Microbial Degradation of Phytotoxic Root Exudates in Portable Ebb-and-Flow Hydroponic Systems as a Factor of Environmental Sustainability in Urban Farming
Aug 2026· Journal of Agricultural Science and Technology· Vol 4, pp. 1· 0 citations· 41 references
Abstract
This study evaluated the effectiveness of consortium-based microbial preparations (EM (Effective Microorganisms), EM-1, EM Agro and EM Bioactive) in degrading phenolic compounds and regenerating nutrient solution in portable ebb-and-flow hydroponic systems during sweet pepper (Capsicum annuum L.) cultivation under controlled conditions, using vertical portable hydroponic units. Microbial preparations were applied to the nutrient solution every 14 days. Total phenolic content, biometric parameters, chlorophyll content (SPAD index, Soil and Plant Analysis Development), nutrient solution parameters and phytotoxicity were assessed. Without regeneration, phenolic compounds accumulated to 458.6 ± 31.4 mg L⁻¹ over 90 days, reducing plant productivity by 51.1 %. A strong significant negative correlation using Spearman’s rank correlation coefficient with perfect rank-order reversal, rs = -1.0, p = 0.017 was found between phenolic compound concentration and productivity. All microbial preparations effectively degraded phytotoxic exudates, with EM Bioactive showing the highest efficiency (89.4 %). This treatment increased plant productivity compared with complete nutrient solution replacement, while reducing water and fertilizer consumption and lowering solution phytotoxicity to a low-toxicity level. The findings indicate that microbial degradation of root exudates is an effective strategy for nutrient solution regeneration, improving environmental sustainability, and resource efficiency of closed portable hydroponic systems for sweet pepper cultivation. As the study was limited to a single crop and a single 90-day cultivation cycle, these conclusions regarding the ecological sustainability of urban farming and closed hydroponic systems more broadly should be regarded as preliminary, pending validation on other vegetable crops (e.g., tomato, cucumber, lettuce) and over multiple nutrient-solution reuse cycles.
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
Soil salinization has become a major constraint on sustainable agricultural development and the improvement of crop productivity. However, the effects of biochar combined with different organic amendments on the microbial ecology of saline–alkaline soils and crop performance remain insufficiently understood. This study evaluated the effects of different amendment strategies, including sole applications of fulvic acid (FA), organic fertilizer (OF), and biochar (BC), as well as their combinations. Soil bacterial community composition, richness, and diversity, oat agronomic traits, hay yield, and forage quality indicators were assessed. Spearman correlation analysis and the Mantel test were employed to examine the relationships among soil physicochemical properties, microbial communities, and crop performance. Combined applications exerted stronger effects on modulating soil bacterial community composition than sole applications, while FA, BC, or their combinations significantly enhanced bacterial richness and diversity. Crop responses exhibited distinct functional differentiation among combined treatments. The biochar combined with fulvic acid (BC + FA) treatment showed the greatest potential for promoting oat growth and increasing yield, with plant height and stem diameter reaching 99.20 cm and 3.99 mm, respectively, and hay yield increasing by 48.5% compared with the control treatment. In contrast, the biochar combined with organic fertilizer (BC + OF) treatment significantly increased crude protein content (CP) and reduced acid detergent fiber (ADF) and neutral detergent fiber (NDF) contents, indicating improved forage quality. Although the crude fat content was numerically higher under BC + OF, no significant differences were observed among treatments. Correlation analyses further revealed that changes in soil physicochemical properties were associated with variations in several dominant bacterial genera, which were correlated with oat agronomic traits and forage quality indicators. Overall, the combined application of biochar with fulvic acid or organic fertilizer improved saline-alkaline soil microbial characteristics and showed potential for enhancing forage oat yield and quality, with BC + FA primarily improving yield production and BC + OF mainly enhancing forage quality.
