainable soil management. This study summarises the key findings from a systematic stocktake of available knowledge about agricultural soil management practices in 23 European countries, which included the identification of soil management practices in use, the associated impacts and the soil challenges addressed. The aim of the study was to understand the current state of knowledge about the impacts of soil management practices, investigated and/or implemented across Europe. The results were analysed at the European level and were also grouped into European Regions and Environmental Zones. Key findings from this study were the identification of knowledge gaps that are key to climate mitigation and adaptation. There is a knowledge gap about soil management practices to avoid greenhouse gas emissions from agricultural soils, as the few reported studies evidence the complexity of the processes governing these emissions. Further knowledge is needed on the impact of tillage practices on long‐term carbon storage and distribution along the soil profile, as the reported knowledge was not consensual about carbon storage in deeper soil layers.
In a one-and-a-half-year study conducted in the ALS6 region in Europe (Ljubljana, Slovenia), the cultivation of microalgae in anaerobic digestate from food waste, mainly Scenedesmus dimorphus and ...Scenedesmus quadricauda, was investigated in three ponds (1260 L each) under a greenhouse. The effects of changing digestate quality and quantity as well as seasonal fluctuations on the productivity of the microalgae were investigated in three stages: Learning/Design (SI), Testing (SII), and Verification/Calibration (SIII). A decision support tool (DST) was developed using easy-to-measure parameters such as pH, temperature, electrical conductivity, mineral nitrogen forms and physical, biological parameters (OD, delayed fluorescence intensity). To control optimal pond operation, we proposed the photosynthetic culture index (PCI) as an early indicator for necessary interventions. Flocculation and nitrite levels (above 3 mg NO2-N L−1) were signals for the immediate remediation of the algae culture. Under optimal conditions in summer SIII, an average algal biomass production of 11 ± 1.5 g m−2 day−1 and a nitrogen use efficiency of 28 ± 2.6 g biomass/g N-input were achieved with the developed DST. The developed DST tool was, in this study, successfully implemented and used for the cultivation of microalgae consortia predominated by Scenedesmus dimorphus and S. quadricauda with biogas digestate. DST offers the possibility to be modified according to producers’ specific needs, facility, digestate and climate conditions, and as such, could be used for different microalgae cultivation processes with biogas digestate as a food source.
Slaughterhouse waste (SW) is potentially a good source of biomethane; however, its excessive ammonia content quickly causes inhibition of microbial processes. Our aim was therefore to remove ammonia ...from SW before putting it into a biogas reactor. Experimental 120 L pressure container was constructed to observe NH3 removal from diluted slaughterhouse waste at constant air flow of 144 NL/min, temperature 130 °C, and at different pressures: 300 kPa, 600 kPa, and 900 kPa. SW was first allowed to hydrolyze for 14 days at 38 °C. The SW was diluted with water (DSW) to 8.4% dry matter (DM) and forcibly aerated for 334 min. From the DSW, 0.7%, 3.8%, and 9% of initial total N were removed at 300 kPa, 600 kPa, and 900 kPa, respectively. However, the C/N ratio changed only slightly, from the initial 4.38 to 3.17, which is not a promising result for biomethanization. Further research on the presented system with the addition of bases might be promising to remove more ammonia.
Abstract
The European Commission has set targets for a reduction in nutrient losses by at least 50% and a reduction in fertiliser use by at least 20% by 2030 while ensuring no deterioration in soil ...fertility. Within the mandate of the European Joint Programme EJP Soil ‘Towards climate‐smart sustainable management of agricultural soils’, the objective of this study was to assess current fertilisation practices across Europe and discuss the potential for harmonisation of fertilisation methodologies as a strategy to reduce nutrient loss and overall fertiliser use. A stocktake study of current methods of delivering fertilisation advice took place across 23 European countries. The stocktake was in the form of a questionnaire, comprising 46 questions. Information was gathered on a large range of factors, including soil analysis methods, along with soil, crop and climatic factors taken into consideration within fertilisation calculations. The questionnaire was completed by experts, who are involved in compiling fertilisation recommendations within their country. Substantial differences exist in the content, format and delivery of fertilisation guidelines across Europe. The barriers, constraints and potential benefits of a harmonised approach to fertilisation across Europe are discussed. The general consensus from all participating countries was that harmonisation of fertilisation guidelines should be increased, but it was unclear in what format this could be achieved. Shared learning in the delivery and format of fertilisation guidelines and mechanisms to adhere to environmental legislation were viewed as being beneficial. However, it would be very difficult, if not impossible, to harmonise all soil test data and fertilisation methodologies at EU level due to diverse soil types and agro‐ecosystem influences. Nevertheless, increased future collaboration, especially between neighbouring countries within the same environmental zone, was seen as potentially very beneficial. This study is unique in providing current detail on fertilisation practices across European countries in a side‐by‐side comparison. The gathered data can provide a baseline for the development of scientifically based EU policy targets for nutrient loss and soil fertility evaluation.
Agro-ecosystems experience huge losses of land every year due to soil erosion induced by poor agricultural practices such as intensive tillage. Erosion can be minimized by the presence of stable soil ...aggregates, the formation of which can be promoted by bacteria. Some of these microorganisms have the ability to produce exopolysaccharides and lipopolysaccharides that "glue" soil particles together. However, little is known about the influence of tillage intensity on the bacterial potential to produce these polysaccharides, even though more stable soil aggregates are usually observed under less intense tillage. As the effects of tillage intensity on soil aggregate stability may vary between sites, we hypothesized that the response of polysaccharide-producing bacteria to tillage intensity is also determined by site-specific conditions. To investigate this, we performed a high-throughput shotgun sequencing of DNA extracted from conventionally and reduced tilled soils from three tillage system field trials characterized by different soil parameters. While we confirmed that the impact of tillage intensity on soil aggregates is site-specific, we could connect improved aggregate stability with increased absolute abundance of genes involved in the production of exopolysaccharides and lipopolysaccharides. The potential to produce polysaccharides was generally promoted under reduced tillage due to the increased microbial biomass. We also found that the response of most potential producers of polysaccharides to tillage was site-specific, e.g.,
had higher potential to produce polysaccharides under reduced tillage at one site, and showed the opposite response at another site. However, the response of some potential producers of polysaccharides to tillage did not depend on site characteristics, but rather on their taxonomic affiliation, i.e., all members of
that responded to tillage intensity had higher potential for exopolysaccharide and lipopolysaccharide production specifically under reduced tillage. This could be especially crucial for aggregate stability, as polysaccharides produced by different taxa have different "gluing" efficiency. Overall, our data indicate that tillage intensity could affect aggregate stability by both influencing the absolute abundance of genes involved in the production of exopolysaccharides and lipopolysaccharides, as well as by inducing shifts in the community of potential polysaccharide producers. The effects of tillage intensity depend mostly on site-specific conditions.
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