17. Ben Gleason – Soil Health Awareness is ‘Mission Accomplished’ at IA Corn

Iowa Corn has several major goals that drive programs and projects for their sustainability platform:

  1. Protect and improve the land, water, and natural resources
  2. Minimize regulations on farmers that could potentially reduce profitability
  3. Maintain farmers’ social license to operate
  4. Be a leader in sustainability, making sure that sustainability is a part of all programming

Ben Gleason, Sustainable Program Manager for Iowa Corn, gets the opportunity to work for Iowa farmers on all of these goals, leveraging partnerships with different stakeholders to move the needle on sustainability in the agriculture industry.

One area he is focusing on is reduced tillage. Tillage changes are one opportunity for farmers to impact on-farm sustainability and have become more prominent as awareness increases. Gleason says the state isn’t all no-till by any means, but is seeing strip-till gain in popularity as it is often “the best of both worlds” – tillage where you need it and residue everywhere you don’t.

Regarding cover crops, Gleason said, “We have seen a big, big jump in cover crops, which is fantastic. We went from virtually zero acres to about two million acres. I think we’ll be well over that this year with an early harvest that will allow more cover crop acres to get seeded.”

Iowa farmers are also experimenting with other practices, like nutrient reduction wetlands, which Gleason says are effective to manage nitrogen loss.

“We’re making progress. We have got a long way to go. Obviously, our water quality issues didn’t pop up overnight, so we’re not planning to solve them overnight either. But we have got a lot of momentum going, and we would like to keep it that way,” he said.

Iowa Corn also has a history of connecting Iowa farmers with the Soil Health Partnership, with both organizations really stressing farmer-to-farmer, peer-to-peer learning. They believe that works best.

“Soil health awareness is huge now. I think that mission is accomplished. [Soil health is] part of the decision-making process now, I believe,” he said.

Learn more about Iowa Corn’s specific water quality and sustainability programming, as well as how they are facilitating farmer-to-farmer learning during a global pandemic, by clicking on the player above or listening to The People of Soil Health in your favorite podcast player.

Livestock Manure’s Role in Soil Health

Livestock manure is known to provide valuable nutrients to the soil. And, if managed correctly, it can also provide additional benefits by improving the soil’s biological, chemical and physical properties.

How livestock manure affects soil health

Manure is composed of four main components: carbon, nutrients, microbial life, and water.

Livestock manure is mainly composed of carbon compounds that have been broken down by the animals’ digestive tracts. Carbon that is incorporated into the soil profile improves many soil health indicators, such as water holding capacity, nutrient cycling, and raising and/or buffering soil pH. 

While many plants and animals can survive at different ranges of pH, it is still important to maintain soil pH values between 6-8 so that soil nutrients are available. Manure has been found to have a liming and buffering effect, which can benefit crops growing in acidic soils.

Manure in the soil also increases the cation exchange capacity, which affects soil’s ability to hold onto available nutrients. Increasing soil carbon through manure adds available sites in the soil where nutrients can bind and be made available to crops throughout the growing season. This increases nutrients in the soil; though, it’s important to note, not all nutrients found in manure are immediately available and some may need to be broken down by microbes or chemical transformation in order to be taken up by plants. 

Most importantly, manure is an important part of recycling nutrients. Livestock that eat and digest the grain or leaf tissues are removing nutrients from the soil. When that manure is applied to the soil, many of those nutrients are returned. This increases soil biological activity by introducing new and important microorganisms from manure, as well as animal saliva while the animal is grazing. Nutrients from manure (when applied correctly) can also mean growers are spending less money on commercial fertilizers.

How to assess the value of manure to your soil

  • Get your manure tested. Nutrient values differ between species, as well as where it’s pulled from in the lagoon or pile. Most universities or state organizations have manure recommendations for this information.
  • Estimate the cost of commercial fertilizer and compare it to the amount of micro- and macronutrients you applied to your soils. Remember, most manure nutrients are not immediately available in the first year and so it will benefit you for up to two years after application!
  • Calculate rates of removal from row crops to know how much manure you need to apply, as well as to know whether you are applying for N or P needs (this is state-specific). Always follow state and local legislation around manure management.
  • Avoid high-risk areas that may impact groundwater or wetlands. We want to improve soil health, but not at the cost of harming other systems. 
  • Incorporation of manure prevents N volatilization (gaseous losses), which gives you more N available for crops but can impact soil aggregation. There is new and existing research looking at what is the best method of application for manure – whether injected, incorporated, or broadcasted – so be sure to do your homework and consider your farm’s available resources (e.g., equipment) to determine the best approach.

