304 research outputs found

    Microbially mediated mechanisms underlie soil carbon accrual by conservation agriculture under decade-long warming

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    Increasing soil organic carbon (SOC) in croplands by switching from conventional to conservation management may be hampered by stimulated microbial decomposition under warming. Here, we test the interactive effects of agricultural management and warming on SOC persistence and underlying microbial mechanisms in a decade-long controlled experiment on a wheat-maize cropping system. Warming increased SOC content and accelerated fungal community temporal turnover under conservation agriculture (no tillage, chopped crop residue), but not under conventional agriculture (annual tillage, crop residue removed). Microbial carbon use efficiency (CUE) and growth increased linearly over time, with stronger positive warming effects after 5 years under conservation agriculture. According to structural equation models, these increases arose from greater carbon inputs from the crops, which indirectly controlled microbial CUE via changes in fungal communities. As a result, fungal necromass increased from 28 to 53%, emerging as the strongest predictor of SOC content. Collectively, our results demonstrate how management and climatic factors can interact to alter microbial community composition, physiology and functions and, in turn, SOC formation and accrual in croplands.</p

    Boosting domestic feed production with less environmental cost through optimized crop distribution

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    Global cropland expansion and associated greenhouse gas (GHG) emissions are largely driven by the growing demand of animal-sourced food. Thus, options are urgently needed to enhancing feed supply at a low environmental cost. Here we explored a set of scenarios about improving domestic feed supply, using a linear optimization model. Results indicate that the total feed (energy and protein) production may be increased by 18–32% through optimizing the spatial distribution of feed crops across provinces, without additional cropland input. GHG emissions and nitrogen and phosphorus inputs per MJ of produced feed decreased by 18–25%, 18–23%, and 16–21%, respectively. The redistribution strategies provide 10–16% additional animal food, which covers the demand of 195–393 million people. Lastly, we provide suggestions for improving the effectiveness of governmental policies related to spatial planning of crops, so as to alleviate the food-feed competition for cropland and to improve environmental sustainability

    Trends in anthropogenic ammonia emissions in China since 1980 : A review of approaches and estimations

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    Ammonia (NH3) emissions from intensive anthropogenic activities is an important component in the global nitrogen cycle that has triggered large negative impacts on air quality and ecosystems worldwide. An accurate spatially explicit high resolution NH3 emission inventory is essential for modeling atmospheric aerosol pollution and nitrogen deposition. However, existing NH3 emission inventories in China are still subject to several uncertainties. In this review we firstly summarize the widely used methods for the estimate of NH3 emissions and discuss their advantages and major limitations. Secondly, we present aggregated data from ten NH3 emission inventories to assess the trends in total anthropogenic NH3 emissions in China over the period 1980–2019. Almost emission estimates reported that NH3 emissions in China have doubled in the last four decades. We find a substantial differences in annual total NH3 emissions, spatial distributions and seasonal variations among selected datasets. In 2012, the median emission (Tg yr−1) and associated minimum-maximum ranges are 12.4 (8.5_17.2) for total emission, 9.9 (8.1_13.8) for agriculture, 0.3 (0.2_1.0) for industry, 0.4 (0.2_1.1) for residential and 0.1 (0.1_0.3) for transport and other emission of 1.5 (0.3_2.6). In general, peak emissions occur in summer but in different months, the higher NH3 emission intensities are concentrated in the NCP area, and in eastern and south-central China but distinct regional discrepancy among selected datasets. Finally, we made an analysis of the reasons and levels of difference in NH3 emission estimates with recommendations for improvement of China’s NH3 emission inventory

    Comprehensive assessment of the utilization of manure in China’s croplands based on national farmer survey data

