Soil microbiome predators boost plant biomass 53% and may cut nitrogen fertilizer need, study finds

A new study published in Global Change Biology found that adding soil microbiome predators — protists and nematodes — to agricultural soil boosted plant biomass by 53%, outperforming the effect of added synthetic nitrogen fertilizer. The findings suggest that managing the soil food web could reduce crop dependence on conventional nitrogen inputs while maintaining or improving yields.

How soil predators outperformed nitrogen fertilizer

The researchers conducted controlled greenhouse experiments using cannabis (hemp) as the test crop. Plants received one of four treatments: a control with no additions, synthetic nitrogen fertilizer alone, soil microbiome predators (protists and nematodes) alone, or a combination of fertilizer and predators. The predator-only treatment produced a 53% increase in aboveground biomass compared to the unfertilized control — a larger gain than nitrogen fertilizer alone delivered.

The mechanism, according to the study’s authors, centers on the “microbial loop” in the rhizosphere. Protists and nematodes feed on soil bacteria, releasing nitrogen locked in bacterial biomass back into plant-available forms. This grazing pressure also reshapes the composition of the bacterial community, favoring species that promote plant growth and nutrient cycling. The result is a more efficient transfer of nitrogen from soil organic matter to the plant.

Implications for nitrogen fertilizer reduction

The study’s authors noted that their findings support a growing body of soil microbiome research showing that biological soil management can partially substitute for synthetic fertilizer inputs. If the results hold at field scale, deliberately introducing or encouraging predator populations could allow farmers to cut nitrogen application rates without sacrificing productivity.

This aligns with the broader industry shift toward biological soil amendments. Switch Bioworks recently launched U.S. field trials for engineered nitrogen-fixing microbes in corn, and companies like Pivot Bio have commercialized microbial nitrogen products targeting the same goal — reducing synthetic fertilizer use through biological pathways.

A food web approach to crop nutrition

Unlike engineered microbes or biological nitrogen fixers, the predator-based approach works with existing soil ecology rather than introducing new organisms. Protists and nematodes are natural components of healthy soils that are often depleted by intensive tillage, fumigation, and heavy fertilizer use. The study suggests that restoring these populations — through reduced tillage, organic matter additions, or targeted inoculation — could unlock nitrogen already present in the soil’s microbial biomass.

The research was conducted using a single crop species in greenhouse conditions, and the authors cautioned that field validation across multiple crops, soil types, and climatic zones is needed before the results can be translated into commercial recommendations. Scaling from greenhouse pots to farm fields introduces variables — including existing soil predator populations, tillage regimes, and chemical inputs — that could affect the magnitude of the biomass response.

For the fertilizer industry, the study adds to evidence that the soil microbiome represents both a competitive threat and a commercial opportunity. Companies that can develop products enhancing beneficial soil food web interactions — rather than simply replacing synthetic nitrogen molecule-for-molecule — may find a differentiated market position as regulators and farmers increasingly prioritize soil health.

Source: Global Change Biology / PMC