Influence of long-term fertilization on soil microbial biomass, dehydrogenase activity, and bacterial and fungal community structure in a brown soil of northeast China

Enhancement of cadmium uptake in Sedum alfredii through interactions between salicylic acid/jasmonic acid and rhizosphere microbial communities

The focus on phytoremediation in soil cadmium (Cd) remediation is driven by its cost-effectiveness and eco-friendliness. Selecting suitable hyperaccumulators and optimizing their growth conditions are key to enhance the efficiency of heavy metal absorption and accumulation. Our research has concentrated on the role of salicylic acid (SA) and jasmonic acid (JA) in facilitating Cd phytoextraction by "Sedum alfredii (S. alfredii)" through improved soil-microbe interactions. Results showed that SA or JA significantly boosted the growth, stress resistance, and Cd extraction efficiency in S. alfredii. Moreover, these phytohormones enhanced the chemical and biochemical attributes of the rhizosphere soil, such as pH and enzyme activity, affecting soil-root interactions. High-throughput sequencing analysis has shown that Patescibacteria and Umbelopsis enhanced S. alfredii's growth and Cd extraction by modifying the bioavailability and the chemical conditions of Cd in soil. Structural Equation Model analysis further verified that phytohormones significantly enhanced the interaction between S. alfredii, soil, and microbes, leading to a marked increase in Cd accumulation in the plant. These discoveries emphasized the pivotal role of phytohormones in modulating the hyperaccumulators' response to environmental stress and offered significant scientific support for further enhancing the potential of hyperaccumulators in ecological restoration technologies using phytohormones.

An investigation on the conversion of infertile soil into fertile soil using crop waste as a remedial (compost) approach and its influence on Vigna mungo biometric and biomolecule profile

The sustainable management of huge volume of agricultural waste in India can be resolved through composting and used as soil amendment. Agriculture waste compost amendments can optimistically alter the physicochemical (pH, C, N, & P) as well as biological nature (microbial activity/biomass and enzymatic activity) of infertile soil. Hence this study, the agriculture wastes such as sugarcane trash, corn stover, and pearl millet stalks were converted to composite through decomposition pit. Interestingly, test crops residues individual composites and their mixed form contained considerable quantity of vital elements like TC, TN, TP, TK, and C:N ratio and can effectively convert infertile soil to fertile soil. These test crop composites also had a significant impact on MBN (42.3 μg g-1), MBC (198.4 μg g-1), and MBP (196.4 μg g-1) in test soil, as well as dehydrogenase and alkaline phosphatase enzyme activity. However, the mixed composite effects are significantly greater than the individual test crop composite effects. Furthermore, it effectively remediates/converts infertile soil to fertile soil, and it ultimately demonstrated positive effects on Vigna mungo biometric (SH, RH, WB, and DB) and biomolecule (total chlorophyll, total carbohydrate, and total proteins) profiles, followed by individual test crop composites. According to the findings of this study, the incorporation of crop residue-based mixed composite significantly transforms infertile soil into fertile soil and promotes the growth of V. mungo.

Long-term fertilization and manuring effects on the nexus between sulphur distribution and SOC in an Inceptisol over five decades under a finger millet-maize cropping system

Our investigation revealed that alterations in sulphur (S) pools are predominantly governed by soil organic carbon (SOC), soil nitrogen (N), microbial biomass, and soil enzyme activities in sandy clay loam (Vertic Ustropept) soil. We employed ten sets of nutrient management techniques, ranging from suboptimal (50% RDF) to super-optimal doses (150% RDF), including NPK + Zn, NP, N alone, S-free NPK fertilizers, NPK + FYM, and control treatments, to examine the interrelation of S with SOC characteristics. Fourier-transform infrared (FT-IR) spectroscopy was utilized to analyze the functional groups present in SOC characterization across four treatments: 100% NPK, 150% NPK, NPK + FYM, and absolute control plots. Principal component analysis (PCA) was then applied to assess 29 minimal datasets, aiming to pinpoint specific soil characteristics influencing S transformation. In an Inceptisol, the application of fertilizers (100% RDF) in conjunction with 10 t ha-1 of FYM resulted in an increase of S pools from the surface to the subsurface stratum (OS > HSS > SO42--S > WSS), along with an increase in soil N and SOC. FT-IR spectroscopy identified cellulose and thiocyanate functional groups in all four plots, with a pronounced presence of carbohydrate-protein polyphenol, sulfoxide (S=O), and nitrate groups specifically observed in the INM plot. The PCA findings indicated that the primary factors influencing soil quality and crop productivity (r2 of 0.69) are SOC, SMBC, SMBN, SMBS, and the enzyme activity of URE, DHA, and AS. According to the study, the combined application of fertilizer and FYM (10 t ha-1) together exert a positive impact on sulphur transformation, SOC accumulation, and maize yield in sandy clay loam soil.

Phosphorus addition increases stability and complexity of co-occurrence network of soil microbes in an artificial Leymus chinensis grassland

Introduction

Understanding the response of cross-domain co-occurrence networks of soil microorganisms to phosphorus stability and the resulting impacts is critical in ecosystems, but the underlying mechanism is unclear in artificial grassland ecosystems.

Methods

In this study, the effects of four phosphorus concentrations, P0 (0 kg P ha-1), P1 (15.3 kg P ha-1), P2 (30.6 kg P ha-1), and P3 (45.9 kg P ha-1), on the cross-domain co-occurrence network of bacteria and fungi were investigated in an artificial Leymus chinensis grassland in an arid region.

Results and discussion

The results of the present study showed that phosphorus addition significantly altered the stem number, biomass and plant height of the Leymus chinensis but had no significant effect on the soil bacterial or fungal alpha (ACE) diversity or beta diversity. The phosphorus treatments all increased the cross-domain co-occurrence network edge, node, proportion of positively correlated edges, edge density, average degree, proximity to centrality, and robustness and increased the complexity and stability of the bacterial-fungal cross-domain co-occurrence network after 3 years of continuous phosphorus addition. Among them, fungi (Ascomycota, Basidiomycota, Mortierellomycota and Glomeromycota) play important roles as keystone species in the co-occurrence network, and they are significantly associated with soil AN, AK and EC. Finally, the growth of Leymus chinensis was mainly due to the influence of the soil phosphorus content and AN. This study revealed the factors affecting the growth of Leymus chinense in artificial grasslands in arid areas and provided a theoretical basis for the construction of artificial grasslands.

The mechanism effects of root exudate on microbial community of rhizosphere soil of tree, shrub, and grass in forest ecosystem under N deposition

Forests are composed of various plant species, and rhizosphere soil microbes are driven by root exudates. However, the interplay between root exudates, microbial communities in the rhizosphere soil of canopy trees, understory shrubs, grasses, and their responses to nitrogen (N) deposition remains unclear. Pinus tabulaeformis, Rosa xanthina, and Carex lancifolia were used to investigate root exudates, rhizosphere soil microbial communities, and their responses to N application in forest ecosystem. Root exudate abundances of P. tabulaeformis were significantly higher than that of R. xanthina and C. lancifolia, with carbohydrates dominating P. tabulaeformis and R. xanthina root exudates, fatty acids prevailing in C. lancifolia root exudates. Following N application, root exudate abundances of P. tabulaeformis and R. xanthina initially increased before decreasing, whereas those of C. lancifolia decreased. Microbial number of rhizosphere soil of C. lancifolia was higher than that of P. tabulaeformis and R. xanthina, but there was insignificant variation of rhizosphere soil microbial diversity among plant species. N application exerted promotional and inhibitory impacts on bacterial and fungal numbers, respectively, while bacterial and fungal diversities were increased by N application. Overall, N application had negative effects on root exudates of P. tabulaeformis, inhibiting rhizosphere soil microbial populations. N application suppressed rhizosphere soil microbial populations by increasing root exudates of R. xanthina. Conversely, N application elevated nutrient content in the rhizosphere soil of C. lancifolia, reducing root exudates and minimally promoting microbial populations. This study highlights the importance of understory vegetation in shaping soil microbial communities within forests under N deposition.

Potential of algal-based products for the management of potato brown rot disease

BACKGROUND

Ralstonia solanacearum causes potato brown rot disease, resulting in lower crop's production and quality. A sustainable and eco-friendly method for controlling the disease is required. Algae's bioactive chemicals have shown the potential to enhance plant defenses. For the first time, the efficacy of foliar application of Acanthophora spicifera and Spirulina platensis seaweed extracts, along with the utilization of dried algal biomasses (DABs) of Turbinaria ornata and a mixture of Caulerpa racemosa and Cystoseira myrica (1:1)on potato yield and brown rot suppression were investigated under field conditions. Field experiments were conducted in three locations: Location 1 (Kafr Shukr district, Kaliobeya governorate), Location 2 (Moneira district, Kaliobeya governorate), and Location 3 (Talia district, Minufyia governorate). Locations 1 and 2 were naturally infested with the pathogen, while location 3 was not. The study evaluated potato yield, plant nutritive status and antioxidants, soil available nitrogen-phosphorus-potassium (N-P-K), and organic matter percentage. Additionally, the shift in soil microbial diversity related to R. solanacearum suppression was examined for the most effective treatment.