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    Abstract China’s rapid increase in mass excreta and its environmental discharge have attracted substantial attention. However, cropland as a main destination of excreta utilization has not been extensively evaluated. Here, a national survey was used to assess the utilization of manure in croplands across China. The data included the inputs of manure nitrogen (N), phosphorus (P), and potassium (K) for cereals, fruits, vegetables, and other crops, along with the manure proportion of total N, P, and K inputs at the county level. The results showed that the manure N, P, and K inputs were 6.85, 2.14, and 4.65 million tons (Mt), respectively, constituting 19.0%, 25.5%, and 31.1% of the total N, P, and K, respectively. The spatial distribution of the manure proportion of total inputs was lower in Eastern China and higher in Western China. The results provide a detailed description of the utilization of manure nutrients in agricultural areas throughout China, which will serve as basic support for policymakers and researchers involved in future agricultural nutrient management in China

    Mycorrhiza-mediated recruitment of complete denitrifying Pseudomonas reduces N₂O emissions from soil

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    Background Arbuscular mycorrhizal fungi (AMF) are key soil organisms and their extensive hyphae create a unique hyphosphere associated with microbes actively involved in N cycling. However, the underlying mechanisms how AMF and hyphae-associated microbes may cooperate to influence N2O emissions from “hot spot” residue patches remain unclear. Here we explored the key microbes in the hyphosphere involved in N2O production and consumption using amplicon and shotgun metagenomic sequencing. Chemotaxis, growth and N2O emissions of isolated N2O-reducing bacteria in response to hyphal exudates were tested using in vitro cultures and inoculation experiments. Results AMF hyphae reduced denitrification-derived N2O emission (max. 63%) in C- and N-rich residue patches. AMF consistently enhanced the abundance and expression of clade I nosZ gene, and inconsistently increased that of nirS and nirK genes. The reduction of N2O emissions in the hyphosphere was linked to N2O-reducing Pseudomonas specifically enriched by AMF, concurring with the increase in the relative abundance of the key genes involved in bacterial citrate cycle. Phenotypic characterization of the isolated complete denitrifying P. fluorescens strain JL1 (possessing clade I nosZ) indicated that the decline of net N2O emission was a result of upregulated nosZ expression in P. fluorescens following hyphal exudation (e.g. carboxylates). These findings were further validated by re-inoculating sterilized residue patches with P. fluorescens and by an 11-year-long field experiment showing significant positive correlation between hyphal length density with the abundance of clade I nosZ gene. Conclusions The cooperation between AMF and the N2O-reducing Pseudomonas residing on hyphae significantly reduce N2O emissions in the microsites. Carboxylates exuded by hyphae act as attractants in recruiting P. fluorescens and also as stimulants triggering nosZ gene expression. Our discovery indicates that reinforcing synergies between AMF and hyphosphere microbiome may provide unexplored opportunities to stimulate N2O consumption in nutrient-enriched microsites, and consequently reduce N2O emissions from soils. This knowledge opens novel avenues to exploit cross-kingdom microbial interactions for sustainable agriculture and for climate change mitigation

    Mycorrhiza-mediated recruitment of complete denitrifying Pseudomonas reduces N2_{2}O emissions from soil.

