Could perennializing potholes reduce nitrate losses?

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Emily Heaton | Assistant Professor of Agronomy, Iowa State University

Are wet spots hot spots for nutrient loss? That is the question Steven Hall will be addressing in the ILF Webinar Oct. 17, and it is one that interests me greatly. What I really want to know is, if wet spots are hot spots, what can we do to cool them off? And boy with all the precipitation, 2018 was a great year to test these questions!

Steve Schomberg

Fig. 1 Steve Schomberg has miscanthus planted on a few hundred acres near Letts, IA. Miscanthus is being used to replace coal for heat and power on the UI campus. Miscanthus’ deep root system and abundant soil residue allows harvesting when bare soil is too wet for equipment. Photo credit: Emily Heaton

Steven is part of a team of researchers, extension specialists, farmers, and farm groups digging into the economic and environmental performance of farmed potholes. As Iowa State University’s Extension Biomass Crop Specialist, I help this team learn if we can improve profit alongside water and nutrient cycling by incorporating perennial biomass crops into farmed potholes.

So, what are biomass crops?

Biomass crops are those harvested for their whole above-ground biomass, not just grain or fruit. The only perennial biomass crops widely grown in Iowa today are forages such as (give examples), but that could change as plants are increasingly used to replace things we get from petroleum today. For example, the University of Iowa is replacing coal in their power plant with the perennial grass miscanthus (Miscanthus x giganteus), grown on ~2,500 acres in the Iowa City area (Fig. 1). The UI expects miscanthus to provide about 10% of the entire university’s heat and power load within the next few years.

As those of us rooted in the prairie Midwest know, perennials have deep root systems that hold soil and clean water. They also require less fertilizer and fossil fuels to thrive and only have to be planted one time! Because of this, their carbon footprint can be considerably lower than the annual crops we currently use for energy, like corn ethanol and soy biodiesel, and there is growing demand for them. Perennials also tend to be more resilient than annuals, including tolerating drought and flood stress that would kill an annual (Fig. 2).

flood stress

Fig. 2. Looking north (top) and south (bottom) at a farmed pothole on the ISU Sorenson farm July 3, 2018 (left) and Oct. 12, 2018 (right). The pothole flooded multiple crops (from top left in top photo: cool-season grass CRP, miscanthus, corn, miscanthus, soybeans, sorghum) multiple times this year. The soybeans and later the corn, were a complete loss. The perennial CRP survived and miscanthus thrived, due largely to growth habits and established roots. Photo credit: Emily Heaton and Nicholas Boersma.

With all this in mind, our team is asking the following questions:

– Could we get feedstock for low-carbon fuels and products by planting crops like miscanthus in farmed potholes?
– Can farmers make more money with a resilient perennial in potholes instead of corn/soy?
– Would planting perennials in potholes change the amount and quality of water leaving farm fields?

We are hoping to find the answer to these questions, and discover new questions to ask, in several experimental plots we’ve established near the ISU campus (Fig. 3) as parts of a USDA NIFA grant and a Dept. of Energy grant. We will be monitoring ponding depth, water quality, greenhouse gas emissions and crop growth in experiments with separated and controlled tile drainage systems (white lines in top left of Fig. 3) as well as in “natural” farmed potholes (red outlines). In both cases we will test both corn/soy and miscanthus, along with the annual crop sorghum, which seems more resilient to environmental stress than corn.

tile drainage systems

Fig. 3. New ISU experiments will assess perennial and annual crop impacts on potholes using controlled drainage experiments (top left; white lines are tile maps) and monitored potholes (bottom right, red lines are ponding outlines) near Ames, Iowa.

To learn more about this exciting research, listen to Steven’s webinar on Wednesday. I know Steve will welcome your questions or insights into what we are doing. And then, in a year or so, once the sites are really established and we have data to share, we will be having public field days. Keep your eyes on this blog to know when and where!

Emily Heaton

Edge of Field Practices Steal the Show

Participants at the August 9th field day in Spirit Lake were treated to burgers, information and one spectacular view.

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Over 50 people attended the Wetland, Saturated Buffer and Bioreactor Field Day hosted by Prairie Lakes Conference and Dickinson County Soil and Water Conservation District. They came to learn how edge of field practices like wetlands, saturated buffers and bioreactors are key to reducing nitrate loss from agricultural land in Iowa. However, they stuck around long after to take pictures and to discuss about how beautiful the project had turned out.

Chris LaRue of the Iowa DNR, and Heather Jobst of the Iowa Natural Heritage Foundation explained, “This is a perfect example of what happens when many partners come together with a shared vision, and stay unified.”

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Golfers can be seen in the distance playing a round at the Okoboji View Golf Course.

One key stakeholder who participated in the wetland restoration project was the Okoboji View Golf Course, which sits right behind the project.  Staff from the golf course led a discussion about their experience and the economic upside to the project.

“We have actually seen an increase in our business as a direct result of the project. It is very beautiful to be out here,” explained a staff member.

