Effects of depth and time of ploughing on yields of spring cereals and potatoes and on soil properties of a morainic loam soil

A tillage trial was performed on morainic loam soil in south‐east Norway over the years 1985–97. Two times of mouldboard ploughing (autumn and spring) were compared, together with four depths of ploughing (0, 10, 20 and 30 cm) on soil previously ploughed to 20 cm. Three crops (spring barley, spring wheat and potatoes) were grown each year in rotation. Soil physical analyses were performed 6 years after the start of the trial and soil chemical analyses after 10 years. A marked plough pan was found at a depth of 23–27 cm with the reference ploughing depth. Deeper ploughing gave a greater storage capacity for plant available moisture, but somewhat lower total nutrient reserves than shallower ploughing. Shallow tillage led to increased soil density, but not to such an extent that soil aeration was likely to be limiting. The concentration of organic matter increased in the surface layer with shallow tillage, but the total amount present differed little between treatments when related to a fixed mass of topsoil...