Drainage Water Quality Impacts of Current Future Agricultural Management Practices

Date: 
Feb 2014

Issue

The Iowa Nutrient Reduction Strategy has increased emphasis on reducing downstream nutrient loss. The strategy’s science assessment highlighted practices that have the potential to reduce nitrogen (N) and phosphorus (P) loss, including some practices where additional information is needed. Winter cover crops is one such practice. There also is a need to better understand how crop rotation, tillage or crop residue removal may impact nutrient loss through drainage systems.

Objective

This study will evaluate the crop production and drainage water quality impacts of various cropping and nutrient management systems. Some specific questions to be addressed include: (1) can nitrate-N and dissolved P losses be decreased when planting a cover crop after both corn and soybean within a corn/soybean rotation; (2) how are dissolved nutrient losses impacted by liquid swine manure application; (3) how does tillage within a corn/soybean system impact dissolved nutrient loss; (4) how does dissolved nutrient loss from a continuous corn system compare to a corn/soybean system; and (5) does removal of corn residue impact dissolved nutrient loss in a continuous corn system?

Approach

This project will be conducted at an existing drainage water quality study site on the Iowa State University Northeast Iowa Research and Demonstration farm. The site includes 36 plots with a state-of-the-art surface and subsurface water quality monitoring system. The project will include collection of both water and soil samples for nutrient analysis.

Project Updates

December 2016

FINAL REPORT

The goal of this study was to evaluate the crop production and drainage water quality impacts of various cropping and nutrient management practices. This project showed cover crops provide a significant reduction in nitrate-nitrogen concentrations in subsurface drainage water. Liquid swine manure applied to corn only resulted in lower nitrate-nitrogen losses when compared to manure applied to both corn and soybean in a corn-soybean system. Management systems with fall application of swine manure had higher nitrate-nitrogen losses compared to systems with spring application of liquid urea-ammonium nitrate. Tillage had no significant impact on dissolved nutrient losses in a corn-soybean rotation when compared to a no-till system. Nitrate-nitrogen losses from continuous corn with annual swine manure application were similar to those from a corn-soybean system with annual application, but were higher than a corn-soybean system receiving swine manure on corn only. Nutrient losses via subsurface drainage were not affected by corn stover removal in the continuous corn system. In addition, there was minimal to no effect on dissolved phosphorus losses when comparing different nutrient management and tillage systems.

September 2016

Field monitoring and agronomic management activities continued at the site this quarter. Results from the 2008-2015 phase of this project are being compiled, and the new phase begun. New treatments on the drainage water quality plots were implemented this season and include timing of liquid swine manure application; use of a winter cereal rye cover crop; corn-soybean rotation versus continuous corn system; impact of a high rate of gypsum on dissolved phosphorus loss; and impact of a nitrogen inhibitor product.

June 2016

All analysis of soil and water samples from 2015 were completed this quarter, as was a summary of the past phase of the project from 2008-2015. Water quality monitoring got underway in mid-March. Field activities for crop production in 2016 began in April. New treatments on the drainage water quality plots are being implemented for this season and include timing of liquid swine manure application; use of a winter cereal rye cover crop; corn-soybean rotation versus continuous corn system; impact of a high rate of gypsum on dissolved phosphorus loss; and impact of a nitrogen inhibitor product.

March 2016

During this quarter, the team worked to get all water quality analysis completed including phosphorus concentrations in drainage. Due to early spring conditions, water quality monitoring started at the site in mid-March. New treatments on the drainage water quality plots are being implemented for this season and include timing of liquid swine manure application; use of a winter cereal rye cover crop; corn-soybean rotation versus continuous corn system; impact of a high rate of gypsum on dissolved phosphorus loss; and impact of a nitrogen inhibitor product.

December 2015

Due to the wet fall, it was possible to continue to collect water samples during this quarter, plus harvest the crops and sample soils after harvest. New treatments for the 2016 crop year will include applying manure, seeding cover crops and applying gypsum. The 2015 crop yield and water quality information was summarized, and reported in the Iowa State University Northeast Research and Demonstration Farm annual progress report. Eight-year average nitrate-nitrogen concentrations in tile water from plots receiving swine manure were the highest in comparison with other treatments/systems. The cover crop system with urea-ammonium nitrate with cover crop had the lowest average concentrations.

September 2015

Water quality samples continue to be collected at the research site at the Iowa State University Northeast Research and Demonstration Farm. This study includes 36 plots with a surface and subsurface water quality monitoring system, and is evaluating the crop production and drainage water quality impacts of various cropping and nutrient management systems. Work during this quarter involved agronomic activities such as rye killing, crop planting and crop management. Results from the project to date were shared at the farm’s field day in June. Discussions are underway on new treatments that will be implemented for the 2016 crop year. 

June 2015

Water quality samples continue to be collected at the research site at the Iowa State University Northeast Research and Demonstration Farm. This study is evaluating the crop production and drainage water quality impacts of various cropping and nutrient management systems, and includes 36 plots with a surface and subsurface water quality monitoring system. Work during this quarter focused on getting water sample analysis completed and water quality data for drainage flow and nitrate-N concentration and loss summarized. 

March 2015

This study is evaluating the crop production and drainage water quality impacts of various cropping and nutrient management systems, and is being conducted at the Iowa State University Northeast Iowa Research and Demonstration farm. Water quality samples are being collected at the research site, which includes 36 plots with a surface and subsurface water quality monitoring system. In this quarter, crops were harvested, manure was applied to the fall manure treatments, and cover crops were seeded in the cover crop plots. Preliminary analysis of nitrate loss and crop yields is underway.

December 2014

This study is evaluating the crop production and drainage water quality impacts of various cropping and nutrient management systems. It is conducted at an existing drainage water quality study site on the Iowa State University Northeast Iowa Research and Demonstration farm. The site includes 36 plots with a state-of-the-art surface and subsurface water quality monitoring system. Water quality samples are collected on a regular basis. Rye seed was purchased for planting after harvest of the cash crop.

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