The Spirit Lake restoration project really is the perfect example of public and private stakeholders coming together with a shared goal. It is also a great example of a project bringing urban and rural issues together.

It’s a win-win for everyone involved, especially the lake.

~Nathan Stevenson

 

 

Water in the Public Domain

Public domain: a concept that evokes thoughts of music, photographs, paintings, and other creative works of art … and their relationships with copyright policy. From another perspective, public domain is all about shared availability, the common good …  much like our natural resources.

As nearly 40 people gathered for a conservation field day at Paustian Family Farm just outside Walcott, IA this past week, this idea of water in the public domain was an ever-present undercurrent in the conversations among area farmers, landowners, rural and urban residents alike.

In addition to in-field conservation practices like reduced tillage, cover crops, and a close eye on nutrient management, host farmer Mike Paustian is now taking conservation to the edge of the field as well. In fall 2017, the Paustians installed a saturated buffer on their land to specifically address the challenge of nitrates in tile drainage water.

Saturated buffers are a field-scale practice, treating subsurface tile drainage water from 30-80 acres of cropland. The presence of an existing streamside vegetative buffer is a great first step, and makes the installation a breeze. In order to “saturate” the existing buffer, a flow control structure and lateral tile line running parallel to the stream (700’ long, in this case) are installed.

Quite a bit of the water then moves through that new perforated tile line parallel to the stream, slowly trickling out of the tile, working its way through the soil. On this journey to the stream, the water is in direct contact with plant roots and the soil itself – where the biological process of denitrification occurs. Under saturated, anaerobic conditions, naturally occurring bacteria breathe in the nitrate, and then transform it to atmospheric N2 gas, sending cleaner water to the stream (to the tune of 40-50% nitrate reduction).

As folks got to see the saturated buffer firsthand, one of the attendees asked Paustian, “As a city person, why should somebody from Davenport, Pleasant Valley, etc. care about what’s going on out here?”

Paustian responded, “We’re all in this together, using the same water. It’s a limited resource. We’ve got to find common ground – urban and rural – being good stewards of our land and water. That’s why saturated buffers matter out here.”

Washington Co. farmer Steve Berger, an early adopter and long-term user of cover crops, emphasized the benefits of cover crops for water quality, promoting infiltration and likewise minimizing soil erosion.  Berger added, “Anything that comes off this field ends up in the public domain somewhere … long-term no-till and cover crops are working together to keep soil and nutrients in place in the field!”

As Iowa’s water quality continues to garner attention locally, statewide, and even on the national level, that concept of water in the public domain resonates strongly. Bringing urban and rural people together to see how we can work for positive improvements in water quality is a step in the right direction. This field day was an excellent example of the engaging conversations and positive dialogue we at Iowa Learning Farms hope to facilitate surrounding water quality, soil health, and our agricultural production systems across the state of Iowa.

Ann Staudt

How will nitrogen reductions economically benefit Iowa?

chuan tangWatch the Iowa Learning Farms webinar on July 18 at 12:00 p.m. with Dr. Chuan Tang to learn how he and his fellow researchers are examining the economic benefits of nitrogen reductions in Iowa through the exploration of the costs of high nitrates and how meeting the Iowa Nutrient Reduction Strategy goals will be beneficial for all Iowans.

Dr. Chuan Tang, postdoctoral research associate with the Center for Agriculture and Rural Development, is exploring the costs of high nitrates in Iowa’s drinking water sources including public water supply systems and private wells. The study also analyzes the recreational benefits of meeting Iowa’s Nutrient Reduction Strategy targets.

“The state of Iowa is currently grappling with designing the best policies to address nitrate pollution in the state. This webinar will discuss an important aspect of this discussion – the benefits of nitrate reductions to all Iowans,” commented Dr. Tang.

Don’t miss this webinar!

DATE: Wednesday, July 18, 2018
TIME: 12:00 p.m.
HOW TO PARTICIPATE: Log on as a guest shortly before 12:00 p.m.:
https://connect.extension.iastate.edu/ilf/ 

More information about this webinar is available at our website. If you can’t watch the webinar live, an archived version will be available on our website: https://www.iowalearningfarms.org/page/webinars.

Webinar Recap: Dan Jaynes Provides Updates on Saturated Buffers

Dan Jaynes, Research Soil Scientist with the National Laboratory for Agriculture and the Environment (USDA-ARS), hit the high points on saturated buffers last week in the latest Iowa Learning Farms webinar. Watch the archived version now.

Saturated Buffer Effectiveness and Price Per Pound of N Removed
Saturated buffers can divert about half of the water coming out of a tile outlet (red bars). From this diverted water, the practice can remove between 8-84% of N (blue bars). Saturated buffers costs about $1 per pound of N removed. The practice ranks similarly to other nitrate reduction edge-of-field practices. A comparison table is shown below.

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Recent Updates to the Conservation Practice Standard
See the most recent conservation practice standard for a saturated buffer here. Watch the presentation to hear the discussion on specific changes.

