Effects of soil compaction on root development of perennial grass leys in northern Norway

The effects of soil compaction on root development in leys were investigated at three locations in northern Norway: Sortland, Tromso and the Pasvik Valley. At these sites, different soil amelioration measures and drainage methods of peat soils had been used. The investigations were carried out in 5-year-old Phleum pratense/Festuca pratensis or P. pratense/Poa pratensis leys. Tractor traffic decreased the maximum root depth at all sites, and the number of roots at 10-25 cm depth in the plough layer. The influence of compaction on root development in the upper 5 cm of the soils varied between the sites. A significant decrease was found for all compaction treatments at the Pasvik Valley, whereas only the heaviest compaction, with the use of double rear wheels, caused a significantly decreased number of roots in the upper 5 cm of the soil at Sortland. Soil compaction significantly decreased the infiltration rate at all sites. A significant positive correlation was found between infiltration rate and air-filled porosity.