● Land use type affects the physicochemical properties of soil. ● The value of OM and TN is high in acacia soils. ● Strong acidity of soil is considered a serious constraint for agriculture. ● Suitable cash crops are acacia, cassava, banana, rice and maize.
Soil fertility is affected by land-use types and land management, which exacerbates soil erosion and various other forms of soil degradation in the mountainous regions of Vietnam. This study was conducted in A Luoi District, Thua Thien Hue, Vietnam to identify the effects of land-use types on specific soil physicochemical characteristics related to soil fertility. Soil physicochemical properties, such as organic matter (OM), total nitrogen (TN), total phosphorous (TP), and K+ were significantly affected by land-use type. The results showed that the soils were sandy in rice but clay loam for acacia and cassava. The mean bulk density value of acacia soil was significantly greater than that of other soils. TN were higher in the acacia soils than those in the rice, maize, and banana soils. The OM content was significantly higher in the acacia, cassava, and banana soils than those in the rice and maize soils. The mean of exchangeable K+ in the rice soil was higher compared to those in other soils and was affected by land-use type. The high exchangeable acidity content in the soils was probably due to intensive precipitation. However, both land use type and management did not affect the CEC value. Overall, the inappropriate land use caused the disturbance of soil physicochemical properties, indicating that the conditions of rice and maize soils are becoming worse than acacia soils. Therefore, lowering the intensity of cultivation, adopting incorporated soil fertility management, and applying organic fertilizer should preserve the existing conditions and enhance soil properties.
● LDPE had no effect on the mortality, growth, and reproduction of earthworms. ● LDPE did not alter the mortality, growth, and reproduction of earthworm caused by Cd. ● LDPE alleviated histopathological damage to earthworms caused by Cd. ● LDPE alleviated DNA damage in earthworm coelomocytes caused by Cd. ● LDPE did not affect the accumulation of Cd in earthworms.
Cadmium (Cd) can accumulate in the food chain, with serious impacts on human health and safety. Microplastics (MPs) such as low-density polyethylene (LDPE) should be considered not only as a single pollutant but also as a carrier of other pollutants. In this study, we investigated the joint effects of 30% LDPE and 313 mg kg−1 Cd on mortality, growth, reproduction, microstructure, DNA damage, oxidative stress, and mRNA levels in the earthworm Eisenia fetida. We found that 313 mg kg−1 Cd inhibited growth and reproduction and damaged the microstructures of the skin and intestine. Meanwhile, LDPE had no effect on the mortality, growth, or cocoon production of earthworms. Moreover, it did not increase the mortality, growth, or inhibition of cocoon production caused by Cd and instead alleviated the DNA damage in coelomocytes caused by Cd treatment. Finally, it did not alter the accumulation of Cd in the worms. These indicators can be used for toxicity safety assessment and soil ecological risk assessment of LDPE and Cd cooccurrence in soil.
● Flue gas desulfurization gypsum and clover planting alleviated the soil salinization stress. ● Soil pH and total phosphorus affected the bacterial communities. ● Total phosphorus affected the fungal communities. ● Flue gas desulfurization gypsum and clover planting improved jujube quality.
The coastal area of Shandong Province, characterized by coastal saline tidal soil, is one of the main production areas of winter jujube in China. However, the low soil fertility and poor soil structure in jujube orchard restricted the development of the jujube industry. The objectives of this study were to 1) evaluate the effect of application of flue gas desulfurization (FGD) gypsum and clover planting on soil quality improvement and soil microbial community structure of jujube orchard; 2) investigate the effects of two measures on the nutrition and quality of winter jujube. The results showed that FGD gypsum reduced the soil total salt content by 65.6%, and clover planting increased the soil organic matter content by 30.7%, which effectively alleviated the soil salinization stress and improved the soil structure. Soil pH and total phosphorus (TP) were the main determinants influencing bacterial community composition, and TP was the dominant factor of the fungal community composition in the saline-alkali soils. Meanwhile, FGD gypsum addition and clover planting significantly increased the sugar degree and Vc content of winter jujube, thus improved jujube quality, and further contributed to the ecological sustainable development of winter jujube industry.
● Nematode identification serves as an important parameter to study their behaviour, importance and pathogenicity. ● Application of classical morphometric based identification methods prove to be lacking due to insufficient knowledge on morphological variations among closely related taxa. Molecular approaches such as DNA and protein-based information, microarray, probing, sequence-based methods and others have been used to supplement morphology-based methods for nematode identification. ● Ascarosides and certain protein-based nematode-associated molecular patterns (NAMPs), can be perceived by the host plants, and can initiate a signalling cascade. ● This review primarily emphasizes on an updated account of different classical and modern tools used for the identification of nematodes. Besides we also summarize the mechanism of some important signalling pathways which are involved in the different plant nematode interactions.