Cover Crop Lessons from an Iowa Farmer: Take Your Time

When Roger Zylstra and his son Wesley started experimenting with cover crops on their central Iowa farm in 2014, they weren’t exactly sure what to expect. They had a goal to improve stewardship of their land and resources but, at the time, didn’t really know where that would take them. Their experiment – cereal rye before soybeans – seemed to be yielding benefits, but they wanted more hard data. So, in 2015, Roger enrolled in an SHP cover crop trial to better understand the impact of this management practice on their farming operation.

Roger and Wesley’s experience with SHP is detailed in a new business case, sharing where they started and what they have learned after conducting their trial for five years. Below are some of the Zylstras’ key learnings. Dig into the full business case to find out more.

Build Soil Health in a Way That Works for Your Farm

In addition to growing corn and soybeans, they also raise hogs on the Zylstra farm. The incorporation of livestock makes manure an important source of nutrients for their cash crops, and it was something Roger and Wesley considered when choosing to implement cover crops.

“We’re working to continue to be competitive with our yields, while striving to improve the health of our soil,” Roger said. “Because we have swine and fall-apply the manure, we think cover crops really help sequester the nitrogen to the soil.”

They chose cereal rye as their cover crop species specifically because of its ability to withstand disturbance caused by injecting manure, recognizing that it bounces back quickly with minimal impact to the stand. Cereal rye also overwinters well, which provides ground coverage and nutrient uptake throughout the fall and spring.

It is Okay to Make Changes Over Time

Roger knows how easy it can be to want to make all the changes at once, but his experience with SHP taught him that it can be valuable to make incremental shifts – evaluating your results and then adapting accordingly.

Here are just a few of the things that have changed in the Zylstras’ approach since 2015:

  • Eliminated use of fall anhydrous and incorporated spring pre-plant and sidedress applications
  • Adjusted cover crop seeding rates
  • Experimented with different methods of cover crop seeding (switching to drilling for a few years before returning to spreading/incorporation with vertical tillage)
  • Moved to 100% liquid application of fertilizer
  • Experimented with planting green

Each of these adjustments from year-to-year allowed them to dial in their system in a way that best met their unique needs around labor, time, and equipment resources. You can read more about the specific reasons for these changes in their business case.

Small Changes Add Up to Real Benefits

By staying committed to building soil health, making incremental changes, and experimenting with different approaches, the Zylstras have seen real benefits to their farming operation. Some of the biggest takeaways include: 

  • Improved nutrient use efficiency – By changing the sources and timing of nitrogen application, they see greater utilization by the crop and reduced leaching of nutrients into the waterways. According to Roger, “We use about the same amount of nitrogen per acre as we did many years ago, but our average [corn] yields have grown from 140-170 bu/acre to 170-200 bu/acre.
  • Increased microbial activity – Results from soil health testing on their SHP field shows that respiration (an indicator of microbial activity) has increased significantly on the cover cropped portion of the field, aiding in an improved rate of residue turnover on those acres.
  • Improved soil structure – The Zylstras credit improvements in soil structure with reducing soil surface compaction during the wet years of 2018 and 2019. In comparison to nearby farms (who faced standing water and ruts in the field), Roger and Wesley experienced fewer equipment tracks and less ponding. At times, it has also allowed them to get into the field a day or two earlier during planting and harvest. 

Digging In

When it comes to building soil health, no two farms are exactly the same. However, there are things we can learn from each other as we experiment, adapt, and experience success. Farmers who leverage manure as a primary source of nutrients can see from the Zylstras’ SHP program one way to implement cover crops and things to take into consideration when getting started. And, no matter what your system looks like, Roger’s advice to take it day-by-day and season-by-season – adjusting your practices over time to find the approach that works best for you and your farm – is something we can all learn from.

Iowa farmers incorporate cover crops into nutrient management strategy

Roger Zylstra and his son, Wesley Zylstra, on their Central Iowa farm

Business Case: Roger and Wesley Zylstra

Farmer Profile

  • Working with SHP since 2015
  • Experimenting with cover crops on their SHP research field
  • Total farmed area is 700 acres
  • Planting corn-soybean or corn-corn rotations
  • Using swine manure and spring/in-season nitrogen applications

Seven years ago, Roger and Wesley Zylstra set out to improve stewardship of their land. By paying attention to their nutrient management and incorporating cover crops, they started down the path of adapting their management system to meet soil health, yield and economic goals.


