Using RZWQM2-P to capture tile drainage phosphorus dynamics in Ohio

Authors: GREWAL, HARMANPREET - McGILL UNIVERSITY - CANADA; QI, ZHIMING - McGILL UNIVERSITY - CANADA; SHEDEKAR, VINAYAK - THE OHIO STATE UNIVERSITY; King, Kevin

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/4/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Hydrology and water quality simulation tools provide a means to assess the impacts of crop production and conservation management as well as future climates on natural resource systems. The RZWQM2-P model was populated, calibrated, and validated with edge-of-field data from a site in Western Lake Erie Basin watershed. Predictions from the validated model indicated that inclusion of cover crops into crop management scenarios are a good option to reduce dissolved phosphorus in tile drainage discharge. The development and calibration of this simulation tool is important for future assessments in tile drained landscapes. Additionally, these findings are important to researchers, conservationists, extension, and practitioners as they seek to identify conservation practices aimed at addressing nutrient transport.

Technical Abstract: Phosphorus (P) loading from tile-drained agricultural lands is linked to water quality and aquatic ecosystem degradation. Extending Dr. Andrew Sharpley and colleagues’ foundational work on environmental risk assessment tools like EPIC and SurPhos, the RZWQM-P model was developed to simulate the fate and transport of P in soil-water-plant systems, especially in tile-drained croplands. Comprehensive evaluation and application of RZWQM2-P, however, remains limited. This study evaluates RZWQM2-P in simulating P dynamics using extensive data and assesses the potential of management practices for mitigating P losses. Subsurface drainage and surface runoff flows were monitored at a tile-drained site from 2017 to 2020 in Ohio, and the water flow and P loss data were summarized on a daily basis. RZWQM2-P was calibrated and validated using those observed data and was subsequently used to assess the effectiveness of controlled drainage and winter cover crops in reducing P losses. The model satisfactorily simulated dissolved reactive P (DRP) loss from tile drainage on daily and monthly bases (NSE=0.50, R2=0.52, IOA=0.84 for daily; NSE=0.73, R2=0.78, IOA=0.94 for monthly) and total P (TP) loss on a monthly basis (NSE=0.64, R2=0.65, IOA=0.88), but the daily TP simulation was less accurate (NSE=0.30, R2=0.30, IOA=0.59). Simulations showed that winter rye cover crops reduced DRP by 16% and TP by 4% compared to the base scenario, whereas controlled drainage increased DRP (60%-129%) and TP (5%-17%) losses at three tested outlet elevations compared to free drainage. RZWQM2-P can capture P dynamics in tile-drained cropland and is a promising tool for effective P management.