Nematodes constitute most diverse and least studied group of soil inhabiting invertebrates. They are ecologically and physiologically important, however, wide range of nematodes show harmful impact on the individuals that live within their vicinity. Plant parasitic nematodes (PPNs) are transparent, pseudocoelomate, free living or parasitic microorganisms. PPNs lack morphometric identification methods due to insufficient knowledge on morphological variations among closely related taxa. As such, molecular approaches such as DNA and protein-based information, microarray, probing, sequence-based methods and others have been used to supplement morphology-based methods for their identification. To invade the defense response of different plant species, parasitic nematodes have evolved different molecular strategies. Ascarosides and certain protein-based nematode-associated molecular patterns (NAMPs), can be perceived by the host plants, and can initiate a signaling cascade. To overcome the host confrontation and develop certain nematode feeding sites, some members can inject effectors into the cells of susceptible hosts to reprogram the basal resistance signaling. This review primarily emphasizes on an updated account of different classical and modern tools used for the identification of PPNs. Besides we also summarize the mechanism of some important signaling pathways which are involved in the different plant nematode interactions.
● Nutrient constraints in low-fertility soil were modified by different species combinations. ● Grass-clover assemblages benefited both species in terms of nutrient procurement. ● Interplay of competition and facilitation is demonstrated. ● An invasive weed removed essential nutrients from the grazing cycle.
To investigate the interplay of competition and facilitation between plants in low-fertility pasture grasslands of New Zealand, we compared nutrient uptake and acquisition of key nutrients of three species from different functional groups. Combinations of Pilosella officinarum (mouse-eared hawkweed, an invasive weed), Trifolium repens (white clover, a nitrogen fixer) and Dactylis glomerata (cocksfoot, a pasture grass) were planted into a soil with low-to-deficient concentrations of key nutrients. Highest yields were achieved by the grass growing alone but, when the clover and grass had grown together, there were complementary benefits in terms of procurement of a wide range of nutrients from soil despite lower root biomass. The invasive weed negated these benefits, and soil nutrients were exploited less efficiently when Pilosella had grown alone or in a mixture with the other species. Competition from the weed removed the benefits of grass-legume coexistence. These findings are interpreted to suggest that requirements for legumes to be the main source of nitrogen in pasture grasslands may be compromised unless competitive weeds are controlled to avoid disrupted procurement of key nutrients. It is likely these constraints to nutrient procurement would similarly impact conservation grasslands.
● Afforestation effectively improved soil microbial communities and significantly increased soil nitrogen mineralization rate ( R m). ● Soil microorganisms drive R m by regulating soil N-cycling genes. ● Soil nitrification genes had a major effect on soil R m than denitrification genes after afforestation.
Assessing the function of forest ecosystems requires an understanding of the mechanism of soil nitrogen mineralization. However, it remains unclear how soil N-cycling genes drive soil nitrogen mineralization during afforestation. In this study, we collected soil samples from a chrono-sequence of 14, 20, 30, and 45 years of Robinia pseudoacacia L. (RP14, RP20, RP30, and RP45) with a sloped farmland (FL) as a control. Through metagenomic sequencing analysis, we found significant changes in the diversity and composition of soil microbial communities involved in N-cycling along the afforestation time series, with afforestation effectively increasing the diversity (both alpha and beta diversity) of soil microbial communities. We conducted indoor culture experiments and analyzed correlations, which revealed a significant increase in both soil nitrification rate (Rn) and soil nitrogen mineralization rate (Rm) with increasing stand age. Furthermore, we found a strong correlation between soil Rm and soil microbial diversity (both alpha and beta diversity) and with the abundance of soil N-cycling genes. Partial least squares path modeling (PLS-PM) analysis showed that nitrification genes (narH,narY,nxrB, narG,narZ,nxrA, hao, pmoC-amoC) and denitrification genes (norB, nosZ, nirK) had a greater direct effect on soil Rm compared to their effect on soil microbial communities. Our results reveal the relationships between soil nitrogen mineralization rate and soil microbial communities and between the mineralization rate and functional genes involved in N-cycling, in the context of Robinia pseudoacacia L. restoration on the Loess Plateau. This study enriches the understanding of the effects of microorganisms on soil nitrogen mineralization rate during afforestation and provides a new theoretical basis for evaluating soil nitrogen mineralization mechanisms during forest succession.
● No consistent variation was found in soil respiration Q10 under various O2 conditions. ● Substrate C quality had a strong effect on Q10 in oxic soils. ● N limitation had a large impact on Q10 in soils under O2 limitation.
