Organic Accelerator: New Study Investigates Grazing Living Mulches for Soil Health

Feb 20, 2024

By Jennifer Howard

North Carolina reported 335 certified organic farms in 2021, a 4% decline since 2019. But nationally, organic foods are hot, with consistent sales growth that has doubled in the last ten years. Despite increasing consumer demand and the expected 15-50% price premiums, fewer NC farm acres are transitioning to organic production.

A key sticking point is the three-year transition period between starting organic practices and beginning to experience the financial payoffs. In the meantime, farmers may need new equipment, organic certification, and soil improvements to replace conventional methods.

But the biggest hurdle is often the change in mindset and techniques. Organic farming requires different pest control, weed control, crop rotation, and soil management strategies, requiring farmers to learn many new skills. Soil health becomes a vital force.

“Transitions are always the unknown,” said NC State Soil Health Specialist Ekrem Ozlu. “There’s a distinct lag between the practice and the benefits, which can be a deterrent to farmers. We hope to find a way to accelerate the organic transition period in a way that’s economically and sustainably feasible.”

USDA Funds $1M Soil Health Grant

In response to this charge, Ozlu and three partner institutions are leading a new four-year USDA NIFA-funded project to investigate whether living mulches can equally benefit soil health and the farmer’s bottom line.

“Living mulches are dynamic ground covers, cover crops, that protect the soil from erosion, improve soil health, increase biodiversity, conserve moisture, suppress weed growth, and contribute to sustainable soil management practices.“

The four-state group plans to compare multiple cover crop species and whether animals grazing cover crops and living mulches can provide a low-cost means of jumpstarting organic soil health and fertility without significant off-farm inputs.

NC State’s research site will be hosted at the Center For Environmental Farming Systems (CEFS) in Goldsboro, NC. Other partner institutions are Washington State University, Oregon State University and the Rodale Institute in Pennsylvania.

Ozlu says that the potential cash crop benefits of living mulches in an organic system are three-fold: reduced fertilizer costs, reduced herbicide and pesticide costs and increased yield.

“Cover crops bring many benefits to a farming system for free that we usually pay a lot of money for, like soil fertility, weed suppression, water retention and even the soil microbiome. And it’s doubly true in organics. The living mulches we are testing will bring a lot of nitrogen and soil improvements into the system for very little cost.”

Legumes Lead the Way

The group plans to compare the performance of annual and perennial legume cover crops on several soil health metrics, including soil compaction and water retention, aggregate size and soil protein, soil fertility, microbial activity and greenhouse gas emissions.

Ozlu’s NC research site will compare four cover crop mixes of rye with crimson clover, kura clover (a perennial), red clover and white clover on rotations of organic corn and soybeans. He will measure the nutrient content, production efficiency, and competition of each legume’s biomass, as well as the following cash crop establishment and yield.

“Finding environmentally and economically sustainable nitrogen sources is a big challenge for organic producers,” Ozlu said. “We think using legumes as a living mulch across an entire field, not just the crop rows, will reduce the weed seed bank, improve soil health and yield.”

Integrated Farm Dynamics

Cover crops are typically terminated chemically or mechanically. For sustainability, researchers added a low-input twist. Beef cattle grazing will terminate the living mulch, potentially improving soil biology further while adding another farm revenue stream from cattle sales.

Integrated farming systems utilize livestock in conjunction with field crops to create a closed-loop system that eliminates (or dramatically reduces) off-farm crop inputs and instead relies on manures and animal activity to stimulate soil health.

Ozlu says using livestock in an organic system is a soil health multiplier.

“Integrating livestock provides cost benefits to organic producers through labor and fuel savings, nutrient cycling for their cropping system and additional animal products.”

Monthly cattle weights will determine the average daily gain for economic analyses.

Greenhouse Gas Emissions Monitoring

Cover crops are well known for their ability to build soil carbon, which improves soil health. But they can also mitigate agriculturally generated greenhouse gas emissions from fallow soil.

Leveraging expertise and equipment from NC State’s Climate Adaption through Agriculture and Soil Management (CASM) group, Ozlu’s site will be the sole research location to study greenhouse gas fluxes.

NC State CASM’s Alex Woodley specializes in agricultural greenhouse gas emissions.

“When incorporating legumes into a system, we need to consider how the nitrogen fixed by these plants impacts greenhouse gas emissions, namely nitrous oxide,” Woodley said. “There are still considerable unknowns about using legumes as the main nitrogen source to the cash crop compared to other organically certified alternatives like composts or manures. By measuring emissions in addition to the soil health metrics, we will be able to determine the co-benefits or trade-offs of this cover crop management strategy.”

Organic Education for All Ages

Most grant-funded research efforts include an outreach component. Ozlu’s study is no different. He’s planning a new integrated livestock extension portal for digital communications and multiple field day events for growers and extension agents.