RESULTS

The results revealed that seaweed extracts significantly increased potato yield at all locations, which correlated with higher phosphorus absorption, while T. ornate DAB increased potato yield only at location 2, accompanied by noticeable increases in soil nitrogen and plant phosphorus. The mixed DABs of C. racemosa and C. myrica demonstrated greater disease suppression than foliar applications. The disease-suppressive effect of the mixed DABs was accompanied by significant increases in flavonoids and total antioxidant capacity (TAC). Moreover, the application of mixed DABs increased soil bacterial biodiversity, with a higher abundance of oligotrophic marine bacterial species such as Sphingopyxis alaskensis and growth-promoting species like Glutamicibacter arilaitensis, Promicromonospora sp., and Paenarthrobacter nitroguajacolicus in all three locations compared to the untreated control. Klebsiella sp., Pseudomonas putida, and P. brassicacearum abundances were increased by the mixed DABs in Location 1. These species were less abundant in locations 2 and 3, where Streptomyces sp., Bacillus sp., and Sphingobium vermicomposti were prevalent.

CONCLUSIONS

The results demonstrated that the used seaweed extracts improved potato yield and phosphorous absorption, while the mixed DABs potentially contributed in disease suppression and improved soil microbial diversity.

Effects of biochar amendment and organic fertilizer on microbial communities in the rhizosphere soil of wheat in Yellow River Delta saline-alkaline soil

The biochar and organic fertilizer amendment have been used as an effective practice to increase soil fertility. Nevertheless, the mechanisms of microbial community response to organic fertilizer and biochar application on saline-alkali soil have not been clarified. This study investigated the effects at different concentrations of organic fertilizer and biochar on the microbial community of wheat rhizosphere soil under field experiment in the Yellow River Delta (China, YRD), using high-throughput sequencing technology. Biochar and organic fertilizer significantly influenced in most soil parameters (p < 0.05), apart from soil moisture content (M), pH, total nitrogen (TN) and soil total phosphorus (TP). Proteobacteria and Actinobacteriota were found in the rhizosphere soil as the main bacterial phyla, and the main fungal phyla were Ascomycota and Mortierellomycota. The soil bacterial and fungal communities under organic fertilizer were distinct from CK. Furthermore, redundancy analysis (RDA) directed that changes in bacterial communities were related to soil properties like pH, available phosphorus (AP), and total organic carbon (TOC), while pH, AP and TP, were crucial contributors in regulating fungal distribution. The correlation between soil parameters and bacteria or fungi varied with the application of biochar and organic fertilizers, and the interaction between the bacteria and fungi in organic fertilizer treatments formed more connections compared with biochar treatments. Our results indicated that biochar was superior to organic fertilizer under the contents set up in this study, and soil parameters increased with biochar and organic fertilizer application rate. The diversity and structure of soil bacteria and fungi differed with the application of biochar and organic fertilizer. The research provides a reference to rational application of organic fertilizer and biochar improvement in saline-alkali soil.

The six-year biochar retention interacted with fertilizer addition alters the soil organic nitrogen supply capacity in bulk and rhizosphere soil

Nitrogen fractions in soil, like organic nitrogen, mineral nitrogen, and free amino acids, are sensitive pointers to the soil nitrogen pools involved in nutrient cycling. As a potential improvement measure, biochar might improve soil fertility and nutrient availability. However, few studies have focused on the long-term effects of biochar retention on the soil nitrogen supply capacity of bulk and rhizosphere soil in brown earth. Therefore, a six-year field experiment was conducted in 2013, concentrating on the impact of biochar retention on soil nitrogen fractions. Four biochar rates were tested: no biochar amendment (CK); 15.75 t ha^-1 of biochar (BC1); 31.5 t ha^-1 of biochar (BC2); 47.25 t ha^-1 of biochar (BC3). Our results showed that the elevated application rates significantly enhanced soil organic matter (SOM), and total nitrogen (TN), and improved pH in both bulk and rhizosphere soils. Acid-hydrolyzable nitrogen (AHN) content in biochar treatments was higher than that of CK in bulk and rhizosphere soil. The content of non-hydrolyzable nitrogen (NHN) was increased in 47.25 t ha^-1 of biochar retention. Ammonium nitrogen (AN) and amino sugar nitrogen (ASN) contents were higher in bulk soil than in rhizosphere soil. Neutral amino acid contents were the highest both in bulk and rhizosphere soil. Principal component analysis (PCA) showed that soil organic nitrogen was significantly influenced by BC3 treatment in bulk soil, and largely influenced by other treatments in rhizosphere soil. Partial least square path modeling (PLSPM) revealed that NH₄⁺-N was mainly derived from amino acid nitrogen (AAN) and AN in bulk soil and AAN and ASN in rhizosphere soil. These results indicate that different biochar retention rates contributed to improve soil nutrients. Amino acid nitrogen was the prominent nitrogen source of NH₄⁺-N in bulk and rhizosphere soils.

Short- and long-term effects of continuous compost amendment on soil microbiome community

Organic amendment, and especially the use of composts, is a well-accepted sustainable agricultural practice. Compost increases soil carbon and microbial biomass, changes enzymatic activity, and enriches soil carbon and nitrogen stocks. However, relatively little is known about the immediate and long-term temporal dynamics of agricultural soil microbial communities following repeated compost applications. Our study was conducted at two field sites: Newe Ya'ar (NY, Mediterranean climate) and Gilat (G, semi-arid climate), both managed organically over 4 years under either conventional fertilization (0, zero compost) or three levels of compost amendment (20, 40 and 60 m3/ha or 2, 4, 6 L/m2). Microbial community dynamics in the soils was examined by high- and low-time-resolution analyses. Annual community composition in compost-amended soils was significantly affected by compost amendment levels in G (first, second and third years) and in NY (third year). Repeated sampling at high resolution (9-10 times over 1 year) showed that at both sites, compost application initially induced a strong shift in microbial communities, lasting for up to 1 month, followed by a milder response. Compost application significantly elevated alpha diversity at both sites, but differed in the compost-dose correlation effect. We demonstrate higher abundance of taxa putatively involved in organic decomposition and characterized compost-related indicator taxa and a compost-derived core microbiome at both sites. Overall, this study describes temporal changes in the ecology of soil microbiomes in response to compost vs. conventional fertilization.

Impacts of Rock Mineral and Traditional Phosphate Fertilizers on Mycorrhizal Communities in Pasture Plants

Intensive fertilizer use can constrain contributions from soil biological processes in pastures, including those associated with arbuscular mycorrhizal (AM) fungi. We evaluated the effect of fertilizers of different P solubility on the colonization of the roots of two common pasture plants by a community of AM fungi in a pasture soil. The treatments were a rock mineral fertilizer, a chemical fertilizer and a microbial inoculant. Subterranean clover and annual ryegrass were grown in pots for 10 weeks. Both fertilizers reduced the proportion and length of roots colonized by naturally occurring AM fungi. However, by 10 weeks, there was a much greater length of mycorrhizal root for annual ryegrass than for subterranean clover. The relative abundance of mycorrhizal fungi in the families Glomeraceae and Acaulosporaceae in roots was not affected by the form of fertilizer, but diversity indices of AM fungi in roots were altered. The chemical fertilizer had a greater negative effect on AM fungal diversity indices in the annual ryegrass roots compared with the subterranean clover roots. The reduction in OTU richness of AM fungi with fertilizer application corresponded with reduced soil pH. Differential effects of P fertilizers on naturally occurring AM fungi in this agricultural soil have the potential to influence the efficacy of P fertilizer use and dominance of plant species in grasslands.

Date Palm Waste Compost Application Increases Soil Microbial Community Diversity in a Cropping Barley (Hordeum vulgare L.) Field

Application of date palm waste compost is quite beneficial in improving soil properties and crop growth. However, the effect of its application on soil microbial communities is less understood. High-throughput sequencing and quantitative real-time PCR (qPCR) were used to evaluate the effect of compost application on the soil microbial composition in a barley field during the tillering, booting and ripening stages. The results showed that compost treatment had the highest bacterial and fungal abundance, and its application significantly altered the richness (Chao1 index) and α-diversity (Shannon index) of fungal and bacterial communities. The dominant bacterial phyla found in the samples were Proteobacteria and Actinobacteria while the dominant fungal orders were Ascomycota and Mortierellomycota. Interestingly, compost enriched the relative abundance of beneficial microorganisms such as Chaetomium, Actinobacteriota, Talaromyces and Mortierella and reduced those of harmful microorganisms such as Alternaria, Aspergillus and Neocosmospora. Functional prediction based on Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) showed that amplicon sequence variant (ASV) sequences related to energy metabolism, amino acid metabolism and carbohydrate metabolism were associated with compost-treated soil. Based on Fungi Functional Guild (FUNGuild), identified fungi community metabolic functions such as wood saprotroph, pathotroph, symbiotroph and endophyte were associated with compost-treated soil. Overall, compost addition could be considered as a sustainable practice for establishing a healthy soil microbiome and subsequently improving the soil quality and barley crop production.

