Sugarcane Rows Reshape Peanut Soil Fungi and Metabolites in Long-Monocultured Fields

In fields of Guangxi, China, where peanut has been planted year after year on the same land, researchers report that simply alternating rows of sugarcane among the peanut plants changed the underground chemistry and fungal life of the soil.

Continuous peanut monocropping is a well-known agronomic problem. Repeated planting of the same crop can lead to what agronomists call soil sickness: nutrient imbalance, deteriorating soil physical and chemical properties, shifts in rhizosphere microbial communities, accumulation of soilborne pathogens, and declining productivity and quality. Peanut-field soil can also serve as a reservoir of Aspergillus and other soilborne fungi, some of which include important plant pathogens and, in certain strains, aflatoxin producers. The research team hypothesized that diversifying the cropping system would alter the chemical environment around peanut roots in ways that recruit beneficial fungi and reduce potentially harmful ones.

The field experiment included five treatments: peanut monoculture at 1.0 meter row spacing, sugarcane monoculture, and the three intercropping configurations, each with three replicate plots in a randomized complete block design. In the intercropped plots, three rows of sugarcane alternated with nine rows of peanut at the two narrower spacings and with fifteen rows at the widest. Rhizosphere soil was collected from peanut plants at harvest by gently removing loose soil and brushing off the soil tightly attached to the roots, pooling five plants per plot to yield twelve composite samples across the four peanut treatments. The peanut growing period lasted approximately 122 days, from sowing in early March to harvest in July.

For the fungal analysis, the team amplified the ITS1 region and sequenced it on an Illumina platform, generating roughly 959,000 raw paired-end reads that were filtered, denoised with DADA2, and taxonomically assigned against the UNITE fungal database. The final feature table contained 1,318 fungal amplicon sequence variants across the twelve samples. Importantly, the authors note that species-level assignments based on ITS1 are putative because this marker does not resolve all fungal lineages equally, so all biological interpretation was made at the genus level or above. Metabolites were profiled by LC–MS/MS and annotated by library matching, which the authors also treat as tentative unless confirmed with authentic standards.

The agronomic results showed a clear overyielding pattern. Peanut yield per hectare was actually highest in monoculture, at 3,985 kilograms per hectare, and significantly lower in the narrower intercropping configurations because peanut planting density was reduced. But when sugarcane and peanut yields were combined into the land equivalent ratio, a standard measure of intercropping efficiency, all three intercropping treatments exceeded 1.0 and significantly outperformed the monocultures. The 2.0-meter spacing achieved the highest total land equivalent ratio at 1.48, followed by 1.42 at 3.0 meters and 1.40 at 2.4 meters. This means less land would be needed under intercropping than under the corresponding monocultures to produce the same combined output.

Kernel quality also shifted with configuration. Crude protein content was significantly higher at the 2.4- and 3.0-meter spacings than in monoculture and the 2.0-meter treatment, while linoleic acid content was significantly higher at 2.0 and 2.4 meters than at 3.0 meters. Crude fat was lowest at 2.0 meters but comparable to monoculture at 2.4 meters. The authors caution that peanut protein, oil, and fatty-acid composition are also governed by genotype, seed development stage, temperature, water availability, and genotype-by-environment interactions, so the mechanisms behind these quality changes remain to be clarified.

The fungal community results were more nuanced than a simple improvement story. Alpha diversity indices did not differ significantly among treatments, and although principal coordinate analysis suggested a directional shift in community composition under intercropping, the overall differentiation did not reach statistical significance in the permutational tests. What did differ was the abundance of particular taxa. Differential-abundance analysis identified 28, 37, and 16 fungal taxa with false-discovery-rate-adjusted significance in the 2.0-, 2.4-, and 3.0-meter comparisons against monoculture, respectively, with the 2.4-meter spacing showing the strongest restructuring. At the phylum level, Ascomycota increased from roughly 38 percent of sequences in monoculture to 46 to 62 percent under intercropping, while Chytridiomycota declined sharply from about 22 percent to 4 to 7 percent.

Among the taxa responding to intercropping, several members of the Aspergillus and Fusarium assemblage were depleted. Asvariants putatively assigned to Aspergillus japonicus and Fusarium asiaticum were reduced under all three intercropping configurations, an Aspergillus flavus assignment was significantly depleted at 2.0 and 3.0 meters, and additional species-level assignments, including Fusarium equiseti, Aspergillus kalimae, and two other Aspergillus species, were depleted at specific spacings. In the opposite direction, assignments putatively identified as Trichoderma species were enriched: Trichoderma yunnanense at 2.0 and 3.0 meters, and Trichoderma simmonsii at 2.4 meters. The authors stress that these are candidate beneficial fungi rather than confirmed biocontrol agents, and that amplicon-based relative abundance alone cannot establish pathogenic activity, strain-level toxigenicity, or absolute population sizes.

The metabolomic data added a chemical dimension to the story. Intercropping enriched several classes of compounds with reported roles in plant defense or fungal inhibition, including stilbenoids such as cis-resveratrol and pinosylvin, phenolic compounds such as vanillic acid, and terpenoids including solavetivone, a sesquiterpenoid phytoalexin. One metabolite feature putatively annotated as aflatoxin B1 by untargeted library matching was less abundant under intercropping, but the authors are explicit that this annotation was not confirmed with an authentic standard and cannot establish aflatoxin concentration, contamination, or any food-safety outcome. Correlations between metabolites and fungal taxa in the data do not demonstrate direct inhibition, and targeted quantification with validated methods would be needed to test any causal role.

The study has clear limitations that the authors acknowledge. It was conducted at a single site during one growing season with only three field replicates per treatment, the fungal data reflect relative rather than absolute abundance, and metabolite identities rest on untargeted library matching. The functional relationships between the fungal and metabolic shifts were not directly tested, and nutrient fluxes, pathogen activity, and microbial functional genes were not measured. Within those constraints, the work suggests that a row-spacing window of 2.0 to 2.4 meters offers the most favorable balance: the narrower spacing maximized land-use efficiency, while the 2.4-meter configuration produced the most extensive fungal and metabolic reorganization alongside favorable kernel protein content. The authors frame these belowground patterns as ecological signatures accompanying crop diversification, hypotheses that will require multi-year, multi-location trials, targeted metabolomics, and manipulation experiments to confirm.

Subject of Research: Effects of sugarcane–peanut intercropping row spacing on rhizosphere fungal communities, metabolites, and land-use efficiency in long-term monocultured peanut fields

Article Title: Sugarcane–peanut intercropping improves rhizosphere fungal communities and metabolites following long-term continuous peanut monoculture

Article References: Pang, Z., Cha, M., Lin, Y., Tang, X., Zhou, Y., Yuan, Z., Lian, J., Tang, R., Wang, T., Zhang, Q., Logrieco, A. F., Wang, X., & Li, P. (2026). Sugarcane–peanut intercropping improves rhizosphere fungal communities and metabolites following long-term continuous peanut monoculture. Frontiers in Microbiology, 17, Article 1957778. https://doi.org/10.3389/fmicb.2026.1957778

Image Credits: AI Generated

DOI: 10.3389/fmicb.2026.1957778

Keywords: sugarcane-peanut intercropping, rhizosphere, fungal community, metabolomics, continuous monoculture, land equivalent ratio, Trichoderma, Aspergillus, Fusarium, row spacing, soil sickness, aflatoxin B1