Die maximal tragbare Radlast – eine zweckmässige Kenngrösse für die Praxis

Compaction in the subsoil caused by high wheel loads is usually long-lasting, adversely affecting soil functions and productivity. Wheel load-carrying capacity is defined as the maximum wheel load for a specific tyre and inflation pressure that does not result in soil stress in excess of soil strength (defined as precompression stress). We calculated the seasonal dynamics in wheel load-carrying capacity for different tyres (standard and low-pressure tyres) and for soil under different tillage and cropping systems (mouldboard ploughing, no till, and permanent grassland in the Oberacker long-term field experiment on a sandy loam soil). Wheel load-carrying capacity was estimated based on in situmeasurements of soil matric potential, measure-ments of precompression stress at various matric potentials, and simulations of soil stress. Calculations were made for a reference depth of 35 cm. Our results show wheel load-carrying capacity to be strongly dependent on soil moisture, and to be higher for low-pressure tyres than for standard tyres. The number of trafficable days – estimated by comparing actural wheel loads of agricultural machinery with the wheel load-carrying capacity – varied between years, and decreased with increasing wheel load of the machinery. Wheel load-carry-ing capacity is a useful and easily interpreted parameter for portraying compaction risk, and is therefore an effective guide for preventing soil compaction.