Recycling of livestock manure in agroecosystems to partially substitute synthetic fertilizer nitrogen (N) input is recommended to alleviate the environmental degradation associated with synthetic N ...fertilization, which may also affect food security and soil greenhouse gas (GHG) emissions. However, how substituting livestock manure for synthetic N fertilizer affects crop productivity (crop yield; crop N uptake; N use efficiency), reactive N (Nr) losses (ammonia (NH3) emission, N leaching and runoff), GHG (methane, CH4; and nitrous oxide, N2O; carbon dioxide) emissions and soil organic carbon (SOC) sequestration in agroecosystems is not well understood. We conducted a global meta-analysis of 141 studies and found that substituting livestock manure for synthetic N fertilizer (with equivalent N rate) significantly increased crop yield by 4.4% and significantly decreased Nr losses via NH3 emission by 26.8%, N leaching by 28.9% and N runoff by 26.2%. Moreover, annual SOC sequestration was significantly increased by 699.6 and 401.4 kg C ha–1 yr–1 in upland and paddy fields, respectively; CH4 emission from paddy field was significantly increased by 41.2%, but no significant change of that was observed from upland field; N2O emission was not significantly affected by manure substitution in upland or paddy fields. In terms of net soil carbon balance, substituting manure for fertilizer increased carbon sink in upland field, but increased carbon source in paddy field. These results suggest that recycling of livestock manure in agroecosystems improves crop productivity, reduces Nr pollution and increases SOC storage. To attenuate the enhanced carbon source in paddy field, appropriate livestock manure management practices should be adopted.
The continuous increase of the greenhouse gas nitrous oxide (N2O) in the atmosphere due to increasing anthropogenic nitrogen input in agriculture has become a global concern. In recent years, ...identification of the microbial assemblages responsible for soil N2O production has substantially advanced with the development of molecular technologies and the discoveries of novel functional guilds and new types of metabolism. However, few practical tools are available to effectively reduce in situ soil N2O flux. Combating the negative impacts of increasing N2O fluxes poses considerable challenges and will be ineffective without successfully incorporating microbially regulated N2O processes into ecosystem modeling and mitigation strategies. Here, we synthesize the latest knowledge of (i) the key microbial pathways regulating N2O production and consumption processes in terrestrial ecosystems and the critical environmental factors influencing their occurrence, and (ii) the relative contributions of major biological pathways to soil N2O emissions by analyzing available natural isotopic signatures of N2O and by using stable isotope enrichment and inhibition techniques. We argue that it is urgently necessary to incorporate microbial traits into biogeochemical ecosystem modeling in order to increase the estimation reliability of N2O emissions. We further propose a molecular methodology oriented framework from gene to ecosystem scales for more robust prediction and mitigation of future N2O emissions.
This review summarizes the major microbial pathways of soil N2O production, and key environmental factors modulating their relative contributions, and further proposes to use a combination of state-of-the-art approaches for better source partitioning and incorporation of microbial datasets to achieve better predictive ecosystem models.
Globally, up to 64% (an average of 18%) of applied nitrogen in synthetic fertilizers was lost as ammonia (NH3).A meta-analysis on the mitigation of agricultural NH3 volatilization was ...conducted.NH3 volatilization could be decreased by 16% (amendment) to 88% (non-urea fertilizer).Adopting NH3 mitigation strategies can also reduce indirect nitrous oxide emission.
Ammonia (NH3) volatilization is a major pathway of nitrogen (N) loss in agricultural systems worldwide, and is conducive to low fertilizer N use efficiency, environmental and health issues, and indirect nitrous oxide emission. While mitigating NH3 volatilization is urgently needed, a quantitative synthesis is lacking to evaluate the effectiveness of mitigation strategies for NH3 volatilization from synthetic fertilizers applied in agricultural systems. To fill this knowledge gap, we conducted a meta-analysis of 824 observations on impacts on NH3 volatilization of ⿿4R Nutrient Stewardship⿿ (right source, rate, place and time), farming practices (irrigation, residue retention, amendments), and enhanced efficiency fertilizers (fertilizers with urease inhibitors, nitrification inhibitors or controlled release coatings). We found that, globally, up to 64% (an average of 18%) of applied N was lost as NH3. The use of non-urea based fertilizers, deep placement of fertilizers, irrigation, and mixing with amendments (pyrite, zeolite and organic acids) significantly decreased NH3 volatilization by 75, 55, 35 and 35%, respectively. In contrast, NH3 volatilization was not affected by split application, but significantly increased with N application rate and residue retention. Among the enhanced efficiency fertilizers, urease inhibitors and controlled release fertilizers decreased NH3 volatilization by 54 and 68% respectively whereas nitrification inhibitors increased NH3 volatilization by 38%. These results confirm that NH3 volatilization represents a substantial loss of N from agricultural systems, and that this N loss can be mitigated through adaption of appropriate fertilizer products and/or improved management practices.
