Cover crop incorporation with moderate nitrogen reduction regulates soil microbial communities to drive C:N stoichiometry for enhanced peanut yield and efficiency

Abstract

Context

Integrating cover crops with optimized nitrogen (N) management is a promising approach for sustainable peanut (Arachis hypogaea L.) production. However, the mechanistic linkages linking soil microbial communities, soil C:N stoichiometry, plant physiological traits, and yield formation remain poorly understood.

Objective

This study aimed to clarify how ryegrass cover crop incorporation combined with reduced N fertilization modulates soil C:N stoichiometry, microbial community structure, enzyme activities, and peanut productivity, with the goal of identifying an optimal strategy to balance yield and nitrogen use efficiency (NUE).

Methods

A two-year field experiment was conducted employing two residue management strategies—cover crop incorporation (H) and biomass removal (N)—under four N rates: 0 (N0), 60 (N60), 90 (N90), and 120 kg N ha⁻¹(N120). This resulted in eight treatment combinations (HN0, HN60, HN90, HN120, N0, N60, N90, and N120). Key measurements included soil C:N stoichiometry (SOC, TN, AN, NO₃⁻–N, and SOC:TN ratio), extracellular enzyme activities (urease, cellulase, invertase), microbial richness and diversity, community composition, leaf physiological traits (SPAD, ΦPSII, SPS, and NR), pod yield, and NUE.

Results

Ryegrass incorporation significantly enhanced peanut pod yield by 19.95 %–22.50 % compared with biomass removal. Notably, under incorporation, a 25 % N reduction (HN90) achieved yields statistically equivalent to the full N rate (HN120) but increased agronomic N efficiency (AEN) by 46.84 % relative to N90. Incorporation increased SOC, TN, AN, NO₃⁻–N, and the SOC:TN ratio while maintaining high enzyme activities comparable to HN120. Microbial richness and diversity were also improved; specifically, HN90 selectively enriched beneficial taxa, including Lysobacter, Bacillus, Brevibacillus, and Gemmatimonas, while suppressing pathogenic genera such as Fusicolla and Fusarium. Although N reduction generally decreased SPAD and ΦPSII, the 25 % N reduction under incorporation caused only minor declines compared with N120. SPS and NR activities followed similar trends. Structural equation modeling confirmed that microbial community structure and enzyme activities directly optimized soil C:N stoichiometry, which in turn positively regulated plant physiological traits and yield formation.

Conclusions

Integrating ryegrass cover crop incorporation with moderate N reduction (25 %) enhances microbial community function, promotes nutrient cycling, sustains photosynthetic performance, and synergistically improves both yield and NUE in peanut systems.

Implications

This management strategy offers an effective pathway to achieve coordinated improvements in soil health, nitrogen efficiency, and crop productivity, providing a mechanistic basis for sustainable peanut production under reduced fertilizer inputs.