FAQs

There are several good reasons, and they span agronomic, environmental, and economic dimensions of production.

We’ve gotten good at growing corn and soybeans by removing anything that might compete with them. It works—but it also means our fields sit bare for much of the year. When that happens, soil is exposed to erosion, nitrogen moves when we don’t want it to, and a significant portion of the sunlight hitting that field goes unused.

Perennial groundcover systems put that “off-season” back to work. By keeping a living plant in the field year-round, you maintain roots in the soil that help hold it in place, improve structure, and take up nutrients that would otherwise be lost. You’re also capturing more sunlight over the course of the year and returning some of that energy to the soil as organic matter.

It’s important to know that PGC isn’t about letting grass run wild in your corn field. Management is everything. The goal is to suppress the groundcover at the right time so your cash crop has the advantage when it needs it. Done right, perennial groundcovers are a practical way to protect soil and water resources while keeping your corn and soybean system productive.

For many producers, reducing soil erosion and nutrient runoff will be key motivators. Others may see an opportunity to reduce the time and labor spent on field prep. In some cases, well-developed PGC can also improve the economic profile of the overall cropping system—and, fundamentally, it can provide these benefits at a lower cost in time and dollars than annual cover cropping.

Annual cover crops and perennial groundcovers are trying to do the same basic thing—keep something growing during the corn and soybean “off-season” to deliver soil and water benefits. The difference is in how they fit into your operation.

First, establishment. Annual cover crops need to be planted every year, and in the Upper Midwest, that’s not always easy. You’re working with a tight window after harvest and limited growing degree days. Some years it works great, some years it doesn’t—but it always demands time and new seed for each acre. Perennial groundcovers are already there. They come out of dormancy on their own, which removes the annual planting pass, eliminates annual seeding costs, and makes it easier to scale across more acres.

Second, management. With annual cover crops, the spring goal is termination—you want them completely gone so you can run a full herbicide program. With perennial groundcovers, you’re not trying to kill them; you’re suppressing them with a combination of mechanical (strip till) and chemical* means. That changes your herbicide options and requires a more deliberate weed control strategy. One upside: perennial systems tend to produce less spring biomass, which reduces the risk of the cover getting away from you when weather delays termination.

Third, residue. Annual cover crops with heavy biomass can create challenges for cash crop planting—they require experience and the right equipment. PGC doesn’t accumulate as much biomass, is suppressed closer to planting, and is therefore easier to plant into for a good stand.

Finally, there’s the economic dimension. A one-time planting investment spread over multiple years can make perennial groundcover a lower-cost cover cropping option over time.
*We are working on approaches that use the groundcover day-length based dormancy to eliminate the need for chemical suppression.

Like most things in agriculture, it depends on what you’re trying to get out of the system.

If your goal is to grow harvestable biomass—fall grazing, forage, bedding—annual cover crops are probably the better fit. They’re designed to put on growth quickly and give you something you can use. But that’s not every farm.

A lot of farmers like the idea of cover crops, but run out of time in the fall, or simply can’t get across as many acres as they’d like. That’s where perennial groundcovers start to make sense. You seed them once, and they’re there year after year. No scrambling after harvest, no extra pass in a tight window.

There’s also a practical cost angle. If you’re not harvesting cover crop biomass, you have to ask what you’re paying for each year. Perennial systems spread that investment out over time and reduce the labor and management pressure each fall—making them a lower-cost, lighter-lift cover cropping option.

PGC systems are designed to save time and input costs compared to annual cover crops, while maintaining or improving crop productivity and mitigating negative on- and off-farm impacts from traditional row-crop systems. They also offer more consistent year-to-year soil coverage, reducing variability in groundcover establishment.

So if you’re looking for a way to keep living roots in the soil, protect water quality, and cover more acres consistently without the annual burden—perennial groundcovers can be a very attractive option.

Not yet—and probably not ever in a single-recipe sense.

