Tile Drainage Flow Partitioning and Phosphorus Export in Vermont USA

Ryan Ruggiero,Donald Ross,Joshua W Faulkner

doi:10.3390/agriculture12020167

Abstract

Tile drainage (TD) has been identified as a potential non-point source of phosphorus (P) pollution and subsequent water quality issues. Three fields with TD in Vermont USA were monitored to characterize hydrology and P export. Fields were in corn silage and used minimal tillage and cover cropping practices. Preferential flow path (PFP) activity was explored by separating TD flow into flow pathway and source connectivity components using two hydrograph separation techniques, electrical conductivity end member unmixing, and hydrograph recession analysis. TD was the dominant P export pathway because of higher total discharge. Drought conditions during this study limited surface runoff, and possibly resulted in maximum PFP activity in the active clay soils. The non-growing season dominated annual P loading for two of the three study years. Peak P concentrations in TD occurred during events following manure injection in the fall, as well as in the spring post cover crop termination and post-planting. Intra-event analysis of rainfall pulses showed that TD flow and P concentrations were higher because of higher intensity pulses. This study highlights the impacts of current manure management, as well as the potential for climate change to increase P transport to TD.

Highlights

Reducing nutrient loss and subsequent water degradation is a challenge for agriculture as we explore the boundaries of crop and livestock yields [1]
An abnormally dry to moderate drought period occurred from June 2020 to August 2021, and during this period, tile drainage (TD) regularly responded to rainfall without surface runoff occurring [51]
Because of the relationships between P export and antecedent moisture condition (AMC), and that P export decreased as the time since P application increased, our findings suggest that TD P loads could be reduced if Manure injection (MI)/P application is timed

Summary

Introduction

Reducing nutrient loss and subsequent water degradation is a challenge for agriculture as we explore the boundaries of crop and livestock yields [1]. Phosphorus (P), among other required nutrients, is applied to farmland to increase fertility; it is transported from the soil to runoff and eventually surface waters, resulting in non-point source P pollution [2]. Accumulated legacy P from long-term application of P fertilizers and manure increases the difficulty of managing agricultural runoff [3,4]. TD alters the hydrologic processes that control P transport during storm events, and in some instances is regarded as a best management practice (BMP) for reducing P in agricultural runoff [9,10,11,12]. PFP permits rapid movement of water, reducing resorption of P to the soil matrix, which results in high P concentrations in TD [15,16]

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Conclusion