Saturated Buffer Design
Saturated buffers should be designed to treat 5% of the drainage system capacity, or asDesign much as is practical based on the available length of the vegetated buffer. To determine the drainage system capacity, use this excellent tool from the Illinois NRCS. Option 1 (determining capacity using slope and diameter) is the most common option used if limited information is available on the drainage system.

Frequently Asked Questions You Should Know
If you field questions from producers about saturated buffers, make sure you know the answers to these commonly asked questions. Dan covered his list of FAQs:

  • Are we trading a water quality problem for an air quality problem?
  • Does denitrification account for all of the nitrate lost?
  • How wide should the buffer be?
  • What should the buffer vegetation be?
  • What about multiple distribution pipes?
  • What about roots plugging distribution pipes?

Roots Plugging Distribution Pipes
On the issue of whether roots plug distribution pipes, Jaynes says that, generally, the answer is no. For a more in-depth look, here is a great video of a look inside a saturated buffer distribution pipe.

To learn more about site suitability for saturated buffers in your local area, explore the ACPF Saturated Buffer Viewing Tool. The suitability of an area in central Iowa is included below. This can be a great tool to determine potential saturated buffer sites (followed by a trip to ground-truth site conditions).

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If you want to learn the latest information about saturated buffers, tune in to the archived webinar!

Julie Winter

Update on Saturated Buffer Research and Installation Standards

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Watch the Iowa Learning Farms webinar on April 18 at 12:00 p.m. to learn more about the latest research, installation standards and best management practices for saturated buffers. Dan Jaynes, Research Soil Scientist with the National Laboratory for Agriculture and the Environment (USDA-ARS), will share research results from several saturated buffers and will cover some of the recent changes in the practice standard. Don’t miss it!

DATE: Wednesday, April 18, 2018
TIME: 12:00 p.m.
HOW TO PARTICIPATE: Log on as a guest shortly before 12:00 p.m.:
https://connect.extension.iastate.edu/ilf/

More information about this webinar is available at our website. If you can’t watch the webinar live, an archived version will be available on our website: https://www.iowalearningfarms.org/page/webinars

Julie Winter

“Chipping Away” at What We Don’t Know About Bioreactors

LauraLast week, Dr. Laura Christianson joined us for our monthly Iowa Learning Farms webinar. Christianson has nine years of experience focused on agricultural drainage water quality and denitrification bioreactors for point and nonpoint nitrogen treatment.

Bioreactors: What We Know

Laura’s experience with bioreactors over the past nine years has led her to study bioreactors with many shapes, sizes and designs. She authored in a meta-analysis on bioreactors that synthesized existing research.

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For bioreactor basics, the meta-analysis found that bioreactors can remove an average of 25-45% of the annual N load leaving a field, although a range of 10% to 100% of N load reduction has been seen. The cost of a bioreactor that treats 50 acres was approximately $10,000. The analysis also found that woodchips in a bioreactor can last approximately 10 years, but a range of 7-15 years has been seen. The woodchips need to be changed not because the bioreactor is running out of a carbon source, but because woodchip degradation causes hydraulic performance decline within the bioreactor. The meta-analysis also investigated different factors that impact nitrate removal effectiveness in a bioreactor. Some of these factor are:

Hydraulic retention time
Water should be retained within a bioreactor for a minimum of six hours. Great visuals and an explanation are covered in the webinar.

Water temperature and age of bioreactor

Water tempWater lower than 43 degrees F affect nitrate load reduction potential. In the first year, bioreactors are incredibly efficient at N load reduction as microbes begin to feast on available carbon and dissolved oxygen in the water. However, Laura says, “Once your bioreactor is more than a year old, that’s when you really settle in to know what your long-term nitrate removal performance is going to be.”

Porosity of the woodchips
wood_creditThere was no significant difference in N removal when using different types of wood (hardwood vs. softwood) in a bioreactor. However, the physical properties of the wood matter. Use chips with particles size between ½ inch and two inches instead of shredded or mulched wood.

 

Bioreactors: The Future

Future research on bioreactors is moving us beyond the first generation of bioreactors.

Bioreactors with bafflesbaffles_credit
Plastic baffles in the bioreactor route the water through the woodchips so all woodchips are utilized in the denitrification process.

 

Paired_creditPaired bioreactors
Two bioreactors are installed side-by-side. One serves as the primary bioreactor, and bypass water from the primary bioreactor is routed to a second bioreactor to continue N removal on bypass water that would normally not be treated.

in-ditch_creditIn-ditch bioreactors
For areas with ditch drainage, the bottom of the ditch is excavated, woodchips are placed, and wooden check bands are installed incrementally throughout the length of the treated ditch bed.

 

PfilterBioreactors paired with
phosphorous-absorbing filters

Water is routed through a phosphorous-absorbing filter prior to its entry into the bioreactor.

 

If you would like to brush up on your bioreactor knowledge, don’t miss this webinar!

Julie Whitson