Most of our work so far has been focused on de-risking these systems in Midwestern corn and corn–soybean production. We’re learning what drives success: how to get a good groundcover stand, how to suppress it at the right time, and how to maintain yields comparable to a clean, conventional system. The direction is encouraging, and we’re getting close to having some “typical recipes” that work more often than not.

But this won’t be a one-size-fits-all approach. Soil type, weather patterns, the equipment you have available, and even the crop genetics in play all matter. What works on a well-drained central Iowa field may need adjustment on heavier soils or in a different climate. Different PGC species, cultivars, and management practices will be required for specific regions.

Germplasm is also part of the picture. Hybrid and cultivar performance under PGC management varies across row crop species, so identifying well-adapted genetics for a given PGC environment is part of making the system work locally. Our three-year testcross evaluations at Ames, Iowa, indicate that hybrids differ meaningfully in how they perform under PGC management, which supports the value of this kind of germplasm screening.

This isn’t a “one lever” economic win—it’s a system that can create value in several ways, depending on how you use it.

PGC started as a way to solve a problem in corn systems where stover is removed for feed, bedding, or biofuels. Once you take that residue off, you’ve increased your erosion risk. In a PGC system, the groundcover protects the soil while allowing higher stover harvest rates. For producers with a stover market, that can push the economics toward net positive.
In places without a stover market – and yes, these are currently the majority – the PGC value proposition is not about generating revenue, but instead about getting key ecosystem service benefits at lower cost, less time, and lower yield risk than annual cover crops. The lower cost and time come because PGCs are planted once for multiple seasons of cover cropping, saving seed and diesel costs. The lower yield risk comes because PGC covers generally produce less biomass than their annual counterparts.

On the economic side, over time, PGCs should improve soil health and fertility, and can reduce saturated soil conditions in wet years—both of which can contribute to higher and more stable grain yields. In systems where animals graze corn stover over winter, PGC may also provide supplemental protein and improve grazing conditions and quality. Relatedly, improvements in water infiltration and holding capacity could make these systems more resilient—less yield loss in tough years, more consistency across variable weather. That’s harder to measure year-to-year, but it compounds over time.

It’s a good idea in principle—diverse, native mixes sound like they should check a lot of boxes. The challenge is how they behave inside a corn or soybean system.

For PGC to work, the groundcover has to stay out of the crop’s way during the growing season. That means shallow rooting, low stature, and growth patterns that don’t line up directly with corn’s peak demand for water, light, and nutrients. Many native perennial mixes—especially taller prairie species—are evolved to do the opposite. They root deep, grow aggressively, and compete hard right when corn is trying to yield.

There is some emerging interest in shorter native grasses. Species like blue grama (a warm-season grass) or Sandberg bluegrass (a cool-season grass) may show promise. Short warm-season native grasses don’t begin actively growing until after corn has emerged, so they may not trigger a shade avoidance response and could negate the need for chemical suppression. That could also open up more herbicide flexibility.

However, there are real tradeoffs. Many short-grass prairie species are not well adapted to humid growing conditions, are difficult to establish, and carry higher seed costs. And using a species mix adds complexity to herbicide management—the rate that suppresses one species may eliminate another entirely.

There’s also a functional concern: if a groundcover species isn’t active in the shoulder seasons—early spring and late fall—you lose much of the water quality benefit. Nutrient capture and erosion protection matter most when the cash crop isn’t there. A system that only grows during the same window as corn may not deliver enough return on that front.
That’s why most PGC work today focuses on species that are active outside the main crop window, including summer-dormant species, which are showing particular promise. Groundcover selection should consider establishment reliability, persistence, and ease of management—not just ecological diversity.

Right now, most of the work is happening in the Midwest—and that’s intentional. We’re focused on corn and soybean systems with 30-inch rows and a fairly long shoulder season in the spring and fall when nothing is growing. That creates a clear fit for perennial groundcovers and a real opportunity to improve soil and water outcomes.