Effect of Drought on the Development of Deschampsia caespitosa (L.) and Selected Soil Parameters during a Three-Year Lysimetric Experiment

This work presents results from a field experiment which was focused on the impact of the drought period on microbial activities in rhizosphere and non-rhizosphere soil. To demonstrate the effect of drought, the pot experiment lasted from 2012 to 2015. Fifteen lysimeters (plastic containers) were prepared in our area of interest. These lysimeters were filled with the subsoil and topsoil from this area and divided into two groups. The first group consisted of two variants: V1 (control) and V2 (84 kg N/ha), which were not stressed by drought. The second group consisted of three variants, V3 (control), V4 (84 kg N/ha), and V5 (84 kg N/ha + 1.25 L lignohumate/ha), which were stressed by drought every year of the experiment for 30 days. Changes in the soil moisture content caused by drought significantly affect the growth of Deschampsia caespitosa L., the microbial activity, and the soil’s capacity to retain nutrients. The measured basal respiration and dehydrogenase activity values confirm the significant effect of drought on microbial activity. These values were demonstrably higher in the period before drought simulation by more than 60%. On the other hand, significant differences between microbial activities in the rhizosphere and non-rhizosphere soil were not found. We did not find a clear effect of drought on the formation of soil water repellency.

Soil Fungal Composition Drives Ecosystem Multifunctionality after Long-Term Field Nitrogen and Phosphorus Addition in Alpine Meadows on the Tibetan Plateau

An ecosystem can provide multiple functions and services at the same time, i.e., ecosystem multifunctionality (EMF). Above- and belowground biodiversity and abiotic factors have different effects on EMF. Human activities increase atmospheric nitrogen (N) and phosphorus (P) deposition, but the mechanism of how atmospheric N and P deposition affect EMF in alpine meadows on the Tibetan Plateau is still unclear. Here, we measured eleven ecosystem parameters to quantify EMF by averaging method and explored the impact of plant and microbial species diversity and abiotic factors on EMF after long-term field N and P addition in alpine meadows on the Tibetan Plateau. Results showed that N addition reduced EMF by 15%, NP increased EMF by 20%, and there was no change due to P addition. N and P addition reduced pH, relative light conditions (RLC), and plant species richness and modified plant and fungal community composition. Structural equation model (SEM) analysis confirmed that fungal community composition was an important and positive driver on EMF. These results provided an understanding of how N and P addition affect EMF directly and indirectly through biotic and abiotic pathways, which was important for predicting the response of EMF to atmospheric N and P deposition in the future. Furthermore, the findings suggested that soil fungal composition was more important driving factors than abiotic factors in the response of EMF to N and P addition and the importance of the interactions between plant and soil microbial species diversity in supporting greater EMF.

Characteristics of soil microbiota and organic carbon distribution in jackfruit plantation under different fertilization regimes

Manure amendment to improve soil organic carbon (SOC) content is an important strategy to sustain ecosystem health and crop production. Here, we utilize an 8-year field experiment to evaluate the impacts of organic and chemical fertilizers on SOC and its labile fractions as well as soil microbial and nematode communities in different soil depths of jackfruit (Artocarpus heterophyllus Lam.). Three treatments were designed in this study, including control with no amendment (CK), organic manure (OM), and chemical fertilizer (CF). Results showed that OM significantly increased the abundance of total nematodes, bacterivores, bacteria, and fungi as well as the value of nematode channel ratio (NCR) and maturity index (MI), but decreased plant-parasites and Shannon diversity (H′). Soil microbial and nematode communities in three soil depths were significantly altered by fertilizer application. Acidobacteria and Chloroflexi dominated the bacterial communities of OM soil, while Nitrospira was more prevalent in CF treatment. Organic manure application stimulated some functional groups of the bacterial community related to the C cycle and saprotroph-symbiotroph fungi, while some groups related to the nitrogen cycle, pathotroph-saprotroph-symbiotroph and pathotroph-saprotroph fungi were predominated in CF treatment. Furthermore, OM enhanced the soil pH, contents of total soil N, P, K, and SOC components, as well as jackfruit yield. Chemical fertilizers significantly affected available N, P, and K contents. The results of network analyses show that more significant co-occurrence relationships between SOC components and nematode feeding groups were found in CK and CF treatments. In contrast, SOC components were more related to microbial communities than to nematode in OM soils. Partial least-squares-path modeling (PLS-PM) revealed that fertilization had significant effects on jackfruit yield, which was composed of positive direct (73.6%) and indirect effects (fertilization → fungal community → yield). It was found that the long-term manure application strategy improves soil quality by increasing SOM, pH, and nutrient contents, and the increased microbivorous nematodes abundance enhanced the grazing pressure on microorganisms and concurrently promoted microbial-derived SOC turnover.

Bacteria and Soil Enzymes Supporting the Valorization of Forested Soils

To decompose forest biomass, microorganisms use specific enzymes from the class of oxidoreductases and hydrolases, which are produced by bacteria and soil fungi. In post-agricultural forest soils, bacteria adapt more easily to changing ecological conditions than fungi. The unique features of bacteria, i.e., tolerance and the ability to degrade a wide range of chemical compounds, prompted us to conduct research that contributes to the improvement of the broadly understood circular management of biomass production and economic efficiency. This study aimed to analyze changes in the microbiological activity and the activities of dehydrogenases, catalase, β-glucosidase, urease, arylsulfatase, acid phosphatase, and alkaline phosphatase in the soil sampled from under Picea abies (Pa), Pinus sylvestris (Ps), Larix decidua (Ld), Quercus robur (Qr), and Betula pendula (Bp), after 19 years. The control object was unforested soil. The studies allowed one to demonstrate the relationship between the activity of soil enzymes and the assemblages of culturable microorganisms and bacteria determined by the metagenomic method and tree species. Thus, it is possible to design the selection of tree species catalyzing enzymatic processes in soil. The strongest growth promoter of microorganisms turned out to be Quercus robur L., followed by Picea abies L., whereas the weakest promoters appeared to be Pinus sylvestris L. and Larix decidua M.

Reduced Chemical Fertilizer Combined With Bio-Organic Fertilizer Affects the Soil Microbial Community and Yield and Quality of Lettuce

Reducing chemical fertilizers in combination with bio-organic fertilizers can limit the use of chemical fertilizers while maintaining soil fertility. However, the effects of combined fertilization on soil chemical properties, microbial community structure, and crop yield and quality are unknown. Using high-throughput sequencing, we conducted field experiments using lettuce plants subjected to five fertilization treatments: chemical fertilizer with conventional fertilization rate (CK), chemical fertilizer reduction by 30% + 6,000 kg ha–1 bio-organic fertilizer (T1), chemical fertilizer reduction by 30% + 9,000 kg ha–1 bio-organic fertilizer (T2), chemical fertilizer reduction by 40% + 6,000 kg ha–1 bio-organic fertilizer (T3), and chemical fertilizer reduction by 40% + 9,000 kg ha–1 bio-organic fertilizer (T4). Compared with CK, the T1–T4 had significantly higher soil pH and soil organic matter (SOM) and showed increased richness and diversity of the bacterial community, and decreased richness and diversity of the fungal community. Principal coordinate analysis evidenced that the bacterial and fungal communities of CK and T1–T4 were distinctly separated. The Kruskal-Wallis H-test demonstrated that the fungal community was more sensitive than the bacterial community to chemical fertilizer reduction combined with bio-organic fertilizer. Among the soil chemical parameters measured, only TN (total nitrogen) was significantly correlated with bacterial and fungal community composition. The T1 and T2 increased lettuce yield. Moreover, T1–T4 characterized reduced nitrate content and increased levels of soluble sugars and vitamin C in lettuce. Overall, the combined application of reduced chemical fertilizer and bio-organic fertilizer effectively improved soil fertility, microbial community structure, and lettuce yield and quality. These findings have valuable implications for vegetable safety and long-term environmental sustainability.

