Biology and Fertility of Soils最新文献

The objectives of this field trial were to collect reliable measurement data on N₂ emissions and N₂O/(N₂O + N₂) ratios in typical German crops in relation to crop development and to provide a dataset to test and improve biogeochemical models. N₂O and N₂ emissions in winter wheat (WW, Triticum aestivum L.) and sugar beet (SB, Beta vulgaris subsp. vulgaris) were measured using the improved ¹⁵N gas flux method with helium–oxygen flushing (80:20) to reduce the atmospheric N₂ background to < 2%. To estimate total N₂O and N₂ production in soil, production-diffusion modelling was applied. Soil samples were taken in regular intervals and analyzed for mineral N (NO₃⁻ and NH₄⁺) and water-extractable Corg content. In addition, we monitored soil moisture, crop development, plant N uptake, N transformation processes in soil, and N translocation to deeper soil layers. Our best estimates for cumulative N₂O + N₂ losses were 860.4 ± 220.9 mg N m⁻² and 553.1 ± 96.3 mg N m⁻² over the experimental period of 189 and 161 days with total N₂O/(N₂O + N₂) ratios of 0.12 and 0.15 for WW and SB, respectively. Growing plants affected all controlling factors of denitrification, and dynamics clearly differed between crop species. Overall, N₂O and N₂ emissions were highest when plant N and water uptake were low, i.e., during early growth stages, ripening, and after harvest. We present the first dataset of a plot-scale field study employing the improved ¹⁵N gas flux method over a growing season showing that drivers for N₂O and N₂O + N₂ fluxes differ between crop species and change throughout the growing season.

Crop-specific cultivation practices including crop rotation, cover cropping, and fertilisation are key measures for sustainable farming, for which soil microorganisms are important components. This study aims at identifying links between agronomic practices, potato yield and quality as well as soil microorganisms. We analysed the roles of cover crops and of the soil prokaryotic, fungal, and protistan communities in a long-term trial, differing in crop rotation, i.e. winter wheat or silage maize as pre-crop, presence and positioning of oil radish within the rotation, and fertilisation, i.e. mineral fertiliser, straw, manure, or slurry. Up to 16% higher yields were observed when oil radish grew directly before potatoes. Losses of potato quality due to infection with Rhizoctonia solani-induced diseases and common scab was 43–63% lower when wheat + oil radish was pre-crop under manure or straw + slurry fertilisation than for maize as pre-crop. This contrast was also reflected by 42% higher fungal abundance and differences in β-diversity of prokaryotes, fungi, and protists. Those amplicon sequence variants, which were found in the treatments with highest potato qualities and differed in their abundances from other treatments, belonged to Firmicutes (2.4% of the sequences) and Mortierellaceae (28%), which both comprise potential antagonists of phytopathogens. Among protists, Lobosa, especially Copromyxa, was 62% more abundant in the high potato quality plots compared to all others, suggesting that specific higher trophic organisms can improve crop performance. Our findings suggest that successful potato cultivation is related (1) to planting of oil radish before potatoes for increasing yield and (2) to fertilisation with manure or straw + slurry for enriching the microbiome with crop-beneficial taxa.

Soil salinization is an abiotic stress factor that can harm plant growth. Root endophytic bacteria may be associated with the resilience of plants to saline–alkaline stress. This study investigated the diversity, composition, and function of endophytic bacterial communities in alfalfa roots under saline–alkali stress, and screened a key bacterial strain associated with saline–alkali resistance. 16 S rRNA amplicon sequencing showed that high levels of saline alkalinity significantly reduced the diversity of endophytic bacterial communities and the relative abundance of beneficial bacterial taxa, such as Rhizobiales and Pseudomonas. Long durations of saline–alkali significantly decreased the abundance of predicted functional genes related to nitrogen metabolism in the alfalfa root endophytic bacterial community. Additionally, we isolated a key strain Pseudomonas with saline-alkali tolerance which could colonise roots and considerably improve physiological characteristics and plant growth. We found that colonization with Pseudomonas can considerably enhance plant resistance to saline-alkali stress and that the composition and function of the endophytic bacterial communities in roots likely contribute to plant tolerance to saline-alkali stress.

Abstract

As the carbon (C) credit market evolves, incorporating organic matter into soils has emerged as a key strategy in C farming. Soil heterotrophic respiration (R_H) plays a pivotal role in maintaining the C balance in terrestrial ecosystems, yet the contrasting impacts of fresh and pyrogenic organic matter applications on soil R_H, and associated underlying mechanisms, have not been fully investigated. Through a 2-year field experiment, we investigated how applying maize straw and its derived biochar affect the physical, chemical, and microbial properties of soil in a subtropical Moso bamboo forest. Results showed that straw application increased soil R_H, while biochar application suppressed it. Soil R_H was correlated positively with β-glucosidase and cellobiohydrolase activities but negatively with RubisCO enzyme activity. Increased soil R_H under straw application was linked to the increased β-glucosidase/cellobiohydrolase activities driven by elevated water-soluble organic C and O-alkyl C levels as well as GH48 and cbhI gene abundances, and the decreased RubisCO enzyme activity caused by reduced cbbL gene abundance. Conversely, reduced soil R_H under biochar application was linked to reductions in β-glucosidase and cellobiohydrolase activities induced by increased aromatic C and decreased GH48 and cbhI gene levels, and increases in RubisCO enzyme activity driven by higher cbbL gene abundance. More importantly, changes in soil R_H were clearly linked to microbial dynamics. Specifically, increases in the relative abundances of Alphaproteobacteria and Sordariomycetes and decreases in AD3 and Tremellomycetes contributed to the enhanced soil R_H under straw application. With biochar application, the reverse effect occurred, ultimately contributing to the reduced soil R_H. Our study demonstrates that maize straw application increases while biochar application decreases soil R_H in the subtropical forest. These findings reveal that biochar reduced soil R_H through changing microbial activity in subtropical forests, providing insight into complex dynamics of soil C cycling in response to diverse interventions.

