Microbial agent, organic fertilizer, and silica powder team up to revive salty soils and supercharge oat harvests

On moderately salinized farmland in arid northwestern China, a two-year field experiment has shown that a three-part soil modifier—a microbial agent, an organic fertilizer, and silica powder—can do together what none of the three achieves alone. The combination, tested on two oat varieties, significantly reshaped the rhizosphere, the narrow zone of soil surrounding living roots where microbes, nutrients, and plant exudates interact. The result was a measurable transformation of soil chemistry, enzyme activity, and microbial community structure, culminating in higher oat yield and forage quality. The findings, published in Frontiers in Microbiology, offer a technical blueprint for converting degraded, salty land into productive forage fields.

The study site, Qianjin Farm in Shizuishan City, Ningxia Hui Autonomous Region, sits in a temperate continental climate where average annual precipitation is just 188.8 millimeters while evaporation reaches 2,512.6 millimeters. The plow-layer soil was moderately saline and notably infertile, with organic matter at 8.08 grams per kilogram, total nitrogen at 0.47 grams per kilogram, and available phosphorus at only 5.47 milligrams per kilogram. Groundwater sat 1.5 meters below the surface, a factor that typically drives salt upward into the root zone. Against this backdrop, researchers from Ningxia University and collaborating institutions designed five treatments: an untreated control, a microbial agent alone, an organic fertilizer alone, a silica powder alone, and the full combination of all three.

The two oat varieties, Tianyan 60 and Musite 2, were chosen because prior work had established Musite 2 as salt-tolerant and Tianyan 60 as salt-sensitive. Both are widely grown in Ningxia’s salinized areas, giving the trial regional representativeness. Plots received identical base fertilization—90 kilograms per hectare of nitrogen, 177 kilograms per hectare of phosphorus pentoxide, and 60 kilograms per hectare of potassium oxide—so that any differences could be attributed to the modifiers rather than to nutrient inputs. The microbial agent, containing at least 200 million Bacillus cells per milliliter, was applied at 30 kilograms per hectare after dilution. The organic fertilizer, derived mainly from cow dung, was applied at 12 tons per hectare. The silica powder, at least 90 percent silicon dioxide, was applied at 105 kilograms per hectare.

The most striking result concerned available phosphorus. In the combined treatment, rhizosphere soil available phosphorus averaged 70.17 percent higher than with the microbial agent alone, 44.91 percent higher than with organic fertilizer alone, and 66.93 percent higher than with silica powder alone over the two years. Compared with the untreated control, the combined treatment raised available phosphorus by 137.65 to 158.28 percent, available potassium by 10.71 to 23.78 percent, soil organic matter by 11.05 to 251.3 percent, and soil water content by 16.27 to 50.58 percent. Simultaneously, soil pH dropped by 4.13 to 10.11 percent and nitrate nitrogen fell by 53.10 to 66.22 percent, indicating reduced salt stress and less nitrogen leaching.

Soil enzyme activity told a parallel story. Alkaline phosphatase and urease activities in the combined treatment were 26.05 to 44.70 percent and 23.46 to 25.87 percent higher than in the control, respectively. Catalase activity rose by 29.97 to 64.47 percent across modifier treatments, with the microbial agent and the full combination performing best. These enzymes are biocatalysts for phosphorus mineralization, urea hydrolysis, and hydrogen peroxide decomposition—processes that directly govern nutrient availability. Their elevation suggests that the modifiers did not merely add nutrients but accelerated the microbial machinery that releases them from organic and mineral reserves.

Shotgun metagenomic sequencing of rhizosphere DNA revealed how the microbial community responded. Dominant bacterial phyla included Pseudomonadota at 44.69 to 47.31 percent relative abundance, Bacteroidota at 13.03 to 15.94 percent, Actinomycetota at 10.11 to 11.63 percent, Acidobacteriota at 6.71 to 8.49 percent, and Gemmatimonadota at 3.47 to 5.66 percent, together accounting for more than 82 percent of bacterial sequences. The relative abundance of Bacteroidota peaked in the combined treatment, 111.92 percent higher than in the control. Among fungi, Ascomycota dominated at 46.40 to 62.21 percent, followed by Mucoromycota at 20.34 to 32.28 percent and Basidiomycota at 9.28 to 23.15 percent. Ascomycota abundance rose by 6.76 to 34.08 percent under modifier treatments, while Mucoromycota declined by 24.32 to 37.01 percent.

The researchers interpret these shifts through ecological strategies. Bacteroidota, an R-strategist with efficient nutrient absorption, thrives when labile organic matter and nitrogen temporarily increase—conditions created by the organic fertilizer and accelerated decomposition by the Bacillus agent. Ascomycota, a key fungal phylum indicating eutrophication, benefits from the same nutrient enrichment and possesses a powerful enzyme system suited to complex organic matter. Mucoromycota, which rapidly colonizes simple carbohydrates, briefly prospers early after amendment but is outcompeted as decomposition proceeds toward complex substrates. The combined treatment also raised bacterial Chao1 richness by 1.68 to 3.54 percent and fungal Chao1 and ACE indices by 22.74 to 35.31 percent and 9.78 to 10.99 percent, respectively, compared with the control.

