Use of acetylene as a nitrification inhibitor to reduce biases in gross N transformation rates in a soil showing rapid disappearance of added ammonium
Use of acetylene as a nitrification inhibitor to reduce biases in gross N transformation rates in a soil showing rapid disappearance of added ammonium
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DOI：
10.1016/j.soilbio.2007.04.014
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发表时间：
2007-09-01
影响因子：
9.7
通讯作者：
Kaetterer, Thomas
中科院分区：
文献类型：
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作者：
Herrmann, Anke M.;Witter, Ernst;Kaetterer, Thomas
违反 N-15 同位素稀释技术中固有的平衡假设和添加氮和天然氮的相同行为可能会对估计的总氮转化率产生很大影响。为了使添加的 N-15 达到平衡，建议将初始采样延迟至添加 N-15 后 24 小时。然而，在具有高硝化潜力的土壤中，这可能不可行，因为 24 小时后可能残留很少的可提取 NH4+-N。为了解决这个问题，有人建议使用乙炔（C2H2）等硝化抑制剂。设计了两项实验室实验，使用 Ultuna 长期土壤有机质实验中的一种土壤处理（稻草+Ca(NO3)(2)）来测试 C2H2 对碳矿化和总氮转化率的影响。评估了添加氮和天然氮的相同行为的假设，并使用动态区室模型识别了可能违反该假设的过程。当硝化作用被完全抑制时，在添加 N-15 之前，在顶部空间短暂暴露于低大气 C2H2 浓度 (0.1-1.0 kPa) 不会显着影响 C 矿化、总 N 矿化或固定率。动态区室模型的结果表明，在没有完全抑制的情况下，天然 NH4+ N 优先硝化，导致总 N 矿化率低估了 24-75%。我们确认使用 24 小时进行初始采样是适当的，因为这样可以完全抑制硝化作用，避免添加 N-15 引起的土壤扰动影响，并最大限度地减少添加和天然 NH4+-N 硝化速率的差异，这种差异在 0.5-24 小时期间最为明显。在添加 N-15 之前施加 1.0 kPa C2H2 可以提供完全的硝化抑制，因此可以在高硝化潜力的土壤中估计 24 小时后的总氮转化率。大量添加 N-15 标记的 NH4+-N 并不能替代抑制硝化作用，因为与在接触 C2H2 之前添加 5 μg N g(-1) 土壤相比，在不添加 C2H2 的情况下添加 20 μg Ng 1 土壤时估计的总氮矿化率显着不同。此外，当添加20μg N g(-1)土壤时，对过程动力学的错误描述导致总硝化速率估计存在较大误差。因此，在具有高硝化潜力的土壤中，我们建议在估算总氮转化率之前使用 1.0 kPa C2H2。 (C) 2007 Elsevier Ltd. 保留所有权利。
Violation of the assumption of equilibrium and identical behaviour of added and native N inherent in the N-15 isotope dilution technique may have a large impact on estimated gross N transformation rates. To allow the added N-15 to equilibrate, initial sampling has been recommended to be delayed until 24 h after addition of N-15. However, in soils with high nitrification potential this may not be feasible as little extractable NH4+-N may remain after 24 h. To circumvent this problem the use of nitrification inhibitors such as acetylene (C2H2) has been suggested. Two laboratory experiments were designed to test the effects of C2H2 on C mineralization and gross N transformation rates using one soil treatment (Straw+Ca(NO3)(2)) from the Ultuna Long-Term Soil Organic Matter Experiment. The assumption of identical behaviour of added and native N was assessed and processes that may have violated the assumption were identified using a dynamic compartmental model. Brief exposure to low atmospheric C2H2 concentrations in the headspace (0.1-1.0 kPa) prior to N-15 addition did not significantly affect C mineralization, gross N mineralization or immobilization rates when nitrification was completely inhibited. Results from the dynamic compartmental model suggested that, in the absence of complete inhibition, native NH4+ N was preferentially nitrified resulting in a 24-75% underestimation of gross N mineralization rates. We confirm the appropriateness of using 24 h for the initial sampling as this allows for complete nitrification inhibition, avoids the effects of soil disturbance caused by N-15 addition and minimizes differences in the nitrification rate of added and native NH4+-N which is most pronounced during the 0.5-24 h period. The application of 1.0 kPa C2H2 prior to N-15 addition provided complete nitrification inhibition so that gross N transformation rates can be estimated beyond 24 h in soils with high nitrification potential. Larger additions of N-15-labelled NH4+-N were not an alternative to inhibition of nitrification as estimated gross N mineralization rates were significantly different when 20 mu g Ng 1 soil was added without C2H2 compared with 5 mu g N g(-1) soil prior C2H2 exposure. In addition, incorrect description of process kinetics led to large errors in gross nitrification rate estimates when 20 mu g N g(-1) soil was added. In soils with high nitrification potential, we therefore recommend the use of 1.0 kPa C2H2 prior to estimation of gross N transformation rates. (C) 2007 Elsevier Ltd. All rights reserved.