A data driven approach to assessing the increased soil compaction risks from combine harvesters over time

Over recent decades, the risk to soil compaction from agricultural machinery and particularly from combine harvesters has significantly increased. It was found that between 1940 and 2020 the mass of combine harvesters (unladen) has, on average, increased from 2000 kg to 17,000 kg with the largest machines weighing 24,000 kg. When the weight of a filled grain tank is included in calculations the average weight of the machines has increased from 3400 kg to 25,000 kg with the largest machines weighing > 35,000 kg. Over the same period of time tyre sizes have increased with front and rear tyre soil-tyre contact areas increasing from 0.15 m 2 and 0.12–0.65 m 2 and 0.43 m 2 , respectively. This increase in tyre sizes has not kept pace with the increase in machinery weights which has led to an increase in soil compaction risks. This paper shows that soil compaction can occur in 3 of the 4 soils assessed even at soil matric potentials of −100 kPa. The results of this work have implications for farmers and growers looking to conserve their soil structures and for machinery design to limit the prevalence of soil compaction under future climate scenarios.