Redundancy analysis showed that soil physicochemical properties explained 84.04 percent of variation in bacterial community structure and 79.58 percent in fungal structure. Dominant bacterial phyla correlated positively with enzyme activity and with soil water content, available phosphorus, available potassium, organic matter, and ammonium nitrogen, and negatively with pH and nitrate nitrogen. The Mantel test confirmed that bacterial community structure correlated with nitrate nitrogen, available potassium, organic matter, pH, water content, and catalase activity, while fungal structure correlated with all physicochemical properties except available phosphorus. Random forest analysis identified soil organic matter as the strongest predictor of oat yield, followed by the relative abundance of Chloroflexota and Ascomycota, available phosphorus, available potassium, and catalase activity.

Forage quality responded accordingly. Crude protein content peaked under the combined treatment for both varieties, reaching 9.28 percent in Tianyan 60 and 9.42 percent in Musite 2, representing two-year average increases of 12.78 to 27.44 percent and 22.02 to 35.08 percent over the control. The relative feeding value of Musite 2 under the combined treatment was 0.47 to 26.49 percent higher than under other treatments, and its acid detergent fiber content was significantly lower, indicating improved digestibility. Hay yield of Musite 2 under the combined treatment was 25.23 percent higher than the control on a two-year average, while organic fertilizer alone raised it by 21.51 percent. Musite 2 also showed higher ammonium nitrogen accumulation, lower nitrate nitrogen leaching, and significantly higher catalase activity than Tianyan 60, suggesting a more developed root system that efficiently captures nitrate from deeper layers and creates an oxidized rhizosphere favoring aerobic catalase-producing bacteria such as Pseudomonadota.

The mechanism, as the authors describe it, is a cascade. The microbial agent accelerates organic fertilizer decomposition and stimulates acid-producing microorganisms. Silica powder slowly hydrolyzes in soil to form silicic acid, which neutralizes alkali metal ions and lowers pH. Lower pH reduces phosphorus and potassium fixation, promotes mineral dissolution, and enhances ammonium adsorption onto soil colloids, curbing volatilization and leaching. Humic acid from the organic fertilizer and silicic acid from the powder combine through coordination bonds to form organic–inorganic composite colloids with porous structures, improving soil cohesion, humus content, porosity, and water-holding capacity. The enriched rhizosphere optimizes microbial habitats, driving community succession and diversity. Core functional microorganisms, notably Chloroflexota and Ascomycota, then secrete hydrolytic enzymes and oxidoreductases that speed nutrient conversion and release, supplying the available nutrients that support oat yield and quality formation.

The authors acknowledge limitations. The trial was conducted at a single site over two years, so transferability to other salinized lands requires additional validation. Three replicates per treatment limit statistical power for high-throughput metagenomic sequencing. The study did not include pairwise combinations of the three components, making it difficult to isolate binary interaction effects. Root morphological and physiological indicators—root length density, root surface area, root activity—were not measured, leaving the genotype-specific response mechanisms unresolved. Long-term continuous silica powder application carries potential environmental risks, including soil silicon accumulation and antagonistic interactions with trace elements such as iron and molybdenum, though no such imbalances appeared during the trial period.

Despite these caveats, the study provides a concrete reference for salinized land use, ecological health maintenance, and sustainable agricultural production in arid regions. It demonstrates that matching salt-tolerant oat varieties with a composite modifier can simultaneously alleviate salt stress, rebuild soil fertility, restructure rhizosphere microbial communities, and enhance forage yield and quality. The authors call for multi-site, multi-year trials with two-component combinations and root measurements to further reveal the regulatory mechanisms of the composite modifier in salinized soil–oat systems, supporting forage-based soil improvement practices across northwest China and beyond.

Subject of Research: The combination of microbial agent, organic fertilizer, and silica powder enhances oat yield and quality through regulating rhizosphere processes

Article Title: The combination of microbial agent, organic fertilizer, and silica powder enhances oat yield and quality through regulating rhizosphere processes

Article References: Chen, P., Luo, Y., Ma, L., He, M., Ma, H., Ma, W., & Sun, Q. (2026). The combination of microbial agent, organic fertilizer, and silica powder enhances oat yield and quality through regulating rhizosphere processes. Frontiers in Microbiology, 17, Article 1901736. https://doi.org/10.3389/fmicb.2026.1901736

Image Credits: AI Generated

DOI: 10.3389/fmicb.2026.1901736

Keywords: combination, microbial, agent, organic, fertilizer, silica, powder, enhances, yield, quality, regulating, rhizosphere