Earthworms’ activities not only increase soil nitrogen (N) uptake by crops but also lead to N losses to environment. However, it remains unclear whether earthworms’ impact on the fate of fertilizer N differs based on the type of fertilizer application. Therefore, the present pot experiment examined the transformation and fate of two types of 15N-labeled fertilizer (synthetic fertilizer urea and organic fertilizer compost applied at rate of 400 mg N/pot) with and without earthworms (Amynthas corticis) in a soil-lettuce system over three seasons of cultivation. Results showed that earthworms increased the fresh biomass of lettuce in all three seasons, regardless of the type of fertilizer used. However, the effect of earthworms on fertilizer N uptake varied depending on the type of fertilizer. With earthworms present, lettuce took up an additional 20.97 mg/pot of synthetic fertilizer N in the first season, which sharply decreased to 2.72 mg/pot and 4.63 mg/pot in the second and third seasons, respectively. In contrast, the uptake of organic fertilizer N by lettuce increased by 10.08–11.24 mg/pot throughout the entire experiment when earthworms were present. The presence of earthworms increased the percentage of synthetic fertilizer N lost to the environment by 0.8 %, due to increased N leaching, N2O emission, NH3 volatilization, etc. In contrast, earthworms decreased the percentage of organic fertilizer N lost to the environment by 1.9 %, primarily through reduced NH3 volatilization, etc. This study underscores the pivotal role of earthworms in modulating fertilizer N dynamics, with organic fertilizer offering superior ecosystem services compared to synthetic fertilizer. Given that only one earthworm species was studied and nearly half of the organic fertilizer remained in the soil, future long-term experiments incorporating diverse earthworm species and changes in the soil’s native N pool are essential to fully understand the role of earthworms in agro-ecosystem N cycling.

中文翻译：

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阐明蚯蚓对合成肥和有机肥施用氮命运的影响


蚯蚓的活动不仅增加了作物对土壤氮 （N） 的吸收，还导致 N 对环境的损失。然而，目前尚不清楚蚯蚓对肥料 N 命运的影响是否因肥料施用的类型而异。因此，本盆栽实验考察了两种 15N 标记肥料（合成肥料尿素和有机肥料堆肥，施用量为 400 毫克 N/盆）在土壤-生菜系统中，在三个季节的栽培中，有和没有蚯蚓 （Amynthas corticis）。结果表明，无论使用何种肥料，蚯蚓在所有三个季节都增加了生菜的新鲜生物量。然而，蚯蚓对肥料氮吸收的影响因肥料类型而异。在蚯蚓存在的情况下，生菜在第一季额外吸收了 20.97 毫克/罐的合成肥料氮，第二季和第三季分别急剧下降到 2.72 毫克/罐和 4.63 毫克/罐。相比之下，当蚯蚓存在时，在整个实验中，生菜对有机肥氮的吸收增加了 10.08-11.24 毫克/盆。由于氮浸出、N2O 排放、NH3 挥发等增加，蚯蚓的存在使合成肥料 N 流失到环境中的百分比增加了 0.8%。相比之下，蚯蚓将有机肥氮流失到环境中的百分比降低了 1.9%，主要是通过减少 NH3 挥发等。这项研究强调了蚯蚓在调节肥料氮动力学中的关键作用，与合成肥料相比，有机肥料提供了卓越的生态系统服务。 鉴于只研究了一种蚯蚓物种，并且近一半的有机肥料仍留在土壤中，未来结合不同蚯蚓物种和土壤天然氮库变化的长期实验对于充分了解蚯蚓在农业生态系统氮循环中的作用至关重要。