RII Track-4: Elucidating controls of sediment phosphorus delivery to tile-drains

地下瓦片排水被广泛用于提高全国排水不良的农业景观的作物产量。来自瓷砖排水的沉积物结合的磷（P）负荷通过水径流导致水体中营养物的过度丰富，并增加下游水体中有害藻类的突出。在了解沉积物侵蚀和通过瓦片排水沟的运输动力学方面存在重大差距，这限制了我们管理农田中这些污染物的能力。 这项研究将提供资金的终身助理教授，并从肯塔基州大学的研究生研究助理在国家土壤侵蚀研究实验室（NSERL）在西拉斐特，印第安纳州进行扩展现场访问。 PI和他的学生将与NSERL的研究人员合作，进行实验室降雨模拟，以研究沉积物侵蚀和通过地下土壤运输的机制。 该研究小组还将加强计算机模拟工具，可以捕捉瓷砖沉积物磷负荷从外地，以改善管理战略。 瓷砖排水越来越多地在PI的肯塔基州以及全国各地的粮食生产系统中实施。 这项研究将改善研究和管理瓷砖排水水质的基础设施，推进PI所在机构的研究生课程，并为STEM中代表性不足的学生提供培训。 最近的研究强调了溶解活性磷（DRP）的重要性，从河床沉积物再生作为流域尺度DRP负荷的主要来源。 现在有新的兴趣，在量化和管理沉积物结合颗粒P（PP）通过瓷砖排水管交付。控制大孔隙中沉积物侵蚀和输运动力学的机制尚未得到很好的理解，特别是生物结皮的发展对大孔隙壁的影响，以及它如何影响流道动力学和沉积物的可蚀性。 此外，PP输送到瓷砖排水沟的现场规模控制已经被假设，但没有量化，这源于缺乏现场数据集和农业水管理模型中通过瓷砖排水沟的地下PP输送的有限代表性。该研究小组将与国家土壤侵蚀研究实验室（NSERL）合作，研究大孔生物结皮发展对沉积物侵蚀和流动通道动力学的影响。 研究金活动包括在生长和控制条件下对原状土壤蒸渗仪进行降雨实验。 该团队还将修改水侵蚀预测项目（WEPP）模型，以包括地下水流通道和沉积物磷侵蚀和瓷砖排水的运输程序，这将使用NSERL管理的长期数据集在实地和流域尺度上进行评估。 本提案中开发的基础设施可用于为从业人员使用的基于实践的工具（如P指数）提供加权因子和模型结构。 拟议的研究活动将提高地下侵蚀过程的机械理解，在地下排水农业生态系统领域流域尺度推进数值模拟基础设施，并将量化导致PP运输到瓦dails.This奖项的突出机制反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

Subsurface tile-drainage is widely used to increase crop yields in poorly drained, agricultural landscapes across the nation. Sediment-bound phosphorus (P) loadings from tile-drainage are contributing to the excessive richness of nutrients in a body of water, through water run-off, and increasing the prominence of harmful algae in downstream waterbodies. There are major gaps in understanding of sediment erosion and transport dynamics through tile-drains, which has limited our ability to manage these contaminants from agricultural fields. This research will provide funding for a tenure-track Assistant Professor, and a graduate research assistant from the University of Kentucky to conduct extended site visits at the National Soil Erosion Research Laboratory (NSERL) in West Lafayette, Indiana. The PI and his student will collaborate with researchers at NSERL to perform laboratory rainfall simulations to study mechanisms of sediment erosion and transport through subsurface soils. The research team will also enhance computer simulation tools that can capture tile sediment P loadings from fields in order to improve management strategies. Tile-drainage is increasingly implemented in the PI’s state of Kentucky, as well as food-production systems across the country. This research will improve infrastructure for researching and managing tile-drainage water quality, advance graduate curricula at the PI’s home institution, and provide training for an underrepresented student in STEM. Recent studies have highlighted the importance of dissolved reactive phosphorus (DRP) that is regenerated from streambed sediments as a major source of watershed-scale DRP loading. There is now renewed interest in quantifying and managing sediment-bound particulate P (PP) delivered through tile-drains. Mechanisms controlling sediment erosion and transport dynamics in macropores are not well understood, particularly the impact of biological crust development on macropore walls and how it influences flow pathway dynamics and sediment erodibility. Further, field-scale controls on PP delivery to tile drains have been hypothesized, but not quantified, which stems from a lack of field datasets and limited representation of subsurface PP delivery through tile drains in agricultural water management models. The research team will collaborate with the National Soil Erosion Research Laboratory (NSERL) to study the impact of macropore biological crust development on sediment erosion and flow pathway dynamics. Fellowship activities include the use of rainfall experiments on undisturbed soil lysimeters with a growth and control condition. The team will also modify the Water Erosion Prediction Project (WEPP) model to include subsurface flow pathways and sediment P erosion and transport routines for tile drainage, which will be evaluated at both field and watershed scales using long-term datasets managed by NSERL. The infrastructure developed in this proposal may be used to inform weighting factors and model structure for empirically-based tools used by practitioners, such as P-indices. The proposed research activities will improve mechanistic understanding of subsurface erosion processes, advance numerical modeling infrastructure at field-watershed scales for subsurface drained agroecosystems, and will quantify the prominent mechanisms causing PP transport to tile drains.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.