Precipitation event–driven runoff and nutrient loss responses from vegetated and unvegetated shallow furrow ditches

Authors: SCHWAB, ELIZABETH - Iowa State University; King, Kevin; Hanrahan, Brittany; KALCIC, MARGARET - University Of Wisconsin; BOYER, ELISABETH - The Ohio State University; SHEDEKAR, VNAYAK - The Ohio State University

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/8/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: Agricultural nutrient loss and manifestation into downstream water quality problems continues to be a focus in the poorly drained, humid regions of the Eastern Corn Belt (ECB). Drainage ditches and/or swales are often constructed in the flat ECB landscape to facilitate surface water movement and crop production. Vegetated versus non-vegetated management on a single pair of surface/furrow ditches was investigated and results indicated that the use of vegetated management tended to decrease total phosphorus loss when compared to non-vegetated treatment with no differences in dissolved phosphorus, nitrate-nitrogen or total nitrogen. The findings should be of interest to conservationists, extension, and action agencies. seeking and promoting conservation management aimed at improving water quality in the poorly drained regions of the world.

Technical Abstract: Artificial surface drainage practices are used worldwide to enable or enhance agricultural production in poorly drained areas, particularly in flat landscapes. While they are designed to remove excess water, these practices may intercept nutrient runoff from agricultural lands, leading to the impairment of downstream waterbodies. This study site is located in a very poorly drained region of northwest Ohio where shallow furrow ditches are one of the options utilized to manage surface water in agricultural fields. While these ditches are typically left unvegetated, vegetation of channels or ditches in order to reduce flow velocity and transport of sediment and nutrients has generally been found to be beneficial for water quality. In this study, differences in hydrograph dynamics (i.e., time to peak discharge and hydrograph duration), as well as eventwise nutrient losses (nitrate (NO3-N), total nitrogen (TN), dissolved reactive phosphorus (DRP), and total phosphorus (TP)), were compared between a vegetated and an unvegetated shallow furrow ditch across precipitation event characteristics and seasons. There were no statistically significant differences in time to peak discharge or event hydrograph duration between furrow ditches. Differences in nutrient loss patterns were evident for TP, with TP loads proportional to discharge for the vegetated furrow but not the unvegetated, and with the unvegetated furrow ditch trending towards greater TP loss for a given discharge compared to the vegetated furrow ditch. Conversely, NO3-N, TN, and DRP loads were generally proportional to discharge, and consequently, for both furrows, greater discharge tended to result in greater total nutrient loads across precipitation event characteristics and seasons. These results suggest that vegetation of shallow furrow ditches may be beneficial, but that the practice is likely to be most effective for erosion protection and reduction of sediment-associated TP losses.