However, these researchers see an opportunity to reach a younger audience. They plan to create a grade 6-12 curriculum on organic farming systems.

Interested middle and high school teachers will be invited to a two-day workshop and farm site visits to interact with researchers and help create the course. This pilot group of educators will guide and pilot the curriculum to match national educational standards.

Collaborator Surendra Singh is a Washington State University associate professor and Director of the Lind Dryland Research Station. He will spearhead the project’s curriculum.

“The key reason behind providing organic farming-related education to K-12 is to provide students with an early understanding of “where the food comes from,” but also to raise awareness about organic farming, healthy food, environmental protection, and human health,” Singh said. “We hope that knowing the importance and challenges of organic farming across the country at this early stage may inspire students to be our next generation of agricultural scientists, farmers, policymakers, and/or ag-related careers.”

Big Potential for Smaller Farms

Since livestock (and all the necessary infrastructure) are an essential component of the research design, will that limit the number of growers who can benefit from the results? Ozlu doesn’t think so.

He says the results of this work could benefit NC growers at any scale operation but sees a sweet spot for smaller farms.

“We have a lot of small and midsize farmers in the NC Piedmont who have livestock and are already grazing crops. This study will produce guidelines for how a conventional grower can move into an organic system while understanding the impacts and timeline of how their soil health will respond.”

The first research updates are expected in late 2024 and will continue until the study’s conclusion in 2027.

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Source : ncsu.edu

Video: Turning Plant Defense Into a Management Strategy

Turning Plant Defense Into a Management Strategy

Understanding how a plant responds to stress is one thing.

Using that knowledge to make better management decisions is another.

Systemic acquired resistance, or SAR, is the plant's more direct defense response. When stress or infection occurs, the plant begins signaling throughout its system and preparing defensive compounds.

But if we know that response exists, can we help prepare the plant before the stress arrives?

The answer starts with understanding what triggers the response and what the plant needs to carry it out.

The Trigger and the Fuel

Salicylic acid plays an important role in triggering the SAR pathway.

Think of it as turning the truck on.

The engine may be running, but it still needs fuel to do the work.

In this case, manganese plays an important role in supporting the enzyme systems involved in the plant's defensive response.

This makes manganese status an important part of the conversation. Whether a producer is using tissue testing, sap analysis, or simply scouting for visible deficiency symptoms, the goal is to make sure the plant has adequate manganese available.

Manganese is required in relatively small amounts, but that does not make its role small.

If the plant receives a signal to defend itself but lacks the nutrition needed to support that response, it may struggle to carry out the process efficiently.

The trigger matters.

The fuel matters too.

Prepare Before the Stress Arrives

The best time to think about stress management is before the plant is overwhelmed.

Once a crop is already struggling, management can quickly turn into a game of catch-up.

This is similar to nitrogen management. Once a plant becomes severely deficient, correcting the problem does not necessarily erase the time and yield potential already lost.

Plant defense can work the same way.

Low-rate, targeted approaches designed to support the SAR pathway may fit best ahead of an expected stress event rather than after significant damage has already occurred.

That requires producers to think about predictable stress.

We may not know exactly what the weather will do tomorrow, but we generally know summer heat is coming. We know certain field conditions increase disease pressure. We know a herbicide application can temporarily stress a crop as the plant processes the chemistry.

Even a properly timed and labeled herbicide application can create a temporary response in the plant.

That does not mean the herbicide is bad.

Weeds can create significantly more yield loss than the temporary stress caused by controlling them.

The question is not whether we should eliminate every stressor.

The question is whether we can better prepare the plant to manage necessary and predictable stress.

Not All Stress Is Bad

Stress is a normal part of plant growth.

A perfectly stress-free environment does not exist in the field.

In fact, some stress is necessary for normal plant development. A plant responds to wind, temperature, moisture, sunlight, and countless other environmental signals throughout the season.

The environment is stress.

The plant's job is to manage it.

Problems begin when the stress load becomes greater than the plant's ability to respond.

Extreme heat, drought, high salt concentrations, disease pressure, and even certain management practices can add to that load.

This is where understanding SAR becomes useful.

Instead of waiting until the plant is visibly struggling, producers can begin identifying periods when stress is likely and make management decisions around those windows.

ISR Starts With the Soil

While SAR is a more direct defense response, induced systemic resistance, or ISR, brings the conversation back to soil health.

The longevity of a farm is closely connected to the health of its soil.

Carbon plays a major role because it supports biological life within the soil. Bacteria, fungi, and other organisms interact with plant roots and influence how the plant grows, accesses nutrients, and prepares for stress.

This is why soil health cannot be reduced to one product or one application.

It is a system.

Keeping living plants in the field longer can support biological activity. Cover crops may fit some operations. Better water management can improve soil conditions.