That said, there’s nothing uniquely “Midwestern” about the concept. Keeping living roots in the soil year-round can translate to other regions—PGC systems are already being researched in cotton production in the Southeast, and the approach has been applied in other countries, including Brazil.

But the way you implement it will look different elsewhere. Crop systems matter a lot. Small grains, for example, are typically drilled in narrow rows and are most active in the spring—right when we’re trying to grow the groundcover in our current systems. That changes the competitive balance and likely the species you’d choose.

So yes, the approach can extend beyond the Midwest—but it won’t be a copy-and-paste. Species selection, timing, and management will all need to be tuned to local crops, weather, and equipment.

In a PGC system, the groundcover isn’t something you’re planning to harvest. Its job isn’t to be a crop—it’s to make the system work better.

The groundcover’s primary role is to provide ecosystem services: protect the soil from erosion, take up nutrients when the cash crop isn’t growing, improve soil structure, and capture sunlight that would otherwise go unused. The goal is to get those benefits while maintaining your current crop yields—and ideally improving the economic profile of the overall system through enhanced agronomic and environmental outcomes.

That said, the groundcover still plays into the economics in indirect ways. By improving soil protection and extending photosynthesis into the shoulder seasons, PGC can support more aggressive corn stover harvest without compromising the soil resource. While you’re not harvesting the groundcover itself, it can enable other harvest opportunities and help maintain long-term field productivity.

In some systems, limited residue grazing by livestock may be possible—and that’s something innovative producers might explore on a small scale. But for our current work, the focus remains on delivering ecosystem services and compatibility with row crop production.

First, we’re not trying to replace annual cover crops. If you’re successfully using them—especially for forage, grazing, or other uses—you should keep doing that. Those systems can create real value, and farmers who do annual cover cropping can and should continue.

But it’s worth remembering that in the Midwest, the vast majority of production acres still aren’t cover cropped at all. A major goal of our effort is about lowering the barrier to entry and getting more fields covered.

Second, most cover crops in the northern Corn Belt aren’t harvested anyway. The growing window is short, and unless you’re set up for something like silage or have livestock in the system, there often isn’t a practical way to capture that biomass. Farmers may also be prohibited from harvesting cover crops for conservation plan compliance.

PGC takes a different approach. It’s not trying to produce a harvestable crop—it’s trying to quietly deliver soil protection, nutrient retention, and system resilience with less management pressure. The residue isn’t wasted; it’s returning valuable carbon to the soil system and contributing to the foundational goal of improving long-term soil health and crop yield. Additionally, fewer passes in the field compared to annual cover cropping systems means less time and fuel.

If forage, mulch, or biomass is the goal, annual cover crops are probably the right fit. But if the challenge is getting acres established, managing spring growth, or reducing risk to your cash crop, perennial groundcovers offer a lighter-lift way to get many of the same environmental benefits—at scale.

Our team recognizes the significant impact of federal farm programs on cropping system management at the farm level.

We are working collaboratively with the United States Department of Agriculture (USDA) to develop risk management products—like crop insurance—and to evaluate programs that can incentivize cost-share conservation adoption on working lands for PGC.

The PGC system is designed with the realities of farm economics in mind. Achieving row crop yield potential affects a farmer’s revenue today and their safety net in the future, and any viable conservation practice needs to be compatible with—not in conflict with—the programs farmers depend on. This remains an active area of effort as the system matures.

You don’t have to remove the stover for a PGC system to provide its benefits, but without a stover market and without any other incentives for conservation practices, PGC systems will be a net cost to a farmer. We think that cost will be significantly less than for an annual cover crop, but we realize it will be a barrier. We believe that in the long term, by providing soil protection, improving water infiltration, retaining nutrients, potentially enhancing soil microbial communities, and improving system resilience, PGC systems may have positive bottom line (yield) influences, but whether those benefits will outweigh the costs is unclear.