Population Distribution of Phosphate-solubilizing Microorganisms in Agricultural Soil

Phosphorus (P) is an essential macronutrient for plant growth and is mainly present in agricultural soil in unavailable forms. Phosphate-solubilizing microorganisms (PSMs) increase soil P availability. The objective of the present study was to assess the population and type of PSMs and their relationships with soil characteristics in the agricultural soil of Manokwari. Twenty-one composite soil samples (0–20‍ ‍cm) were collected at the rhizospheres of plants in the Prafi and Masni Districts. A dilution technique and plate count method on Pikovskayas agar medium were used to examine the PSM population, phosphate-solubilizing index (PSI), and various soil properties. The results obtained showed that the total population of phosphate-solubilizing bacteria ranged between 25×10³ and 550×10³ CFU g^–1 of soil, while that of phosphate-solubilizing fungi was between 2.0×10³ and 5.0×10³ CFU g^–1 of soil at all locations. The PSI of the isolates ranged between 1.1 to 3.6‍ ‍mm, with the most efficient and highest PSI being obtained for Bacillus sp. (strain 8) and the lowest for Pseudomonas sp. (strain 15). Six isolates found at all locations were identified at the genus level: Chromobacterium sp., Pseudomonas sp., Bacillus sp., Micrococcus sp., Caulobacter sp., and Aspergillus sp. A correlation was observed between the number of PSMs and the level of soil P availability and moisture content, indicating an increase in soil P availability with a greater abundance of PSMs in soil.

Difference responses of soil fungal communities to cattle and chicken manure composting application

AIMS

Cattle and poultry manure composting are often applied on agricultural lands but the fungal community composition before and after application in soils is still unclear. Describe soil fungal diversity after manure applications contribute to the correct resource use of livestock and poultry manures.

METHODS AND RESULTS

Fresh manure samples were obtained from 10 beef cow farms and 12 egg-laying poultry farms at five distinct phases of rearing. Surface soil samples were collected from vegetable plots within the farms after manure application at 15, 30 and 45 t hm^-2 . Using high-throughput sequencing techniques, the ITS region was utilized to describe soil fungus populations. The fungal OTUs, Chao1 and ACE of cattle manure were relative higher in fattening stage (>12 months), the OTUs and ACE of chicken manure were the highest in the initial laying stage (16-24 weeks). The fungal diversity indices of vegetable soils hadn't linear change after cow or chicken manure application compared with the control. Ascomycota (84.7% of total sequences), Neocallimastigomycota (9.69%), and Basidiomycota (4.6%) were the dominant phyla in cattle manure. Ascomycota (88.9%) also predominated in chicken manure, followed by Basidiomycota (8.9%). Following both cattle and chicken manure application, the abundance of Ascomycota decreased, while Basidiomycota and Chytridiomycota increased in the soils. None of the dominant genus increased or decreased linearly with the increase of cattle and chicken composting application rate. The fungal dominant genera of the soils with and without manure composting application were mostly affected by soil pH and EC than manure. Pearson's correlation analysis revealed that organic matter, Cu and Hg contents were strongly linked to the fungal diversity and the abundance of specific taxa in cattle manure. In chicken manure, OM, TN and Zn were major factors controlling the fungal diversity and community composition. Soil pH, EC, and Cu, Zn, Cd, Hg and As content had pronounced effects on beneficial and pathogenic genus in soil with and without manure composting. Beneficial fungal genus such as Aspergillus, Plectosphaerella, Acremonium, Meyerozyma and fungal pathogenic like Fusarium, Cladosporium, Verticillium were sensitive to properties (EC, pH, OM) and heavy metals (Cu, Zn, Hg) contents of environment, relatively. The study can serve as an applicable contribution helping in farms management (especially to cattle and poultry breeding) and improve their resource use of livestock and poultry manure.

CONCLUSIONS

Soil heterogeneity rather than manure determines fungal communities in the vegetable fields, but we can encourage the sensible use of cattle and chicken manure in agroecosystems.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study will help the farmers regulate the dosage of feed components which can increase the number of beneficial fungal genus or reduce the number of pathogenic fungal genus, improve their resource use of livestock and poultry manure, and encourage the sensible use of cattle and chicken manure in agroecosystems.

Role of Environment Variables in Spatial Distribution of Soil C, N, P Ecological Stoichiometry in the Typical Black Soil Region of Northeast China

The effects of environmental factors on topsoil nutrient distribution have been extensively discussed, but it remains unclear how they affect spatial characteristics of soil carbon (C), nitrogen (N), and phosphorus (P) stoichiometry at different depths. We collected 184 soil samples in the typical black soil region of northeast China. Ordinary kriging was performed to describe the spatial distribution of soil C, N, and P eco-stoichiometry. Redundancy analysis was used to explore relationships between C:N:P ratios and physicochemical characteristics. The soil classification was studied by hierarchical cluster analysis. The mean C, N, and P contents ranged from 15.67 to 20.08 g·kg−1, 1.15 to 1.51 g·kg−1, and 0.80 to 0.90 g·kg−1 within measured depths. C, N, and P concentrations and stoichiometry increased from southwest to northeast, and the Songhua River was identified as an important transition zone. At 0–20 cm, soil water content explained most of the C, N, and P content levels and ratios in cluster 1, while latitude had the highest explanatory ability in cluster 2. For 20–40 cm, soil bulk density was the main influencing factor in both clusters. Our findings contribute to an improved knowledge of the balance and ecological interactions of C, N, and P in northeast China for its sustainability.

Fertilization and Soil Microbial Community: A Review

The present paper reviews the most recent advances regarding the effects of chemical and organic fertilizers on soil microbial communities. Based on the results from the articles considered, some details are presented on how the use of various types of fertilizers affects the composition and activity of soil microbial communities. Soil microbes have different responses to fertilization based on differences in the total carbon (C), nitrogen (N) and phosphorus (P) contents in the soil, along with soil moisture and the presence of plant species. These articles show that the use of chemical fertilizers changes the abundance of microbial populations and stimulates their growth thanks to the nutrient supply added. Overall, however, the data revealed that chemical fertilizers have no significant influence on the richness and diversity of the bacteria and fungi. Instead, the abundance of individual bacterial or fungal species was sensitive to fertilization and was mainly attributed to the changes in the soil chemical properties induced by chemical or organic fertilization. Among the negative effects of chemical fertilization, the decrease in enzymatic activity has been highlighted by several papers, especially in soils that have received the largest amounts of fertilizers together with losses in organic matter.

The Effect of Manure Application on Arsenic Mobilization and Methylation in Different Paddy Soils

Organic matter plays an important role in controlling arsenic(As) release and transformation in soil, however, little is known about the effect of manure application on As behavior in soils with different As contents. In this study, waterlogged incubations using various As-contaminated paddy soils with manure amendment were conducted to investigate how manure application influence As mobilization and methylation in different paddy soils. The results indicated that manure application increased As release in paddy soils with high As (> 30 mg kg^-1) contents. Moreover, our findings also showed that manure application increased the relative abundance of arsM-harboring Euryacheota and Planctomycetes at the phylum level and arsM-harbouring Methanocellaceae, Anaerolinea and Bellinea at genus level, thereby promoting As methylation. These results provide important insights for the significant variation in As mobilization and methylation in paddy soils amended with manure. Moreover, our results suggest that serious consideration should be given to the manure application in As-contaminated paddy soil.

Different Fertilizers Applied Alter Fungal Community Structure in Rhizospheric Soil of Cassava (Manihot esculenta Crantz) and Increase Crop Yield

Soil microbes play an important role in the ecosystem and have a relationship with plant growth, development, and production. There are only a few reports on the effects of planting patterns of cassava on the microbial community structure in the rhizospheric soil. Here, we investigated the effects of different fertilization on the microbial community structure in the cassava rhizospheric soil. SC205 cultivar was used in this study as the experimental material. Compound fertilizer (CF) and reduced fertilizer (RF) were applied to the soil prior to planting. Soil samples were collected before harvest, and fungi were analyzed using IonS5^TMXL sequencing platform. Results showed that CF and RF treatments significantly increased cassava yield. Amplicon sequencing result indicated that the fungi richness in rhizospheric soil of cassava was increased after CF was applied, and the diversity was decreased. However, the fungal diversity and richness were decreased in rhizospheric soil after RF was applied. The most dominant fungal phylum was Ascomycota, which increased after fertilization. In addition, the abundance of beneficial fungi such as Chaetomium increased after fertilization, while that of pathogenic fungi such as Fusarium solani was decreased. The composition of the fungal community in rhizospheric soil with CF and RF applied was similar, but the richness and diversity of fungi were different. Canonical correspondence analysis (CCA) indicates there was a positive correlation between soil nutrition and fungal community structure. Overall, our results indicate that fertilization alters the fungal community structure of cassava rhizospheric soil, such that the abundance of potentially beneficial fungi increased, while that of potentially pathogenic fungi decreased, thereby significantly promoting plant growth and yield of cassava. Thus, during actual production, attention should be paid to maintain the stability of cassava rhizospheric soil micro-ecology.

