The large amount of ammonia released during agricultural application of urea fertilizer can result in a partial loss of applied nitrogen, having a detrimental effect on air quality. Although Chamomile recutita has nitrogen transformation inhibitory properties, providing potential agricultural and environmental benefits, the full extent of the effects of the major constituents of this plant on urease activity and NH₃ volatilization in soils is currently unknown. Soil incubation experiments were established using 2-Cyclopenten-1-one and Eugenol, two major constituents of C. recutita, to evaluate their effects on inorganic soil nitrogen pools, urease activity, and NH₃ volatilization in grey desert soil and red soil. An application rate of 0.25 g N kg⁻¹ soil fertilizer was applied as urea with and without additives. An unfertilized treatment was also included as a control. In order to compare results, N(butyl) thiophosphoric triamide (NBPT), a common synthetic urease inhibitor, was also used. NBPT, 2-Cyclopenten-1-one and Eugenol were applied at a rate of 0.00125 g kg⁻¹ soil (equivalent to 0.5% N). The results indicated that the rate of urea hydrolysis was higher in grey desert soil compared to red soil. Soil in the urea-only treatments recorded urea hydrolysis to be almost complete within seven days of application. The rate of hydrolysis was inhibited by the two natural compounds, and higher concentrations of urea were maintained for more than two weeks. Soil amended with the two materials exhibited strong soil urease inhibition in both soil treatments (75.1% in the alkaline grey desert soil and 72.8% in the acidic red soil). The strongest inhibitory effect occurred one to three days after incubation in the Eugenol treatment. Moreover, the inhibitory effects of Cyclopenten-1-one and Eugenol were superior to that of NBPT in the two soils. Cyclopenten-1-one and Eugenol also significantly reduced soil NH₃ emissions by 14.2 to 45.3%, especially in the acidic red soil. Molecular docking studies confirmed inhibition mechanisms, highlighting that natural compounds interacted with the amino acid residues of the urease active center. This action resulted in the urease active pocket being blocked, thereby inhibiting enzyme activity. Overall, our findings suggest that 2-Cyclopenten-1-one and Eugenol are both capable of hindering urease activity and reducing the risk of N loss in the two tested soils. Results highlight their applicability as urease inhibitors and their effect in delaying the release of ammonia nitrogen, thereby increasing fertilizer N use efficiency. However, in order to fully assess N use efficiency and the N balance due to the presence of Chamomile extract in soil-crop systems, further field scale investigations are required.

中文翻译：

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洋甘菊植物材料在两种农业土壤中抑制脲酶活性和减少 NH3 挥发的潜力

尿素肥料在农业施用过程中释放的大量氨会导致施用的氮部分流失，对空气质量产生不利影响。尽管洋甘菊具有抑制氮转化的特性，提供潜在的农业和环境效益，但该植物的主要成分对土壤中脲酶活性和 NH ₃挥发的影响程度目前尚不清楚。使用 2-Cyclopenten-1-one 和丁香酚（C. recutita 的两种主要成分）建立了土壤孵化实验，以评估它们对土壤无机氮库、脲酶活性和 NH _{3 的影响}在灰色沙漠土壤和红壤中挥发。施用量为 0.25 g N kg ^-1土壤肥料，以尿素形式施用，添加和不添加添加剂。未受精处理也包括作为对照。为了比较结果，还使用了常见的合成脲酶抑制剂 N(丁基) 硫代磷酰三胺 (NBPT)。NBPT、2-Cyclopenten-1-one 和丁香酚的施用量为 0.00125 g kg ^-1土壤（相当于 0.5% N）。结果表明，与红壤相比，灰色沙漠土壤的尿素水解率更高。仅尿素处理中的土壤记录尿素水解在施用后 7 天内几乎完成。水解速率受到两种天然化合物的抑制，较高浓度的尿素可维持两周以上。用两种材料改良的土壤在两种土壤处理中都表现出强烈的土壤脲酶抑制作用（碱性灰色沙漠土壤为 75.1%，酸性红壤为 72.8%）。在丁香酚处理中孵育后一到三天出现最强的抑制作用。此外，Cyclopenten-1-one和丁香酚对两种土壤的抑制作用均优于NBPT。Cyclopenten-1-one和丁香酚也显着降低了土壤NH₃排放量减少 14.2% 至 45.3%，尤其是在酸性红壤中。分子对接研究证实了抑制机制，强调天然化合物与脲酶活性中心的氨基酸残基相互作用。该作用导致脲酶活性口袋被阻断，从而抑制酶活性。总体而言，我们的研究结果表明 2-Cyclopenten-1-one 和丁香酚都能够阻碍脲酶活性并降低两种测试土壤中氮流失的风险。结果突出了它们作为脲酶抑制剂的适用性及其在延迟氨氮释放方面的作用，从而提高了肥料氮的利用效率。然而，为了充分评估由于土壤作物系统中洋甘菊提取物的存在而导致的氮利用效率和氮平衡，需要进一步的田间规模调查。