Sustainable rice cultivation in acid soils requires innovative approaches that enhance root function and soil biological health. To address this challenge, a pot experiment (2023) followed by a field experiment (2024) was conducted at the Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, Thiruvananthapuram, to evaluate the effects of biostimulants on soil biological properties in a wetland ecosystem using the rice variety Uma. The study followed a completely randomized design with three replications and included treatments such as T1: RDF + Seaweed extract (Kappaphycus alvarezii) at 12.5 kg ha−1, T2: RDF + Humic acid at 10 kg ha−1, T3: RDF + Fulvic acid at 5 kg ha−1, T4: RDF + Lignosulphate humate at 10 kg ha−1, T5: RDF + plant-derived protein hydrolysate at 2.5 kg ha−1, T6: RDF + Vrikshayurveda preparation (Panchagavya) at 3%, T7: RDF + PGPR mix-1 at 2%, T8: RDF + Pseudomonas at 2%, T9: RDF as per KAU POP, and T10: Absolute control. Biostimulant application markedly enhanced root morphology, microbial colonization, and root-associated metabolites in wetland acid soils. Among treatments, PGPR mix-1 consistently recorded superior performance in both pot and field conditions, recording 25–30% higher root length, 35–40% greater root dry weight, and nearly 45% higher root volume compared with control. The bacterial endophyte count increased to 5.38 log CFU g⁻¹ root, indicating a 42% rise over the control. Scanning Electron Microscopy revealed dense microbial colonization, distinct biofilm-like structures, and well-organized root cell wall layers under PGPR treatment. Moreover, phenolic acid concentrations such as p-coumaric (0.632 mg L⁻¹), vanillic (0.432 mg L⁻¹), and syringic acid (2.140 mg L⁻¹) were substantially higher (30–60%) than in other treatments. Overall, RDF integrated with PGPR mix-1 significantly enhanced root development, microbial activity, and metabolite synthesis under acidic wetland conditions. This study demonstrates the novel potential of PGPR-based biostimulants to improve soil biological fertility and plant resilience, contributing to sustainable rice production in acid-prone ecosystems. Graphical abstract

Biostimulants induced changes in root phenomics and soil microbial dynamics in rice under wetland conditions

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发表日期：

2026年1月28日

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B. Kamali,
B. Aparna,
B. Rani

摘要

Sustainable rice cultivation in acid soils requires innovative approaches that enhance root function and soil biological health. To address this challenge, a pot experiment (2023) followed by a field experiment (2024) was conducted at the Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, Thiruvananthapuram, to evaluate the effects of biostimulants on soil biological properties in a wetland ecosystem using the rice variety Uma. The study followed a completely randomized design with three replications and included treatments such as T₁: RDF + Seaweed extract (Kappaphycus alvarezii) at 12.5 kg ha⁻¹, T₂: RDF + Humic acid at 10 kg ha⁻¹, T₃: RDF + Fulvic acid at 5 kg ha⁻¹, T₄: RDF + Lignosulphate humate at 10 kg ha⁻¹, T₅: RDF + plant-derived protein hydrolysate at 2.5 kg ha⁻¹, T₆: RDF + Vrikshayurveda preparation (Panchagavya) at 3%, T₇: RDF + PGPR mix-1 at 2%, T₈: RDF + Pseudomonas at 2%, T₉: RDF as per KAU POP, and T₁₀: Absolute control. Biostimulant application markedly enhanced root morphology, microbial colonization, and root-associated metabolites in wetland acid soils. Among treatments, PGPR mix-1 consistently recorded superior performance in both pot and field conditions, recording 25–30% higher root length, 35–40% greater root dry weight, and nearly 45% higher root volume compared with control. The bacterial endophyte count increased to 5.38 log CFU g⁻¹ root, indicating a 42% rise over the control. Scanning Electron Microscopy revealed dense microbial colonization, distinct biofilm-like structures, and well-organized root cell wall layers under PGPR treatment. Moreover, phenolic acid concentrations such as p-coumaric (0.632 mg L⁻¹), vanillic (0.432 mg L⁻¹), and syringic acid (2.140 mg L⁻¹) were substantially higher (30–60%) than in other treatments. Overall, RDF integrated with PGPR mix-1 significantly enhanced root development, microbial activity, and metabolite synthesis under acidic wetland conditions. This study demonstrates the novel potential of PGPR-based biostimulants to improve soil biological fertility and plant resilience, contributing to sustainable rice production in acid-prone ecosystems.

Graphical abstract