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.