The Zylstras farm 700 acres in Central Iowa on primarily silt loam soils. They grow corn and soybeans, and their land is typically in a corn-soybean or corn-corn rotation. Roger and Wes also raise hogs on the farm, and swine manure provides an important source of nutrients for their cash crops.

When they started down the path of improving stewardship in 2014, the Zylstras were relying on fall-applied manure and anhydrous to meet the needs of the growing cash crop in the spring. They were interested in trying cover crops, but knew they would need to consider changing the source and timing of their nutrient applications if they were going to adapt their management system. Average farm-level corn yields in 2014 were around 170-190 bu/acre.

Crop management changes on the Zylstra farm

Cover crop trials began
  • The Zylstras used manure application and fall anhydrous until 2014.
  • On their own, they tested 12 acres of cover crops in 2014.
Cover crops on all soybean acres 
  • The Zylstras joined SHP to trial cover crops on one field in 2015.
  • They planted cover crops on all soybean acres using a broadcast spreader and incorporated cover crop seed with vertical tillage.


First year drilling cover crops
  • In 2016, they drilled cover crops to get better seed-to-soil contact and moisture availability.
  • The Zylstras timed nutrient application to meet cash crop needs with pre-plant and sidedress nitrogen (eliminated fall anhydrous).
Dialed in their system
  • The Zylstras adjusted cover crop seeding rates and methods in 2017.
  • During this season, they planted 70-90% of their acres to cover crops.
Determined best practices for their farm
  • In 2019, the Zylstras added liquid P and K to the planter & added zinc to their starter to further support yields.
  • They returned to broadcast-seeding cover crops and incorporating with vertical tillage, due to maintenance and time constraints.
Advanced soil health practices
  • In 2020, the Zylstras met their goal of eliminating dry fertilizer.
  • Due to weather, they attempted planting soybeans green into 2-foot-tall cereal rye with beneficial results (more on this below).

Choosing the right cover crop

In 2014, the Zylstras planted their first 12 acres of cover crops to cereal rye before soybeans.

To better measure the impact of cover crops on one of their fields, the Zylstras joined the Soil Health Partnership in 2015. They quickly transitioned to planting cover crops on all soybean acres in 2015. To start, they seeded cereal rye at 60 lbs/acre with a spreader and used a vertical tillage tool to incorporate the seed.

The Zylstras chose cereal rye because they were looking for a cover crop that withstood the disturbance caused by injecting manure; they found that cereal rye bounces back quickly in this situation and the stand was minimally affected. And, since cereal rye overwinters, it provides ground coverage and nutrient uptake throughout the fall and into the spring.

Roger Zylstra and son Wesley inspecting a no-till drill on their Central Iowa farm
Roger Zylstra and son Wesley inspecting a no-till drill on their Central Iowa farm

Adapting cover crop and nutrient management practices

Between 2016-2018, the Zylstras made a number of management changes in order to dial-in their system.

Eliminated use of fall anhydrous and incorporated spring pre-plant and sidedress applications.

These changes made nitrogen available to the corn plant in the spring – during the period of rye stover breakdown – and also timed nitrogen availability throughout the season for optimal cash crop uptake and minimal loss to the environment. Although injected nitrogen was their end goal, they used dry fertilizer spread on the soil surface during the transition.

Adjusted cover crop seeding rate.

In order to reduce the amount of biomass produced (and associated potential issues in establishing the next cash crop), as well as to lower overall cover crop seed cost, the Zylstras lowered seeding rates for cereal rye to 25-35 lbs/acre.

Experimented with different methods of seeding cover crops.

Beginning in 2016, Roger and Wes experimented with drilling their cover crop in order to get better seed-to-soil contact and to improve moisture availability. They liked the benefits of drilling; however, by 2019, they had decided to return to spreading and incorporating cover crop seed with vertical tillage. Using a spreader and vertical tillage, they lowered their equipment maintenance costs and were able to seed more acres in less time.

Advanced cover crop and nutrient management practices

Since 2019, Roger and Wes are taking even more steps to achieve their management goals – including experimenting with new cover crop management practices and advancing nutrient management on their operation.

100% liquid application of fertilizer.

In 2019, the Zylstras added liquid application equipment to the planter to allow for banded application of P and K on both sides of each planter row (1 in. over and 3 in. down), along with in-furrow, low-salt starter and extra liquid nitrogen (if no manure was applied).

