Analysis of the MANAGE drain concentration database to evaluate agricultural management effects on drainage nutrient concentrations

Authors: CHRISTIANSON, LAURE - University Of Illinois; PITTELKOW, CAMERON - University Of Illinois; Harmel, Daren; HERTZBERGER, ALLAN - University Of Illinois

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/29/2019
Publication Date: 7/1/2019
Citation: Christianson, L., Pittelkow, C., Harmel, R.D., Hertzberger, A. 2019. Analysis of the MANAGE drain concentration database to evaluate agricultural management effects on drainage nutrient concentrations. Transactions of the ASABE. 62(4):929-939. https://doi.org/10.13031/trans.13230.
DOI: https://doi.org/10.13031/trans.13230

Interpretive Summary: Agricultural systems are substantial contributors of non-point nitrogen (N) and phosphorus (P) pollution, and loss of dissolved forms of these nutrients is exacerbated in subsurface drained (“tile drained”) landscapes. The majority of reviews summarizing drainage nutrient losses have focused on N and P loads, but closer inspection of drainage concentrations is necessary to more directly link cropping management factors with water quality outcomes. More than 1,500 site-years of drainage N and P concentration data were recently compiled into the Measured Annual loads from AGricultural Environments (MANAGE) Drain Concentration database and used to statistically analyze the impacts of crop rotation, nutrient management, and tillage type on annual drainage nutrient concentrations. The highest annual mean nitrate-N concentrations across the database were from corn, corn and soybean, and soybean site-years (13.98, 13.53, and 12.09 mg/L, respectively). However, crop selection was not a significant factor for annual average dissolved P concentrations in drainage. Nitrogen application rates below 75 kg/ha for corn did not reduce annual nitrate-N concentrations compared to rates greater than 75 kg/ha. There was no significant difference in annual drainage nitrate-N concentrations from site-years reporting a split N application versus site-years without split application. The MANAGE database will continue to evolve and remain a resource for new exploratory efforts to better understand and reduce nutrient losses from agricultural systems.

Technical Abstract: Agricultural systems are substantial contributors of non-point nitrogen (N) and phosphorus (P) pollution, and loss of dissolved forms of these nutrients is exacerbated in subsurface drained (“tile drained”) landscapes. The majority of reviews summarizing drainage nutrient losses have focused on N and P loads, but closer inspection of drainage concentrations is necessary to more directly link cropping management factors with water quality outcomes. More than 1,500 site-years of drainage N and P concentration data were recently compiled into the Measured Annual loads from AGricultural Environments (MANAGE) Drain Concentration database and used to statistically analyze the impacts of crop rotation, nutrient management, and tillage type on annual drainage nutrient concentrations. The highest annual flow-weighted mean nitrate-N concentrations across the database were from corn, corn and soybean, and soybean site-years (13.98, 13.53, and 12.09 mg/L, respectively). However, crop selection was not a significant predictor for annual average drainage dissolved reactive P concentrations. Nitrogen application rates below 75 kg/ha for corn did not reduce annual nitrate-N concentrations compared to rates greater than 75 kg/ha. There was no significant difference in annual drainage nitrate-N concentrations from site-years reporting a split N application versus site-years without split application. Stepwise regression analysis of nitrate-N concentrations had an overall model R2 of 0.59 (n=254) and indicated N application rate had the greatest effect on nitrate-N concentrations in corn site-years followed by fertilizer timing and tillage type. Regression analysis of dissolved reactive P concentrations had an overall R2 of 0.94, and although the model was much less robust due to a very small sample size (n=47), fertilizer timing was most correlated with annual dissolved reactive P concentrations. The MANAGE database will continue to evolve and remain a resource for new exploratory efforts to better understand and reduce nutrient losses from agricultural systems.