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Applied Soil Ecology
Elsevier Science B.V.
Applied Soil Ecology

Elsevier Science B.V.

0929-1393

Applied Soil Ecology/Journal Applied Soil EcologySCIISTP
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    Microbial processes and community structure as influenced by cover crop residue type and placement during repeated dry-wet cycles

    Thapa R.Tully K.L.Schomberg H.H.Mirsky S.B....
    11页
    查看更多>>摘要：? 2021 Elsevier B.V.Soil microorganisms play a critical role in cover crop (CC) residue decomposition and nutrient cycling in agroecosystems. However, the impact of CC residue management and dry-wet cycles on soil and residue microbiota and their potential ecosystem functions is largely unknown. To fill these knowledge gaps, an incubation experiment was conducted with two CC residues, crimson clover (Trifolium incarnatum L.) and cereal rye (Secale cereale L.), and two residue placements (incorporated vs surface-applied). Each CCs by placement treatment was subjected to four dry-wet cycles (20-d each) for a total of 80-d. Crimson clover residues had higher water storage capacities than cereal rye, and the rate at which water was lost from surface-applied CC residues increased after each successive wetting event. Rapid drying of surface-applied CC residues quickly suppressed CO2 fluxes, which increased immediately upon rewetting. Incorporated CC residues maintained water content for longer duration than surface-applied residues and showed greater colonization by soil prokaryotes and saprophytic fungi. Thus, significantly more C and N were mobilized from incorporated residues by 80-d than from surface-applied residues (p < 0.05). Due to differences in residue chemistry, CC residue types have a stronger impact on soil N levels than residue placement. Thus, residue chemistry strongly influenced soil prokaryotic and fungal diversity, community structure, and functionality. While crimson clover-amended soils (N-rich environments) were dominated by copiotrophs, oligotrophs dominated cereal rye-amended soils (N-poor soil environments). On the other hand, residue placement may have a greater effect than residue type in determining residue microbiota, particularly prokaryotes. Based on these findings, we can conclude that the effect of residue placement on C and N mineralization during repeated dry-wet cycles is primarily explained by differences in water dynamics between incorporated and surface-applied CC residues.
      原文链接:
    • NSTL
    • Elsevier

    The dynamics of soil microbial community structure and nitrogen metabolism influenced by agriculture practices and rainfall

    Xiao N.Huang J.J.Mulligan C.N.
    9页
    查看更多>>摘要：? 2021Agriculture practices, such as fertilization and cultivation, inevitably modify the soil ecological environment by altering the soil microbial community structure and the nitrogen (N) metabolism processes. The influences of rainfall combined with agriculture practices on microbial community structure and soil N metabolism were not well understood. It is important to investigate the combined effects of rainfall and agriculture practices on the soil N metabolism in varied soil layers for better agriculture management. In this paper, the effects of fertilization, cultivation as well as rainfall on N metabolism related microorganisms and key functional genes at various depths in a vegetable field were investigated. Results showed that Soil microbial community structure of 30 cm depth is more sensitive to soil properties change. Nitrogen-fixing bacteria (NFB) was promoted (from 0.07% to 1.43%) after fertilization, and cultivation shifted the dominance of NFB from Ensifer to Bacillus in 20–30 cm soil layer. Denitrifier Pseudomonas in 20 cm (from 0.93 to 5.01%) and comammox Nitrospira in 30 cm (from 3.3% to 3.82%) were promoted after rainfall. Soil C/N is a major determinant of soil N metabolism-related microorganisms. Fertilization before rainfall and cultivation at 30 cm is recommended. The findings in this paper could provide the scientific basis for better agriculture management practices.
      原文链接:
    • NSTL
    • Elsevier

    Networks of free-living nematodes and co-extracted fungi, associated with symptoms of apple replant disease

    Kanfra X.Heuer H.Wrede A.Mahnkopp-Dirks F....
    11页
    查看更多>>摘要：? 2021 The AuthorsApple replant disease affects tree nurseries and apple production globally. After repeated planting in the same soil, apple roots show accumulation of phytoalexins, stunting, and blackening. Recently, we showed that nematodes extracted from replanted soil and co-extracted microbes triggered these symptoms, while pathogens or plant-parasitic nematodes could not explain the early disease development. To identify nematode-microbe complexes that coincide with replant disease, apple rootstocks were grown in the greenhouse in soils from five replanted sites for eight weeks. Nematodes were extracted by floatation from pots with stunted or normal plant growth, washed on a 20-μm sieve, and used for DNA extraction. Nematode communities and co-extracted fungi and bacteria were analyzed by high-throughput sequencing of amplified ribosomal fragments. The experiment was repeated in the next year. Regardless of soil type or year, the nematode and fungal communities significantly differed between pots with differential plant growth. Bacteria were not significantly associated with growth depression. Plant-parasitic nematodes or pathogens were not abundant in numbers that could explain the observed root damage. Free-living nematodes Prsimatolaimus, Acrobeles, Tylencholaimus, Acrobeloides, and Aphelenchus, and associated fungi Exophiala, Hohenbuehelia, Naganishia, Psathyrella, and unidentified members of Orbiliales, Helotiales, and Rhytismataceae significantly correlated with reduced plant growth. Isolating and investigating such disease complexes will give a chance to understand external biotic stress of apple roots and design mitigation measures.
      原文链接:
    • NSTL
    • Elsevier

