Developmental biomass partitioning and decomposition dynamics of winter rye residues governed by placement

Abstract The contributions of winter rye (WR; Secale Cereale L.) roots and stubble to soil carbon (C) and nitrogen (N) cycling have often been overlooked. A key novelty of the current study is quantifying root and stubble‐derived C and N, along with nutrients allocation among plant parts across WR developmental stages. Treatments consisted of WR growth stage and plant parts. Post‐termination decomposition dynamics were evaluated for plant parts, with aerial residues either retained on the soil surface (no‐till) or incorporated into the soil (conventional tillage) systems. Although spring N application did not significantly affect biomass, total WR biomass increased from 2684 kg ha −1 at the vegetative stage to 5738 kg ha −1 at boot and 7964 kg ha −1 at heading, with progressive shift toward aerial tissues while stubble remained relatively stable. Carbon accumulation was part‐specific: root C increased 5.4% from stem elongation to boot but declined to 4.5% at heading, whereas shoot C rose 3.9% initially and accelerated to 7.4% by heading; stubble C fluctuated minimally. Nitrogen partitioning exhibited pronounced shifts, with shoots storing ∼50 kg N ha −1 compared to ∼10 and ∼5 kg N ha −1 in stubble and roots, respectively. These shifts in C and N resulted in progressively higher C:N reaching ∼50 at heading, indicating a potential for N immobilization in subsequent crops. Under identical residue placement, incorporated shoot residues decomposed most rapidly (64%), followed by stubble (40%) and roots (30%). Overall, these findings underscore the importance of residue quality in regulating decomposition rates, nutrient cycling, and long‐term soil C sequestration.