This integrated approach offers a practical, sustainable alternative for intensive vegetable systems currently facing degradation from over-reliance on chemical inputs.
Researchers at the Shanghai Academy of Agricultural Sciences, the Ministry of Agriculture and Rural Affairs and the Shanghai Key Laboratory of Horticultural Technology discovered that using earthworms alongside a 30% reduction in chemical fertiliser — compensated for by organic inputs and resulted in a total vegetable yield increase compared to conventional farming that uses only full chemical fertiliser.
The study confirmed that the co-cultivation of earthworms with vegetables, known as the vegetable–earthworm co-cultivation (VE) system, was a potent biotillage strategy that improves soil nutrient balance and stabilises the essential microbial communities responsible for soil fertility.
Earthworms reshape the soil environment
Long-term, intensive use of chemical fertilisers often leads to soil degradation, including acidification and microbial imbalance. The research found that the presence of earthworms (in this case, a native species called Pheretima guillelmi) actively mitigated these problems.
The researchers explained that the earthworms’ continuous burrowing and casting activities enhanced soil aeration and aggregate stability, directly boosting crop productivity. In fact, earthworm inoculation markedly enhanced vegetable yields.
The annual total yield of the partially organic-substituted group was 26.02% greater than that of the full chemical fertiliser group without earthworms. This improvement primarily resulted from the multifaceted functions of earthworms, whose activities enhanced soil aeration and improved nutrient availability and uptake efficiency.
The study highlighted a key benefit: earthworm activity successfully moderated the soil pH, shifting it toward near-neutral conditions (ranging from 6.68 to 6.89), which is crucial for optimal nutrient availability and microbial function.
A crucial balance: The 30% threshold
The researchers tested several fertilisation regimes, but the combination of the VE system with a 30% reduction in chemical nitrogen fertiliser replaced by organic fertiliser (VE_IF70) proved to be the most beneficial for soil health and yield stability.
While the full chemical fertilisation with earthworms (VE_IF100) produced the highest yield (30.86% higher than the control), it caused a sharp microbial imbalance. This treatment decreased the soil’s carbon-to-nitrogen (C/N) ratio and drastically reduced bacterial abundance while accelerating fungal proliferation, which caused the critical bacteria-to-fungi (B/F) ratio to plummet from 3.51 to 0.53.
According to the paper, a low B/F ratio, alongside fungal enrichment, might also increase pathogen pressure and weaken microbial network stability. In contrast, the VE_IF70 strategy maintained high yields while fostering a more resilient ecosystem.
Partial organic substitution restored the B/F balance to a stable 1.65 and increased fungal diversity, which was consistent with the view that the B/F ratio was a useful indicator of soil microbial equilibrium and stress responses.
The VE_IF70 treatment exhibited a higher C/N ratio and significantly elevated available hydrolysable nitrogen, suggesting a more balanced and efficient nutrient conversion process that sustained nitrogen supply for crop uptake.
Microbial communities restructured for health
The beneficial effect of the partial organic substitution was most evident in the restructuring of the soil’s microbial communities. The VE_IF70 system actively enriched functional groups that were essential for nutrient cycling and disease suppression. The study also identified an increase in bacterial genera such as Brevundimonas and Anaeromyxobacter, which are known to promote plant growth and assist in nutrient cycling.
Fungal taxa with well-documented antagonistic or biocontrol activities, including Chaetomium and Arthrobotrys, were also more abundant in the VE_IF70 treatment. These compositional changes indicated that the interaction between earthworms and organic amendments selectively promoted functional groups beneficial to nutrient transformation and pathogen suppression.
Furthermore, a functional prediction analysis revealed that the VE_IF70 group contained a lower abundance of potential pathogenic bacteria and higher proportions of arbuscular mycorrhizal fungi, which form symbiotic relationships with plants to enhance nutrient and water uptake.
Key drivers for crop yield
The researchers used advanced statistical modelling to determine the most important factors influencing vegetable yield in the two main cultivation systems. In the conventional system (CK), soil pH and bacterial abundance were the primary drivers of yield variation, reflecting the high stress placed on the system by full chemical use without earthworms.
However, in the earthworm-inoculated VE system, fertilisation regime and available phosphorus emerged as the top yield predictors, followed by microbial diversity. The VE system exhibited stronger coupling between nutrient availability, microbial diversity, and yield, underscoring the enhanced regulatory role of earthworm inoculation in promoting crop productivity.
Paving the way for resilient agriculture
The findings provide a clear directive for agricultural practitioners and policymakers seeking to transition toward more sustainable and low-carbon farming methods. The combined strategy of earthworm inoculation and partial organic fertiliser substitution offers a practical framework for targeted microbial management in intensively cultivated or degraded vegetable fields, thereby advancing sustainable and resilient agricultural systems.
The research team acknowledged that future studies should employ multi-site, long-term field experiments across different soil types and integrate direct pathogen monitoring to fully validate the strategy’s long-term effectiveness and generalisability.
However, the current results demonstrate a clear fertilization threshold effect: integrating a moderate 30% organic substitution with earthworm biotillage sustains productivity comparable to full chemical use, while successfully preserving microbial balance and improving soil health.
Source: Microorganisms “Organic Fertilizer Substitution Modulates Soil Properties and Microbial Communities in a Vegetable–Earthworm Co-Cultivation System” https://doi.org/10.3390/microorganisms13122742 Authors: Cai Shumei, et al.