    Investigating the effect of microbial inoculants Frankia F1 on growth-promotion, rhizosphere soil physicochemical properties, and bacterial community of ginseng

    Qi Y.Liu H.Geng M.Wang J....
    13页
    查看更多>>摘要：? 2021 The AuthorsGinseng root rot caused by Fusarium solani (F. solani) is a highly destructive soil-borne disease that happens worldwide, which seriously affects the growth and development of many types of crops. Frankia casuarinae CcI3 (Frankia F1) microbial inoculants F1 on the mycelial integrity of pathogenic fungus F. solani, the growth of ginseng plants, and the structure of rhizosphere microbial community were carefully studied in the rhizosphere soil of ginseng infected with ginseng disease. Under the normal ginseng growth and F. solani infected environment, plant height, root length, dry weight, stem diameter, leaf area, and chlorophyll content increased by 40.57%, 68.98%, 92.09%, 56.67%, 23.29%, and 39.60% in T2 (50 mL microbial inoculants F1) compared with CK (natural control without treatment). Increased enzyme activity of phenylalanine ammonia-lyase (PAL), peroxidase (POD), polyphenol oxidase (PPO), β-1, 3-glucanase, and chitinase showed improved disease resistance and stress resistance of plants in ginseng leaves having inoculation. Our present study demonstrated that the soil pH value, cation exchange capacity, organic matter, total nitrogen, available nitrogen, phosphorus, and potassium increased by 8.00%, 50.78%, 18.81%, 43.36%, 23.25%, 14.00%, and 5.11% in T2 compared with CK. Furthermore, the soil enzyme activities of catalase, sucrase, and urease in T2 treatment were increased by 12.14%, 27.56%, and 22.60%, respectively. Amplicon sequencing analysis revealed that the diversity of soil bacteria decreased after microbial inoculants F1 treatment. More specifically, the T2 treatment inhibited the growth of F. solani, and promoted that the relative abundance of Xanthomonadales, Sphingomonadales, Sphingobacteriales, Frankiales, and Propionibacteriales. The PICRUSt data predicted an array of bacterial functions, and microbial inoculants F1 primarily increased the abundance of functional genes related to bacterial metabolism in ginseng soil we confirmed. Collectively, we found that the optimal inoculation amount of Frankia F1 for inhibiting F. solani and promoting the growth of ginseng plants was 50 mL (T2), which could effectively regulate the soil microbial community structure during ginseng production. It helped to promote the sustainable development of Chinese agriculture.
      原文链接:
    • NSTL
    • Elsevier

    Agricultural practices of perennial energy crops affect nitrogen cycling microbial communities

    Kim H.Lee D.K.Voigt T.B.Yannarell A.C....
    9页
    查看更多>>摘要：? 2021 Elsevier B.V.Production of perennial bioenergy crops on farmland that is suboptimal for food crops may mitigate nitrous oxide emissions and reduce nutrient loss while producing bioenergy feedstocks. The ability of bioenergy crops to provide these multiple ecosystem services depends on interactions between the soil N cycle and the bioenergy production system, but our understanding of these interactions is limited. The objective of this study was to determine the effects of perennial energy crop management practices, including grass species (switchgrass, prairie cordgrass, Miscanthus × giganteus, and a grass mixture), harvest timing (at anthesis and after a killing frost), and N application rate (0, 56, and 112 kg N ha?1) on populations of N-cycling soil microorganisms. We quantified the abundances of genes encoding N cycling enzymes involved in ammonia oxidation (amoA), nitrite ammonification (nrfA), denitrification (nirK, nirS, norB, and nosZ), and N fixation (nifH). We found that N application significantly affected the abundance of N-cycling genes. The abundance of bacterial amoA (AOB) increased as N fertilization increased, thereby increasing the proportion of AOB compared to archaeal amoA (AOA). The nitrite reductase genes, nrfA and nirS, were more abundant in the plots with 56 kg N ha?1 applied; however, the nirK nitrite reductase did not differ across N applications. Overall, AOA, nrfA, and norB were correlated with each other as were AOB, nirK, and nosZ. Our data imply that management practices of perennial grasses, especially N application, could have significant impacts on functionally important soil microbial communities within the soil.
      原文链接:
    • NSTL
    • Elsevier