The increasing antimicrobial resistance in manure-amended soil can potentially enter food chain, representing an important vehicle for antibiotic resistance genes (ARGs) transmission into human ...microbiome. However, the pathways for transmission of ARGs from soil to plant remain unclear. Here, we explored the impacts of poultry and cattle manure application on the patterns of resistome in soil and lettuce microbiome including rhizosphere, root endosphere, leaf endosphere and phyllosphere, to identify the potential transmission routes of ARGs in the soil-plant system. After 90 days of cultivation, a total of 144 ARGs were detected in all samples using high-throughput quantitative PCR. Rhizosphere soil samples harbored the most diverse ARGs compared with other components of lettuce. Cattle manure application increased the abundance of ARGs in root endophyte, while poultry manure application increased ARGs in rhizosphere, root endophyte and phyllosphere, suggesting that poultry manure may have a stronger impact on lettuce resistomes. The ARG profiles were significantly correlated with the bacterial community, and the enrichment of soil and plant resistomes was strongly affected by the bacterial taxa including Solibacteres, Chloroflexi, Acidobacteria, Gemm-1 and Gemmatimonadetes, as revealed by the network analyses. Moreover, the overlaps of ARGs between lettuce tissues and soil were identified, which indicated that plant and environmental resistomes are interconnected. Our findings provide insights into the transmission routes of ARGs from manured soil to vegetables, and highlight the potential risks of plant resistome migration to the human food chain.
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•We established a glasshouse experiment to explore the transmission pathways of ARGs in the plant-soil system.•Diverse ARGs were detected in soil and lettuce microbiomes.•Poultry manure application significantly increased the ARG abundance in root endophyte and phyllosphere of lettuce.•Two transmission routes of ARGs are proposed by identifying the shared resistome between manured soils and lettuce.
It is widely recommended that crop straw be returned to croplands to maintain or increase soil carbon (C) storage in arable soils. However, because C and nitrogen (N) biogeochemical cycles are ...closely coupled, straw return may also affect soil reactive N (Nr) losses, but these effects remain uncertain, especially in terms of the interactions between soil C sequestration and Nr losses under straw addition. Here, we conducted a global meta‐analysis using 363 publications to assess the overall effects of straw return on soil Nr losses, C sequestration and crop productivity in agroecosystems. Our results show that on average, compared to mineral N fertilization, straw return with same amount of mineral N fertilizer significantly increased soil organic C (SOC) content (14.9%), crop yield (5.1%), and crop N uptake (10.9%). Moreover, Nr losses in the form of nitrous oxide (N2O) emissions from rice paddies (17.3%), N leaching (8.7%), and runoff (25.6%) were significantly reduced, mainly due to enhanced microbial N immobilization. However, N2O emissions from upland fields (21.5%) and ammonia (NH3) emissions (17.0%) significantly increased following straw return, mainly due to the stimulation of nitrification/denitrification and soil urease activity. The increase in NH3 and N2O emissions was significantly and negatively correlated with straw C/N ratio and soil clay content. Regarding the interactions between C sequestration and Nr losses, the increase in SOC content following straw return was significantly and positively correlated with the decrease in N leaching and runoff. However, at a global scale, straw return increased net Nr losses from both rice and upland fields due to a greater stimulation of NH3 emissions than the reduction in N leaching and runoff. The trade‐offs between increased net Nr losses and soil C sequestration highlight the importance of reasonably managing straw return to soils to limit NH3 emissions without decreasing associated C sequestration potential.
Straw return to croplands is widely recommended to increase soil C storage. However, because C and N cycles are tightly coupled, straw return also affects soil reactive N (Nr) losses, but these effects remain uncertain. Therefore, we use the method of meta‐analysis to address this knowledge gap. We found that straw return increased soil C sequestration, but simultaneously increased net Nr losses from global croplands due to greater stimulated NH3 emissions. This result highlights the importance of reasonably managing straw return to soils to limit NH3 emissions without decreasing associated C sequestration potential.
Wine production is a complex process from the vineyard to the winery. On this journey, microbes play a decisive role. From the environment where the vines grow, encompassing soil, topography, weather ...and climate through to management practices in vineyards, the microbes present can potentially change the composition of wine. Introduction of grapes into the winery and the start of winemaking processes modify microbial communities further. Recent advances in next-generation sequencing (NGS) technology have progressed our understanding of microbial communities associated with grapes and fermentations. We now have a finer appreciation of microbial diversity across wine producing regions to begin to understand how diversity can contribute to wine quality and style characteristics. In this review, we highlight literature surrounding wine-related microorganisms and how these affect factors interact with and shape microbial communities and contribute to wine quality. By discussing the geography, climate and soil of environments and viticulture and winemaking practices, we claim microbial biogeography as a new perspective to impact wine quality and regionality. Depending on geospatial scales, habitats, and taxa, the microbial community respond to local conditions. We discuss the effect of a changing climate on local conditions and how this may alter microbial diversity and thus wine style. With increasing understanding of microbial diversity and their effects on wine fermentation, wine production can be optimised with enhancing the expression of regional characteristics by understanding and managing the microbes present.
