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


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.

yield results

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.
nitrate reduction

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?


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

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.: 

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:

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.


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.


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 (

Jake Hansen

Lessons Learned from Farmer Interviews of the Lyons Creek Watershed Project

Today’s guest post was provided by Steve Hopkins, Nonpoint Source Coordinator with the Iowa DNR’s Watershed Improvement Section.

The University of Northern Iowa’s Center for Social and Behavioral Research recently completed a study of farmers and stakeholders involved with the Lyons Creek Watershed Project about the farmers’ participation in the project and their attitudes toward adopting conservation practices.  The study was a post-project evaluation done at the end of the Lyons Creek Watershed Project, administered through the Hamilton County SWCD in north central Iowa.

The primary goal of the watershed project was to reduce nitrate levels in Lyons Creek, which has the highest nitrate levels of all of the tributaries of the Boone River.  The Boone River is a tributary of the Des Moines River, which is a source of drinking water for the city of Des Moines.


Despite the fact that the primary goal of the project was to reduce nitrate levels, and that the project coincided with the release of the Iowa Nutrient Reduction Strategy, the project fell short of its goals due to a lack farmer participation and adoption of nitrate-reducing practices.  The purpose of the study was to find out why.

The study, based on in-depth interviews with farmers and project stakeholders, found both positive and negative factors related to farmer participation in the watershed project:



The study included recommendations for future watershed projects, including providing funding for a full-time project coordinator, involving farmers early on in project planning, and making project goals clearer.

UNI will be presenting the results of the study at the 2017 Iowa Water Conference in March.

This study, funded by Iowa DNR with EPA Section 319 funds, is available on the DNR Watershed Improvement webpage under “Watershed News” at

Steve Hopkins


Q & A with Matt Helmers on Nitrate Reduction and Drainage

By popular demand Dr. Matt Helmers set out to address some of the common questions, and sometimes misconceptions, about nitrate loss and drainage in this month’s Iowa Learning Farms webinar.  Helmers is the Dean’s Professor in the College of Agriculture and Life Sciences and Professor in the Department of Agricultural and Biosystems Engineering at Iowa State University.

Although the questions are straightforward, the answers are not as simple as yes or no.  Helmers uses research from his team, as well as other researchers in the Midwest, to provide the best available answers to the very complex questions of water quality. Watch the full archived webinar on the Iowa Learning Farms website.

Here is a sampling of the questions (and summarized answers):

 Q. Is Elevated Nitrate Primarily a Nitrogen Rate Problem?

A. Nitrogen rate management is the first place to start, but it is not enough on its own to reach our goals established by the Iowa Nutrient Reduction Strategy.  Moving from 150lb N to the Maximum Return to Nitrogen (MRTN), or economic efficiency of nitrogen, results in about a 9% reduction in nitrate loss. A necessary step on the path of meeting our goals of 41% from non-point sources!

Q. How Does Nitrate Leaching Vary From Year to Year?

A. Precipitation plays a large role in how water moves through the soil profile and the loss of nitrates. Under consistent N-rates, research data shows in years with lower precipitation a higher concentration of nitrates (which is the measurement used to determine water quality e.g. 10 mg/L is the standard for drinking water).ilf-webinar-10-16

Q. Do Cover Crops Really Reduce Nitrate Loss?

A. Yes – 34-36% reductions were observed when a cereal rye cover crop was drilled following crop harvest near Gilmore City in North Central Iowa.  This reduction is a conservative estimate as the nitrate loss reduction has been shown to improve with more cover crop growth (achieved with an earlier planting date).

Q. How Do We Reach Our Goals?

A. We need it all – nitrogen management, cropping practices and landuse changes, and edge of field practices like wetlands, bioreactors and more!


Credit:, USDA National Institute of Food and Agriculture

Q. What’s New on Drainage?

A. Keep an eye out for the new practice – drainage water recycling.  The practice looks to store spring drainage water for use later in the growing season and has the potential to also aid in nitrate reduction.

Be sure to watch the full webinar on our Webinar Archives page to check out remaining questions and more information on the hydrologic impacts of drainage on our landscape.

Tune in next month…
The next Iowa Learning Farms webinar will be Wednesday, November 16 at 1:00 p.m., featuring our own Ann Staudt digging into our newest cover crop project – earthworms!

Liz Juchems

Working Together – Nutrient Reduction Practices and Tax Implications

A recent post by the Center for Agricultural Law and Taxation shed some light on the tax implications of various water quality measures including those addressing nitrogen reduction. Read the original version here.

Using the Iowa State University Publication, Reducing Nutrient Loss: Science Shows What Works as a guide, they reviewed a few common practices for their tax consequences and provided the general overview below.

