2026· Journal of the Indian Society of Soil Science· Vol 74, pp. 196-206· 0 citations
Abstract
Sewage sludge is widely explored as an organic nutrient source, but its ecological effects on soil microbial communities remain context dependent. This study evaluated the effects of sewage sludge and NPK fertilizers on soil microbial populations associated with kale (Brassica oleracea L. cv. ‘GM Dari’) and spinach (Spinacia oleracea L. cv. ‘Shalimar Green’). A two-season field experiment (rabi and kharif) was conducted at the Experimental Farm, Wadura Campus, Sher-e-Kashmir University of Agricultural Sciences and Technology of Kashmir, using a randomized complete block design with nine treatment combinations and three replications. Results showed that sewage sludge amendments significantly increased the abundance and diversity of soil microorganisms compared to control and solely chemical fertilizer treatments. Rhizospheric soils of kale and spinach contained Flavobacterium, Bacillus, and Alcaligenes species, while fungal genera such as Aspergillus, Trichoderma, Mucor, and Paecilomyces were predominant in sludge-amended soils. The highest bacterial counts (39.30 × 10x CFU g-1 for kale and 39.25 × 10x CFU g-1 for spinach) and fungal counts (16.70 × 10t CFU g-1 for kale and 16.39 × 10t CFU g-1 for spinach) were recorded under 100% sewage sludge, followed closely by the combined treatment of 75% sludge + 25% NPK, whereas the control plots exhibited the lowest microbial abundance. The findings demonstrate that sewage sludge effectively enhances soil microbial activity and diversity, improving soil biological fertility. Partial substitution of mineral fertilizers with sludge (75% sludge + 25% NPK) appears optimal for maintaining microbial health and supporting sustainable vegetable production in the Kashmir Valley.
Treated wastewater (TWW) is increasingly used as an alternative irrigation source to alleviate water scarcity in agriculture; however, its effects on soil microbial communities and potential microbial contamination remain a concern. This study evaluated the chemical and microbial quality of TWW for irrigation and its effects on selected soil chemical properties and microbial communities using tomato (
Solanum lycopersicum
) as a test crop. A 90-day greenhouse pot experiment was conducted using two tomato cultivars (Roma and Rodade), irrigated with TWW from four wastewater treatment plants (Bochum, Polokwane, Mankweng, and Lebowakgomo), with tap water serving as the control. Soil samples collected at crop maturity were analysed for pH (water and potassium chloride), electrical conductivity (EC), beneficial microorganisms (
Actinomycetes
,
Pseudomonas putida
, and phosphate-solubilising bacteria), pathogenic bacteria (
Escherichia coli
,
Salmonella
,
Staphylococcus
,
Shigella
,
Vibrio cholerae
, Enteric bacteria, and
Pseudomonas aeruginosa
), and total bacterial and fungal counts. Irrigation water source was the main factor influencing soil chemical and biological properties, while tomato cultivar effects were negligible. Compared with the pre-irrigation soil, TWW irrigation increased soil EC by 109%–528% and soil pH by 24.5%–41.6%, whereas tap water reduced EC by 68.9%. Beneficial microbial populations increased under TWW irrigation, with
Actinomycetes
,
P. putida
, and phosphate-solubilising bacteria increasing by 131%–136%, 117%–124%, and 88%–96%, respectively. Total fungal and bacterial populations increased by up to 195.5% and 131.7%, respectively. However, TWW irrigation also elevated populations of several pathogenic bacteria, with
E. coli
, enteric bacteria,
Salmonella
, and
Staphylococcus
increasing by up to 72%, 141%, 73%, and 75%, respectively. In irrigation water, pathogen concentrations frequently exceeded the FAO and WHO guideline of 1,000 CFU/100 mL for unrestricted irrigation. Overall, TWW enhanced soil microbial activity and beneficial microorganisms, demonstrating its potential as a sustainable irrigation source in water-scarce regions. Nevertheless, routine monitoring and improved wastewater treatment are required to minimise pathogen transfer and support safe agricultural reuse practices.
