Five-Year Cover Crop Mixtures Study: Significant Nitrate Reduction and Unchanged Crop Yields

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The results of a five-year study conducted by the Iowa Learning Farms, Iowa State University Extension and Outreach and Practical Farmers of Iowa, reinforced that cover crops added to a corn-soybean rotation have no negative effect on yield and result in statistically significant reductions in nitrate concentration in subsurface water. The details of the study are included in a brand new infographic now available for download.

Throughout the 22 site-years of yield data, there was no significant difference in cash crop yields between control strips without cover crops and those planted with cover crops. Is it important to note that planter settings may impact yield if not properly managed to accommodate residue from the cover crops.

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Iowa soils are highly vulnerable to nitrate losses between April and June when natural nitrate production exceeds typical crop demands. The analysis of water samples from those three months, showed a statistically significant reduction in nitrate concentration in the cover crop strips.
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We are really excited to see this significant reduction in nitrate concentration when cover crops are present, as addressing nitrate levels is a key component to reaching our Iowa Nutrient Reduction Strategy goals.

Project MapSince this project had locations located throughout the state, we were able to see how the different cover crop species performed in different soil regions and weather patterns. We observed consistent establishment and biomass production of the rye and oats at all sites and gained the largest reduction in nitrate concentration from those single species treatments. Rye and oats provided the most biomass and had the lowest cost of establishment, helping make them the top choice for cover crops in Iowa!

The infographic is available online at the ILF website. Funding for this study was provided by NRCS Conservation Innovation Grant and Leopold Center for Sustainable Agriculture.

-Liz Juchems

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).

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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.

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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

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

Webinar Recap: Exploring Economic Benefits of Nitrogen Reductions in Iowa

On July 18th, Dr. Chuan Tang, postdoctoral research associate with the Center for Agriculture and Rural Development (CARD), joined us for our monthly webinar series to  discuss an ongoing project looking to provide economic valuation to the benefit of reducing nitrate in Iowa’s water.

The economic costs of nutrient pollution are relatively well known, but to develop good policy directed at reducing nutrients in our waters it is important to estimate the economic benefits too.  To help provide policy makers this important resource Dr. Tang worked along with Dr. Gabriel Lade, Assistant Professor in the Department of Economics at ISU, Dr. David Kaiser, Assistant Professor in the Department of Economics at ISU and the head of CARD’s Resource and Environmental Economics division, and Dr. Catherine Kling, former CARD Director to conduct this study. Together they divided the benefits into three categories:Slide9During his presentation Dr. Tang explored each of these categories more closely, but here are a few highlights –

  • About 90% of Iowans receive their water from a public water supply system that are monitored for nitrate levels. Of those systems – 55% rely on groundwater and 45% on surface water sources.
  • The remaining 10% use private wells. Private well users can contact their county health department to receive free test supplies to monitor the health of their water supply.
  • Lakes and other water bodies provide an estimated $30M each year in recreational benefits.
  • In addition to acute health impacts like Blue Baby Syndrome, health researchers are examining the chronic issue from long term exposure to high nitrate levels.

Be sure to watch the archive version of the webinar for more information and check out the related publication “Economic Benefits of Nitrogen Reductions in Iowa“.

Liz Juchems

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 highlights cover crop, water quality connections

In case you missed it, this past week’s Iowa Learning Farms webinar offered an excellent overview of the research findings related to the potential of winter cover crops to reduce nitrate leaching in corn and soybean cropping systems. Dr. Tom Kaspar, plant physiologist with the USDA-Agricultural Research Service, shared results from numerous studies that show the ability of cover crops to reduce nitrate concentrations and loads in tile drainage water.

The press headlines about nitrates and water quality are seemingly ubiquitous, and Kaspar provided solid data that help to paint a complete picture of the challenges and opportunities. Our land uses have changed dramatically, and over the past 60-70 years, our cropping systems have likewise changed dramatically with significant reductions in small grains, hay and perennial vegetation.  With corn and soybeans having a 7-month brown gap when they are not actively uptaking nutrients, that leaves a significant amount of time with nutrients vulnerable to leaching.