Current studies on the temperature sensitivity (Q10) of soil organic matter (SOM) decomposition mainly focus on aerobic conditions. However, variations and determinants of Q10 in oxygen (O2)-deprived soils remain unclear. Here we incubated three grassland soils under oxic, suboxic, and anoxic conditions subjected to varying temperatures to compare variations in Q10 in relation to changing substrates. No consistent variation was found in Q10 under various O2 conditions. Further analysis of edaphic properties demonstrated that substrate carbon quality showed a strong influence on Q10 in oxic soils, whereas nitrogen limitation played a more important role in suboxic and anoxic soils. These results suggest that substrate carbon quality and nitrogen limitation may play roles of varying importance in determining the temperature sensitivity of SOM decomposition under various O2 conditions.
● Integrated grain cropping systems promote soil health (SH) and sustainability. ● Microbial biomass and activity (MBA) and community structure (MCS) are key to SH. ● Integration of maize with Urochloa pastures strongly impacts MBA and MCS. ● MBA is more sensitive than MCS to shifts in grain cropping systems. ● Systems under continuous Urochloa increased microbial activity and AMF abundance.
Tropical soils are prone to degradation. Adoption of conservation agricultural practices is essential to improve soil health, which is influenced by soil microbes. In this study we analyzed shifts in microbial biomass and activity (MBA) and microbial community structure (MCS) based on fatty acid methyl esthers (FAMEs) between five no-till agricultural practices: maize monoculture (MM); maize annualy intercropped with Urochloa decumbens (M/Ud); M/Ud with soybean rotation every other year (M/Ud–S); M/Ud keeping the pasture for the next two years (M/Ud–Ud–Ud); and maize intercropped with U. ruziziensis keeping the pasture for the next two years (M/Ur–Ur–Ur). Results indicated that MBA was affected by the inclusion of Urochloa intercropping and by rotation with soybean. Systems under a longer residence time with Urochloa in the field had higher β-glucosidase activity and soil basal respiration, indicating a greater microbial activity. MCS was less affected than MBA by the investigated cropping systems. MCS changed only in the continuous pasture systems, which were enriched in arbuscular mycorrhyzal fungi (AMF). Additionally, the continuous pasture systems had lower microbial stress ratios than the other agricultural practices. In sum, our study showed that utilization of Urochloa spp. under longer periods in no-till agricultural practices contributes to increase microbial activity, AMF abundance and decrease microbial stress ratio. These changes are primarily beneficial for soil health.
● Response of growth rate and antioxidative system of ten Bacillus strains to acid stresses was assayed. ● Strong acid treatment significantly decreased the growth rate of the strains. ● Acid stresses increased the GPX activity and GSSG content of the tested strains. ● Divergent changes occurred in ROS and antioxidative system (SOD, CAT, GR, MDA and GSH).
Environmental changes including soil acidification exert obvious stresses on soil ecosystems and influence soil microorganisms. In this study, ten microbial strains were incubated under different acid treatments to investigate responses of microbial growth and antioxidative system to acid stress. All the strains belong to Bacillus genus, but exhibit distinct ecological functions. We observed that these microbial strains had obviously different pH tolerance threshold, in spite of the close phylogenetic classification among strains. Acid stresses exerted significant effects on microbial antioxidative system, including superoxide dismutase (SOD), catalase (CAT) and glutathione transferring enzymes (GPX and GR) and reactants (GSH and GSSH), but the effects were strain specific. Furthermore, we found acid stress effects on total variances of the investigated microbial antioxidative system along the first two principal components (PCs). Activities of CAT and SOD contributed substantially to PC1 that reflected obvious acid effects on NC7 and ZC4, and closely related to intracellular malondialdehyde content. The GSSG activities and GSH/GSSG contributed greatly to PC2 that unveiled acid stress effects on most of the microbial strains. Our results highlight substantially heterogeneous responses of microbial strains to acid stress and support that phylogenetic closeness does not imply functional similarity of soil microorganisms under environmental changes.
● Sewage water in agriculture threatens human health and soil ecosystems through metal pollution. ● Nematodes show promise as bioindicators of soil health due to their abundance and position in soil food webs. ● Metal-polluted water decreased abundance of certain nematode groups and Sigma Maturity Index. ● Metal pollution positively affected nematode groups with r-selected life cycles.
Sewage water has been inappropriately used in agriculture, posing possible threats to human health and the soil ecosystems by its constituent pollutants, especially heavy metals. Correct evaluation of its influences on soil biomes needs to consider the response of soil fauna. Among soil organisms, nematodes are seen as the best promising candidates for bioindicators of soil health. Here in, we collected soil samples from fresh water irrigated field from three sites (S1, S2 and S3) and sewage water irrigated distance gradient (5 m−40 m), to assess the influence of metal (Cu, Zn, Cd, Mn, Pb) polluted water on various characteristics of nematode communities. The results indicated that the heavy metals decreased the abundance of C-p3 nematodes, herbivores, and predatory nematodes as well as sigma maturity index, whereas, C-p1, C-p2, bacterivore and fungivore nematodes abundance and diversity positively responded to the metal pollution. Generally, nematode genera with r-selected life cycle were positively affected and those with K-selected life cycle were negatively affected by metal pollution. Overall nematode community has potential to be used as indicator of pollution stress in agricultural soils to check soil health and sustainability.
