Year: 2026
Type: editorial
Abstract: Legume rotations and cereal-legume intercropping form the largest group of contributions. Nan et al. (2026) found that wheat-peanut and wheat-soybean rotations improved wheat yield and quality relative to wheat-maize, with the wheat-peanut system producing the strongest gains, accompanied by enrichment of Acidobacteria and Chloroflexi and greater complexity of fungal co-occurrence networks. In soybean-maize strip intercropping, F. Liu et al. (2026) reported that maize yield was maintained and nifH gene abundance increased in the soybean rhizosphere, whereas nitrogen-fixer diversity and richness declined (Shannon -18.2%, Chao1 -12.5%). Reducing nitrogen input by 25% increased Shannon diversity by 15.7%, primarily through greater evenness rather than increased richness. This decoupling of abundance from diversity is among the most instructive findings in the collection. In a maize-peanut system, Y. Zheng et al. (2026) found that phosphorus fertilization and intercropping increased productivity and were associated with greater relative abundance of Nitrospirae and Mortierellomycota and reduced relative abundance of Ascomycota, a phylum containing numerous plant-pathogenic taxa; the intercropping yield advantage rose by 60.77%, although the gain in land equivalent ratio was modest (+2.54%). Wu et al. (2026) showed that combining chemical and microbial fertilizers in sugarcane-peanut intercropping increased microbial diversity relative to chemical fertilizer alone, enriched rhizobia, increased soil organic matter, and alleviated acidification. Together, these studies illustrate that microbiome responses to crop diversification are closely intertwined with nutrient management.Perennial systems are represented by Q. Liu et al. (2026), who found that intercropping tea with leguminous green manures, particularly hairy vetch, was associated with greater nutrient availability, altered enzyme activities, and changes in predicted microbial functional potential related to carbon, nitrogen, and phosphorus cycling. Together with the annual-system studies, this suggests that legumeassociated shifts in community composition and predicted function can occur across production systems, although much of the evidence remains associative and requires direct functional validation.Two contributions broaden the scope beyond conventional legume cropping. H. Zheng et al. (2025) compared monoculture Polygonatum cyrtonema with intercropping involving Paris polyphylla or Ganoderma lucidum. Both systems promoted rhizosphere nutrient accumulation, but neither significantly affected P. cyrtonema yield; only intercropping with P. polyphylla improved selected quality traits, including water-soluble extract (+2.8%) and polysaccharide content (+12.1%). By contrast, Su et al. (2025) found that intercropping P. polyphylla with G. lucidum increased available potassium by 50.28%, strongly enriched Trichoderma, and increased yield by 51.30% together with polyphyllin content, whereas intercropping with P. cyrtonema enriched nitrogen-fixing taxa and increased available phosphorus by 26.78%. These contrasting responses reinforce that intercropping effects are system-specific rather than universally positive.Ramos Armaulia et al. ( 2026) broaden the methodological and geographical scope of the collection. From Inga sp. nodules, Quararibea sp. roots, and rhizosphere soil in cadmium-affected cocoa agroforestry systems in the Peruvian Amazon, 93 bacterial isolates were obtained, of which 53 grew under cadmium screening and 12 yielded high-quality 16S rRNA sequences. No rhizobia sensu stricto were recovered from Inga nodules; the recovered nodule isolates were non-rhizobial endophytes. Cadmium tolerance was strongly strain-dependent, with hormetic responses in some isolates. The authors caution that the apparent absence of rhizobia may reflect cultivation conditions rather than true ecological absence, underscoring the value of complementary culture-independent approaches.Several cross-cutting observations emerge. Legume-based diversification was frequently associated with improved soil nutrient status, shifts toward potentially beneficial microbial taxa, and enhanced crop performance, but responses were strongly context-dependent and varied with cropping system, soil conditions, fertilizer management, companion species, and microbial groups. Microbial abundance, diversity, and predicted function did not necessarily respond in parallel. Reduced nitrogen inputs may, under some conditions, support microbial diversity while reshaping nifH-harboring communities. The collection spans culture-dependent isolation, amplicon sequencing, functional-gene quantification, microbial fingerprinting, functional prediction, and enzyme assays. This methodological breadth is a strength, but it also constrains direct quantitative comparison among studies.Future work should move beyond descriptive community profiling toward stronger functional and causal inference. Priorities include culture-independent verification of rhizobial occurrence in legume nodules under environmental stress; multi-year rotation experiments, which remain scarce relative to intercropping studies; direct validation of microbial functions inferred from sequencing; and explicit linkage of community structure with expressed genes, nutrient fluxes, and crop performance. Coordinated multi-site experiments integrating microbiome analyses with diversified cropping trials under field conditions will be valuable for determining whether these effects are reproducible across soils, climates, and management systems.Collectively, the studies in this Research Topic demonstrate both the potential and the complexity of managing soil microbiomes through crop diversification. Rather than revealing a single microbial signature of successful intercropping or rotation, they show that plant identity, nutrient management, environmental context, and microbial interactions jointly determine outcomes. We thank all authors, reviewers, and the Frontiers editorial team for their contributions and hope that this collection stimulates further interdisciplinary research linking crop diversification, microbial ecology, and sustainable soil management.
Source: Frontiers in Microbiology
Language: English
Subfield: Agronomy and Crop Science
Domain: Life Sciences
SDGs: Zero hunger, Life on land
Open Access status: gold
Estimated APC paid: $3,801
OpenAlex ID: W7221813839