Note that in situations where stover is not removed, residue management still matters. In high-yield systems, large amounts of residue can create challenges for groundcover vigor and stand establishment. How residue is processed at harvest—chopping, sizing, and distributing it evenly—becomes critical. Poor residue management can smother the groundcover and set the system back.

You can leave the stover, and in many cases, that’s a good fit with PGC systems. But it’s not quite as simple as “more residue = more soil carbon.”

Soil carbon is a balance between what you add and how fast it breaks down. When you till residue into the soil, you increase both carbon inputs and carbon losses through oxidation—which is why tilled systems tend to settle into a lower steady-state carbon level than undisturbed systems like prairie. (Note: soil organic matter is roughly 60% carbon, so improvements in soil carbon directly reflect gains in organic matter.)

PGC starts to shift that balance. You’re adding carbon not just from crop residue, but from a living root system that’s active for more of the year. And because PGC needs reduced (strip) tillage, more of that carbon is protected from rapid breakdown. Early results suggest that combination can increase soil carbon over time.

However, residue management still matters—a lot. In high-yield systems, leaving all the stover
can create a thick mat that interferes with groundcover vigor and stand persistence. How you size and distribute residue at harvest is critical. If the groundcover gets smothered, stand life will be shortened and system performance will suffer.

Related: Does a PGC system build soil organic matter?

We think it can—but you have to look at the whole system.

PGC increases the amount of sunlight your field captures over the year, and that translates into more carbon entering the system (an increase in net primary production, as ecologists would say). Instead of only corn or soybean residue, you’re also getting carbon from a living root system that’s active in the shoulder seasons. That adds both more carbon and a different kind of carbon—which tends to support a more active and diverse soil biology.

Early work suggests this helps build soil organic matter, especially since these systems often reduce tillage in the groundcover zone, which slows carbon loss through oxidation.

But there’s a balance. If you start harvesting more stover, you’re removing carbon. If you change tillage practices, you may speed up or slow down carbon breakdown. The outcome depends on how those pieces fit together and what your starting carbon level was.

What PGC does is raise the ceiling. You’re putting more carbon into the system and spreading inputs across more of the year. Whether that turns into meaningfully higher soil organic matter depends on how you manage residue, tillage, and harvest—but the potential is real.

Nutrient management in a PGC system is less about a single answer and more about how the whole system shifts.

On the nitrogen side, there are a couple of competing effects. If you’re harvesting stover, you often see faster soil warming in the spring and potentially more nitrogen mineralization, especially in cooler, wetter regions like Iowa. That can reduce nitrogen needs in the short term. On the flip side, if you’re also reducing tillage, you may slow down organic matter breakdown and nitrogen release. Which effect dominates depends on soils, management, and weather. In our experience thus far, year-to-year weather variability probably has a bigger impact on the optimum nitrogen rate than the system change itself.

Phosphorus and potassium are more straightforward. If you remove stover, you’re exporting nutrients, so you’ll need to replace them, especially phosphorus and potassium depending on how much was washed from the residue before it was harvested.

Longer term, this is where PGC may really matter. Less erosion means less phosphorus leaving the field. More living roots and carbon inputs may improve nutrient cycling and efficiency. We think those trends are positive, but how much they change your fertilizer bill is still something we’re working to quantify.

From an operations standpoint, PGC doesn’t add a lot of extra passes. Because a well-established and managed groundcover can persist for years (4-10), you’re not reseeding annually (saves a pass), and you are strip-tilling, which is lower emission than conventional tillage. The main management step is spring suppression to keep the groundcover from competing with the crop. That’s typically done with a contact herbicide timed around planting, and it can usually be combined with your normal burndown or early-season herbicide pass, so you’re not adding a separate trip. For these reasons, the added CO₂ from equipment use is likely small.

