Soil microorganisms play crucial roles in nutrient cycling and determining soil quality and fertility; thus, they are important for agricultural production. However, the impacts of long-term fertilization on soil microbial community remain ambiguous due to inconsistent results from different studies. The objective of this study was to characterize changes in bacterial and fungal diversity and community structures after 12 years of different fertilization in aeolian sandy soil by analyzing 16S rRNA and ITS rRNA gene sequences and the soil properties to discover the driving factors. Eight different fertilizer treatments have been set up since 2009: no fertilizer (CK), chemical N fertilizer (N), chemical N and P fertilizer (NP), chemical N, P and K fertilizer (NPK), pig manure only (M), pig manure plus chemical N fertilizer (MN), pig manure plus chemical N and P fertilizer (MNP), pig manure plus chemical N, P, and K fertilizer (MNPK). The results indicated that the long-term application of chemical fertilizer reduced soil pH, whereas the addition of pig manure alleviated a decrease in soil pH value. Chemical fertilizer plus pig manure significantly improved soil available nutrients and soil organic carbon. Long-term MNPK fertilization resulted in changes in bacterial diversity due to effects on specific bacterial species; by contrast, all fertilization treatments resulted in changes in fungal diversity due to changes in soil properties. Principal component analysis indicated that fertilization had a significant effect on soil microbial community structure, and the effect of chemical fertilizer combined with pig manure was greater than that of chemical fertilizer alone. Soil available phosphorus, total phosphorus, and pH were the most important factors that influenced bacterial taxa, whereas soil pH, total phosphorus, organic carbon, ammonium nitrogen and nitrate nitrogen were the most important factors influencing fungal taxa after 12 years of fertilization in aeolian sandy soil.

Soils with an albic horizon (characterized by a bleached, nutrient-poor eluvial layer), classified primarily as Albic Planosols and associated groups (e.g., Albic Luvisols and Retisols) in the World Reference Base for Soil Resources (WRB), are widespread in Northeast China and suffer from inherent poor nutrient availability and low crop productivity. The present study aimed to evaluate the efficacy of novel microbial–enzyme composite biofertilizers in ameliorating Albic soils. This comprehensive assessment investigated their effects on soil nutrient availability, microbial community structure, and the activities of key enzymes involved in nutrient cycling (e.g., dehydrogenase and phosphatase). Concurrently, the impact on maize crop performance was determined by measuring changes in agronomic traits, including chlorophyll content, stem diameter, and final grain yield. A field experiment was conducted in Heilongjiang Province during the 2023 maize growing season using a randomized block design with six treatments: CF (conventional chemical fertilizer, 330 kg·ha⁻¹ NPK), OF (chemical fertilizer + 1500 kg·ha⁻¹ organic carrier), BF1 (OF + 75 kg·ha⁻¹ marine actinomycetes), BF2 (OF + 75 kg·ha⁻¹ actinomycetes + 45 kg·ha⁻¹ phytase), BF3 (OF + 75 kg·ha⁻¹ actinomycetes + 45 kg·ha⁻¹ mycorrhizal fungi + 45 kg·ha⁻¹ phytase), and BF4 (OF + 75 kg·ha⁻¹ actinomycetes + 45 kg·ha⁻¹ mycorrhizal fungi + 45 kg·ha⁻¹ phytase + 45 kg·ha⁻¹ β–glucosidase). The results showed that biofertilizers significantly increased microbial abundance and enzyme activity. The integrated treatment BF4 notably enhanced topsoil fungal abundance by 188.1% and dehydrogenase activity in the 0–20 cm layer, while also increasing available phosphorus by 92.6% at maturity. Although BF4 improved soil properties the most, BF3 produced the highest maize yield—boosting grain output by 18.3% over CF—and improved stem diameter and chlorophyll content. Strong correlations between microbial parameters and enzyme activities indicated a nutrient-cycling mechanism driven by microorganisms, with topsoil fungal abundance positively linked to alkaline phosphatase activity (r = 0.72) and subsoil bacterial abundance associated with available phosphorus (r = 0.65), demonstrating microbial–mediated carbon–phosphorus coupling. In conclusion, microbial–enzyme biofertilizers, particularly BF4, provide a sustainable strategy for enhancing Albic soil fertility and crop productivity.

Aeolian sandy soils are typically characterized by low organic matter content and loose structural stability, which severely restrict soil carbon sequestration capacity and farmland productivity. Soil aggregates are the primary carriers and protective barrier for soil organic carbon (SOC), dominating the processes of SOC accumulation and stabilization. Long-term fertilization is a critical field management strategy for regulating soil structure and carbon sequestration; however, the way in which both applying organic fertilizer alone or in combination with mineral fertilizer mediate aggregate distribution, structural stability, and aggregate-associated SOC sequestration in aeolian sandy soils under continuous peanut monoculture conditions remains largely unexplored. This study was based on a 16-year continuous field fertilization experiment conducted on aeolian sandy soil in Northeast China. The experimental treatments included: CK (control, no fertilization), NPK (balanced mineral fertilization), M (organic fertilizer alone), and MNPK (a combination of organic and mineral fertilizers). The topsoil samples (0–20 cm) were collected after the peanut harvest. The aggregate was classified into four fractions using the wet-sieving method: coarse macro-aggregate (>2 mm), fine macro-aggregate (0.25–2 mm), micro-aggregate (0.053–0.25 mm), and the silt–clay fraction (0.25 mm) and enhanced the soil aggregate stability. The addition of manure resulted in significantly better effects than the application of mineral fertilizers alone. In comparison with the CK, SOC stocks in the NPK, M and MNPK treatments increased by 18.3%, 44.9%, and 65.5%, respectively. The SOC stock (9.3 Mg·ha⁻¹) and peanut yield were highest under the MNPK treatment. With equal exogenous manure-carbon inputs for the M and MNPK treatments, a strong organic–mineral synergistic effect was observed in the MNPK treatment. This synergy reinforced the sequestration of exogenous organic carbon. Correlation analysis confirmed that SOC sequestration in aeolian sandy soil was predominantly governed by macroaggregate formation and internal carbon enrichment, rather than changes in microaggregate and silt–clay fractions. Our results reveal that combined organic–mineral fertilization effectively facilitates macroaggregate formation, improves aggregate stability and enhances organic carbon sequestration in macroaggregates of aeolian sandy soils, while increasing crop yield. Hence, organic–mineral combined fertilization is a promising agronomic practice for soil improvement, carbon sequestration and sustainable production in aeolian-sandy peanut cropping systems, offering practical field references for low-carbon sustainable management of sandy farmland.