Organic and biochar-based fertilizers reshape bacterial communities and enhance fertility in acidic rubber plantation soils

Novel-processed organic fertilizers improve rice yield, soil fertility, and increase microbial community diversity in double-cropping paddy fields

Field Evidence: Microbial Fertilizer Drives Rhizosphere Phosphorus Transformation and Acidity Regulation to Synergistically Promote Chlorogenic Acid Accumulation in Lonicera macranthoides

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.

Potential of Composted Macrophytes as a Sustainable Organic Fertilizer: Environmental and Agronomic Insights

This study evaluated the agronomic potential and environmental impact of a macrophyte-based fertilizer (OMF) in maize cultivation. OMF was previously characterized in accordance with regulatory standards and applied to sandy loam and clayey soils at six rates (0, 2, 4, 6, 8, and 10 g dm⁻³). The experimental design also included a mineral fertilizer (MF) control receiving N, P, and K amounts equivalent to the 10 g dm⁻³ application, arranged in a randomized block design. After 45 days in greenhouse conditions, maize biomass and total nutrient accumulation, soil macronutrient concentrations, and the activities of arylsulfatase, β-glucosidase, and acid phosphatase were quantified. Basal soil respiration (BSR) and nutrient leaching were also evaluated through laboratoy-based analyses. OMF increased BSR, with CO₂ release in sandy loam and clayey soils highest under OMF (11.5; 10.7 mg g⁻¹), moderate under sludge compost (7.06; 7.51 mg g⁻¹), and lowest in unfertilized soil (2.34; 3.40 mg g⁻¹). OMF also promoted linear increases in soil P, K, Ca, Mg, and S, as well as in maize biomass and total N, P, and K accumulation. However, the highest OMF dose achieved only 20–31% of MF biomass. Moreover, organic fertilizers consistently reduced NO₃⁻-N, NH₄⁺-N, and K⁺ leaching compared with MF. In sandy soil, NO₃⁻-N leaching decreased by 31.2% and 38.5%, NH₄⁺-N by 45.6% and 37.4%, and K⁺ by 71.3% and 24.3% under SSC and OMF, respectively. In clayey soil, reductions reached 44.6% and 46.4% for NO₃⁻-N, 24.0% and 20.9% for NH₄⁺-N, and 35.9% and 15.7% for K⁺ under SSC and OMF, respectively. OMF offers environmental advantages by decreasing NO₃⁻-N leaching and supplying a slow-release K⁺ source, although it remains less effective than mineral fertilizer in promoting maize growth.

Optimizing biochar use under different soil pH conditions for sustainable crop production and soil carbon sequestration

Biochar has been widely recognized as a soil amendment capable of improving soil quality and enhancing carbon sequestration. In South Korea, the interaction between biochar application rate and contrasting initial soil chemical conditions remains insufficiently understood. This study evaluated the agronomic and soil carbon sequestration to pepper residue biochar under different soil pH conditions (Soil A: pH 5.8; Soil B: pH 6.8) in a field cultivation of Chinese cabbage. The biochar was prepared from pepper residue through pyrolysis at 400 °C for 2 h. Treatments included no fertilizer, inorganic fertilizer (N-P2O5-K2O = 32.0-7.8-19.8 kg 10a-1), and biochar applied at 100, 200, 300, and 500 kg 10a-1 combined with inorganic fertilizer. In Soil A, soil organic carbon stock increased with increasing biochar rate, reaching 36.8 t C ha-1 at 500 kg 10 a-1. In contrast, in Soil B, SOC stock increased up to 33.8 t C ha-1 at 300 kg 10 a-1 but showed limited gains at higher rates. Crop yield peaked at 300 kg 10 a-1 in Soil A (6,403 kg 10 a-1) and at 200 kg 10 a-1 in Soil B (4,200 kg 10 a-1). The results demonstrate that biochar efficiency in crop productivity and carbon accumulation is strongly influenced by initial soil chemical properties rather than application rate alone. When both crop productivity and soil carbon accumulation are considered, 200–300 kg 10 a-1 provides a balanced management strategy under the conditions examined. This study highlights the importance of soil-specific optimization of biochar application for sustainable agricultural carbon management.