● Responses of soil DIRB to lignocellulosic fractions during a 6-week microcosm incubation were investigated. ● Anaeromyxobacter , Bacillus , and Clostridium maintained their dominance throughout the incubation. ● Distinct DIRB groups proliferated under specific lignocellulosic fraction amendments. ● Limits of insufficient ferric iron on the proliferation varied by DIRB group.
Dissimilatory iron reducing bacteria (DIRB) are phylogenetically and physiologically diverse in paddy soils, where iron reduction closely couples with the oxidation of rice straw-derived carbon in the straw returning scenarios. However, few studies have addressed the niche differentiation within DIRB groups during the degradation of lignocellulosic fractions of rice straw. This study conducted a 6-week microcosm incubation experiment to reveal the distinct responses of DIRB groups under specific lignocellulosic fraction amendments with and without ferrihydrite (Fh) addition in a flooded paddy Ultisol. Results showed that the total absolute abundance of the 19 detected DIRB groups did not vary significantly during the incubation. Anaeromyxobacter, Bacillus, and Clostridium were the dominant DIRB groups for all lignocellulosic treatments whereas Thermincola was dominant but only under xylan amendment with Fh addition. DIRB-nodes in the co-occurrence networks of bacterial community mainly belonged to Anaeromyxobacter and Bacillus. Clostridium and Thermincola, Alkaliphilus and Anaeromyxobacter, and Alicyclobacillus, Desulfobulbus, and Desulfosporosinus were specifically proliferated under xylan, cellulose, and lignin amendments, respectively. Whether the proliferation was limited by insufficient ferric iron varied by bacterial group. These findings suggested the lignocellulosic fraction-induced niche differentiation within DIRB groups, which advanced our understanding of the ecology of DIRB in paddy soils under straw returning.
● The unique gut habitat led to a core intestinal microbiome in diverse soil ecosystems. ● The collembolan guts may help eliminate soil pathogens. ● Host-selection carried more weight on community assembly of gut microbiome.
Soil invertebrates are widely distributed in the ecosystem and are essential for soil ecological processes. Invertebrate gut microbiome plays an important role in host health and has been considered as a hidden microbial repository. However, little is known about how gut microbiome in soil invertebrates respond to diverse soil ecosystems. Based on a laboratory microcosm experiment, we characterized the assembling of microbiome of soil collembolans (Folsomia candida) from six representative regions of the soil ecosystem which they inhabit. Results showed that collembolan gut microbial communities differed significantly from their surrounding soil microbial communities. A dominant core gut microbiome was identified in gut habitat. Community analyses indicated that deterministic process dominated in the community assembly of collembolan gut microbiome. The results further demonstrate a dominant contribution of host selection in shaping gut microbiome. It is also worthy to mention that pathogens, such as common agricultural phytopathogenic fungi Fusarium, were involved in core microbiome, indicating that collembolans could act as vectors of pathogens. Our results unravelled the existence of gut core microbiome of collembolans in soil ecosystems and provided new insights for understanding the crucial role of gut microbiome of soil fauna in maintaining microbial biodiversity and stability of soil ecosystems.
● The use of human excrement as fertilizer is a characteristic of traditional Chinese agriculture. ● The application of excrement from urban residents in agriculture since the Song Dynasty has ensured the cleanliness and hygiene of ancient Chinese cities. ● As early as the Ming Dynasty, the Chinese people defined the principle of fertilizing fields with human excrement from the perspective of material circulation. ● The concept Peri-URban ecosystems (PURE) provides inspiration for urban-rural symbiosis regarding circular economy.
The use of human excrement in fertilization is a major attribute differentiating the Chinese traditional agriculture from the agriculture in other regions around the world. Despite the fact that the exact record showing that human excrement was used as fertilizer in China emerged in the Western Han Dynasty (B.C. 202–A.D. 8), such records did not become prevalent until the Southern Song Dynasty (A.D.1127−1279). In the Ming and Qing eras (A.D.1368−1912), human excrement was even considered “top-class fertilizer” and served as the most essential fertilizer in farmland fertilization. The importance of human excrement in the Ming and Qing was mainly reflected by farmers’ purchase of human excrement from urban areas. As fertilization practices became increasingly popular during the period, men of letters built a localized theoretical system centering on human excrement. Although the use of human excrement had both positive and negative impacts on public health and the ecological environment, the positive overshadowed the negative as a whole. Today, it is worth pondering on how the utilization of human excrement as an agricultural resource can be improved so that a material cycle system can be rebuilt to re-connect the urban and rural areas.