Cover Crops
Cover_crop_April_Berger_FarmOne of the key strategies for reducing nitrate concentration in row crop farm ground is to plant cover crops. If a farm operator plants cover crops, they may deduct the cost of the seed and/or fertilizer as a trade or business expense in the year they plants the cover crop.[i]

            Cost Share: Often, cost sharing programs are available to fund these practices. If a farmer receives an EQIP payment, for example, to cover the cost of the cover crops, that payment would be treated as ordinary income, subject to self-employment tax. Cost-sharing payments are only eligible for income exclusion under the tax code if the payment is not associated with a deductible expense.[ii]

Conservation Reserve Program (CRP)
Another option for improving water quality is to enroll targeted lands in CRP. Under this program, farm operators or landowners receive annual payments for contractually agreeing to keep enrolled acres out of production. CRP payments are typically reported as Schedule F Income, subject to self-employment tax. (more information)

             Cost Share: Cost-share payments received under the CRP may be eligible for income exclusion to the extent permitted under IRC §126 (see full article).

Conservation Easements
Conservation easements can be an effective method of enhancing or maintaining water quality. These binding agreements implementing permanent land use restrictions can be purchased or donated or they may be implemented through a combination of both.

A purchased easement would include a Wetland Reserve Easement purchased by the Natural Resources Conservation Service (NRCS). Permanent and 30-year easements are treated for tax purposes like a sale of the property.

  • The landowner would reduce his or her basis in the property in the amount of the purchase price of the easement.
  • Any amount below zero would be IRC § 1231 gain reported on Form 4797. It is taxed at long-term capital gains rates as long as the property was owned for more than one year.
  • Easement payments offered for easements in place less than 30 years are taxed as ordinary income.
  • Easement payments are not subject to self-employment tax.
  • Easements granted for 30 years or more can qualify for like-kind exchange treatment under IRC § 1031.

Landowners can also donate conservation easements for the purpose of improving water quality. Such an easement, for example, might allow for the implementation of a wetland on a portion of current crop ground.  If tax code requirements are met, the landowner can claim the deduction as a charitable contribution and recognize significant tax savings. This is a complex area of tax law that requires the assistance of an experienced tax practitioner.

Saturated Buffers, Diversion Ditches, Filter Strips, Grade Stabilization, TerracesDSCN9206
Active farmers may be able to presently deduct the cost of conservation practices implemented as part of an NRCS (or comparable state)-approved plan.

Farmer Landowners:
The IRC § 175 soil and water conservation deduction (which is taken in the year the improvements are made) can be elected for conservation expenditures in an amount up to 25 percent of the farmer’s gross income from farming. The deduction can only be taken for improvements made on “land used for farming.” Excess amounts may be carried forward to future tax years.[ix]

Non-farming landowners:
Those who cash rent their ground) must capitalize these expenses (add the cost of the improvement to the basis of the property) because the IRC § 175 deduction only applies to taxpayers “engaged in the business of farming.”

           Cost share: Cost sharing or incentive payments received to implement these conservation programs would be taxed as ordinary income.

Drainage Water Management
Drainage tile modifications or installations are generally depreciable over a 15-year period. This should include the cost of most water control structures that are part of the system and the cost of the installation. Farming operators would also be eligible for IRC § 179 expensing and 50 percent bonus depreciation for the cost of new tile installation. Non-farming landowners could also depreciate the cost of the drainage tile improvements over a 15-year period. Although they would not be eligible for IRC § 179 expensing (since they are not in the business of farming), they would be eligible for 50 percent bonus depreciation for the cost of new tile.

            Cost share: Cost sharing or incentive payments would be taxed as ordinary income, unless determined to be excluded from income under IRC § 126. This might be especially useful for non-farming landowners not eligible for IRC § 179 expensing.

Stout bioreactor_installationBioreactors have become a very popular tool for removing significant amounts of nitrates from water passing out of a drainage tile system. These structures can cost thousands of dollars and don’t increase production or otherwise improve the bottom line of a farming operation. As such, economic incentives to implement bioreactors are particularly important.

A bioreactor does not show up on any MACRS table. It would likely be depreciated over a seven-year period. Materially participating producers installing a bioreactor would be eligible for Section 179 and 50 percent bonus depreciation. Non-farming landowners could likely depreciate the cost of the bioreactor over a 7-year period (as equipment) and would be eligible for 50-percent bonus depreciation.

           Cost share: Cost sharing or incentive payments could likely be excluded under IRC §126.This might be especially useful for non-farming landowners not eligible for IRC § 179 expensing.

To read the full article visit For questions, contact the author Kristine Tidgren at 515-294-6365 or

Liz Juchems