Abstract

Nitric oxide (NO), as a short-lived climate forcer, has direct and indirect detrimental impacts on environmental quality and human health. The amount of nitrogen (N) fertilizer application to agricultural soils is considered a robust predictor of total NO emissions, but the estimates of cropland NO emissions have large uncertainties due to the widely used constant emission factors (EF) as e.g., default values recommended by Intergovernmental Panel on Climate Change (IPCC) methodologies. By compiling 223 field experiments with at least three N-input levels across various croplands, we performed a meta-analysis to determine how soil NO emissions respond to N inputs. Our results showed for the first time that the mean change in EF per unit of additional N input (∆EF) across all available data was significantly higher as compared to zero, indicating that the NO response to N additions increased significantly faster than the assumed linear. On average, upland grain crops showed significantly higher ∆EF than that of horticultural crops or lowland rice. A higher ∆EF was also appeared in sites with mean annual precipitation < 600 mm, mean annual temperature ≥ 15 °C, soil organic carbon ≥ 14 g C kg^− 1 or total N ≥ 1.4 g N kg^− 1, and where synthetic N fertilizers were usually applied. By assuming various N application rates, the IPCC default (0.7% or 1.1%) EF model would have overestimated or underestimated NO emissions compared to our ∆EF model. Overall, our meta-analysis results exert high potential to improve estimates of cropland NO inventories, and help address disparities in global NO budgets and develop more targeted mitigation efforts.

The discovery of complete ammonia oxidizers (comammox) challenged our cognition of the nitrification process. Ammonia oxidizing archaea (AOA), ammonia oxidizing bacteria (AOB) and comammox can carry out soil autotrophic nitrification process together. However, the differentiation of the ecological niche of three types of ammonia oxidizers in different environments has not been fully discovered. In this study, a typical black soil collected from northeast China was adjusted to different pH (original and adjusted pH were 4.29 and 7, respectively) and NH₄⁺-N concentrations (weekly adding and without adding 100 mg NH₄⁺-N kg^− 1 soil). The activities of AOA, AOB and comammox were examined using DNA stable isotope probing approach with ¹³CO₂, the phylogenetic information of active ammonia oxidizers was detected by high-throughput sequencing. The results showed that niche differentiation of AOA, AOB and comammox in black soils differed with soil pH. AOA dominated the nitrification process in acidic soils, while AOA, AOB and comammox Clade A taken part in the nitrification process in neutral soils. Among them, AOB showed strong activity in the soils with the high N treatment. The active AOA mainly belonged to Nitrososphaera in acidic and neutral soils. The active AOB and comammox Clade A mainly belonged to Nitrosospira and Clade A.2 in neutral soils, respectively. Taken together, the results highlighted the significance of canonical ammonia oxidizers in nitrification process of black soils, and comammox Clade A played an active role in neutral condition.

Information on microbial biomass carbon (MBC) is crucial to assess their stocks and role for plant nutrient release in soil. Next to fumigation-extraction, molecular methods are routinely used to estimate the contribution of fungi, bacteria, and archaea to the soil microbial community. However, more information on the links between these different indices would deepen the understanding of microbial processes. The current study is based on 11 datasets, which contain MBC and MBN data obtained by fumigation-extraction and information on bacterial, archaeal, and fungal gene abundance, totalling 765 data points from agricultural, forest, and rangeland soils. Some of these datasets additionally provide information on double-stranded deoxyribonucleic acid (dsDNA) and fungal ergosterol. MBC varied around the median of 206 µg g⁻¹ soil. MBN followed with a median MB-C/N ratio of 4.1. Median microbial gene abundance declined from bacteria (96 × 10⁸) to archaea (4.4 × 10⁸) to fungi (1.8 × 10⁸). The median ratio of MBC/dsDNA was 15.8 and that of bacteria/dsDNA was 5.8 × 10⁸ µg⁻¹. The relationships between MBC and dsDNA as well as between bacterial gene abundance and dsDNA were both negatively affected by soil pH and positively by clay content. The median ergosterol/MBC and fungi/ergosterol ratios were 0.20% and 4.7 (n × 10⁸ µg⁻¹), respectively. The relationship between fungal gene abundance and ergosterol was negatively affected by soil pH and clay content. Our study suggests that combining fumigation-extraction with molecular tools allows more precise insights on the physiological interactions of soil microorganisms with their surrounding environment.

