Runoff and soil erosion were measured in a two-phase experiment for seven consecutive years from 1979 through 1986 on a 44·3 watershed comprising 12 sub-watersheds of 2–4 ha each. These experiments were conducted at Ibadan, Nigeria, which is characterized by two growing seasons per year. The first season lasts from mid-March through mid-July, and the second season from mid-August to early November. Experiments were conducted in two phases comprising different treatments. The six treatments during Phase I (1979–1981), involving different combinations of land clearing and tillage methods, were: (1) manual clearing (MC) with plough-till (PT); (2) MC with no till (NT); (3) shear-blade (SB) clearing with NT; (4) tree-pusher (TP) clearing with PT; (5) TP clearing with NT; (6) traditional clearing and farming (TF). The five farming-system treatments during Phase II (1982–1987) were: (A) alley cropping with Leucaena leucocephala planted on the contour at 4 m intervals, (B) fallowing with mucuna (Mucuna utilis) on severely degraded soils; (C) fallowing with mucuna on moderately degraded soils; (D) ley farming on severely degraded soils; (E) ley farming on moderately degraded soils. The traditional farming treatment of Phase I was discontinued in 1982 at the beginning of Phase II and the land was returned to natural fallowing.