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    BACKGROUND: Arbuscular mycorrhizal fungi (AMF) are key soil organisms and their extensive hyphae create a unique hyphosphere associated with microbes actively involved in N cycling. However, the underlying mechanisms how AMF and hyphae-associated microbes may cooperate to influence N2_{2}O emissions from "hot spot" residue patches remain unclear. Here we explored the key microbes in the hyphosphere involved in N2_{2}O production and consumption using amplicon and shotgun metagenomic sequencing. Chemotaxis, growth and N2_{2}O emissions of isolated N2_{2}O-reducing bacteria in response to hyphal exudates were tested using in vitro cultures and inoculation experiments. RESULTS: AMF hyphae reduced denitrification-derived N2_{2}O emission (max. 63%) in C- and N-rich residue patches. AMF consistently enhanced the abundance and expression of clade I nosZ gene, and inconsistently increased that of nirS and nirK genes. The reduction of N2_{2}O emissions in the hyphosphere was linked to N2_{2}O-reducing Pseudomonas specifically enriched by AMF, concurring with the increase in the relative abundance of the key genes involved in bacterial citrate cycle. Phenotypic characterization of the isolated complete denitrifying P. fluorescens strain JL1 (possessing clade I nosZ) indicated that the decline of net N2_{2}O emission was a result of upregulated nosZ expression in P. fluorescens following hyphal exudation (e.g. carboxylates). These findings were further validated by re-inoculating sterilized residue patches with P. fluorescens and by an 11-year-long field experiment showing significant positive correlation between hyphal length density with the abundance of clade I nosZ gene. CONCLUSIONS: The cooperation between AMF and the N2_{2}O-reducing Pseudomonas residing on hyphae significantly reduce N2_{2}O emissions in the microsites. Carboxylates exuded by hyphae act as attractants in recruiting P. fluorescens and also as stimulants triggering nosZ gene expression. Our discovery indicates that reinforcing synergies between AMF and hyphosphere microbiome may provide unexplored opportunities to stimulate N2_{2}O consumption in nutrient-enriched microsites, and consequently reduce N2_{2}O emissions from soils. This knowledge opens novel avenues to exploit cross-kingdom microbial interactions for sustainable agriculture and for climate change mitigation

    Global mean nitrogen recovery efficiency in croplands can be enhanced by optimal nutrient, crop and soil management practices

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    Abstract An increase in nitrogen (N) recovery efficiency, also denoted as N use efficiency (NUEr), is crucial to reconcile food production and environmental health. This study assessed the effects of nutrient, crop and soil management on NUEr accounting for its dependency on site conditions, including mean annual temperature and precipitation, soil organic carbon, clay and pH, by meta-regression models using 2436 pairs of observations from 407 primary studies. Nutrient management increased NUEr by 3.6-11%, crop management by 4.4–8%, while reduction in tillage had no significant impact. Site conditions strongly affected management induced changes in NUEr, highlighting their relevance for site-specific practices. Data driven models showed that the global mean NUEr can increase by 30%, from the current average of 48% to 78%, using optimal combinations of nutrient (27%), crop (6.6%) and soil (0.6%) management. This increase will in most cases allow to reconcile crop production with acceptable N losses to water. The predicted increase in NUEr was below average in most high-income regions but above average in middle-income regions

    Mycorrhiza-mediated recruitment of complete denitrifying Pseudomonas reduces N2O emissions from soil

    No full text
    Background Arbuscular mycorrhizal fungi (AMF) are key soil organisms and their extensive hyphae create a unique hyphosphere associated with microbes actively involved in N cycling. However, the underlying mechanisms how AMF and hyphae‑associated microbes may cooperate to influence N2O emissions from “hot spot” residue patches remain unclear. Here we explored the key microbes in the hyphosphere involved in N 2O production and consumption using amplicon and shotgun metagenomic sequencing. Chemotaxis, growth and N2O emissions of isolated N2O‑reducing bacteria in response to hyphal exudates were tested using in vitro cultures and inoculation experiments. Results AMF hyphae reduced denitrification‑derived N 2O emission (max. 63%) in C‑ and N‑rich residue patches. AMF consistently enhanced the abundance and expression of clade I nosZ gene, and inconsistently increased that of nirS and nirK genes. The reduction of N2 O emissions in the hyphosphere was linked to N2O‑reducing Pseudomonas specifically enriched by AMF, concurring with the increase in the relative abundance of the key genes involved in bacterial citrate cycle. Phenotypic characterization of the isolated complete denitrifying P. fluorescens strain JL1 (possessing clade I nosZ) indicated that the decline of net N 2 O emission was a result of upregulated nosZ expression in P. fluorescens following hyphal exudation (e.g. carboxylates). These findings were further validated by re‑inoculating sterilized residue patches with P. fluorescens and by an 11‑year‑long field experiment showing significant positive correlation between hyphal length density with the abundance of clade I nosZ gene. Conclusions The cooperation between AMF and the N2O‑reducing Pseudomonas residing on hyphae significantly reduce N2O emissions in the microsites. Carboxylates exuded by hyphae act as attractants in recruiting P. fluorescens and also as stimulants triggering nosZ gene expression. Our discovery indicates that reinforcing synergies between AMF and hyphosphere microbiome may provide unexplored opportunities to stimulate N 2 O consumption in nutrient‑enriched microsites, and consequently reduce N2O emissions from soils. This knowledge opens novel avenues to exploit cross‑kingdom microbial interactions for sustainable agriculture and for climate change mitigation

