Water Quality Performance of Prairie Strips
The STRIPs project at the Neal Smith National Wildlife Refuge near Prairie City has documented water quality benefits by integrating tallgrass prairie vegetation into rowcropped watersheds. Now there is a need to evaluate water quality benefits when prairie strips are implemented on a full farm field scale.
This project will monitor surface water runoff quantity and quality on a 152- acre site at the Whiterock Conservancy. This will make it possible to evaluate water quality benefits on three newly installed prairie strips, with project information shared through field days and presentations.
The site has a paired area with and without prairie strips. The area has similar slope, area and soil conditions; crop management will be the same. For each monitored area, a distinct surface flow outlet point will be identified where a flume will be installed to monitor volume and rate of surface runoff. Each of these locations also will have an automated water sampler to obtain flow measurements and collect flow proportional water samples. Water samples will be analyzed for nitrate-nitrogen, total nitrogen, total suspended solids and total phosphorus. Water sample data will be used with flow data to calculate the export of nutrients and sediment from prairie strip and non-prairie strip areas.
Note: Project reports published on the INRC website are often revised from researchers' original reports to increase consistency.
The experimental sites, both in 2016 and 2017, experienced somewhat rare conditions in terms of a relatively few number of significant surface runoff-producing rain events. More runoff events occurred in 2018 and 2019, enabling us to collect a greater amount of surface runoff flow data as well as more samples for nutrient analyses.
Prairie strips seem to have reduced runoff volume , with the main exception being the McNay site. The field where prairie strips are located at McNay is noticeably wetter than the field without prairie strips due to side-slope seeps. We suspect the wet conditions reduce infiltration and therefore contribute to the higher amount of runoff in the treatment field compared to the control field. In addition, we noticed that in 2017, runoff in the control field was being diverted past the monitoring equipment by a significant “lip” on the edge of the grassed waterway. A small berm was constructed into the cropped area before the 2018 monitoring season to remedy this, however a small percentage of runoff continued to miss being measured. Furthermore, in 2019, runoff began to carve a new route around the control drainage’s grassed waterway and bypass the flume once again. A plan is made for the farm manager to perform a major overhaul on the grassed waterway in 2020 to address this issue.
Nutrient and sediment loss summaries show variable results between the treatment and control fields. These will require further and deeper investigation to better understand, and will most likely require analysis on a single runoff event scale, not the entire monitoring season. Differences in measured benefits of prairie strips compared to the results at the NWR are likely due to other conservation practices (i.e., grassed waterways) already implemented in the fields.
As part of this project we were able to add additional monitoring sites beyond the original plan of three paired sites due to leveraging of funding from USDA-National Institute for Food and Agriculture, ISU College of Agriculture and Life Sciences and the USDA-Farm Service Agency to complete the monitoring at these sites. We also partnered with Dickinson County Soil and Water Conservation District and Lakeside Laboratory for monitoring at the Spirit Lake site. In addition, we partnered with the Iowa Soybean Association for monitoring at Whiterock with funding support from the USDA-Farm Service Agency. In addition to assessing surface water runoff and runoff water quality at these sites, with funding from the McKnight Foundation and USDA-AFRI we have been able to begin assessing the impacts of the prairie strips on sediment deposition; soil quality through measurements of particulate organic matter carbon and nitrogen, water stable aggregates, and soil bulk density; and shallow groundwater nitrate concentrations.
Samplers were deployed and enabled to collect data beginning March 22. On March 27, the samplers had to be to shut back down due to below-freezing conditions. Monitoring resumed in April 2018. Time-lapse cameras were installed in the flumes to capture flow at five-minute intervals. Five runoff events occurred this quarter. The team is summarizing results from this quarter as part of a final report.
The samplers were deployed and enabled to collect data on March 22. However, on March 27, freezing conditions forced the samplers to be shut down. Data collection will resume once temperatures consistently remain above freezing. Groundwater data from the Whiterock monitoring site has been analyzed. In 2016, there was one runoff sample collected from the control site (field without prairie strips), and no runoff samples from the treatment site (field with prairie strips). Using this single sample, estimates of the sediment and nutrient losses from the control site for the 2016 season are 3.139 lbs/ac of sediment, 0.0018 lbs/ac of nitrate – nitrogen and 0.0002 lbs/ac of dissolved phosphorus. No runoff samples were collected in 2017, so no nutrient or sediment loss estimates can be made.
Regular monthly site visits were made by the Iowa Soybean Association. The lack of precipitation precluded any further visits or any surface water samples. Tile water samples were collected every other week from both basins when flow was present. Samplers were retrieved from the site due to winter freezing conditions, and will be deployed again in spring 2018.
Regular monthly site visits were made this quarter by the Iowa Soybean Association. The lack of precipitation precluded any further visits or any surface water samples. Tile water samples were collected every other week from both basins when flow was present.
Regular monthly site visits were made this quarter. The lack of precipitation precluded any further visits or any surface water samples. Tile water samples were collected every other week from both basins when flow was present.
The two monitoring stations were set-up in March for the season, and monitoring will continue throughout 2017. Groundwater depth from ground surface and samples have been collected monthly, beginning in December 2016. The wells are 4.57 meters deep, and in December 2016, groundwater depth was below the bottom of all of the wells. Therefore, an arbitrary value of 6 meters was assigned for that month’s depth. Water quality data is being analyzed.
This quarter, the two monitoring stations consisting of flumes and autosamplers were maintained, and runoff was collected for two events. The Iowa Soybean Association continued weekly tile discharge monitoring, and samples have been submitted to the laboratory for analysis.
This project is monitoring surface water runoff quantity and quality on a prairie strips site at the Whiterock Conservancy. The two monitoring stations consisting of flumes and autosamplers were maintained, and there was one runoff event this period. The Iowa Soybean Association continued weekly tile discharge monitoring. These samples have been submitted to the laboratory for analysis.
This project is monitoring surface water runoff quantity and quality on a prairie strips site at the Whiterock Conservancy. Two monitoring stations consisting of flumes and autosamplers were installed this quarter. Monitoring began, but no runoff occurred during this period. The Iowa Soybean Association began weekly tile discharge monitoring, with samples submitted to the laboratory for analysis.
The objectives of this project are to monitor surface water runoff quantity and quality on a prairie strips site at the Whiterock Conservancy. Work in the first quarter of 2016 focused on sizing flumes and identifying field monitoring locations. Installation was scheduled to begin as soon as the 2016 weather allowed. Sampling will begin immediately after monitoring equipment is in place.
The objectives of this project are to monitor surface water runoff quantity and quality on a prairie strips site at the Whiterock Conservancy. The water quality benefits of three newly installed prairie strips will be evaluated, and project information shared through field days and presentations throughout the state. Work this quarter focused on identifying locations for the H-flumes, which will be used to sample the prairie strip field, plus a control field that does not have prairie strips. Flume installation will begin as soon as spring weather permits, and sampling will begin soon thereafter.