The subsurface transport of dissolved reactive phosphorus (DRP) from artificially drained agricultural fields can impair water quality, especially in no-till fields. The distribution of soil P in the wheat (Triticum aestivum L.)-dominated Palouse region in the inland U.S. Pacific Northwest varies greatly due to its steep and complex topography, and a legacy (∼130 yr) of excessive soil erosion and deposition processes. The primary goal of this research was to better understand the magnitude and temporal dynamics of DRP export from an artificial drain line and the variability of subsurface DRP leaching within a long-term, no-till field. Dissolved reactive P in drain line effluent was monitored across three water years. Large intact soil cores were extracted at contrasting field locations (toe and top slope positions) to measure DRP leachate concentration and relative P sorption. Drain line DRP concentration was predominantly >0.05 mg L-1 and often exceeded 0.1 mg L-1 during winter and early spring. Mean leachate DRP levels were significantly higher in toe slope cores than in top slope cores (0.11 and 0.02 mg L-1 , respectively). Saturated hydraulic conductivity varied widely across cores and was not correlated with leachate DRP concentration. All soil cores exhibited high P sorption potential, even under conditions of preferential flow. These findings suggest that much of the DRP transport in these landscapes is derived from P hotspots located in toe slope positions. Application of soil P fertilizer amounts in variable rates that account for spatial variability in P transport may minimize P enrichment and subsequent leaching in these locations.

中文翻译：

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复杂地形半干旱免耕流域中溶解活性磷的来源和地下传输

来自人工排水农田的溶解活性磷 (DRP) 的地下传输会损害水质，尤其是在免耕农田。美国太平洋西北部内陆以小麦（Triticum aestivum L.）为主的帕卢斯地区土壤磷的分布由于其陡峭和复杂的地形以及过度土壤侵蚀和沉积过程的遗留（约 130 年）而变化很大。本研究的主要目标是更好地了解人工排水管输出 DRP 的幅度和时间动态，以及长期免耕田地地下 DRP 浸出的可变性。对排水管线流出物中溶解的活性磷进行了三年的监测。在对比的现场位置（脚趾和顶部斜坡位置）提取大型完整土壤核心，以测量 DRP 渗滤液浓度和相对 P 吸附。排水管 DRP 浓度主要 >0.05 mg L-1，并且在冬季和早春时常超过 0.1 mg L-1。趾坡岩心的平均渗滤液 DRP 水平显着高于顶坡岩心（分别为 0.11 和 0.02 mg L-1）。饱和导水率在岩心间变化很大，并且与渗滤液 DRP 浓度无关。即使在优先流动的条件下，所有土壤核心都表现出高 P 吸附潜力。这些发现表明，这些景观中的大部分 DRP 传输来自位于脚趾斜坡位置的 P 热点。