Experimenting with “planting green”

The Zylstras typically terminate their cover crop early to minimize the chance of cover crops interfering with the establishment of the cash crop. This usually also allows them to plant sooner. However, in 2020, there was a field they were unable to spray on time, due to unfavorable weather conditions. As a result, they planted soybeans “green” – or directly into the still-growing cover crop. Roger felt they experienced slightly better weed control on that field, while also benefiting from more spring cover crop growth and more desirable timing in terms of when they could get in the field. With that in mind, the Zylstras are considering experimenting with planting green on more acres in the future.

“We use about the same amount of nitrogen per acre as we did many years ago, but our average [corn] yields have grown from 140-170 bu/acre to 170-200 bu/acre.” – Roger Zylstra


Respiration (in mg CO2/g dry weight) – an indicator of microbial activity – increased significantly on the cover cropped portion of the field, as noted in the chart above.

Add up the small changes and they bring real benefits

The Zylstras changed their management system by making incremental changes and experimenting over a number of years. What benefits do they see?

Same amount of nitrogen, higher yields.

The primary benefit that Roger and Wes see is the ability to improve nutrient use efficiency by changing sources and timing of application. While a liquid fertilizer program does cost more per unit, the nutrients are able to be used more efficiently by the crop. “In corn years, we allow the corn to utilize more of the nutrients,” Roger says. “And we are able to prevent nitrogen from leaching into our creeks and streams.”

Soil health testing suggests cover crops have increased microbial activity.

Results from soil health testing on the Zylstra’s Soil Health Partnership field show that respiration – an indicator of microbial activity – has increased significantly on the cover cropped portion of the field. One tangible benefit of this increased microbial activity at the farm scale has been an increased rate of residue turnover on acres with cover crops.

Improved soil structure.

The Zylstras credit improvements in soil structure with reducing soil surface compaction during the wet years of 2018 and 2019. In comparison to other farms in their area that created ruts in their field and had water standing after large rainfall events, they see fewer equipment tracks and less ponding. These improvements in soil structure also reduce the potential for erosion during times of maximum disturbance.

Brian Martin

Brian Martin farms 35 percent of Martin Row Crops in Centralia, Missouri.  He is a fifth-generation farmer on a family farm that once focused on diversified crops and livestock, but now features row crops and a cow-calf operation.  Brian entered the partnership in 2003 while still in high school and continues to grow his part of the farm will also providing independent crop consulting services for other farmers.

Brian has 80 acres dedicated to the Soil Health Partnership practices, including no-till corn and soybeans, cover crops like radishes, turnips, rye, wheat, and barley, and a nutrient management plan based on 2.5 acre grids from which soil samples help him determine how to split apply nitrogen.

“I joined the Soil Health Partnership in 2017 because of my interest and passion for soil conservation and so that we can show that these management practices have a long-term economic benefit to our industry and future generations,” Brian said.

As much as anything, Brian has benefitted by learning from other farmers also in the partnership, best practices and sharing of ideas. He says that some of these practices have improved water infiltration rates and soil porosity on his farm. However, many of the metrics measuring improvement can take many years to change. It is a long-term process.

“Ultimately, I believe it is very important that we share what we’re doing with end-users and consumers as often as possible,” Brian said, “and that we are ever striving to become more efficient and environmentally conservative, as well as sustainable.”

Jason Lay

Jason is the third generation in his family to farm this land. After working in the corporate world, Jason had the opportunity to buy out his uncle and began farming the 2,500 acre farm in Bloomington-Normal, Illinois full-time in 2003.

The Lay farm grows a rotation of corn and soybeans. For the last nine years, Jason has utilized strip tillage for his corn acres. He added no-till on soybeans in 2011. Jason has also added cover crops to his practices, primarily using rye grass, and occasionally oats and crimson clover. He currently has 200 acres in cover crops.

Increased testing is one of the biggest improvements Jason has made in his farming practices—testing soil and stalk nitrate levels. Jason also uses Variable Rate Technology to precisely target what his soil needs in nutrients and when.

“I am personally impressed with the partners that have come together as part of the Soil Health Partnership. Corporate partners, conservation partners and farmers—all working together toward the same goals. I plan on farming for a long while, and we have to be smarter as an industry how we do things. I can help bring about that change by adopting new practices and setting an example for others to follow.”

Kirk Kimble

Kirk and Tiona Kimble are the fifth generation farming their 2000 acres in Chillicothe, Illinois. They are invested in preserving this family heritage for their three daughters, all of which help on the farm today.

Kirk has used numerous covers and combinations through the years: cereal rye, annual rye, vetch, oats, radishes, sunflowers and sun hemp. He puts a cover crop on every acre.