Biochar and Bioorganic Fertilizer Amendment Improved Soil Qualities and Altered Bacterial Communities in Quinoa Rhizosphere Soils of the Yellow River Delta

The application of biochar and bioorganic fertilizer (BOF) in agricultural systems has garnered increasing attention in recent years. Nevertheless, research remains scarce on the impacts of biochar and BOF on the rhizosphere microecological characteristics of saline-alkali soils. This research involved the execution and analysis of 16S rRNA sequencing using Illumina technology to explore how biochar, whether used alone or in conjunction with BOF, along with varying application rates, impacts the microbial community in the saline-alkali rhizosphere soil during quinoa cultivation. In the conducted field trial, sole BOF application, sole biochar application, and their combined application (referred to as BOFB) led to a substantial enhancement of 23.88%, 74.08–97.00%, and 188.88–220.59% in quinoa aerial biomass, respectively. Meanwhile, sole biochar application or biochar combined with BOF reduced soil electrical conductivity (EC) by 26.42–39.81%. Biochar and BOF significantly improved most soil parameters, with the exception of total phosphorus (TP). In comparison to the control (CK), the relative abundances of Pseudomonas, Arthrobacter, Skermanella, and Bacillus were elevated in the biochar and BOFB treatments, while Sphingomonas was more abundant in the BOF treatment. In addition, Skermanella exhibited a significant positive correlation with EC and available potassium (AK). Biochar exerted a stronger effect on soil bacterial community structure than BOF. Furthermore, the complexity of the bacterial community in biochar and BOFB treatments far exceeded that in the BOF and CK treatments. Overall, the application of biochar effectively reduced soil EC and improved soil fertility, enhanced bacterial community stability, and optimized bacterial community structure, thereby increasing quinoa aerial biomass. Under the conditions of this study, the optimal application rate for biochar was 15 t/ha, and the combined application of biochar and BOF produced superior effects relative to either amendment alone.

Biochar-earthworm-plant interactions regulate soil organic carbon stabilization and Cd immobilization in vegetable and corn cropping system.

A dual strategy for carbon (C) sequestration and Cd remediation was developed by leveraging the synergistic effects of biochar and earthworms on soil organic C transformation and Cd bioavailability. However, the combined capacity of these amendments to simultaneously enhance soil organic C storage and reduce crop Cd uptake, particularly through the regulation of dynamic organic C pools, remains insufficiently understood. A field experiment was conducted to evaluate the individual and combined effects of biochar (600 g plot⁻¹) and earthworms (Amynthas aspergillum; 50 worms plot⁻¹) on soil organic C dynamics and Cd transfer in corn (Zea mays) and vegetables (Brassica campestris). To account for soil heterogeneity, samples were collected from non-planted, bulk, and rhizosphere soil zones. Microbial biomass was highest in corn fields treated with biochar alone, whereas earthworm activity significantly altered microbial community structure, particularly the Gram-positive-to-Gram-negative (G+/G-) and fungal-to-bacterial (F/B) ratios. Distinct soil organic C stabilization patterns were observed between crop systems: vegetable fields exhibited increased mineral-associated organic C (MAOC) and dissolved organic C (DOC), while corn fields promoted particulate organic C (POC) and higher POC/MAOC ratios. Redundancy analysis (RDA) revealed that POC was positively correlated with amorphous Fe and the activities of catalase, urease, and fluorescein diacetate (FDA) hydrolase, whereas MAOC was significantly associated with invertase activity and microbial community ratios (G+/G- and F/B). Partial least squares (PLS) analysis identified POC as the dominant organic C pool, primarily regulated by crop type and mediated by soil chemistry, microbial structure, and Fe oxide forms. Biochar application immobilized Cd by increasing POC content, the POC/MAOC ratio, exchangeable Ca, free Fe, and urease activity, while also promoting more stable Cd fractions, including oxidizable and residual forms. Consequently, biochar reduced Cd uptake by 8% in vegetables and 6% in corn. In contrast, earthworm activity enhanced MAOC, DOC, soil electrical conductivity (EC), and microbial community ratios (G+/G- and F/B), but also mobilized soil Cd, increasing total Cd accumulation by 15% in vegetables and 8% in corn under the combined treatment system. Random forest analysis identified crop biomass and the POC/MAOC ratio as the primary drivers of Cd uptake. Pearson correlation analysis further demonstrated that POC negatively correlated with Cd uptake, whereas MAOC positively influenced crop Cd accumulation. Overall, this study provides important insights into how the co-application of earthworms and biochar influences soil organic C storage and Cd dynamics in agricultural systems. While the combined strategy may improve soil C sequestration, caution is warranted because it may simultaneously compromise Cd stabilization, thereby increasing Cd bioavailability and accumulation in crops.