    An iron-reduction-mediated cascade mechanism increases the risk of carbon loss from mineral-rich peatlands

    Qin L.Zou Y.Wang G.Yang L....
    5页
    查看更多>>摘要：? 2021 Elsevier B.V.Iron (Fe) oxides promote carbon store stability in conventional (aerated) soils, and yet emerging evidence shows that Fe may also contribute to C decomposition in at redox interfaces. Mineral soil addition is common during peatland cultivation, but high content of Fe in mineral soil may lead to carbon loss upon flooding of agricultural peatlands (e.g. paddies). However, the mechanisms arising in such peatlands are poorly understood. We investigated different forms of Fe, including reactive Fe associated with organic carbon (FeR-OC), in field (natural and agricultural peatlands) and in vitro incubation experiments to in order to elucidate potential pathways of Fe-mediated decomposition. Our results show that FeR and short-range-order Fe (with Fes of particular importance due to its high capacity for carbon sorption) were enriched in agricultural peatlands compared with natural peatlands, while FeR-OC level was similar in both. Although Fes accounted for 60–80% of FeR, ferrous Fe accounted for 85–90% of Fes in agricultural peatlands, suggesting that high ferrous Fe levels counteract the role of Fes in forming Fe-carbon complexes in such flooded conditions. Furthermore, controlled experiments with Fe and phenol oxidase additions demonstrated that Fe reduction could initiate a cascade effect on carbon mineralization by acting as a terminal electron acceptor, releasing dissolved organic carbon from Fe?carbon complexes, promoting oxidative decomposition and mobilizing dissolved organic carbon in flooded agricultural peatlands. In conclusion, our study demonstrates that increased Fe levels can aggressively accelerate carbon loss in flooded agricultural peatlands through previously underestimated pathways.
      原文链接:
    • NSTL
    • Elsevier

    Nematode assemblages in four ecosystems of Parque Nacional del Agua, Costa Rica

    Abolafia J.Pena-Santiago R.Guevara-Mora M.Ferris H....
    11页
    查看更多>>摘要：? 2021 Elsevier B.V.The soil nematode fauna of five locations situated in Parque Nacional del Agua (PNA) in Costa Rica is characterized and analyzed. Four ecosystems were sampled in each location: primary (undisturbed) forest, secondary (naturally regenerated) forests, tree plantations (cleared and replanted with timber trees), and pastures (cleared of trees). Five soil samples of 100 g were analyzed in each location and ecosystem, resulting in a total of 100 samples. One hundred and thirty-one nematode genera were identified, and their abundance and biomass were estimated and analyzed by means of nonmetric multidimensional scaling (NMDS) and redundancy analysis (RDA). The observed nematode abundance was 1237 ± 520 specimens per soil sample for the whole survey, similar to previously reported from tropical soils. Dominance-diversity curves, based on nematode abundance, follow a similar ‘hollow curve’ pattern, with only 20 of the genera representing 84.6% of the total abundance, and only 12 of the genera representing 88% of the total biomass. Helicotylenchus, tylenchids, criconematids, Belondira, Longidorus, Xiphinema, Monotrichodorus, Prismatolaimus and Steinernema are important in the assemblages due their abundance or biomass in the different samples. Monotrichodorus and Discocriconemella appear related to undisturbed ecosystems, and they could have potential as disturbance indicators. Biomass-based dominance-diversity curves have similar qualitative and quantitative behavior to those observed in abundance distribution, but the dorylaims, Aporcelinus and Aporcelaimoides, which represented only the 0.35% of the abundance, having a major part of the total biomass (4.33%). NMDS analysis segregated locations into two groups, sampled sites were arranged according to the life zone where they belong. Ecosystems were segregated into natural ecosystems and plantations but having overlapping zones. Whereas RDA analysis indicated that organic matter and Cu are the most relevant edaphic variables for explaining the distribution of nematode assemblages, however few genera appear important in the ordination, Mesocriconema, Longidorus, Xiphinema and Belondira between them.
      原文链接:
    • NSTL
    • Elsevier

    Biosolarization restructures soil bacterial communities and decreases parasitic nematode populations

