Crop residues are the main source of carbon (C) inputs to soils in cropping systems, and their subsequent decomposition is crucial for nutrient recycling. The interactive effects of residue chemical quality, residue placement and soil mineral nitrogen (N) availability on carbon and N mineralization dynamics were experimentally examined and interpreted using a modelling approach with the deterministic-functional, dynamic decomposition module of the Simulateur mulTIdisciplinaire pour les Cultures Standard (STICS) model. We performed a 120-day incubation at 25 °C to evaluate how the mineralization of C and N from residues would respond to residue type (residues of 10 crop species with C:N ratios varying from 13 to 105), placement (surface or incorporated) and initial soil mineral N content (9 or 77 mg N kg⁻¹ dry soil). A reduced C mineralization rate was associated with N limitation, as observed for high-C:N ratio residues, and shaped by residue placement and initial soil mineral N content. This was not observed for low-C:N ratio residues. Overall, increased net N mineralization corresponded with reduced N availability. Using the optimization procedure in the STICS decomposition module to explain the C and N dynamics of surface-decomposing residues, we estimated that 24% of the total soil mineral N would be accessible to decomposers. The STICS decomposition module reproduced the C and N dynamics for each treatment well after five parameters were optimized. The optimized values of the biomass C:N (CNbio), residue decomposition rate (k), humification coefficient of microbial C (h), and microbial decomposition rate (λ) were significantly correlated with total N availability across all 40 treatments. Under low total N availability, CNbio increased, while k, h and λ decreased compared to their values under high N availability, suggesting functional changes in the microbial community of decomposers. Our results show that an N availability approach could be used to estimate residue C dynamics and net N mineralization in the field in response to crop residue quality and placement and demonstrate the potential to improve decomposition models by considering the effects of N availability on C dynamics.

作物残留物是种植系统中土壤碳 (C) 输入的主要来源，其随后的分解对于养分循环至关重要。残留物化学质量、残留物放置和土壤矿质氮 (N) 可用性对碳和氮矿化动力学的交互影响通过模拟多学科培养标准的确定性功能、动态分解模块的建模方法进行了实验检查和解释(STICS) 模型。我们在 25 °C 下进行了 120 天的孵化，以评估残留物中 C 和 N 的矿化如何对残留物类型（C:N 比率从 13 到 105 不等的 10 个作物物种的残留物）、放置（表面或掺入) 和初始土壤矿物质 N 含量（9 或 77 mg N kg ^-1干土）。C 矿化率降低与 N 限制有关，如高 C:N 比残留物所观察到的那样，并受残留物放置和初始土壤矿物质 N 含量的影响。对于低 C:N 比的残基，没有观察到这一点。总体而言，净氮矿化增加与氮可用性降低相对应。使用 STICS 分解模块中的优化程序来解释表面分解残留物的 C 和 N 动态，我们估计总土壤矿物质 N 的 24% 可被分解者获得。STICS 分解模块在优化五个参数后再现了每个处理井的 C 和 N 动态。生物量C:N( CNbio)、残渣分解率( k)、微生物C腐殖化系数的优化值(h)和微生物分解率(λ)与所有 40 种处理的总氮可用性显着相关。在低总氮可用性下，CNbio增加，而k、h和λ与其在高氮可用性下的值相比降低，表明分解者微生物群落的功能发生了变化。我们的结果表明，氮可用性方法可用于估计田间残留碳动态和净氮矿化，以响应作物残留质量和放置，并证明通过考虑氮可用性对碳动态的影响来改进分解模型的潜力。