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Background and aims <p>Nurse cropping with broomcorn millet (<i>Panicum miliaceum</i> L.) is widely practiced to facilitate alfalfa (<i>Medicago sativa</i> L.) establishment on the semiarid Loess Plateau, yet the mechanisms by which row configuration mediates rhizosphere nutrient cycling, microbial community assembly, and metabolite composition remain poorly understood.</p> Methods <p>A field experiment compared alfalfa monoculture with four broomcorn millet nurse cropping row configurations (1P1M, 1P2M, 1P3M, 2P3M). We quantified aboveground yield, land equivalent ratio (LER), soil nutrients, microbial biomass C/N/P, arbuscular mycorrhizal fungal (AMF) and diazotrophic (<i>nifH</i>) communities, and rhizosphere metabolites.</p> Results <p>All nurse cropping configurations increased land-use efficiency (LER 1.08–1.28). The 1P1M configuration maximized alfalfa yield and microbial biomass while reducing microbial biomass carbon: nitrogen (MBC: MBN) and microbial biomass carbon: phosphorus (MBC: MBP) ratios, indicative of tighter stoichiometric coupling under intensified interspecific competition, which promotes more balanced microbial nutritional needs. However, AMF and <i>nifH</i> α-diversity were significantly reduced under 1P1M. Compared with the 1P1M configuration, the 2P3M configuration maintained comparable productivity, increased soil total N, and supported greater <i>nifH</i> diversity. Structural equation modeling identified AMF abundance (β = 0.743) and putatively annotated rhizosphere 2-aminophenol enrichment (β = 0.567) as significant positive predictors of alfalfa yield, whereas plant-derived C was the primary driver of <i>nifH</i> community composition.</p> Conclusion <p>Row configuration influenced the balance between short-term productivity and rhizosphere functional indicators in nurse cropping systems. The 2P3M configuration integrates acceptable productivity with enhanced soil N reserves and diazotrophic diversity, offering an ecologically balanced option for alfalfa establishment in semiarid agroecosystems.</p> Graphical Abstract <p></p>

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Row configuration modulates rhizosphere microbiomes and metabolites in alfalfa–broomcorn millet nurse cropping on the semiarid Loess Plateau

  • 期刊论文

  • 发表日期：

    2026年7月10日

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  • Yitong Chen,
  • Mandi Wu,
  • Kaining Liu,
  • Tongyu Wu,
  • Xiaojin Liu,
  • Mingxiu Long,
  • Shubin He

摘要

Background and aims

Nurse cropping with broomcorn millet (Panicum miliaceum L.) is widely practiced to facilitate alfalfa (Medicago sativa L.) establishment on the semiarid Loess Plateau, yet the mechanisms by which row configuration mediates rhizosphere nutrient cycling, microbial community assembly, and metabolite composition remain poorly understood.

Methods

A field experiment compared alfalfa monoculture with four broomcorn millet nurse cropping row configurations (1P1M, 1P2M, 1P3M, 2P3M). We quantified aboveground yield, land equivalent ratio (LER), soil nutrients, microbial biomass C/N/P, arbuscular mycorrhizal fungal (AMF) and diazotrophic (nifH) communities, and rhizosphere metabolites.

Results

All nurse cropping configurations increased land-use efficiency (LER 1.08–1.28). The 1P1M configuration maximized alfalfa yield and microbial biomass while reducing microbial biomass carbon: nitrogen (MBC: MBN) and microbial biomass carbon: phosphorus (MBC: MBP) ratios, indicative of tighter stoichiometric coupling under intensified interspecific competition, which promotes more balanced microbial nutritional needs. However, AMF and nifH α-diversity were significantly reduced under 1P1M. Compared with the 1P1M configuration, the 2P3M configuration maintained comparable productivity, increased soil total N, and supported greater nifH diversity. Structural equation modeling identified AMF abundance (β = 0.743) and putatively annotated rhizosphere 2-aminophenol enrichment (β = 0.567) as significant positive predictors of alfalfa yield, whereas plant-derived C was the primary driver of nifH community composition.

Conclusion

Row configuration influenced the balance between short-term productivity and rhizosphere functional indicators in nurse cropping systems. The 2P3M configuration integrates acceptable productivity with enhanced soil N reserves and diazotrophic diversity, offering an ecologically balanced option for alfalfa establishment in semiarid agroecosystems.

Graphical Abstract