Responses of Arbuscular Mycorrhizal Fungi Diversity and Community to 41-Year Rotation Fertilization in Brown Soil Region of Northeast China

Arbuscular mycorrhizal fungi (AMF) play vital roles in the growth and development of plants, ecosystem sustainability, and stability in agroecosystem, such as transporting nutrients to host plants, improving soil physical structure, and enhancing the stress resistance of host plants. However, the effects of fertilization on AMF diversity and community in brown soil areas are still unclear. The purpose of this study is to explore changes in AMF diversity and community structures and finding out the factors that influenced the changes after 41 years of fertilization in brown soil. Samples were collected from five treatments of the long-term fertilization experiment in June 2019, including CK (no fertilizer), N (mineral nitrogen fertilizer), NP (mineral nitrogen and phosphate fertilizer), M (pig manure), and MNP (pig manure, mineral nitrogen, and phosphate fertilizer). Illumina HiSeq sequencing was used to determine AMF diversity and community structure. The relationship between AMF communities in soil and roots and environmental factors was analyzed by redundancy analysis. The results showed that the soil nutrient content of manure treatments was generally higher than that of chemical fertilizer treatments and no fertilizer treatment. Long-term fertilization increased AMF spore density, which increased with the increase of soil fertility. The moderate content of soil available phosphorus was beneficial to the colonization of AMF. AMF diversity in soil decreased with soil fertility, but AMF diversity in roots was influenced only by soil nitrate–nitrogen and pH. Glomus was the dominant genus in both soil and root samples. AMF community structure in soil and roots had a different response to long-term fertilization. Application of manure had a greater impact on AMF community structure in soil, whereas application of exogenous phosphate fertilizer had a greater impact on that in roots. Soil ammonium nitrogen, nitrate–nitrogen, total nitrogen, organic carbon, total potassium, and available potassium were the most important factors that influenced taxa of AMF in soil, whereas soil ammonium nitrogen, nitrate–nitrogen, total nitrogen, organic carbon, total potassium, available potassium, available phosphorus, and plant phosphorus and potassium content were the most important factors influencing taxa of AMF in maize roots under long-term fertilization in brown soil.

Rhizosphere Microbial Communities Are Significantly Affected by Optimized Phosphorus Management in a Slope Farming System

Soil rhizosphere microorganisms play crucial roles in promoting plant nutrient absorption and maintaining soil health. However, the effects of different phosphorus (P) managements on soil microbial communities in a slope farming system are poorly understood. Here, rhizosphere microbial communities under two P fertilization levels-conventional (125 kg P2O5 ha-1, P125) and optimal (90 kg P2O5 ha-1, P90)-were compared at four growth stages of maize in a typical sloped farming system. The richness and diversity of rhizosphere bacterial communities showed significant dynamic changes throughout the growth period of maize, while different results were observed in fungal communities. However, both the P fertilization levels and the growth stages influenced the structure and composition of the maize rhizosphere microbiota. Notably, compared to P125, Pseudomonas, Conexibacter, Mycobacterium, Acidothermus, Glomeromycota, and Talaromyces were significantly enriched in the different growth stages of maize under P90, while the relative abundance of Fusarium was significantly decreased during maize harvest. Soil total nitrogen (TN) and pH are the first environmental drivers of change in bacterial and fungal community structures, respectively. The abundance of Gemmatimonadota, Proteobacteria, and Cyanobacteria showed significant correlations with soil TN, while that of Basidiomycota and Mortierellomycota was significantly related to pH. Additionally, P90 strengthened the connection between bacteria, but reduced the links between fungi at the genus level. Our work helps in understanding the role of P fertilization levels in shaping the rhizosphere microbiota and may manipulate beneficial microorganisms for better P use efficiency.

Contrasting Effects of Forest Type and Stand Age on Soil Microbial Activities: An Analysis of Local Scale Variability

Simple Summary

The potentially important role of forests in climate change mitigation suggests a strong need for a more detailed understanding of these ecosystems. Besides climatic conditions, diverse forest vegetation creates varied conditions for the activity of soil microorganisms, and particular attention should be focused on a comprehensive study on the influence of different forest types on microbial activities. We conducted an experiment on six different forest soils (two coniferous, two deciduous, and two mixed sites comprising trees of different ages) collected from the same region (Lublin Upland, Poland) to assess the relationship between forest type and seasonal changes in microbial parameters. The annual mean values of the soil microbial indicators suggest that the mature deciduous stand was the most sustainable in microbial activities among the forest soils investigated. The diversity of the forest environment and the multifactorial dependence of the microbiological activity of forest soils necessitates further research in this field, especially using the same soil types. An understanding of forest ecosystem functioning can also be useful for forest management.

Abstract

Understanding the functioning of different forest ecosystems is important due to their key role in strategies for climate change mitigation, especially through soil C sequestration. In controlled laboratory conditions, we conducted a preliminary study on six different forest soils (two coniferous, two deciduous, and two mixed sites comprising trees of different ages) collected from the same region. The aim was to explore any differences and assess seasonal changes in soil microbial parameters (basal respiration BR, microbial biomass C_mic, metabolic quotient qCO₂, dehydrogenase activity DHA, and C_mic:C_org ratio). Indicator- and forest-specific seasonality was assessed. In addition to litter input, soil parameters (pH, nutrient content, texture and moisture) strongly regulated the analyzed microbial indicators. PCA analysis indicated similarity between mature mixed and deciduous forests. Among annual mean values, high C_mic and DHA with simultaneously low qCO₂ suggest that the mature deciduous stand was the most sustainable in microbial activities among the investigated forest soils. Research on the interrelationship between soil parameters and forest types with different tree ages needs to be continued and extended to analyze a greater number of forest and soil types.

Petroleum hydrocarbon rhizoremediation and soil microbial activity improvement via cluster root formation by wild proteaceae plant species

Rhizoremediation potential of different wild plant species for total (aliphatic) petroleum hydrocarbon (TPH)-contaminated soils was investigated. Three-week-old seedlings of Acacia inaequilatera, Acacia pyrifolia, Acacia stellaticeps, Banksia seminuda, Chloris truncata, Hakea prostrata, Hardenbergia violacea, and Triodia wiseana were transplanted in a soil contaminated with diesel and engine oil as TPH at pollution levels of 4,370 (TPH1) and 7,500 (TPH2) mg kg^-1, and an uncontaminated control (TPH0). After 150 days, the presence of TPH negatively affected the plant growth, but the growth inhibition effect varied between the plant species. Plant growth and associated root biomass influenced the activity of rhizo-microbiome. The presence of B. seminuda, C. truncata, and H. prostrata significantly increased the TPH removal rate (up to 30% compared to the unplanted treatment) due to the stimulation of rhizosphere microorganisms. No significant difference was observed between TPH1 and TPH2 regarding the plant tolerance and rhizoremediation potentials of the three plant species. The presence of TPH stimulated cluster root formation in B. seminuda and H. prostrata which was associated with enhanced TPH remediation of these two members of Proteaceae family. These results indicated that B. seminuda, C. truncata, and H. prostrata wild plant species could be suitable candidates for the rhizoremediation of TPH-contaminated soil.

Long-term effects of maize straw return and manure on the microbial community in cinnamon soil in Northern China using 16S rRNA sequencing

Excessive use of chemical fertilizers in agricultural practices have demonstrated a significant impact on microbial diversity and community in soil by altering soil physical and chemical properties, thereby leading to a certain degree of soil salinization and nutritional imbalances. As an organic amendment, maize straw has been widely used to improve soil quality; however, its effect on the soil bacterial community remains limited in Calcarie-Fluvie Cambisols soil in semi-humid arid plateau of North China. In the present experiment, we investigated the effects of continuous straw utilization and fertilization on bacterial communities in Shouyang, Shanxi province, China. Soil samples were collected from 5 different straw utilization and fertilization modes in the following ways: straw mulching (SM), straw crushing (SC), cattle manure (CM), in which way straw is firstly used as silage and then organic fertilizer, control with no straw return (NSR), and control without fertilizers (CK), same amount of N+P fertilizer was applied to the regimes except CK. High-throughput sequencing approaches were applied to the V3-V4 regions of the 16S ribosomal RNA for analysis of the bacterial abundance and community structures. Different long-term straw returning regimes significantly altered the physicochemical properties and bacterial communities of soil, among which CM had the most significant effects on soil fertility and bacterial diversity. Proteobacteria, Actinobacteria, Chloroflexi, Acidobacteria, and Gemmatimonadetes were consistently dominant in all soil samples, and Redundancy analysis (RDA) showed significant association of total nitrogen (TN), total phosphorus (TP) and available potassium (AK) with alternation of the bacterial community. Cattle manure had the most beneficial effects on soil fertility and bacterial diversity among different straw utilization and fertilization modes.

