Crop growth, hydrology, and water quality dynamics in agricultural fields across the Western Lake Erie Basin: Multi-site verification of the Nutrient Tracking Tool (NTT)

Authors: GUO, TIAN - Heidelberg University, Ohio; CONFESOR, REMEGIO - Heidelberg University, Ohio; SALEH, ALI - Tarleton State University; King, Kevin

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/4/2020
Publication Date: 4/7/2020
Citation: Guo, T., Confesor, R., Saleh, A., King, K.W. 2020. Crop growth, hydrology, and water quality dynamics in agricultural fields across the Western Lake Erie Basin: Multi-site verification of the Nutrient Tracking Tool (NTT). Science of the Total Environment. 726:138485. https://doi.org/10.1016/j.scitotenv.2020.138485.
DOI: https://doi.org/10.1016/j.scitotenv.2020.138485

Interpretive Summary: Hydrology and water quality models are essential to assess the field and watershed scale impacts of adopting conservation and crop production management practices. However, the models are often applied without calibration, leading to considerable uncertainty in predictions. A multi-site calibrated version of the Nutrient Tracking Tool (NTT) was developed using measured data from the USDA-ARS edge-of-field network in the Western Lake Erie Basin (WLEB) watershed. Hydrology, water quality and crop yield predictions from the calibrated model were within suggested tolerance limits. The calibrated version of NTT can confidently be applied across the WLEB watershed to further explore the potential water quality impacts of conservation and various crop production practice adoption.

Technical Abstract: Agricultural field- and watershed-scale water quality models are used to assess the potential impact of management practices to reduce nutrient and sediment exports. However, long term measured data are often not available to calibrate and verify these models. Three years of data from the USDA Agricultural Research Service's (USDA-ARS) 12 paired edge-of-field (EOF) sites in northwest Ohio were used calibrate and validate the Nutrient Tracking Tool (NTT). The goal of this study was to identify a single optimal parameter set of NTT in simulating annual crop yields, water balance, and nutrient loads across the Western Lake Erie Basin (WLEB). A multi-site and multi-objective auto-calibration subroutine was developed in R to perform model calibration across the EOF sites. The statistical metrics and evaluation criteria in choosing the best parameter set were: Cohen's D Effect Size (Cohen's D) (< 0.20) and Percent bias (PBIAS) (± 10% for crop yields, tile discharge, and surface runoff and ± 25% for dissolved reactive phosphorus (DRP) and nitrate nitrogen (NO3) in tile discharge, and DRP, particulate phosphorus (PP), and NO3 in surface runoff). In both calibration and validation, the Cohen's D and PBIAS for annual crop yields, subsurface (tile) discharge, surface runoff, DRP, PP, and NO3 were within the evaluation criteria limits. We suggest that the tile drainage and phosphorus transport subroutines in the NTT should be further improved to realistically simulate the dynamics of discharge and phosphorus transport through subsurface drainage. Stakeholders can use the verified NTT to evaluate the potential effectiveness of conservation practices to improve water quality across the WLEB.