A new Internet tool illustrates the impact of traffic in the field and may help farmers choose suitable combinations of wheel loads and tyres.

The agricultural soil in Denmark is threathened when trafficked by modern agricultural machinery. The mechanical stresses are illustrated by a new Danish tool on the Internet. The tool has been developed by scientists from the Faculty of Agricultural Sciences (DJF) at the University of Aarhus in collaboration with The Danish Agricultural Advisory Service and the tyre company Nordisk Dæk Import A/S. The tool is called ’JORDVÆRN online’ (Soil Protection Online) and can be found on the website www.planteinfo.dk , menu topic ’Jord’.

JORDVÆRN online gives the user the possibility to select tyre type, inflation pressure and wheel load, after which the system predicts the stresses that particular combination will transfer to the soil. Three graphs show the contact area, the stress distribution within this contact area, and the stress transmission in the soil profile.

On the basis of a comprehensive measurement programme with seven different tyre types and varying load and inflation pressure, the scientists have set up equations that can predict the stresses underneath a tyre. The investigation was financed with funds from the Ministry of Food, Agriculture and Fisheries, and the new tool includes predictions for approximately 200 different tyres (over 5,000 combinations of tyre type, inflation pressure and wheel load).

- We hope that JORDVÆRN online may inspire farmers and machine contractors to regulate tyre inflation pressure correctly according to the recommendations for field traffic and thereby reduce soil compaction. All too often we see too high inflation pressures whereby the good qualities of the tyres are not fully utilized, says senior scientist Per Schjønning from the Department of Agroecology and Environment at DJF.

The predictions in the programme are, strictly speaking, only applicable on relatively wet sandy soil. On dry soil, especially clay soil, the conditions may be different. This is especially the case for transfer of stresses in the soil profile.

The scientists have therefore applied for new research funds with the aim of making JORDVÆRN online more flexible and thereby developing a real decision support system. The ambition is that each individual farmer any place in Denmark can get an indication, whether his soil with the given moisture content can carry the actual machine that he plans to use.

For more information please contact: Senior scientist Per Schjønning, Department of Agroecology and Environment, Faculty of Agricultural Sciences, University of Aarhus, telephone: +45 8999 1766, e-mail: Per.Schjonning@agrsci.dk