Reduced tillage: Influence on erosion and nutrient losses in a clayey field in southern Finland

Reduced tillage was compared with traditional ploughing in terms of erosion and phosphorus (P) and nitrogen (N) losses in an experimental field in southern Finland. One part of the field has been ploughed (treatment PF) and the other part harrowed (treatment NPF) every autumn since 1986. Flow volume and water quality data was collected separately from surface runoff and subsurface drainage waters during 1991-1995 (surface runoff volume since 1993). Erosion was higher in PF (on average 234 kg ha(-1)yr(-1) in drainage flow and 479 kg ha(-1)yr(-1) in surface runoff) than in NPF (158 kg ha(-1)yr(-1) in drainage flow and 160 kg ha(-1)yr(-1) in surface runoff). Total N loss in drainage flow was also higher in PF (7.2 kg ha(-1)yr(-1)) than in NPF (4.6 kg ha(-1)yr(-1)). Total P losses did not differ much; approximately 0.7 kg ha(-1)yr(-1) was transported from both fields. Dissolved reactive P loss in surface runoff was higher in NPF (0.21 kg ha(-1)yr(-1)) than in PF (0.05 kg ha(-1)yr(-1)). This was probably attributable to the higher accumulation of P in the surface soil in NPF. The differences between the treatments were largely similar to those found in previous studies.