The impacts of soil properties and urea fertigation on nitrous oxide (N2 O) emissions from uncropped areas of furrow-irrigated Vertisol paddocks are unknown. We sampled soils from the head-ditch end (upslope) and sediments from the tail-drain end (downslope) of 10 Vertisols under irrigated cotton (Gossypium hirsutum L.) production in northeastern Australia. Four replicates of each sample were incubated in open-top polyvinyl chloride (PVC) chambers at 25 ± 2°C for 25 d. Nitrous oxide emissions were measured periodically after simulated irrigations on Days 0 and 15 with either water or, for soils, urea solution. Compared with the soils, sediments were enriched in silt, total organic carbon (TOC), total nitrogen (TN), ammonium N, and dissolved organic C (DOC) but had lower pH and sand content. Sediments emitted more N2 O than soils from the same paddocks after water irrigations. Nitrous oxide fluxes varied by two orders of magnitude between paddocks, with most variation explained by baseline nitrate N, TOC, pH (inversely), and sand content. Urea solution applied to soils at 30 kg N ha-1 irrigation-1 increased N2 O emitted, but more so after the second irrigation. In irrigated cotton systems, tail-drain sediments are a potential hotspot for N2 O emissions that has not previously been documented.

中文翻译：

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尾排水沉积物是用于种植棉花的沟灌 Vertisol 中一氧化二氮排放的潜在热点：一项实验室孵化研究

土壤特性和尿素施肥对来自犁沟灌溉的 Vertisol 围场的未耕种区域的一氧化二氮 (N2 O) 排放的影响尚不清楚。我们对澳大利亚东北部灌溉棉花 (Gossypium hirsutum L.) 生产的 10 个 Vertisols 的头沟末端（上坡）的土壤和尾沟末端（下坡）的沉积物进行了采样。每个样品的四个重复在 25±2°C 的开顶聚氯乙烯 (PVC) 室中孵育 25 天。在第 0 天和第 15 天用水或尿素溶液进行模拟灌溉后，定期测量一氧化二氮的排放量。与土壤相比，沉积物富含淤泥、总有机碳 (TOC)、总氮 (TN)、铵态氮和溶解有机碳 (DOC)，但 pH 值和砂含量较低。水灌溉后，沉积物排放的 N2 O 比来自同一围场的土壤更多。围场之间的一氧化二氮通量变化两个数量级，大多数变化由基线硝酸盐 N、TOC、pH（相反）和沙子含量解释。以 30 kg N ha-1 灌溉-1 向土壤施用尿素溶液会增加 N2 O 排放，但在第二次灌溉后排放量更大。在灌溉棉花系统中，尾流沉积物是 N2 O 排放的潜在热点，以前没有记录。