Intercropping is a powerful practice to alter the allocation of photosynthetic carbon (C) to belowground ecosystems via promotion of diversified plant communities. The feedback of soil C stability to intercropping is controlled by microbial C use efficiency (CUE). Despite its significance, there is currently insufficient evidence to decipher how soil microbial CUE reacts to intercropping. By combining a 10-year-long intercropping experiment with a substrate-independent ¹⁸O-H₂O labelling approach and high-throughput sequencing, we elucidated the performance of intercropping on soil C pool and microbial metabolic traits as well as their relationships with soil microbial communities. Compared with monoculture, maize intercropping with peanut and soybean significantly increased soil C storage, soil mineral-associated organic C (MAOC), soil dissolved organic (DOC), and soil microbial biomass (MBC) contents at maize four growth stages. Soil microbial CUE increased significantly, especially at maize flowering and mature stages, as a consequence of enhanced microbial growth and biomass turnover rate after maize intercropping with peanut and soybean. Soil C storage and accessibility indicators (e.g., MAOC, DOC, and MBC contents) could significantly predict the changes of soil microbial diversity and core taxa. Meanwhile, the beta-diversity (community composition) of soil bacteria, fungi, saprotroph and protists, as well as rare fungal taxa were positively correlated with soil microbial CUE, and these indicators showed a high prediction of the microbial CUE. Soil C storage and accessibility indicators directly and indirectly influenced soil microbial CUE by regulating microbial diversity and key taxa. Soil microbial diversity and core taxa directly and indirectly influenced microbial CUE by mediating microbial respiration, growth, biomass, and enzyme activity, which mediated by soil C storage and accessibility. These findings provide an evidence for the associations between microbial diversity, CUE, and soil C stability, highlighting the importance of intercropping-driven soil microbiome to enhance soil microbial CUE.

Abstract

Climate change has been intensifying soil drying and rewetting cycles, which can alter the soil microbiome structure and activity. Here we hypothesized that a soil drying-rewetting cycle enhances biodegradation and, hence, decreases the effectiveness of nitrification inhibitors (NIs). The effectiveness of DMPP (3,4-Dimethylpyrazole phosphate) and MP + TZ (3-Methylpyrazol and Triazol) was evaluated in 60-day incubation studies under a drying and rewetting cycle relative to constant low and high soil moisture conditions (40% and 80% water-holding capacity, WHC, respectively) in two different textured soils. The measurements included (i) daily and cumulative N₂O-N emissions, (ii) soil NH₄⁺-N and NO₃⁻-N concentrations, and (iii) the composition of bacterial soil communities. Application of DMPP and MP + TZ reduced the overall N₂O-N emissions under drying-rewetting (-45%), as well as under 40% WHC (-39%) and 80% WHC (-25%). DMPP retarded nitrification and decreased N₂O-N release from the sandy and silt loam soils, while MP + TZ mitigated N₂O-N production only from the silt loam soil. Unexpectedly, between days 30 and 60, N₂O-N emissions from NI-treated soils increased by up to fivefold relative to the No-NI treatment in the silt loam soil at 80% WHC. Likewise, the relative abundance of the studied nitrifying bacteria indicated that the NIs had only short-term effectiveness in the silt loam soil. These results suggested that DMPP and MP + TZ might trigger high N₂O-N release from fine-textured soil with constant high moisture after this short-term inhibitory effect. In conclusion, DMPP and MP + TZ effectively reduce N₂O-N emissions under soil drying and rewetting.

Manure-derived biochars have a fertilizer potential as pyrolysis concentrates non-volatile nutrients. The addition of magnesium (Mg) to poultry manure enhances its Mg/Ca ratio and could increase soluble P by phosphate-solubilizing bacteria (PSB). Our objective was to assess the potential of PSB strains to solubilize P from both unenriched and Mg-enriched biochar and to evaluate the growth of maize in an Oxisol fertilized with biochar (100 mg kg⁻¹ total P) to satisfy plant P needs. We examined the strains: Paraburkholderia fungorum UFLA 04–155, Pseudomonas anuradhapurensis UFPI B5-8A, Paenibacillus chondroitinus UFLA 03–116, Acinetobacter pittii UFLA 03–09, and Rhizobium tropici CIAT 899. Biochar was made from poultry manure at temperatures of 350 °C, 500 °C, and 650 °C. Maize growth and P uptake were assessed in plants after 15 and 30 days under greenhouse conditions. The strain P. anuradhapurensis UFPI B5-8A significantly released more P from Mg-biochar (82% of the total P added) than from the unenriched biochar (74% of the total P added). Furthermore, this strain released tartaric and gluconic acids when mixed with the Mg-biochar, whereas malic acid was primarily exuded when applied to unenriched biochar. Similarly, P. anuradhapurensis UFPI B5-8A inoculation or Mg enrichment resulted in a 20% increase in P uptake by maize compared to unenriched biochar. Therefore, a synergistic approach using Mg-biochar and inoculation with PSB increases phosphate availability from poultry manure and maize P use efficiency.