New terrace‐tile inlet technologies reduce sediment and nutrient losses

Abstract

Surface inlets such as Hickenbottom risers (HBRs) are often used to drain closed depressions and potholes across agricultural landscapes in the US Midwest. Although HBRs provide efficient drainage, they also transport substantial nutrient and sediment losses from fields. The objective of this study was to compare discharge and runoff water quality in a no‐till, terraced field affected by four surface inlet technologies: HBR, HBR with channel laterals (HBR + CL), water quality inlet (WQI), and blind inlet (BI). The study was conducted from 2023 to 2025, and water quality was monitored at tile outlets. Across the study period, HBR had the highest median daily discharge (0.26 mm), followed by HBR + CL, WQI, and BI. Discharge differences were observed in 2023 and 2025, while there were no significant differences in 2024. The HBR consistently had the highest sediment and nutrient losses. The WQI reduced median sediment losses by 11%–76% compared with BI, HBR + CL, and HBR, while BI reduced total suspended solids (TSS) losses by 95% compared with HBR in 2025. Field observations revealed that HBR + CL accelerated soil drying and reduced waterlogging in terrace channels due to the installed subsurface drain pipes. BIs were effective in reducing most cation and anion losses, sediments, and discharge through filtration, adsorption, and precipitation on limestone media. The WQI also reduced several nutrients through settling during temporary ponding. Overall, alternative inlet technologies, particularly BI, demonstrated strong potential to reduce sediment and nutrient losses from terraced tile‐drained fields while maintaining efficient drainage.