    Potential sources and occurrence of macro-plastics and microplastics pollution in farmland soils: A typical case of China

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    Plastic debris (including macro-plastics, microplastics (MPs), and nanoplastics), defined as an emerging contaminant, has been proven to significantly affect soil ecosystem functioning. Accordingly, there is an urgent need to robustly quantify the pollution situation and potential sources of plastics in soils. China as the leading producer and user of agricultural plastics is analyzed as a typical case study to highlight the current situation of farmland macro-plastics and MPs. Our study summarized information on the occurrence and abundance of macro-plastics and MPs in Chinese farmland soils for the first time based on 163 publications with 728 sample sites. The results showed that the average concentration of macro-plastics, and the abundance of MPs in Chinese farmlands were 103 kg ha−1 and 4537 items kg−1 (dry soil), respectively. In addition, this study synthesized the latest scientific evidence on sources of macro-plastics and MPs in farmland soils. Agricultural plastic films and organic wastes are the most reported sources, indicating that they contribute significantly to plastic debris in agricultural soils. Furthermore, the modeling methods for quantifying macro-plastics and MPs in soils and estimating the stock and flow of plastic materials within agricultural systems were also summarized.</p

    Model-based optimal management strategies to mitigate soil acidification and minimize nutrient losses for croplands

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    Enhanced nitrogen (N) and phosphorus (P) fertilizer applications have strongly elevated agricultural productivity, but also caused significant soil acidification (by N) and increased N and P losses to water bodies leading to eutrophication. There is an urgent need to integrate soil acidification amendment and nutrient management strategies to stimulate sustainable soil use and minimize environmental risks. This study aimed to derive the optimal combination of fertilizer, manure and lime to mitigate soil acidification and minimize nutrient losses by assessing the impacts of different nutrient management strategies on soil pH and nutrient budgets at a field level. The dynamic soil acidification model VSD+ was calibrated on measured pH changes in a long-term fertilization experiment (1990–2018), in which variable amounts of inorganic N, P and potassium (K), lime (L) and organic manure (M) were applied annually to a maize-wheat rotation on red soil. Adding NPK inorganic fertilizers only sharply decreased the soil pH by 1.5 units within 10 years. The pH remained relatively constant, however, in the experiment in which 70% of the N given by fertilizer was replaced by manure (NPKM) while lime addition after 20 years of NPK addition (NPKL) increased the pH by approximately 1.5 units. Historic soil pH changes were well reconstructed by VSD+. The model quantified that nitrogen transformations contributed up to 89% of the total acidity production in the NPK treatment, which could be fully neutralized by replacing 70% of the total N fertilizer input with manure. Scenarios were assessed to explore the future impacts of adapted nutrient management on soil acidification and nutrient surplus. Balancing the N and P input with crop demand (BNP) significantly reduces the N and P surplus but hardly affects the acidification rate compared to Business as Usual (BAU, equal to the NPK treatment). Balancing the N input and substituting N fertilizer with manure (BM) counteract acidification and maintain the optimal soil pH of 6.5 but strongly increase the annual P surplus. An optimized combination of fertilizer, manure and lime (OPT) was thus identified to minimize acidification and unnecessary P accumulation in soils, by balancing crop N, P and base cation (BC) demands and unavoidable N and BC leaching. We conclude that the VSD+ model can be used as a sustainable nutrient and acid management tool to derive optimal application rates of fertilizer, manure and lime in agricultural systems
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