Reduced tillage with 25% organic substitution enhances forage yield and reduces carbon footprint via a physical-chemical-biological cascade in an oasis intercropping system

Achieving high forage yield while minimizing environmental footprint is a central challenge for sustainable crop production in water-limited oasis regions. We hypothesized that reduced tillage combined with organic fertilizer substitution could enhance yield and lower carbon footprint through a physical-chemical-biological cascade. A three-year field experiment was conducted in a silage maize-laba bean intercropping system using a split-plot design with two tillage methods (conventional tillage, CT; reduced tillage, RT) and four fertilization regimes (100% chemical fertilizer, F1; 75% chemical + 25% organic fertilizer, F2; 50% chemical + 50% organic fertilizer, F3; 25% chemical + 75% organic fertilizer, F4). Results showed that the RTF2 treatment achieved the highest forage yield, increasing by 8.7% compared to RTF1. Beyond yield gains, RTF2 reduced N 2 O emissions by 23.6%, greenhouse gas emission intensity by 11.4%, and yield-scaled carbon footprint by 44.2% relative to RTF1. This win-win outcome was underpinned by a physical-chemical-biological cascade: RT first improved soil physical conditions (soil temperature +4.0%, water‑filled pore space +2.6%), which amplified the benefits of F2, leading to the highest soil nutrient pools (SOC, TN, available nutrients) and microbial activity (MBC, MBN, enzyme activities); this biological activation drove soil multifunctionality to its peak. Structural equation modeling confirmed that management effects on yield were entirely mediated through this cascade, with microbial activity as the proximate determinant of productivity ( β = 0.968), We conclude that reduced tillage synergized with 25% organic substitution optimizes the trade-off between yield enhancement and environmental sustainability in oasis cropping systems, providing a practical and transferable strategy for sustainable intensification of forage production in water‑limited agricultural regions worldwide.