However, Kaspar’s research clearly demonstrates that cover crops help transition that brown gap to a green gap, providing the ability to “capture” nutrients in the soil that would otherwise be vulnerable to leaching loss. One of Kaspar’s long-term research studies in central Iowa found that rye cover crops in a corn-soybean cropping system reduced nitrate concentrations in tile drainage water by 57%. Additional studies by Kaspar and collaborators around the state found nitrate reductions of anywhere from 20% to 40%. This variability is expected, with different amounts of cover crop growth, weather, rainfall, soil types, tile systems, and field histories.

Kaspar also pointed out that it takes quite some time for nitrate to move through the system – there is a noticeable lag effect.  For instance, Kaspar and collaborators found that nitrate concentrations in subsurface tile drainage continued to decrease through the summer, long after spring cover crop termination.

Check out the full webinar, Lessons Learned from Using Cover Crops to Reduce Losses of Nitrate for 15 Years, on the Iowa Learning Farms webinar archives page.  And to hear more perspectives from Dr. Kaspar, tune in to Episode 06 of the Conservation Chat podcast!

Ann Staudt

Iowa CREP Wetlands

Today’s guest post is by Jake Hansen, Chief of the Water Resources Bureau Division of Soil Conservation & Water Quality at Iowa Department of Agriculture and Land Stewardship (IDALS). 

The Iowa Conservation Reserve Enhancement Program (CREP) is a joint effort of the Iowa Department of Agriculture and Land Stewardship (IDALS) and USDA’s Farm Service Agency, in cooperation with local soil and water conservation districts (SWCDs). The program provides incentives to landowners to voluntarily restore shallow, semi-permanent wetlands in the heavily tile-drained regions of Iowa to improve surface water quality while providing valuable wildlife habitat and increased recreational opportunities.

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The goal of the program is to reduce nitrogen loads and the movement of other agricultural chemicals from croplands to streams and rivers by targeting wetland restorations to “sweet spots” on the landscape that provide the greatest water quality benefits. CREP wetlands are positioned to receive tile drainage by gravity flow; they remove nitrate and herbicides from the water before it enters streams and rivers. Excess nitrogen not only affects Iowa’s waters but is also one of the leading causes of hypoxia in the Gulf of Mexico. CREP wetlands are one strategy to help reduce nitrogen loading to those waters.

Targeted results. To ensure that wetlands are sited in the most advantageous locations, IDALS uses advanced geographic information system (GIS) analyses to find locations that are properly sized and situated to provide large nitrogen removal benefits. The CREP wetland criteria are based on over two decades of research and monitoring conducted by Iowa State University.

This research and monitoring has demonstrated that strategically sited and designed CREP wetlands remove 40 to 70 percent of nitrates and over 90 percent of herbicides from cropland drainage waters. Nitrogen reduction is achieved primarily through the denitrifying bacteria that occur naturally in wetlands. Through denitrification, the bacteria remove nitrate from the water and release it into the air as nitrogen gas (N2), an innocuous end product.

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The highly targeted nature of this program has led to 83 wetlands currently restored and another 12 under development. During their lifetimes, these wetlands are expected to remove more than 100,000 tons of nitrogen from 122,350 acres of cropland. In 2016 the number of restored wetlands reached an annual capacity of removing over 1,300,000 lbs of nitrogen. These 95 targeted restorations total more than 891 acres of wetlands and 3,100 acres of surrounding buffers planted to native prairie vegetation.

More than nitrogen removal. Even with the impressive results so far, Iowa continues to explore and develop new technologies to optimize wetland performance by incorporating additional considerations for habitat, hydraulic efficiency, and temporary flood storage benefits. CREP wetlands are already providing high-quality wildlife habitat and recreational opportunities in addition to water quality benefits. Studies conducted by USGS have shown dramatic increases in the presence of several frog species at CREP wetland sites. The high-quality buffers, in conjunction with the shallow wetland habitats, have proven to be a tremendous boon to a multitude of wildlife species commonly found in these areas. Populated by birds ranging from trumpeter swans to shorebirds, these areas have shown that targeting wetland restoration for water quality benefits does not come at the expense of mutual habitat and recreational benefits.

To see additional photographs of CREP wetlands across Iowa and to read more about the program, click here (http://www.iowacrep.org).

Jake Hansen