Effect of Organic Fertilizer on Soil Bacteria in Maize Fields

Soil microorganisms play an important role in agricultural ecosystems, but their response to organic fertilizer application has not been thoroughly elucidated. Thus, high-throughput sequencing was used to investigate the responses of soil bacterial to organic fertilizer amendment (composted from pig manure) in the field during the entire growth cycle of maize plants. Four treatments were studied: treatment with 2 kg·m−2 organic fertilizer application (OF_2), treatment with 4 kg·m−2 organic fertilizer application (OF_4), treatment with 6 kg·m−2 organic fertilizer application (OF_6), and a controlled treatment (CK) without fertilization. The results revealed that the bacterial richness in OF_2 was significantly lower than that of CK (p < 0.05). Soil eutrophication bacteria Bacteroidetes increased effectively in all fertilized soils, relative abundance in OF_2, OF_4, and OF_6 for the entire maize growth cycle was 68.00%, 71.40%, and 77.93% higher than that in CK, respectively. In addition, soil nitrobacteria (Nitrospirae, Nitrospira), were markedly decreased (p < 0.05) with fertilization amount. The relative abundance of the nitrogen-fixing genus Adhaeribacter in OF_6 was 209.28%, 72.8% and 35.66% higher than that in CK, OF_2 and OF_4 at mature stage. The pathogenic genus Flavolibacterium was significantly increased (p < 0.05) in fertilized soil at the seeding stage. The driving factor governing the variations of bacterial community in CK, OF_2, OF_4 and OF_6 were pH value, available phosphorus, available phosphorus, and chromium, respectively. The findings highlight that part of the soil functional or pathogenic bacteria population was susceptible to organic fertilizer application; and the driving factor of bacterial composition change was associated with the rate of fertilization. More targeted experiments are needed to enhance the understanding of functional bacteria and the synergistic effect of soil physicochemical property physical on soil bacteria.

Effect of Long-Term Fertilization on Ammonia-Oxidizing Microorganisms and Nitrification in Brown Soil of Northeast China

The objective of this study was to find out changes in ammonia oxidation microorganisms with respect to fertilizer as investigated by real-time polymerase chain reaction and high-throughput sequencing. The treatments included control (CK); chemical fertilizer nitrogen low (N) and high (N₂); nitrogen and phosphorus (NP); nitrogen phosphorus and potassium (NPK) and organic manure fertilizer (M); MN; MN₂; MNPK. The results showed that long-term fertilization influenced soil fertility and affected the abundance and community of ammonia-oxidizing microorganisms by changing the physical and chemical properties of the soil. The abundance and community structure of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) was influenced by soil organic carbon, total nitrogen, total soil phosphorus, available phosphorus, available potassium, and soil nitrate. Soil environmental factors affected the nitrification potential by affecting the structure of ammonia-oxidizing microorganisms; specific and rare AOA and AOB rather than the whole AOA or AOB community played dominant role in nitrification.

Soil fungal diversity and biological activity as indicators of fertilization strategies in a forest ecosystem after spruce disintegration in the Karpaty Mountains

Forest soils are being exposed to nutrient deficiency and acidification at increasing rates as a result of intensive management. Mineral fertilization, however, provides a way to improve soil nutrient balance. The aim of this study is to present the effects of mineral fertilization on the properties of forest soil 11 years after fertilization. Our research investigated the effects of dolomite, magnesite and serpentinite fertilization on the physicochemical properties of the soil, soil biological activity, and fungal diversity. We also determined the condition of a new generation of fir trees after mineral fertilization. In autumn, 2008, fertilizers (dolomite, magnesite and serpentinite, specifically) in the amount of 4000 kg^.ha^-1 were added to plots in the Wisła Forest District in Poland; one area was left unfertilized to act as the control area for this research. Our results reveal that all fertilization improved the selected soil's physicochemical properties (pH, Ca and Mg content) and accordingly, its biochemical activity; in particular, we found that dolomite (4000 kg^.ha^-1) contributed heavily to soil improvement. The findings also showed that soil pH and calcium content were strongly dependent on enzymatic activity, while dolomite fertilization resulted in a significant increase in biomass size in the fir trees included in this study. In addition to being associated with the highest plant biomass and amounts of enzymatic activity, dolomite-fertilized soil also had the highest number of fungal operational taxonomic units (OTUs): 403, compared to 322 OTUs in the control soil. Finally, the fungal communities in the control soil varied significantly from the fungal communities in soils fertilized with dolomite and serpentinite. The results of this research support mineral fertilization, and in particular, fertilization using dolomite in amounts of 4000 kg^.ha^-1, to improve soil nutrient supply and to shape the biological activity expressed by the enzymatic activity of forest soils.

Would fertilization history render the soil microbial communities and their activities more resistant to rainfall fluctuations?

Water stress and nutrient supply are two of the most ubiquitous global changes that surely drive substantial variations not only in agricultural productivity but also extend to alert soil living organisms. The present study aims to understand the intrinsic changes in the composition of soil populations and their functions due to the interaction between long-term fertilization and rainfall fluctuations, seeing whether fertilization history would render the soil microbial communities and their activities more resistant to water stress or not. The experiment was established in 1988 on a typical meadow soil (Vertisols) as a rainfed maize monoculture receiving six elevated rates of NPK annually. The 30-year average annual precipitation of the growing season in this region is 345.1 mm. However, in 2010 rainfall was 106.1% greater than the average, while in 2011 it was 26.5% lower. The results show that long-term NPK fertilization has made the soil microbes more tolerant to changes in soil moisture content resulting from rainfall fluctuations. Soil microbes and their activities, however, did not follow a dose-response relationship of NPK as soil moisture content was the main driving factor. Numbers of total fungi, cellulose decomposing bacteria, and nitrifying bacteria increased as rainfall in 2010 increased. Moreover, microbial biomass carbon in 2010 was almost 2-fold higher than in 2009. Soil respiration in 2010 was 11 and 35% higher than in 2009 and 2011, respectively. Otherwise, high rainfall in 2010 significantly diminished soil NO₃^- content and nitrification rate. Soil enzyme activity showed a higher response to soil moisture than the rate of NPK. The highest activity of phosphatase, dehydrogenase, and saccharase was measured in the driest year (2011), while urease displayed its highest activity in 2010. High rates of NPK significantly reduced soil dehydrogenase activity. These results illustrate how important it is for fertilizer programs to be flexible to match expected climate change in order to improve productivity and reduce environmental pollution.

An Assessment of Climate Induced Increase in Soil Water Availability for Soil Bacterial Communities Exposed to Long-Term Differential Phosphorus Fertilization

The fate of future food productivity depends primarily upon the health of soil used for cultivation. For Atlantic Europe, increased precipitation is predicted during both winter and summer months. Interactions between climate change and the fertilization of land used for agriculture are therefore vital to understand. This is particularly relevant for inorganic phosphorus (P) fertilization, which already suffers from resource and sustainability issues. The soil microbiota are a key indicator of soil health and their functioning is critical to plant productivity, playing an important role in nutrient acquisition, particularly when plant available nutrients are limited. A multifactorial, mesocosm study was established to assess the effects of increased soil water availability and inorganic P fertilization, on spring wheat biomass, soil enzymatic activity (dehydrogenase and acid phosphomonoesterase) and soil bacterial community assemblages. Our results highlight the significance of the spring wheat rhizosphere in shaping soil bacterial community assemblages and specific taxa under a moderate soil water content (60%), which was diminished under a higher level of soil water availability (80%). In addition, an interaction between soil water availability and plant presence overrode a long-term bacterial sensitivity to inorganic P fertilization. Together this may have implications for developing sustainable P mobilization through the use of the soil microbiota in future. Spring wheat biomass grown under the higher soil water regime (80%) was reduced compared to the constant water regime (60%) and a reduction in yield could be exacerbated in the future when grown in cultivated soil that have been fertilized with inorganic P. The potential feedback mechanisms for this need now need exploration to understand how future management of crop productivity may be impacted.

