University of Kentucky Study Highlights the Benefits of Mixing Cover Crops

Jul 19, 2024

By Jordan Strickler

A new University of Kentucky study entitled “Productivity benefits of cereal-legume cover crop mixtures under variable soil nitrogen and termination times” suggests that mixing cover crops is a beneficial strategy for modern agriculture.

Published in the European Journal of Agronomy, the research reveals that mixing cereal rye and crimson clover as cover crops can significantly improve productivity, with associated benefits for soil health.

This research, led by Patricia Moreno-Cadena and her UK Department of Plant and Soil Sciences team at the UK Martin-Gatton College of Agriculture, Food and Environment and conducted at the UK North Farm, demonstrated that these mixed cover crops can offer more advantages than planting them separately making them a valuable tool for farmers.

Cover crops, such as cereal rye and crimson clover, play a critical role in sustainable agriculture by preventing soil erosion, enhancing soil organic matter and improving nutrient cycling. Cereal rye is known for its rapid growth and ability to cover the ground quickly, which helps protect the soil and retain nutrients. However, it can also immobilize nitrogen, making the nitrogen less available for subsequent crops like corn. Conversely, crimson clover, a legume, adds nitrogen to the soil but does not provide as much ground cover, especially in the fall.

"Our findings suggest that using a mix of cereal rye and crimson clover can provide significant benefits, particularly in fields with low nitrogen levels,” said first author and former post-doctoral student Moreno-Cadena. “By understanding the conditions under which these mixtures thrive, farmers can make informed decisions to improve their crop management practices."

The study, conducted over two years, involved planting rye alone, clover alone and a mixture of both on long-term corn fields with varying nitrogen levels. The researchers measured the growth, nitrogen content and ground cover of these crops from fall 2020 through spring 2022. They found that mixed cover crops adapted better to different soil nitrogen levels and management practices than single-species crops.

"I've been interested in cover crop mixtures for years because they merge benefits and moderate negative attributes of individual cover crop species," explained Hanna Poffenbarger, associate professor in the Department of Plant and Soil Sciences, also a researcher on the project.

A significant discovery was that the blend of rye and clover generated greater plant material (biomass) and took up more nitrogen than each crop grown independently, particularly under moderate soil nitrogen levels.

"Under moderate nitrogen levels, the mixed cover crops produced more biomass than both monocultures,” Poffenbarger noted. “At low and high nitrogen levels, the mixed crops performed similarly to clover alone and rye alone, respectively."

The study also highlighted the importance of the timing of cover crop termination -- the point at which cover crops are killed to prepare for the main crop. Early termination favored rye, while late termination favored clover.

If a farmer prefers to plant their main crop earlier and wants to avoid too much residue, the mixture might not be as beneficial. But if the cover crop is allowed to grow longer into the spring, the mixture can provide more benefits.

Furthermore, the adaptability of mixed cover crops makes them particularly valuable. In fields with varying soil nitrogen levels, mixed crops can adjust their growth patterns to make the best use of available nutrients. For example, in areas with low nitrogen, clover thrives and adds nitrogen to the soil, which benefits the next crop. In contrast, in areas with high nitrogen, rye grows more vigorously, helping to take up potentially leachable nitrogen and reduce erosion.

More biomass means more organic matter is added back to the soil, improving soil structure and fertility over time. This study shows that cover crop mixtures can be more productive and beneficial for the soil than single-species cover crops.

The study suggests that mixed cover crops are more adaptable and can provide consistent benefits across different field conditions. They are particularly beneficial in fields with low nitrogen levels, where clover can thrive and add valuable nitrogen to the soil. However, if a field has high nitrogen levels, rye will dominate, and the added cost of clover seed may not be justified.

Poffenbarger highlighted another important aspect from the study.

"If farmers know their soil has a lot of nitrogen leftover from the previous crop, including clover, then mixing might not be worth the extra cost. But in fields with low nitrogen, the mixture can offer significant advantages."

Poffenbarger also addressed the broader implications of this research for soil health and sustainability.

“This research provides valuable insights for farmers looking to enhance their crop management practices,” she noted. “By using a mix of cereal rye and crimson clover, they can improve soil health, increase biomass production and optimize nutrient cycling, ultimately leading to more sustainable and productive farming systems.”

Source : uky.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.