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

地下瓦片排水被广泛用于在全国排水不良的农业景观中提高作物产量。瓦片排水的沉积物结合磷(P)负荷通过水径流导致水体中营养物质过度丰富，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瓷砖排水管的运输动力学方面存在重大差距，这限制了我们管理这些农田污染物的能力。这项研究将为肯塔基大学的一名终身助理教授和一名研究生研究助理提供资金，以在印第安纳州西拉斐特的国家土壤侵蚀研究实验室（NSERL）进行长期的实地考察。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。研究小组还将改进计算机模拟工具，以便从田地中捕获瓦片沉积物P负荷，以改进管理策略。在PI所在的肯塔基州，以及全国各地的食品生产系统，瓷砖排水系统越来越多地得到实施。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领域代表性不足的学生提供培训。最近的研究强调了从河床沉积物中再生的溶解活性磷（DRP）作为流域尺度DRP负荷的主要来源的重要性。现在，人们对量化和管理通过瓷砖排水管输送的与沉积物结合的颗粒P （PP）重新产生了兴趣。控制大孔中沉积物侵蚀和输运动力学的机制尚不清楚，特别是生物壳发育对大孔壁的影响及其对流动路径动力学和沉积物可蚀性的影响。此外，对PP向瓦片排水沟输送的田间控制已经进行了假设，但没有量化，这源于缺乏田间数据集和农业水管理模型中通过瓦片排水沟输送地下PP的代表性有限。研究小组将与美国国家土壤侵蚀研究实验室（NSERL）合作，研究大孔生物结皮发育对泥沙侵蚀和流动路径动力学的影响。研究活动包括在生长和控制条件下的未受干扰的土壤溶渗仪上进行降雨试验。该团队还将修改水侵蚀预测项目（WEPP）模型，以包括地下流动路径和沉积物P侵蚀以及瓦排水的运输程序，这将使用NSERL管理的长期数据集在野外和流域尺度上进行评估。本提案中开发的基础设施可用于告知从业者使用的基于经验的工具的权重因子和模型结构，例如p指数。拟议的研究活动将提高对地下侵蚀过程的机制理解，推进地下排水农业生态系统在田间流域尺度上的数值模拟基础设施，并将量化导致PP向地沟输送的主要机制。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.