That said, CO2 from field passes is usually not the main driver of a cropping system’s greenhouse gas footprint. In most row-crop systems, nitrous oxide (N2O) from nitrogen cycling is the bigger piece. So, if we’re asking how PGC affects climate impact, changes in N2O matter more than changes in trips across the field. We continue to work on understanding how N2O emissions are changed in PGC systems.

Keep in mind that with more year-round growth and living roots, PGC can increase carbon inputs to the soil. If that carbon is retained, especially with reduced tillage, you can offset emissions and potentially lower the overall footprint.

PGC was conceived as a conservation practice that would be low cost (and in some visions, even zero cost or revenue generating).

The biggest cost is upfront: establishing the groundcover. That typically requires a seeding pass with a grain drill, and perennial groundcover seed costs can be higher than those of annual cover crops. However, because you’re not paying that every year, seeding cost gets spread out and starts to look very competitive, often cheaper, than reseeding annual covers every fall.

After establishment, the primary management step is spring suppression, and in most cases that can be combined with your normal herbicide pass, so you’re not adding a separate trip across the field. Suppression and strip tillage are critical to maintaining a crop-growth-zone to avoid yield drag – in no-till systems, adding a strip till pass will add cost.

Suppressing the PGC can theoretically be combined with existing herbicide passes, but additional passes may be necessary to ensure good crop yield if suppression is not adequate. As the PGC technology matures, easier and more effective establishment and suppression methods will be developed; these are major focal areas in RegenPGC.

We’re still learning about herbicide programs and weed control. Because you’re suppressing – not terminating – the groundcover, your herbicide options change. We are actively researching how that impacts product selection, effectiveness, and cost.

Groundcover longevity varies by species/cultivar. Research is being conducted to identify persistent groundcovers with minimal grain yield drag.

The goal is for the groundcover to last multiple years. In some of our trials, a combination of heavy wheel traffic, high stover amounts, and aggressive suppression has led to stand decline after just 3 years. Responding to those findings, we are exploring targeted approaches to avoiding stand loss and have seen some good results in year 2 of that work.

This is one of the bigger unknowns with PGC, and something we’re actively working on. Anytime you change the cropping environment, you change pest dynamics. A year-round groundcover will influence weeds, insects, and diseases, likely in both positive and negative ways. For example: A well-managed groundcover might suppress certain weeds by occupying space and reducing opportunities for establishment. Alternatively, groundcovers could serve as a “green bridge” for insects or diseases, allowing them to persist when they otherwise wouldn’t. Currently, we assume pest pressure will change, scout accordingly, and use the tools we already have to manage issues while we build a better understanding.

The goal with PGC is to avoid direct competition with the grain crop. That’s why we focus on shallow-rooted summer dormant groundcovers: if they’re not actively growing during peak crop demand, their water use is limited.

Groundcovers can improve water infiltration and reduce evaporation by protecting the soil
surface, essentially acting like a mulch after suppression. In some conditions, that can actually increase the amount of water available to the crop. This doesn’t always happen – the effects are weather-dependent and influenced by how dense the groundcover is, how well and when it’s suppressed, and how long that residue persists. In a dry year, if suppression is late or incomplete, the groundcover is more likely to compete for water.

Done right, the risk of moisture competition can be minimized, and in some cases even flipped into a benefit. Our research continues to seek ways of realizing these benefits.

We manage this risk via strip tillage. This creates a crop growth zone (CGZ) where the maize is planted, giving that seed zone a chance to warm up much like it would in a conventional system. The center of the CGZ warms up similarly to controls, and when the planting is centered in the crop growth zone, we haven’t seen an issue with delayed germination.

The groundcover can influence moisture, which ties into temperature. Early in the spring, an actively growing groundcover can help pull moisture out of the soil, potentially helping it dry faster. After suppression, the remaining biomass can act more like a mulch, slowing evaporation. When you suppress the groundcover relative to rainfall and planting conditions, it can shift whether you’re helping or hurting those early-season conditions.

