Nitrate (NO₃^--N) accumulation in soils resulting from excessive nitrogen (N) fertilization increases risks of N loss to the environment. Microbial NO₃^--N immobilization (I_NO3) can be stimulated by adding high-organic carbon (C) materials to soils and has potential to control N loss from agricultural soils during periods of NO₃^--N accumulation. It is therefore important to screen for such organic materials that show a rapid and high capacity of I_NO3. The C/N ratio of organic materials is considered a primary factor controlling soil I_NO3, but this is challenged for high-organic C soil amendments that have similar C/N ratios but contain components with very different microbial degradability. Our objective was to identify better predictors of the I_NO3 potential of high organic C materials with comparable C/N ratios. Using a ¹⁵N-tracing laboratory experiment on one nitrate-rich agricultural soil with and without 11 types of organic C materials, we observed that those with similar C/N ratios (>18) increased the I_NO3 to varying degrees. Once organic amendments exceed a C/N ratio of 18, this ratio may no longer be an ideal index for estimating rapid I_NO3 potential. We provide evidence that the C mineralization of high-organic C soil amendments, determined as CO₂ emission over 12 days, more accurately predicts the potential for rapid I_NO3 in soil.

过量施氮(N) 导致土壤中硝酸盐(NO ₃ ^{- -N) 积累，增加了氮流失到环境中的风险。}通过向土壤中添加高有机碳（C）材料可以刺激微生物NO ₃ ^- -N固定（I _{NO3 ），并且有可能在NO 3} ^- -N积累期间控制农业土壤的氮损失。因此，筛选具有快速、高 INO3 容量的有机材料非常_重要。有机材料的C/N比被认为是控制土壤I _NO3的主要因素，但这对于具有相似C/N比但含有微生物降解性截然不同的成分的高有机C土壤改良剂来说是一个挑战。我们的目标是找到具有可比 C/N 比的高有机 C 材料的I _NO3潜力的更好预测因子。通过对含有或不含 11 种有机 C 材料的富含硝酸盐的农业土壤进行¹⁵ N 示踪实验室实验，我们观察到具有相似 C/N 比 (>18) 的土壤不同程度地增加了I _{NO3 。}一旦有机改良剂的 C/N 比率超过 18，该比率可能不再是估算快速I _NO3潜力的理想指标。我们提供的证据表明，高有机碳土壤改良剂的碳矿化（按 12 天内的 CO ₂排放量确定）可以更准确地预测土壤中快速I _NO3的潜力。