Agri-Environment Branch, Agri-Food and Biosciences Institute (AFBI), Newforge Lane, Belfast, BT9 5PX, Northern Ireland.
Agri-Environment Branch, Agri-Food and Biosciences Institute (AFBI), Newforge Lane, Belfast, BT9 5PX, Northern Ireland.
Sci Total Environ. 2017 Jan 1;575:474-484. doi: 10.1016/j.scitotenv.2016.07.063. Epub 2016 Oct 28.
Rates and quantities of legacy soil phosphorus (P) lost from agricultural soils, and the timescales for positive change to water quality, remain unclear. From 2000 to 2004 five 0.2ha grazed grassland plots located on a drumlin hillslope in Northern Ireland, received chemical fertiliser applications of 0, 10, 20, 40, 80kgPhayr resulting in soil Olsen P concentrations of 19, 24, 28, 38 and 67mgPL, respectively, after which applications ceased. Soil Olsen P and losses to overland flow and drainage were monitored from 2005 to 2011 on an event and weekly flow proportional basis, respectively. Soluble reactive P and total P time series were synchronised with daily rainfall and modelled soil moisture deficits. From 2005 to 2011 soil Olsen P decline was proportional to soil P status with a 43% reduction in the plot at 67mgPL in 2004 and a corresponding 12% reduction in the plot with lowest soil P. However, there was no significant difference in the flow-weighted mean concentration for overland flow among plots, all of which exceeded 0.035mgL in >98% of events. Strong interannual and event variations in losses were observed with up to 65% of P being lost during a single rainfall event. P concentrations in drainage flow were independent of Olsen P and drain efficiency was potentially the primary control on concentrations, with the highest concentrations recorded in the plot at 38mgL Olsen P in 2004 (up to 2.72mgL). Hydrological drivers, particularly antecedent soil moisture, had a strong influence on P loss in both overland and drainage flow, with higher concentrations recorded above a soil moisture deficit threshold of 7mm. This study demonstrates that on some soil types, legacy P poses a significant long term threat to water quality, even at agronomically optimum soil P levels.
从 2000 年到 2004 年，在北爱尔兰的一个冰碛丘陵斜坡上，有五个 0.2 公顷的放牧草地试验区，分别接受了 0、10、20、40、80kgPhayr 的化肥施用，导致土壤奥尔森磷浓度分别为 19、24、28、38 和 67mgPL，之后停止了施肥。从 2005 年到 2011 年，以事件和每周流量比例为基础，分别监测了土壤奥尔森磷和径流水和排水中的损失。可溶性反应磷和总磷时间序列与每日降雨量和模拟土壤水分亏缺同步。从 2005 年到 2011 年，土壤奥尔森磷的下降与土壤磷状况成正比，2004 年 67mgPL 土壤中磷的减少了 43%，而土壤磷最低的土壤减少了 12%。然而，在径流水的流量加权平均浓度方面，各试验区之间没有显著差异，所有试验区在超过 98%的事件中都超过了 0.035mgL。在径流水和排水中，观测到磷损失的年际和事件变化很大，在一次降雨事件中损失了多达 65%的磷。排水中磷浓度与奥尔森磷无关，排水效率可能是浓度的主要控制因素，在 2004 年奥尔森磷浓度为 38mg/L 的试验区记录到最高浓度（高达 2.72mg/L）。水文驱动因素，特别是前期土壤湿度，对径流水和排水中的磷损失有很强的影响，在土壤湿度亏缺阈值超过 7mm 时，记录到的浓度更高。本研究表明，在某些土壤类型上，即使在农业上最佳的土壤磷水平下，遗留磷也对水质构成了重大的长期威胁。