Simulating and Predicting Crop Yield and Soil Fertility under Climate Change with Fertilizer Management in Northeast China Based on the Decision Support System for Agrotechnology Transfer Model

The risks of climate change and soil degradation for the agricultural environment and crop production are increasingly prominent. Based on the limitations of land resources, it is important to explore a sustainable and effective fertilization strategy to reduce risks and ensure there is a high yield of grain and sustainable development of agriculture. Soil fertility underpins cultivated land, which is the most important resource of agricultural production, and is also the key for maintaining agricultural sustainability. The central elements of soil fertility are soil organic carbon (SOC) and soil nitrogen (SN). This study applied the Decision Support System for Agrotechnology Transfer-Cropping System Model (DSSAT-CSM) and the CENTURY-based soil module to simulate the trends of crop yields, SN storages and SOC storages until the end of this century under different climate change circumstances, based on a 36-year long-term experiment established at Shenyang site, China. Four fertilizer practices were applied: control (CK), combined chemical fertilizer of nitrogen, phosphorus, and potassium (NPK), NPK with manure (MNPK), and NPK fertilizers plus a high application rate of manure (hMNPK). The outcomes indicated that the DSSAT model can fully simulate the yields of maize and soybean as well as the dynamic stocks of the SN and SOC. Three Representative Concentration Pathways (RCP 2.6, RCP 4.5, RCP 8.5) for future development were chosen from the fifth assessment report of the United Nations Intergovernmental Panel on Climate Change (IPCC). Moreover, a baseline was installed. Crop yields, SN, and SOC storages from 2016 to 2100 were estimated under four climate scenarios (RCP 2.6, RCP 4.5, RCP 8.5, and Baseline). The RCP scenarios in some treatments reduced SN and SOC stocks and maize yield, and had no effect on soybean yield. However, the application of NPK with manure could improve crop yields, while it increased SN and SOC storages substantially. To some extent, the negative effects of climate scenarios could be mitigated by applying manure. In the RCP 4.5, maize yields of NPK, MNPK, and hMNPK treatments declined by 14.8%, 7.7%, and 6.2%, respectively, compared with that of NPK under Baseline. The NPK fertilizers plus manure treatments could cut the reduction of maize yield caused by climate change in half. Additionally, the SOC storage and SN of chemical fertilizers plus manure treatments under RCP scenarios increased by 20.2%–33.5% and 13.7%–21.7% compared with that of NPK under baseline, respectively. It was concluded that a rational combination of organic and inorganic fertilizer applications is a sustainable and effective agricultural measure to maintain food security and relieve environmental stresses.

Responses of microbial communities to a gradient of pig manure amendment in red paddy soils

Microbial communities play a key role in maintaining agroecosystem functioning and sustainability, but their response to excessive animal manure application and relevant mechanisms have not been thoroughly elucidated to date. This study investigated the responses of soil bacterial and fungal communities to pig manure (PM) amendment in red paddy soils. High-throughput sequencing revealed that PM amendment significantly reduced the relative abundance of Acidobacteria yet increased that of Bacteroidetes, Ignavibacteriae, Firmicutes, and Rozellomycota. The Cu and available phosphorus were the primary impact factors influencing bacterial and fungal diversity, respectively. Bacterial alpha-diversity tended to sharply decrease when the content of soil Cu was >30.70 mg kg^-1, while fungal alpha-diversity did not continuously increase when the content of soil available phosphorus was >82.84 mg kg^-1. Bacterial communities with a wider niche breadth showed significantly lower structural variation, whereas fungal communities with a narrower niche breadth showed greater variation in community structure. Soil heavy metals, primarily Cu and Zn, were the primary factors that affected bacterial communities, whereas soil fungal communities were mainly influenced by soil phosphorus. Bacterial and fungal communities showed distinct co-occurrence patterns, with bacterial communities showing a higher degree, a clustering coefficient, and betweenness centrality, but a lower closeness centrality. The findings highlighted that bacteria and fungi responded differently to PM amendment because of their discrepant niche breadth, interspecific relationships, and different tolerance to heavy metal and soil nutrient.

Plant-Dependent Soil Bacterial Responses Following Amendment With a Multispecies Microbial Biostimulant Compared to Rock Mineral and Chemical Fertilizers

Biostimulants are gaining momentum as potential soil amendments to increase plant health and productivity. Plant growth responses to some biostimulants and poorly soluble fertilizers could increase soil microbial diversity and provide greater plant access to less soluble nutrients. We assessed an agricultural soil amended with a multispecies microbial biostimulant in comparison with two fertilizers that differed in elemental solubilities to identify effects on soil bacterial communities associated with two annual pasture species (subterranean clover and Wimmera ryegrass). The treatments applied were: a multispecies microbial biostimulant, a poorly soluble rock mineral fertilizer at a rate of 5.6 kg P ha^-1, a chemical fertilizer at a rate of 5.6 kg P ha^-1, and a negative control with no fertilizer or microbial biostimulant. The two annual pasture species were grown separately for 10 weeks in a glasshouse with soil maintained at 70% of field capacity. Soil bacteria were studied using 16S rRNA with 27F and 519R bacterial primers on the Mi-seq platform. The microbial biostimulant had no effect on growth of either of the pasture species. However, it did influence soil biodiversity in a way that was dependent on the plant species. While application of the fertilizers increased plant growth, they were both associated with the lowest diversity of the soil bacterial community based on Fisher and Inverse Simpson indices. Additionally, these responses were plant-dependent; soil bacterial richness was highly correlated with soil pH for subterranean clover but not for Wimmera ryegrass. Soil bacterial richness was lowest following application of each fertilizer when subterranean clover was grown. In contrast, for Wimmera ryegrass, soil bacterial richness was lowest for the control and rock mineral fertilizer. Beta diversity at the bacterial OTU level of resolution by permanova demonstrated a significant impact of soil amendments, plant species and an interaction between plant type and soil amendments. This experiment highlights the complexity of how soil amendments, including microbial biostimulants, may influence soil bacterial communities associated with different plant species, and shows that caution is required when linking soil biodiversity to plant growth. In this case, the microbial biostimulant influenced soil biodiversity without influencing plant growth.

Effects of Biochar and Straw Application on the Physicochemical and Biological Properties of Paddy Soils in Northeast China

Applying biochar to soil has been proposed as a strategy to enhance soil quality and crop productivity. To further evaluate the influence of biochar and straw application on soil fertility and crop yield, a five-year fixed site field experiment was conducted in a paddy field in Northeast China. The experimental design included six treatments: control (CK), biochar (C), straw (S), chemical fertilizers (NPK), biochar with chemical fertilizer (CNPK) and straw with chemical fertilizer (SNPK). The results showed that compared with the NPK treatment, CNPK and SNPK significantly increased soil total porosity, soil air permeability coefficient, soil organic carbon (SOC), C/N ratio, soil microbial biomass carbon (SMBC)‚ soil microbial biomass nitrogen (SMBN), invertase activity and rice yield. Furthermore, amendment of biochar had a better effect on SOC, C/N ratio, SMBC, and SMBN than that of straw. In addition, SMBC, SOC, and total nitrogen (TN) had significant correlations with soil enzyme activities. Therefore, amendment of biochar with chemical fertilizer is an effective measure to improve rice production and soil quality in the northeast of China.

Antimicrobial Activity and Mechanism of Action of Dracocephalum moldavica L. Extracts Against Clinical Isolates of Staphylococcus aureus

Background: Dracocephalum moldavica L. is a popular traditional medicine used by many countries, which has a wide range of pharmacological effects. The aim of this work was to investigate the antimicrobial effects of D. moldavica L. extracts against clinical isolates of Staphylococcus aureus. Our results demonstrated that the minimal inhibitory concentration (MIC) for 50 and 90% of S. aureus isolates (MIC₅₀ and MIC₉₀) of the ethyl acetate (EtOAc) fraction from D. moldavica L. ethanol extract were 780 and 1,065 μg/ml, respectively. We further observed that the EtOAc fraction disrupted 24-h biofilm caused cell membrane damage and irregular cell shape. Additionally, the EtOAc fraction showed slight to moderate toxic effects on human epidermal keratinocyte (HaCaT) cells. Moreover, the results of the differential proteome revealed that 231 proteins were upregulated, while 61 proteins were downregulated in S. aureus after treatment with the EtOAc fraction. The differentially expressed proteins were functionally categorized by the Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway. These proteins contribute to membrane damage, inhibition of biofilm formation, and changes in energy metabolism. Thus, the EtOAc fraction of D. moldavica L. ethanol extract, as a natural product, has the potential to be used as an antimicrobial agent to control the clinical isolates of S. aureus.

Change of soil microbial community under long-term fertilization in a reclaimed sandy agricultural ecosystem

The importance of soil microbial flora in agro-ecosystems is well known, but there is limited understanding of the effects of long-term fertilization on soil microbial community succession in different farming management practices. Here, we report the responses of soil microbial community structure, abundance and activity to chemical (CF) and organic fertilization (OF) treatments in a sandy agricultural system of wheat-maize rotation over a 17-year period. Illumina MiSeq sequencing showed that the microbial community diversity and richness showed no significant changes in bacteria but decreased in fungi under both CF and OF treatments. The dominant species showing significant differences between fertilization regimes were Actinobacteria, Acidobacteria and Ascomycota at the phylum level, as well as some unclassified genera of other phyla at the genus level. As expected, soil organic matter content, nutrient element concentrations and bacterial abundance were enhanced by both types of fertilization, especially in OF, but fungal abundance was inhibited by OF. Redundancy analysis revealed that soil enzyme activities were closely related to both bacterial and fungal communities, and the soil nutrient, texture and pH value together determined the community structures. Bacterial abundance might be the primary driver of crop yield, and soil enzyme activities may reflect crop yield. Our results suggest a relatively permanent response of soil microbial communities to the long-term fertilization regimes in a reclaimed sandy agro-ecosystem from a mobile dune, and indicate that the appropriate dosage of chemical fertilizers is beneficial to sandy soil sustainability.