Prairie strips are narrow vegetative filter strips placed downslope from a drainage area. They intercept and slow surface flow, causing soil sediment to be deposited within the strip. They are remarkably effective in reducing sediment delivery to streams, and they are a reminder of the disproportionate benefits that can occur with some conservation practices. However, outside the strip itself, prairie strips do not reduce soil displacement or infield soil erosion. Perennial groundcover coupled with strip tillage on the contour significantly reduces both and may interfere less with field operations than prairie strips, allowing the land dedicated to PGC to remain in row crop production.

Related: We see the PGC approach as a potentially widely applicable conservation tool for large-scale commodity farming systems. As such, it is one of many practices (e.g., annual cover cropping, prairie strips, edge-of-field practices like saturated buffers and nitrate bioreactors) that farmers and landowners can use. It is not our intent to suggest that one of these is best – the inherent variability of the landscape and individual farmer/landowner needs and values means that one size does not fit all. Our goal is to create a scalable, low-barrier-to-entry practice that addresses the root-cause issue of bare soil on the production landscape. We are committed to doing so in a transparent way that shares both the benefits and challenges of PGC as we move through the development process. Individual farmers and landowners are the people who will decide whether PGC makes sense for them.

Based on our experiences in the first four years of RegenPGC, we identified the following six primary risk factors: (1) Groundcover establishment (seeding); (2) Groundcover suppression; (3) Crop-growth-zone management; (4) Herbicide program limitations; (5) Groundcover persistence; (6) Lack of insurability. We are actively working on all of these issues.

We have characterized the two leading candidate groundcovers on each of the primary risk factors. Radix Hybrid bulbosa (RHb) has been demonstrated to be more reliable at establishing – particularly in the dry conditions that have typified the first three field seasons – and generally has a lower yield risk than KBG. However, RHb longevity – particularly in wetter and high-traffic conditions – has caused concern – but we are in year 3 of an experiment to explore how we can leverage the differences in corn and soybean responses to groundcover to actively manage an RHb stand for longevity.

Based on the above, we believe that a farm with the following practices/capabilities can trial (at small scale – say 5 acres or less) an RHb PGC instance at low grain yield risk: (A) Corn-Soybean Rotation (1:1) – allows recovery time for RHb, thereby extending RHb life. (B) Strip-till and have ready access to a strip-till bar. (C) Precision capability – center the grain in the crop growth zone. (D) In-row fertility capability. (E) Ready access to a sprayer; able to prioritize timely suppression to avoid competition. (F) Ready access to a drill; able to prioritize PGC planting to avoid failed establishment.

The most successful implementation of PGC with corn and soybean thus far has been with strip tillage. With strip tillage, only a fraction of the soil surface is disturbed. This makes it possible to till the soil between strips of perennial groundcover. This tilled zone is where the grain crop is planted and where other inputs can be applied and incorporated. A related question is whether perennial groundcovers can be used in a no-till system. Research suggests that it can work, but has greater risk to grain yield than the strip-till approach.

The grass species used as groundcover in a PGC system are not prolific forage producers by design. Forage cultivars are too competitive to use in row-crop production unless a producer is willing to sacrifice some row-crop productivity in favor of the forage. Most promising groundcover species, however, would benefit producers that pasture cows on maize residues. The groundcover would provide a cleaner grazing environment, protect the soil from excessive trampling, and likely provide adequate protein to the grazing animal in the fall. 

The PGC system attempts to minimize competition between the groundcover and row-crop by compartmentalizing them in space. There is little competition for sunlight and soil moisture in a well-managed system. That said, the groundcover does change nutrient cycling, especially in the top several inches of soil. PGC systems will immobilize mineral nitrogen by converting it into organic forms. Furthermore, greater N is retained in both PGC root and soil microbial biomass – PGC thus retains N in these “slower-release” forms. Once the organic N pool stabilizes, however, no additional N fertilizer should be needed. The work being done in this RegenPGC project will provide more insight into this question.