Markfysikaliska och markkemiska effekter av plöjningsfri odling i Sverige

The effects of ploughless tillage on physical and chemical properties of soils were investigated during the period 1980-1984 in field trials on Ultuna (heavy clay), Lanna (heavy clay), Rudsberg (silt loam) and Lönnstorp (clayey till). Trial plots on Ultuna, Lanna and Lönnstorp were laid down in the autumn of 19?3 and those on Rudsberg in the autumn of 1974. In the unploughed experimental plots, conventional autumn ploughing to 20-25 cm was replaced by two or three stubble cultivations to approximately 10 cm depth. Preparation of the seedbed and sowing, on all plots, were carried out using conventional methods. Straw was not removed from any of the plots but was chopped at harvesting. The aim of these investigations was primarily to study the effects of 5-10 years shallow tilling on physical and chemical properties of soils. Soil physical investigations revealed several differences between unploughed and ploughed treatments. Some effects of ploughless tillage were: increased degree of compaction in the middle topsoil: improved saturated hydraulic conductivity in the lower topsoil and upper subsoil; reduced rate of infiltration in field measurements; a shallower and somewhat coarser seedbed; improved aggregate stability in the seedbed. In a pilot experiment during the summer 1984, it was also observed that the unploughed treatment offered a better protection against evaporation, particularly after rainfall. After approximately 10 years of ploughless tillage the content of ammonium lactate extractable phosphorus and potassium has increased in the surface layer and decreased in the middle and lower layers of the topsoil. Organic matter content has followed a similar pattern. Ploughless tillage has not significantly influenced the organic matter, P or K contents of the subsoil. There was no apparent relationship between tillage method and pH in either top- or subsoil. In the discussion, results of these investigations are used to form the basis of a method to assess the suitability of a site for ploughless or conventional tillage.