Effects of cultivation depth in reduced tillage on soil physical properties, crop yield and plant pathogens

Two long-term experiments were started in 1991 on fine-textured soils near Uppsala, Sweden, to study the effects of cultivation depth in ploughless tillage. Five primary tillage treatments were included: mouldboard ploughing to 20-25 cm, chisel ploughing to 10, 15 or 20 cm, and disc cultivation to 10 cm. Chisel cultivation to 20 cm was almost as effective in soil loosening as mouldboard ploughing, as assessed by bulk density and penetration resistance. Bulk density and penetration resistance in the 10-25-cm layer was higher, and aggregate tensile strength in the surface soil lower, in shallow-tilled compared to mouldboard ploughed soil. Shallow tillage also increased the saturated hydraulic conductivity in the former plough sole. Increasing the tillage depth resulted in a higher yield. When barley was grown after barley, the occurrence of leaf scald [Rhyncosporium secalis, (Sacc.) Shoemaker] in 1995 and 1996 was higher in all treatments that were not mouldboard-ploughed. This shows the importance of the crop rotation when using reduced tillage in practical farming. (C) 1998 Elsevier Science B.V. All rights reserved.