What do a modern combine harvester and a diplodocus have in common? One possible answer is your weight. A study led by scientists from Sweden and Switzerland has concluded that the current trend of increased weight of agricultural vehicles is not sustainable, that the stresses they cause in the soil have reached critical values for the ecological functioning of the subsoil root zones, and that almost 20% of the arable land is at risk of chronic compaction in regions critical to global food production.
The weight of today’s largest agricultural machinery is close to that of sauropods, the largest animals that have inhabited the Earth. The largest weighed around 60 tons (ten times more than the average weight of an adult African elephant), the same as a fully loaded state-of-the-art combine harvester..
Tractors and other machinery used on farms have become much heavier as the intensive agriculture on a large scale has become widespread. A combine harvester is almost ten times heavier today than it was in the 1960s. And that circumstance is affecting the ground.
The weight of animals and machines is important because soils can only withstand so much pressure before they become chronically compacted. Y 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 apply pressure, crushing pores, not just on the surface but deeper as well.
Increased risk of flooding
Soil compaction can reduce plant and crop growth and increase the risk of flooding because the water runs off the land and reaches the watercourses more quickly.
Scientists involved in the study measured the compaction that giant agricultural machines are causing and compared it to sauropods that lived until about 66 million years ago. His conclusion is that current machinery is as guilty of soil compaction as those colossal lizards.
The study notes that as the weight of farm machinery has increased, tire size has skyrocketed too, adjusting the contact area between the vehicle and the ground to reduce pressure on the surface and help prevent sinking. Everything indicates that animals evolved with a similar strategy: increase the size of the legs with weight to avoid sinking into the ground.
It is true that the pressure on the soil surface has generally remained fairly constant as farm machinery has gained weight, but the authors point out that stresses in the ground continue to increase below the surface and they penetrate deeper as vehicles (or animals) get heavier.
Today’s agricultural machinery (and the sauropods of the past) is so heavy that it “irreparably compacts the soil below the top twenty centimeters, where it is not tilled”scientists warn.
This fact restricts the depth to which crop roots can grow to search for water and nutrients. and also create low oxygen conditions for the plants and organisms with which they share the soil.
The images of ‘Jurassic Park’, unlikely
All this creates what the researchers call “sauropod paradox”. The dinosaurs and the loads transmitted through their feet were so great that they likely would have caused significant damage to the subsurface, destroying the soil’s ability to support the plants and ecosystems they would have relied on for food.
So The image of sauropods roaming and feeding freely as shown in the film ‘Jurassic Park’ seems to scientists “unlikely”as they would have had an unsustainable influence on their environment.
So how did they survive? The study’s authors speculate that they may have traveled mostly along busy roads, which would have limited their impact. But how exactly a sauropod could live in equilibrium with the ground remains a mystery…for now.
A more pressing puzzle is how to reconcile soil compaction by agricultural vehicles with sustainable food production.
The study estimates that 20% of the planet’s farmland is at high risk of losing productivity due to subsoil compaction by agricultural vehicleswith the highest risks in Europe and North America, where there are larger farms using the largest machines.
The authors call for changes in machinery design to help maintain soil structure. They also suggest reducing the need for such large machines, growing food on smaller plots of land.
“Finding ways to partition vast monoculture landscapes makes sense for many other reasons. For example, Wildflower field margins, hedgerows and trees can help sequester carbon, manage water quality and support biodiversity”, highlight the researchers.
The final message from scientists is clear: “Human beings must act to reduce the pressure on the soil, or we risk going the way of the dinosaurs”.
Reference study: https://www.pnas.org/doi/full/10.1073/pnas.2117699119
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