Methionine is one of the many amino acids in the soil. In order to study the role of methionine in acidic forest soil, the effect of methionine (Met) was compared with control together with addition of ammonium (Met + A), nitrite (Met + N), and glucose (Met + C) under 60% or 90% water holding capacity (WHC), because ammonium and nitrite are important factors in nitrification, and glucose affect the heterotrophic nitrification and nitrogen immobilization. We found that methionine addition significantly reduced NO₃⁻ concentration in acidic forest soil. Compared to Met, Met + A and Met + N treatments non-significantly enhanced nitrification; however, Met + C treatment decreased NH₄⁺ concentration which suggested that soil autotrophic and heterotrophic nitrification were limited in the presence of methionine at 60% WHC. Further, our findings of ¹⁵N-labeled treatment showed the impact and priming effect of methionine was negative for NO₃⁻ concentration and positive for N₂O emission, which were observed mainly from the soil N source rather than methionine. At 90% WHC, Met + C treatment significantly lessened concentrations of NH₄⁺ and NO₃⁻, nonetheless improved N₂O compared to Met treatment. Therefore, besides the denitrification and dissimilatory NO₃⁻ reduction to ammonia, the immobilization might be the key factor to explain this decrease in NO₃⁻ concentration at 90% WHC, while these processes were induced with the C addition. This study indicated that the positive role of amino acids in soil N cycling might be overrated.

蛋氨酸是土壤中许多氨基酸之一。为了研究蛋氨酸在酸性森林土壤中的作用，将蛋氨酸（Met）与对照的效果进行了比较，并在以下条件下添加了铵（Met + A），亚硝酸盐（Met + N）和葡萄糖（Met + C） 60％或90％的持水量（WHC），因为铵和亚硝酸盐是硝化的重要因素，而葡萄糖会影响异养硝化和固氮。我们发现，中添加蛋氨酸显著减少NO ₃ ^-酸性土林浓度。与Met相比，Met + A和Met + N处理无明显增强的硝化作用；但是，Met + C处理降低了NH ₄ ⁺浓度表明在60％WHC的蛋氨酸存在下，土壤的自养和异养硝化作用受到限制。此外，我们的研究结果的¹⁵ N-标记的处理显示的影响，以及蛋氨酸的启动效应是为NO负₃ ^-浓度和阳性Ñ ₂ O排放，其观察到主要来自土壤氮源，而不是甲硫氨酸。在90％WHC，蛋氨酸+ C处理显著减轻NH的浓度₄ ⁺和NO ₃ ^- ，尽管如此改进Ñ ₂ ö相比Met的治疗。因此，除了反硝化和异化NO ₃ ^-还原成氨，固定可能是解释这种降低NO的关键因素₃ ^-浓度为90％WHC，而这些过程在与C除了诱导。这项研究表明氨基酸在土壤氮循环中的积极作用可能被高估了。