B. Hlophe, P. M. Kgopa, M. R. Masevhe et al.· Frontiers in Environmental S...· 0 citations
This study evaluated the effects of sewage sludge composted (SSC, mixed with sugarcane bagasse at 1:1 ratio) and microbial biopromoters on soil fertility and early growth of Astronium fraxinifolium, a native tree with high recovery potential in the Brazilian Cerrado. In a randomized block design (2 × 4 factorial), treatments consisted of two SSC levels (with and without 23 g pot⁻¹ of chemically characterized, environmentally safe compost) and four inoculation treatments (control; Bacillus subtilis - BS; Rhizophagus clarus - RhC; and BS + RhC) with five replicates in 6-L pots. After 150 days, growth, root morphology, gas exchange, and soil properties were evaluated. SSC improved soil fertility (reduced aluminum, increased P, sum of bases, base saturation, and essential micronutrients Fe, Mn, Zn) without inducing heavy metal toxicity, increasing plant height. The SSC + RhC interaction significantly promoted shoot and root biomass, stem diameter, and root surface area/volume. Seedling Quality Index (SQI) was highest under SSC + RhC and SSC + BS. Furthermore, SSC and inoculants significantly enhanced gas exchange parameters, translating into substantially higher photosynthetic performance. Overall, combining this specific SSC rate with biopromoters, particularly Rh. clarus, effectively improved soil chemical properties and seedling vigor. While limited to nursery conditions, these findings demonstrate that this approach successfully promotes high-quality seedlings, establishing a promising baseline for future long-term field validation and dose-response trials in degraded lands.
P. Silva, Adrielle Rodrigues Prates, D. M. Fernandes et al.· New forests· 0 citations
Microbial fertilizers may improve phosphorus availability and pH in acidic soils, but field evidence linking these changes with medicinal plant biomass and specialised metabolite accumulation remains limited. Here, a one-season field experiment was conducted in acidic yellow soil in Guizhou Province, China, using four fertilization regimes for Lonicera macranthoides: an organic fertilizer plus compound fertilizer control (CK), a bacterial consortium (T1), a simplified bacterial combination (T2), and a fungal agent (T3). Soil chemical properties, soil aggregate composition, flower-bud biomass, and chlorogenic-acid-related compounds were measured. T1 and T3 increased soil available phosphorus and pH at the pre-flowering stage and increased the proportion of water-stable macroaggregates (>5 mm). Both treatments also increased fresh and dry biomass. T1 showed the highest numerical chlorogenic acid content, whereas T3 was more favourable for the accumulation of isochlorogenic acids A and C. Across plot-level observations, available phosphorus was positively correlated with fresh weight (r = 0.804) and dry weight (r = 0.781), and pH was positively correlated with chlorogenic acid (r = 0.687). Univariate regression and redundancy analysis further indicated that available phosphorus and pH were the soil factors most closely associated with biomass and chlorogenic acid accumulation. These findings provide preliminary field indications that microbial fertilizers may improve yield and medicinal quality in acidic-soil L. macranthoides production. However, the single-season, single-site nature of the experiment warrants cautious interpretation and further validation across broader conditions. The observed associations are consistent with, but do not prove, a mechanistic pathway involving microbe-mediated phosphorus transformation and acidity regulation.
Organic fertilizer and season are established sources of variation in tea plantation soil microbiomes. A repeated-measure field experiment was conducted in Yunnan, China, comprising an unfertilized control (CK), sheep manure (SM), pig manure (PM), rapeseed cake manure (RM), and commercial organic fertilizer (OF). The same 15 mature tea trees were sampled in spring, summer, and autumn, yielding 45 composite soil samples. Soil properties, as well as 16S rRNA gene and ITS amplicon profiles, were evaluated using mixed-effect models, restricted-permutation PERMANOVA, and design-adjusted partial redundancy analysis (pRDA). Fertilization regime, season, and their interaction showed property-specific associations, most clearly for alkali-hydrolyzable nitrogen, available phosphorus, and available potassium. Bacterial alpha diversity was more responsive than fungal alpha diversity. Both factors were significantly associated with bacterial and fungal community structures. Season accounted for most bacterial variation (68.70%), whereas fungal variation was associated more evenly with season (27.33%) and fertilization regime (18.61%); no significant interaction was detected for either group. Nine fungal genera retained significant treatment-associated differences after FDR correction, whereas the bacterial genus-level patterns remained exploratory. After conditioning for fertilization regime and season, measured soil variables collectively explained 6.51% and 13.56% of bacterial and fungal variation, respectively, but no individual variable remained significant after FDR correction. Because fertilizer inputs were not nutrient-standardized, treatment contrasts represent integrated material-and-dose regimes rather than isolated fertilizer-type effects. These context-specific results illustrate the value of repeated seasonal sampling with design-adjusted analyses for evaluating practical fertilization regimes.
