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Farm Vehicles are now Heavier than most Dinosaurs: Why that's a Problem

Farm Vehicles are now Heavier than most Dinosaurs: Why that's a Problem

By Jess Davies and John Quinton

What does a modern combine harvester and a Diplodocus have in common? One answer, it seems, may be their big footprints on the soil. A new study led by researchers from Sweden and Switzerland has found that the weight of farming machinery today is approaching that of the largest animals to have ever roamed the Earth—the sauropods.

Depicted as the giant, friendly "veggiesaurus" in the movie "Jurassic Park," sauropods were the biggest of the dinosaurs. The heaviest were thought to weigh in at around 60 metric tons—similar to the weight of a fully laden combine harvester. Tractors and other machinery used on farms have grown enormously heavier over the past 60 years as intensive, large-scale agriculture has become widespread. A combine harvester is almost ten times heavier today than it was in the 1960s.

The weight of animals or machines matters because soils can only withstand so much pressure before they become chronically compacted. They may not look it, but soils are ecosystems containing fragile structures—pores and pathways which allow air to circulate and water to reach  and other organisms. Tires, animal hooves and human feet all apply pressure, squashing the pores, not just at the surface but deeper down too.

Soil compaction can cut plant growth and harvests, and increase the risk of floods as water runs off the land and reaches waterways more quickly. The scientists involved in the new study took a look at how much compaction is being caused by these giant farming machines and compared it with the sauropods who lived over 66 million years ago. They found both to be big culprits of compaction.

Under pressure

The study points out that as the weight of farm machinery has grown, tire sizes have ballooned too, adjusting the area of contact between the vehicle with the  to reduce the pressure on the surface and help avoid sinking. It seems that animals evolved with a similar strategy—increasing foot size with weight to help avoid sinking into the soil.

Overall, pressure at the  has remained fairly constant as farm 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) get heavier. Farm machinery today (and the sauropods of the past) are now so heavy that they irreparably compact soil below the first 20 cm, where it isn't tilled. Aside from restricting how deep the roots of crops can grow to seek water and nutrients further down in the soil, this can also create low-oxygen conditions that are not good for plants or the organisms they share the soil with.

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