College of Science, Health, Engineering and Education, Murdoch University, 90 South Street, Western Australia 6150, Australia; ChemCentre, Building 500, Manning Rd, Bentley, WA 6102, Australia.
College of Science, Health, Engineering and Education, Murdoch University, 90 South Street, Western Australia 6150, Australia.
Sci Total Environ. 2021 Jun 1;771:145371. doi: 10.1016/j.scitotenv.2021.145371. Epub 2021 Jan 23.
Managing phosphorus (P) is a global priority for environmental water quality due to P lost from agricultural land through leaching, runoff and subsurface flow. In Western Australia (WA), following decades of P fertiliser application to crops and pastures in low rainfall regions, questions have been raised about this region's contribution to environmental P loss. This study was conducted on the Fitzgerald River catchment in the south Western Australia (WA) with mixed cropping and grazing land uses and a Mediterranean climate with low mean rainfall (~350 mm yr). Phosphorus forms were monitored continuously over a three-year period in five separate streams, each draining a defined sub-catchment. The P concentrations in streams consistently exceeded Australian and New Zealand Environment Conservation Council (ANZECC) trigger values throughout the monitoring period. Of the measured total P concentration, ~75% was dissolved P (DRP; <0.45 μm) and 80% of that fraction was in the filterable reactive form (FRP). These water quality measurements and other independent soil investigations at this site, suggest that transport of dissolved P rather than erosion of sediment-bound P was dominant in this environment. Based on extractable soil P (Colwell P) and the P buffering index (PBI), predicted concentrations of dissolved reactive P (DRP) in soil solution in topsoils (0-10 cm) across this catchment, generally exceeded ANZECC's values of 0.07 mg PL. The level of exceedance was spatially variable. Streams draining areas with the lowest predicted DRP concentrations also had the lowest measured FRP concentrations. Elsewhere stream water FRP concentrations depended on both DRP concentration and the PBI of the land being drained. Our findings suggest that deployment of practices that physically filter runoff, for example riparian vegetation, would be ineffective in restricting P transport into stream in this environment. This conclusion is consistent with previous findings of the ineffectiveness of riparian buffers on coarse textured sandy soils in higher rainfall areas of southwest WA. A reduction in DRP losses without yield loss could be achieved by following evidence-based fertiliser advice from soil testing to limit losses of legacy P".
管理磷（P）是环境水质的全球优先事项，因为 P 从农田中通过淋溶、径流和地下水流失。在西澳大利亚州（WA），经过几十年在低降雨量地区对农作物和牧场施用 P 肥料，人们对该地区对环境 P 流失的贡献提出了质疑。本研究在西澳大利亚州西南部的菲茨杰拉德河集水区进行，该地区采用混合种植和放牧土地利用方式，气候为地中海式，降雨量低（约 350 毫米/年）。在三年的时间里，在五条不同的溪流中连续监测磷形态，每条溪流都有一个定义明确的次流域。在整个监测期间，溪流中的 P 浓度始终超过澳大利亚和新西兰环境保护委员会（ANZECC）的触发值。在测量的总 P 浓度中，约 75%为溶解 P（DRP；<0.45 μm），其中 80%为可过滤的反应性形式（FRP）。该地点的这些水质测量值和其他独立的土壤调查表明，在这种环境中，溶解 P 的迁移而不是侵蚀与沉积物结合的 P 是主要的。根据可提取土壤 P（Colwell P）和 P 缓冲指数（PBI），预测该集水区表层土壤（0-10 cm）中土壤溶液中溶解反应性 P（DRP）的浓度，普遍超过 ANZECC 的 0.07 mg PL 值。超标程度存在空间差异。从预测 DRP 浓度最低的区域排水的溪流，其测量的 FRP 浓度也最低。在其他地方，溪流水中的 FRP 浓度取决于 DRP 浓度和排水土地的 PBI。我们的研究结果表明，在这种环境中，部署物理过滤径流的措施（例如河岸植被）在限制 P 进入溪流方面将是无效的。这一结论与先前在西澳大利亚州西南部降雨量较高地区粗质地沙质土壤上河岸缓冲区无效的发现一致。通过遵循基于土壤测试的肥料建议，减少 DRP 损失而不降低产量，可以实现减少“遗留 P”损失的目标。