Yun-Qi Huang, Mi Hu, Huiting Zhu et al.· Microorganisms· 0 citations
Abstract The effects of wastewater irrigation on antibiotic resistance genes (ARGs), mobile genetic elements (MGEs), and bacterial communities in plant-associated microbiomes and soils are still poorly understood. We conducted a column experiment using Leptosol and Vertisol monoliths, planted with cilantro (Coriandrum sativum) and irrigated for eight weeks with untreated or treated (TWW) wastewater, with or without spiked antibiotics and disinfectants. Total community-DNA was analyzed by qPCR and 16S rRNA gene sequencing. Third-generation cephalosporin-resistant (3GCR) enterobacteria were isolated. Spiked WW irrigation increased ARG and MGE relative abundances in preferential flow path soil. In the rhizosphere, Leptosol exhibited higher ARG and MGE relative abundances than Vertisol. Spiking increased relative abundances of class 1 integrons, sulfonamide, tetracycline resistance genes in soil and rhizosphere, and erythromycin and fluoroquinolone resistance genes in phyllosphere. Soil type primarily shaped bacterial community composition in preferential flow path soil and rhizosphere, followed by spiking, whereas WW type influenced only rhizosphere bacterial community composition. 3GCR strains of the Citrobacter freundii complex genotype Ci-1a_Bx-C2 were isolated exclusively from soil and rhizosphere enrichments irrigated with (spiked or unspiked) TWW. We demonstrate the need to combine cultivation-independent and cultivation-based methods to investigate the effects of WW irrigation on soil and plant-associated microbiomes.
Sara Gallego, Leila Soufi, Ioannis D. Kampouris et al.· FEMS Microbiology Ecology· 0 citations
Introduction Understanding the effects of different soil amendments on bacterial community structure and diversity in acidic rubber plantation soils is essential for biological remediation and the targeted restoration of these degraded systems. Methods In this study, a 2.5-year long field experiment was conducted in a second-generation 25-year-old rubber plantation at Dongfeng Farm in Jinghong City, southern Yunan, China. The experiment included five fertilization treatments: (1) unfertilized control (CK), (2) microbial fertilizer (T1), (3) biochar-based fertilizer (T2), (4) tobacco ash and oil cake organic fertilizer (T3), and (5) bio-organic fertilizer combined with polyacrylamide (T4). Soil samples were collected from the 0–20 cm layer in October 2022, and bacterial communities were analyzed using Illumina MiSeq high-throughput sequencing. Key environmental drivers were identified by integrating sequencing data with soil physicochemical properties. Results The application of soil fertilizers significantly altered the tested soil physicochemical properties and bacterial community composition. Compared with CK, T1 and T4 increased soil pH. T2 and T3 significantly enhanced soil organic matter, available phosphorus, and total nitrogen. In addition, T2 specifically increased exchangeable Ca2+ and Mg2+ concentrations and elevated the Chao1 richness index. Both T2 and T3 enriched beneficial taxa, including Proteobacteria and BradyRhizobium, while principal coordinate analysis (PCoA) revealed distinct shifts in bacterial community structure. The T4 treatment resulted in the most complex bacterial co-occurrence network. Mantel tests identified organic matter, total nitrogen, available phosphorus, and available nitrogen as the primary drivers of bacterial diversity. Further analysis using structural equation modeling indicates that soil conditioners alter bacterial community structure and diversity by influencing soil fertility and pH. Discussion Collectively, these findings demonstrate that organic matter, total nitrogen, available phosphorus, and available nitrogen serve as key environmental factors shaping bacterial community structure and diversity in acidic rubber plantation soils. Organic fertilizers and biochar have proven highly effective in enhancing soil fertility and buffering capacity, while significantly increasing the abundance of dominant bacterial taxa. Therefore, organic and biochar-based amendments should be prioritized as effective and sustainable strategies for restoring soil health and promoting continuous soil quality improvement in acidified rubber plantations.
Jifen Yang, Xiaoling Shi, Shunjun Geng et al.· Frontiers in Microbiology· 0 citations
