Increasingly heavy agricultural vehicles are destroying soil health

This article was republished by The Conversation under a Creative Commons license. Read the original article.

What does a modern combine mean and a Diplodocus do we have in common? One answer, it seems, may be their large footprints on the soil. A new study led by researchers from Sweden and Switzerland found that the weight of agricultural machinery today is close to that of the largest animals that have ever orbited the Earth – sauropods.

Depicted as the giant, friendly “vegetarian” in the film Jurassic Park, sauropods were the largest of the dinosaurs. It is estimated that the heaviest ones weigh about 60 tons – similar to the weight of a fully loaded combine. Tractors and other machinery used on farms have increased significantly over the last 60 years as intensive, large-scale agriculture has become widespread. The combine today is almost ten times heavier than in the 1960s.

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The weight of animals or machines is important because soils can only withstand so much pressure before they become chronically compacted. It may not look like that, but soils are ecosystems that contain fragile structures – pores and pathways that allow air to circulate and water to reach the roots of plants and other organisms. Tires, animal hooves and human feet exert pressure, crushing pores not only on the surface but also deeper.

Soil compaction can reduce plant growth and yield and increase the risk of flooding as water leaks from the ground and reaches waterways faster. Scientists in the new study looked at how much compaction is caused by these giant agricultural machines and compared it to sauropods that lived more than 66 million years ago. They found that both were the big culprits for the sealing.

Under pressure

The study shows that as the weight of agricultural machinery increases, tire sizes have also increased, adjusting the area of ​​contact between the vehicle and the ground to reduce surface pressure and avoid sinking. Animals seem to have evolved with a similar strategy – increasing the size of the feet by weight to avoid sinking into the soil.

Large wheels (or feet) help distribute the weight of the body on the soil surface, but the damage continues deeper. Photo of Spruce, Shutterstock.

In general, the pressure on the soil surface remains relatively constant, as agricultural machinery has gained weight. But the authors suggest that stresses on the soil continue to increase below the surface and penetrate deeper as vehicles (or animals) become heavier. Agricultural machinery today (and the sauropods of the past) are so heavy that they irreparably compact the soil below the first 20 centimeters where it is not cultivated. In addition to limiting how deep the roots of crops can grow to seek water and nutrients further down the soil, it can also create low-oxygen conditions that are not good for the plants or organisms they share soil with. .

Where did the dinosaurs go for dinner?

This creates a “sauropod paradox,” as researchers call it. Dinosaurs and the loads passed through their feet were so large that they were likely to cause significant underground damage to soils wherever they roam, potentially destroying the soil’s ability to sustain the plants and ecosystems they would rely on as food sources.

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The image of sauropods roaming widely and feeding freely, as depicted by Jurassic Park, seems unlikely, as they would have an unsustainable impact on the environment. So how did they survive?

Scientists behind the study speculate that they may have adhered to well-trodden paths, limiting their impact while examining the canopy with its long necks. How exactly a sauropod can live in balance with the soil remains a mystery.

Great food for thought

A more pressing puzzle is how to combine soil compaction with agricultural vehicles with sustainable food production today. The risk of soil compaction varies depending on the type of machine and the way it is used, as well as the type of soil and the moisture involved.

The study estimates that 20 percent of the world’s arable land is at high risk of losing productivity due to compaction of the subsoil by modern agricultural vehicles, with the highest risk in Europe and North America, where it is relatively wet and has more large farms using the largest machines. It is clear that this is a problem in arable landscapes, but the problem also extends to pastures where silage is baled and urban landscapes where the movement of construction vehicles on green areas is not well controlled.

Compacted soil cannot easily absorb water. Photo by Aisyaqilumaranas, Shutterstock.

The authors call for changes in the design of the machines to maintain the structure of the soil. We offer another option. To reduce their impact on the soil, we could reduce the need for such large machines in the first place by growing food using smaller machines on smaller plots of land, especially in high-risk areas. Finding ways to break up huge monocultural landscapes makes sense for many other reasons. For example, fields of wildflowers, hedges and trees can help release carbon, manage water quality and maintain biodiversity.

The soil can only withstand so much pressure – whether from compaction or other threats such as continuous harvesting, erosion or pollution. Humans need to act to reduce soil pressure, or we risk taking the dinosaur path.

Jess Davis is Professor of Sustainability at the University of Lancaster and Director of the Center for Global Eco-Innovation. She is an interdisciplinary researcher focused on nature-based solutions that help us tackle climate change and environmental risks and create healthier, more sustainable and sustainable landscapes, cities and food systems. John Quinton has spent the last 30 years working to understand and predict soil erosion processes that impair soil function, soil monitoring, how we can better protect soils and how soils can be managed to mitigate floods and pollution. surface waters. He is co-chair of the LEC’s Sustainable Soils Research Group.

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