Long-Term Organic Farming Manipulated Rhizospheric Microbiome and Bacillus Antagonism Against Pepper Blight (Phytophthora capsici)

Soil-borne diseases are often less severe in organic farms, possibly because of the recruitment of beneficial microorganisms by crops. Here, the suppressiveness of organic, integrated, and conventionally managed soils to pepper blight (Phytophthora capsici) was studied in growth chamber experiments. Disease incidence was 41.3 and 34.1% lower in the soil from an organic farming system than in either the soil from the integrated or from the conventional farming systems, respectively. Beta-diversity of rhizospheric microbial communities differed among treatments, with enrichment of Bacillus, Sporosarcina, Acidobacteria Gp5, Gp6, Gp22, and Ignavibacterium by the organic soil. Cultivation-dependent analysis indicated that 50.3% of in vitro antagonists of P. capsici isolated from the rhizosphere of healthy peppers were affiliated to Bacillus. An integration of in vitro antagonists and bacterial diversity analyses indicated that Bacillus antagonists were higher in the rhizosphere of pepper treated by the organic soil. A microbial consortium of 18 in vitro Bacillus antagonists significantly increased the suppressiveness of soil from the integrated farming system against pepper blight. Overall, the soil microbiome under the long-term organic farming system was more suppressive to pepper blight, possibly owing to Bacillus antagonism in the rhizosphere. This study provided insights into microbiome management for disease suppression under greenhouse conditions.

Long-term farming systems modulate multi-trophic responses

Soil microbiome and multi-trophic relationships are essential for the stability and functioning of agroecosystems. However, little is known about how farming systems and alternative methods for controlling plant pathogens modulate microbial communities, soil mesofauna and plant productivity. In this study, we assessed the composition of eukaryotic microbial groups using a high-throughput sequencing approach (18S rRNA gene marker), the populations of parasitic and free-living nematodes, plant productivity and their inter-relationships in long-term conventional and organic farming systems. The diversity of the fungal community increased in the organic farming system compared to the conventional farming system, whereas the diversity of the protist community was similar between the two farming systems. Compared to conventional farming, organic farming increased the population of free-living nematodes and suppressed plant parasitic nematodes belonging to Meloidogynidae and Pratylenchidae. Fungal diversity and community structure appeared to be related to nematode suppression in the system receiving organic fertilizer, which was characterized by component microbial groups known to be involved in the suppression of soil pathogens. Unraveling the microbiome and multi-trophic interactions in different farming systems may permit the management of the soil environment toward more sustainable control of plant pathogens.

Total and available metal concentrations in soils from six long-term fertilization sites across China

Approximately 19% of agricultural soils in China are contaminated by heavy metals. However, the effects of agricultural management practices on soil contamination are not well understood. Taking advantage of six long-term (23-34 years) field sites across China, this study examined the effects of different agricultural fertilization treatments, including control (no fertilization), inorganic nitrogen, phosphorus and potassium fertilization (NPK), manure fertilization (M), and NPK plus manure fertilization (NPKM), on the total and available metal concentrations in soils. The results showed that after 23-34 years of fertilization, the M and NPKM treatments significantly increased the total concentration of cadmium (Cd), copper (Cu), and zinc (Zn) in soils compared with the concentrations measured for the control and NPK treatments. In contrast, the fertilization treatments had almost no influence on soil lead (Pb) and nickel (Ni) concentrations. The results of analysis via diffusive gradients in thin films demonstrated that long-term sheep or cattle manure fertilization increased the available metals, especially Cd, Cu, and Zn, but long-term swine manure application decreased the available metals, except for Cu and Zn, in soils. Further analysis revealed that the manure source, soil pH level, and biogeochemical properties of metals affected the availability of Cd, Cu, Pb, Zn, and Ni in soils. Collectively, organic fertilizers had the potential to reduce metal uptake by crops, but caution should be taken to reduce metal concentrations in manure.

Characteristics of the rhizosphere bacterial community across different cultivation years in saline-alkaline paddy soils of Songnen Plain of China

The characteristics of the rhizosphere microbial community across different cultivation years (from 1, 3, 5, 15, 20, and 50 years) in saline-alkaline paddy soils in Songnen Plain of China were investigated based on sequence variation of 16S rDNA using Illumina MiSeq sequencing. The results showed that the microbial community diversity varied across cultivation years, showing higher diversity in cultivation years >15 than in cultivation years <15. The dominant microbial community of the rhizosphere was mainly composed of Proteobacteria, Acidobacteria, Firmicutes, and Bacteroidetes. Furthermore, soil microbial diversity appeared to be affected directly by changes in soil properties corresponding to cultivated years. Diversity of Proteobacteria decreased as cultivated years increased; however, that of Acidobacteria showed the opposite direction. In addition, the soil microbial communities were clustered into two main groups: one from the sites cultivated for fewer than 15 years, and the other from the sites cultivated for more than 15 years. The abundance of nitrogen-fixing microorganisms in the soil sample was significantly higher in soils cultivated for under 15 years than in those cultivated for over 15 years (P < 0.05). Moreover, there was an obvious negative correlation between the cultivated years and Methanosarcina. Our findings on the dynamics of microbial community and its specific function in response to variable soil conditions are important for understanding and improving physical and chemical characteristics of saline-alkaline soil in Songnen Plain of China.

Effects of long-term grassland management on the carbon and nitrogen pools of different soil aggregate fractions

Common grassland management practices include animal grazing and the repeated addition of lime and nutrient fertilizers to soils. These practices can greatly influence the size and distribution of different soil aggregate fractions, thus altering the cycling and storage of carbon (C) and nitrogen (N) in grassland soils. So far, very few studies have simultaneously addressed the potential long-term effect that multiple management practices might have on soil physical aggregation. Here we specifically ask whether and how grazing, liming and nutrient fertilization might influence C and N content (%) as well as C and N pools of different soil aggregate fractions in a long-term grassland experiment established in 1991 at Silwood Park, Berkshire, UK. We found that repeated liming applications over 23years significantly decreased the C pool (i.e. gCKg^-1 soil) of Large Macro Aggregate (LMA>2mm) fractions and increased C pools within three smaller soil aggregate fractions: Small Macro Aggregate (SMA, 250μm-2mm), Micro Aggregate (MiA, 53-250μm), and Silt Clay Aggregate (SCA<53μm). Soil C (and N) accrual in smaller fractions was mainly caused by positive liming effects on aggregate fraction mass rather than on changes in soil C (and N) content (%). Liming effects could be explained by increases in soil pH, as this factor was significantly positively related to greater soil C and N pools of smaller aggregate fractions. Long-term grazing and inorganic nutrient fertilization had much weaker effects on both soil aggregate-fraction mass and on soil C and N concentrations, however, our evidence is that these practices could also contribute to greater C and N pools of smaller soil fractions. Overall our study demonstrates how agricultural liming can contribute to increase C pools of small (more stable) soil fractions with potential significant benefits for the long-term C balance of human-managed grassland soils.

Evaluation of vegetable-faba bean (Vicia faba L.) intercropping under Latvian agro-ecological conditions

BACKGROUND

Monoculture is used mostly in conventional agriculture, where a single crop is cultivated on the same land for a period of at least 12 months. In an organic and integrated growing approach, more attention is paid to plant-environment interactions and, as a result, diverse growing systems applying intercropping, catch crops, and green manure are being implemented. Thus, field experiments for evaluation of vegetable/faba bean full intercropping efficiency, in terms of vegetable and faba bean yield and protein content, were set up during two consecutive growing seasons (2014 and 2015).

RESULTS

Data obtained showed that the most efficient intercropping variants were cabbage/faba bean (cabbage yield 1.27-2.91 kg m^-2 , immature faba bean pods 0.20-0.43 kg m^-2 ) and carrot/faba bean (carrot yield 1.67-2.28 kg m^-2 , immature faba bean pods 0.10-0.52 kg m^-2 ), whilst onion and faba bean intercrop is not recommended for vegetable growing since it induces a very low onion yield (0.66-1.09 kg m^-2 ), although the highest immature faba bean pod yield was found in the onion/faba bean intercropping scheme (up to 0.56 kg m^-2 ).

CONCLUSION

Vegetable/faba bean intercropping can be used in practical horticulture for carrot and cabbage growing in order to ensure sustainable farming and environmentally friendly horticultural production. © 2017 Society of Chemical Industry.