Reducing Pesticide Pollution And The Intensity Of Harvesting Can Increase Crop Yield And Contribute To Climate Change Mitigation

Feb 09, 2023

In two studies, researchers at the University of Turku in Finland have found that carbon sequestration and plant resilience as well as forage pasture yield can be increased through key adjustments in agricultural management. The results provide a roadmap for reducing pesticide loads in soils and the first steps towards increasing climate change mitigation while improving crop yield in grasslands.

Soil properties are an essential driver of plant quality, including resilience against climatic extremes and resistance against insect pests and pathogens.

The increasing food demand of the rising global population together with technological advancement and novel synthetic agrochemicals have resulted in agricultural intensification with the goal to maximise crop production.

“However, in recent decades, we have observed both a reduction in plant resilience and crop yields and the degradation of soil quality. This has resulted in an exponential need for chemical fertilizers and pesticides,” says Docent Benjamin Fuchs from the Biodiversity Unit of the University of Turku, Finland.

“Only in recent years, we have started to realise that intensive agriculture and agrochemical pollution in fact contribute to a reversal of the intended purpose. Soils are polluted with pesticides and at the same time, extreme weather events erode soil nutrients,” Dr Fuchs continues.

Intensive harvesting and pesticide residues in soil limit root growth

One key challenge in the research was to find practical and sustainable ways to improve plant resilience and elevate crop yield while mitigating the carbon (CO₂) emissions caused by human activity by enhancing carbon sequestration in the soil.

The researchers conducted two independent experiments at the University of Turku’s research facilities at the Ruissalo Botanical Gardens in Turku, Finland. In the greenhouse and common garden studies, the research team showed that the intensity of mowing has a great impact on pastures. By reducing the intensity of the mowing and cutting the plant higher, the overall yield of the pasture increased and the plants developed bigger roots. This indicates a higher atmospheric carbon sequestration into belowground storage.

What was surprising, Fuchs emphasises, is that the researchers found a detrimental effect of herbicide residues in soil on root growth regardless of the intensity of the yield harvest.

“This demonstrates a tremendous limitation to the potential carbon binding and storage belowground when soils are polluted by pesticide. Considering the vast amount of pesticides applied to agricultural fields yearly, we can conclude that the impact on soil quality is a major driver of limited root growth, carbon sequestration, and consequently plant resilience and productivity,” Dr Fuchs says.

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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.