“I know I have my topsoil and it isn’t washed down the river. It’s a justifiable cost,” he said.

Kirk also practices no-till on every acre. When Kirk began farming, he tried no-till to save money by not purchasing more equipment, and he liked the results. With the big rain events occurring more frequently, Kirk says it just works well on his land for keeping erosion at bay.

He soil tests regularly, and depending on the results, does either variable rate or blanket rate application of nutrients. He does not do fall application of nitrogen.

“I believe in the practices that I have implemented, but the Soil Health Partnership is documenting them scientifically,” said Kirk. “I like seeing what is happening in my soil, year over year, and understanding how I can make it better. I like being part of a group that is promoting soil health and conserving our soil resource.”

Angela Knuth

A third-generation farmer, Kerry Knuth started out farming with his dad and grandfather. Today, Kerry and Angela Knuth farm 2,200 acres with their two sons Gregory and Garrison in Mead, Nebraska. 

The Knuths moved to no tillage for their soybeans and corn, including some strip tillage for some corn acres in 2005.  

“We like the cost savings we’ve seen on no-till. We don’t have to own tillage equipment and we don’t have to run it across the field,” said Angela. “We have been pleased to see no decrease in yield. We’re hoping to see that continued decrease in our cost of production and improvement in the soil tilth and microbe activity.”

Since 2012, the Knuths have been moving toward a more diversified rotation alongside traditional corn and soybeans. They have added wheat, sorghum sudan grass, and cover crops for grazing into their rotation, and are beginning the transition process to non-GMO/organic on a portion of their acres.

“We joined the Soil Health Partnership in 2017 because we want to learn how to make our soils better, regenerate them and we need help with that,” said Angela. “We’re not scientists and we want to know how these practices improve our soil. We look forward to learning more with the partnership.” 

Learning more is starting with fall soil sampling and building a history of each farm.  The Knuths look forward to combining that data with the latest software and hardware technology to create and apply a plan for each field.

Terry Bachtold

Terry Bachtold of Strawn, Illinois, has been farming his entire life. He grew up with cattle and hogs along with an annual rotation of oats, soybeans, corn and hay.

He appreciates cover crops to naturally increase organic matter and values the return to the old ways via a shorter term, similar rotation system.

“We have come a long way in technology as far as nutrient management, but I think the next leap forward is going to be improving soil through practices like cover crops and no-till,” said Terry. “Organic matter is basically what holds the soil together. If you don’t have organic matter, you’re not going to raise a crop.”

Terry is also interested in cover crops because of their ability to suppress weeds and hold nitrogen for use by growing plants in the next crop year.

He’s hopeful that incorporating cover crops will reduce his commercial application of nitrogen, but only time—and research with the Soil Health Partnership—will tell.

“As you increase the organic matter, you also increase the amount of nitrogen as it decomposes from plants will release back naturally,” Terry explains. “Each one percent of organic matter is basically 20-30 pounds of nitrogen that’s available to the crop and gets released every year out of your soil.”

SHP and TFI publish Nutrient Management Profiles

In partnership with The Fertilizer Institute (TFI), SHP published two profiles discussing SHP farmers who are implementing soil health management practices and the changes in their nutrient management strategy.

Properly managed nutrients and soil health can provide economic and environmental benefits; however, cropping systems are complex. Nutrient management decisions must align with soil health management decisions for optimal results. 4R Nutrient Stewardship provides a framework to achieve cropping system goals, such as increased production, increased farmer profitability, enhanced environmental protection, and improved sustainability.

The two profiles discuss mobile macronutrients and immobile macronutrients.

Profile: Immobile Macronutrients – Phosphorus and Potassium

Potassium helps strengthen the plant’s ability to resist disease and plays an important role in increasing crop yields and overall quality, including strengthening the plant’s root system. Phosphorus is linked to a plant’s ability to use and store energy, being necessary for overall growth and normal development. Phosphorus and potassium nutrients are typically lost through surface water, washing away the fertilizer source or erosion.

This profile highlights two U.S. farmers who incorporate 4R practices into their soil health management system to keep the phosphorus and potassium they apply in the soil.

Profile: Mobile Macronutrients – Nitrogen

Nitrogen fertilizer is commonly applied to row crops, such as corn, to improve yield and quality of the harvested crop. However, nitrogen that is not used by a crop or leaves the field can be released into the air(ammonia and nitrous oxide), surface, and groundwater (nitrate).

This profile highlights two U.S. farmers who incorporate 4R practices into their soil health management system to optimize nitrogen use.

Check out other SHP resources here.