Microbial immobilization of nitrate (NO₃⁻) is considered to be an important process in reducing NO₃ ⁻ accumulation and regulating nitrogen (N) retention capacity in soils. Accurately quantifying the rate of microbial NO₃⁻ immobilization is, therefore, necessary to predict its role in lowering NO₃⁻ accumulation in soils. We compared microbial NO₃⁻ immobilization rates using a ¹⁵NO₃⁻ labelling technique in three different ways: (a) ¹⁵N pool dilution, (b) organic ¹⁵N recovery and (c) microbial biomass ¹⁵N recovery, in a nitrate‐rich upland soil with and without amendment with organic materials with differing carbon‐to‐nitrogen ratios (C/N). The three methods generated similar NO₃⁻ immobilization rates, except when the soil was amended with easily decomposable organic materials (glucose and sucrose). We also developed a microbial NO₃⁻ immobilization‐specific quality index that incorporates the C/N ratio, lignin, cellulose and hemicellulose contents and pH for slowly decomposing organic materials (plant residues). This study provides direct empirical evidence that the results of different methods for calculating soil microbial NO₃⁻ immobilization rates are affected by the characteristics of organic materials added to the soil.

中文翻译：

---

有机物质输入的特性会影响土壤微生物对NO3-的固定率，采用不同方法计算得出

硝酸盐（NO的微生物固定化₃ ^- ）被认为是一个重要的过程中减少NO ₃ ^-的积累和调节土壤中的氮（N）保留容量。精确量化微生物NO的速率₃ ^-固定化，因此，有必要在降低NO预测其作用₃ ^-在土壤中积累。我们比较微生物NO ₃ ^-使用固定化率¹⁵ NO ₃ ^-以三种不同方式标记技术：（1）¹⁵氮库稀释，（b）中的有机¹⁵氮肥利用率和（c）的微生物生物质¹⁵在富含硝酸盐的旱地土壤中，采用或不采用碳氮比（C / N）不同的有机物质对氮进行恢复。这三种方法产生的相似NO ₃ ^-的固定化率，当土壤用易分解有机物质（葡萄糖和蔗糖）修正除。我们还开发了微生物NO ₃ ^-固定化特定的质量并入对于缓慢分解有机材料（植物残基）的C / N比，木质素，纤维素和半纤维素含量和pH值的索引。这项研究提供了直接的经验证据表明，不同的方法来计算土壤微生物NO结果₃ ^- 固定速率受添加到土壤中的有机材料特性的影响。