Teng Wang, Zhen Li, Shilan Shao et al.· Land· 0 citations
It is suggested that selected halotolerant isolates possess multifunctional traits including salt tolerance and potential nutrient-solubilizing capacity, making them promising candidates for biofertilizer development and sustainable agriculture in salt-affected regions.
H. Dixit, Ranjan Singh, Sanjay Arora et al.· Journal of Soil and Water Co...· 0 citations
Valorizing bacterial biomass and phosphate sludge derived from phosphate extraction byproducts supports the circular economy and provides a sustainable strategy for mitigating the growing impact of drought stress, a major constraint on crop productivity under climate change. The present study aimed to assess the potential of a bioformulated consortium of six PGPR to improve drought tolerance in chia (
Salvia hispanica
L.) grown in pots containing soil amended with 5% phosphate sludge under semicontrolled greenhouse conditions and exposed to severe drought stress (25% field capacity) for 30 days. The results showed that PGPR inoculation significantly mitigated the adverse effects of drought stress by maintaining plant growth and physiological performance. Compared with noninoculated drought‐stressed seedlings, PGPR‐inoculated seedlings exhibited significant increases in shoot length (32.7%), leaf number (56.9%), and internode distance (31.0%). In parallel, soil bioavailable phosphorus increased by 19.7‐fold following inoculation compared with the noninoculated treatment. Moreover, PGPR‐inoculated seedlings showed significantly increased chlorophyl
a
and
b
contents and a decrease in osmolyte accumulation, including proline and soluble sugars, indicating improved photosynthetic performance and reduced osmotic stress. Overall, these findings demonstrate that the PGPR consortium enhances drought tolerance through synergistic effects on nutrient mobilization, plant growth, and stress regulation, supporting its use with phosphate sludge as a sustainable strategy for chia cultivation under arid and semiarid conditions.
Abdelghani Chakhchar, A. Kouchou, E. Ait-Ouakrim et al.· New Zealand journal of crop...· 0 citations
It is demonstrated that combined PGPR and AMF inoculation represents an effective and sustainable strategy to enhance soil biological functioning, nutrient cycling, and drought tolerance of O. ficus-indica in water limited environments.
Ilham Zouitane, Mohamed Ferioun, Sana Mounaimi et al.· 3 Biotech· 0 citations
To investigate the associations of a biofertiliser derived from fermentation effluent with microbial community composition and soil physicochemical properties in northern maize cropping systems, we conducted a field trial with three fertilisation treatments (macronutrients only, T1; macronutrients plus micronutrients, T2; and fermentation effluent combined with nutrients, T3) and one conventional control (CK) in continuously cropped maize soils. Soil physicochemical properties, microbial diversity and community composition, and predicted functional potential were analysed using high-throughput amplicon sequencing and standard soil assays. The results indicated that, compared with other treatments, the biofertiliser treatment (T3) was associated with significantly higher soil electrical conductivity, available phosphorus and alkali-hydrolysable nitrogen, but showed no significant effect on total organic carbon or organic matter. Bacterial community diversity did not differ significantly among treatments, whereas the fungal community appeared more sensitive to fertilisation. Principal coordinate analysis (PCoA) supported by PERMANOVA tests revealed that the treatments significantly altered fungal community structure. The phyla Acidobacteriota, Actinobacteriota and Firmicutes (including the genus Bacillus) were relatively enriched in the T3 treatment, while Ascomycota and Mortierellomycota were the dominant fungal phyla across all treatments. Redundancy analysis (RDA) indicated that available potassium, available phosphorus, and pH were key factors associated with microbial community structure. Functional gene inference, based on taxonomic annotation, suggested that the biofertiliser was correlated with predicted functional potential related to soil carbon and nitrogen cycling. In conclusion, the biofertiliser derived from fermentation effluent was correlated with improved soil nutrient availability and with putative shifts in microbial community composition in northern maize fields, thereby providing technical support for the resource utilisation of agricultural waste and the conservation of black soil.