    Shea E.A.Parr A.E.Lopez E.Achmon Y....
    13页
    查看更多>>摘要：? 2021 The AuthorsBiosolarization is a soil disinfestation technology that combines passive solar heating and organic amendments to generate multiple pest-inactivating stressors. The objectives of this study were to assess the performance of almond (Prunus dulcis) processing residues in biosolarization to control infestations of root lesion (Pratylenchus vulnus) and ring nematodes (Mesocriconema xenoplax) during the pre-planting period of an almond orchard. The broader effects on soil microbial community composition were assessed by 16S rRNA gene sequencing immediately before and after biosolarization, as well as two months after treatment ended. Soil organic acids with nematicidal activity peaked after 9 days in biosolarized plots. Temperatures in biosolarized plots and solarized control plots reached maximum values 9–12 °C higher than untreated control plots. Biosolarization and solarization also enriched for specific Firmicutes, Actinobacteria, and Proteobacteria taxa associated with nematode suppression, some of which remained enriched two months post treatment. Biosolarization led to 100% mortality of P. vulnus in the upper 0–30 cm soil layer by 9 days of treatment. In contrast, reductions in plant-parasitic nematode densities between non-amended, solarized treatments and untreated controls were not observed until day 41 of treatment.
      原文链接:
    • NSTL
    • Elsevier

    Deciphering bacteria associated with a pre-parasitic stage of the root-knot nematode Meloidogyne hapla in nemato-suppressive and nemato-conducive soils

    Topalovic O.Santos S.S.Vestergard M.Heuer H....
    9页
    查看更多>>摘要：? 2021 The AuthorsNematode-suppressive soils are characterized by the ability of soil microbial communities to reduce populations of plant-parasitic nematodes (PPN) either directly or by inducing systemic resistance in plants. Various microorganisms have been recognized as antagonists of PPN in suppressive soils using culture-dependent and culture-independent methods. However, the associations that PPN form with microorganisms in nematode-conducive soils have been poorly studied. Here we drenched tomato rhizospheres with microbial suspensions from nine different soils and followed their effects on plant growth and root invasion of the infective second-stage juveniles (J2) of the northern root-knot nematode species Meloidogyne hapla. Based on the number of invaded J2, four soils were determined as nematode-suppressive, while five soils were categorized as nematode-conducive. To reveal bacteria attached to the J2 cuticle in soils with varying suppressiveness, we incubated J2 in suspensions from three suppressive and three conducive soils, and analyzed J2-attached bacteria using amplicon sequencing of the V3-V4 region of 16S rRNA gene. Our results suggest that the soil origin had a major effect on the composition of J2-attached bacteria, while the highest bacterial abundance and richness were observed on J2 from two suppressive soils. In addition, the highest number of indicator amplicon sequence variants (ASVs) was associated with J2 in two suppressive soils, but they had a very distinct bacterial profile. Further studies are needed to resolve the complexity of nemato-microbial interactions in soil and to determine the exact function of nematode-attached microorganisms in suppressive and conducive soils and their role in nematode suppression and protection.
      原文链接:
    • NSTL
    • Elsevier

    Short-term effects of cover crops on soil properties and the abundance of N-cycling genes in citrus agroecosystems

    Smyth A.R.Kadyampakeni D.M.Castellano-Hinojosa A.Strauss S.L....
    12页
    查看更多>>摘要：? 2021 Elsevier B.V.Limited information is available on the influence of cover crops (CCs) on soil nutrient cycling and the abundance of bacterial and archaeal communities, nitrogen (N)-fixers, nitrifiers, and denitrifiers in tree crops. We examined the effect of replacing the traditional weedy inter-row middle of a commercial citrus orchard in Florida with two different mixtures of CCs: legumes and non-legumes (LG + NL) and non-legumes only (NL). A no-treatment/grower standard was used as a control (GSC). After one year of CCs, the use of NL and LG + NL CCs significantly increased soil carbon (C) availability in the row middles compared to GSC as shown by increases in permanganate oxidizable C, and to a lesser extent, soil organic matter. Treatment with LG + NL significantly increased soil ammonium content compared to the NL and GSC treatments. Improved C cycling in soils treated with CCs was related to increased abundance of bacteria and archaea. Changes in the size of the soil N pool were accompanied by increases in the abundance of N-fixation (nifH) and nitrification (amoA) genes in soils treated with LG + NL, likely due to greater N-mineralization and N-fixation by legumes. The use of CCs significantly altered the abundance of the nirK, nirS, norB, nosZI, and nosZII denitrification genes after one year compared to the GSC treatment. Changes of the ratio between genes involved in nitrous oxide (N2O) production and reduction showed a greater abundance of N2O producers in soils treated with NL compared to the GSC and the LG + NL treatments. Nitrous oxide fluxes determined over a 1-month period after one year of CCs were also significantly higher in NL than in LG + NL and GSC soils. The lower N2O fluxes from soils treated with LG + NL were accompanied by significantly greater abundances of genes involved in N2O reduction (nosZI and nosZII). Overall, our data suggest enhanced soil nutrient cycling and nutrient availability and associated nitrogen-cycling microorganisms in Florida citrus orchards after only one year of CC treatments. These impacts depended on the composition of the CC mixture and appear to be accelerated in sandy soils under warm humid climate such as in Florida.
      原文链接:
    • NSTL
    • Elsevier