Nitrification inhibitors show promise in decreasing nitrous oxide (N2O) emission from agricultural systems worldwide, but they may be much less effective than previously thought when both direct and ...indirect emissions are taken into account. Whilst nitrification inhibitors are effective at decreasing direct N2O emission and nitrate (NO3–) leaching, limited studies suggest that they may increase ammonia (NH3) volatilization and, subsequently, indirect N2O emission. These dual effects are typically not considered when evaluating the inhibitors as a climate change mitigation tool. Here, we collate results from the literature that simultaneously examined the effects of nitrification inhibitors on N2O and NH3 emissions. We found that nitrification inhibitors decreased direct N2O emission by 0.2–4.5 kg N2O‐N ha−1 (8–57%), but generally increased NH3 emission by 0.2–18.7 kg NH3‐N ha−1 (3–65%). Taking into account the estimated indirect N2O emission from deposited NH3, the overall impact of nitrification inhibitors ranged from −4.5 (reduction) to +0.5 (increase) kg N2O‐N ha−1. Our results suggest that the beneficial effect of nitrification inhibitors in decreasing direct N2O emission can be undermined or even outweighed by an increase in NH3 volatilization.
Microplastics and nanoplastics are emerging pollutants of global importance. They are small enough to be ingested by a wide range of organisms and at nano-scale, they may cross some biological ...barriers. However, our understanding of their ecological impact on the terrestrial environment is limited. Plastic particle loading in agroecosystems could be high due to inputs of some recycled organic waste and plastic film mulching, so it is vital that we develop a greater understanding of any potentially harmful or adverse impacts of these pollutants to agroecosystems. In this article, we discuss the sources of plastic particles in agroecosystems, the mechanisms, constraints and dynamic behaviour of plastic during aging on land, and explore the responses of soil organisms and plants at different levels of biological organisation to plastic particles of micro and nano-scale. Based on limited evidence at this point and understanding that the lack of evidence of ecological impact from microplastic and nanoplastic in agroecosystems does not equate to the evidence of absence, we propose considerations for addressing the gaps in knowledge so that we can adequately safeguard world food supply.
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•We estimate maximum loadings in agroecosystem using existing regulations.•Lifetime loading of 2.8–63t·ha−1 of microplastics from biosolids use alone.•Biotic response is mediated by the organism, soil and plastic properties.•We deduce ecosystem impact by linking organismal response to ecological role.•Estimated loadings can be used to set up ecotoxicology experiments.
Abstract
Mitigating agricultural ammonia (NH
3
) emissions in China is urgently needed to avoid further damage to human and ecosystem health. Effective and feasible mitigation strategies hinge on ...integrated knowledge of the mitigation potential of NH
3
emissions and the associated economic costs and societal benefits. Here we present a comprehensive analysis of marginal abatement costs and societal benefits for NH
3
mitigation in China. The technical mitigation potential of agricultural NH
3
emissions is 38–67% (4.0–7.1 Tg N) with implementation costs estimated at US$ 6–11 billion. These costs are much lower than estimates of the overall societal benefits at US$ 18–42 billion. Avoiding unnecessary fertilizer use and protein-rich animal feed could provide 30% of this mitigation potential without additional abatement costs or decreases in agricultural productivity. Optimizing human diets with less animal-derived products offers further potential for NH
3
reduction of 12% by 2050.
The impact of microplastic pollution on terrestrial biota is an emerging research area, and this is particularly so for soil biota. In this study, we addressed this knowledge gap by examining the ...impact of aged low-density polyethylene (LDPE) and polyester fibres (i.e. polyethylene terephthalate, PET) on a forest microbiome composition and activity. We also measured the corresponding physicochemical changes in the soil. We observed that bacteria community composition diverged in PET and LDPE treated soils from that of the control by day 42. These changes occurred at 0.2% and 0.4% (w/w) of PET and at 3% LDPE. Additionally, soil respiration was 8-fold higher in soil that received 3% LDPE compared to other treatments and control. There were no clear patterns linking these biological changes to physicochemical changes measured. Taken together, we concluded that microplastics aging in the environment may have evolutionary consequences for forest soil microbiome and there is immediate implication for climate change if the observed increase in soil respiration is reproducible in multiple ecosystems.
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•We investigate the response of forest soil bacteria community to microplastics.•Soil respiration increased 8-fold with 3% low-density polyethylene (LDPE).•Soil microbiome diverged in polyester fibre (PET) and LDPE treated soils.•Evolutionary and climate change effects of microplastics need further research.
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