The amount of rainfall and eroded soil were measured under natural rainfall for two bare sloping fields of kuroboku soil with (a) 2m in width, 20 m in slope length, 5°45' in slope gradient, and (b) 2m in width, 10m in slope length, 10°07' in slope gradient.<BR>Applying these data to Universal Soil Loss Equation (1), the following results were obtained.<BR>1. Field (a):<BR>(i) annual rainfall factor R_y (=E·I₆₀) =271m² t/ha/hr, annual amount of soil loss E_ry=7.49t/ha and factor K·SL=0.0276 hr/m² for 27 measurements (July 1976-June 1977).<BR>(ii) R_y (=E.I₆₀) =477m² t/ha/hr, E_ry= 11.2t/ha and K·SL=0. 0236 hr/m² for 21 measurements (July 1977-June 1978).<BR>(iii) R_y (<BR>E·I₆₀) =592m² t/ha/hr, E_ry= 23.0 t/ha, and K·SL=0.0398 hr/m² for 29 measurements (July 1978-June 1979).<BR>2. Field (b):<BR>(i) annual rainfall factor R_y (=E.I₆₀) =313m² t/ha/hr, annual amount of soil loss E_ry=20. it/ha and factor K·SL=0.0642 hr/m² for 19 measurements (July 1977-June 1978).<BR>(ii) R_y (=E.I₆₀) =622 m² t/ha/hr, E_ry=56.2 t/ha and K·SL=0.0904 hr/m² for 30 measurements (July-1978-June 1979).<BR>3. If we express steepness and length of slope factor SL by Equation (3) and define that 20m-5°45'slope field is standard, SL was described as follows, <BR>SL=√L (-0.772s+29.6s²)<BR>Using this equation, the estimation equation of annual amount of eroded soil E_ry at the same soil fi eld were obtained, <BR>E_ry=0.0321·R_y√L (-0.772s+29.6s²)<BR>where, 0.0321 is an average value in 20m-5°45' slope field for 2 years (July 1977-June 1979).<BR>4. E_ry on bare sloping field of 20m in length and 10° in slope inclination were obtained as follows, <BR>E_ry=0.112 R_y<BR>5. When we estimate the amount of eroded soil for every continuous rainfall somewhat roughly, follwing functions of El or I on E_r may be used.<BR>At 20m sloping field:<BR>At 10m sloping field:<BR>E_r=0.00439 R₆₀^1.45 (r=0.869)<BR>E_r=0.00274 R₃₀^1.45 (r=0.891)<BR>E_r=0.000319 I₆₀^2.45 (r=0.814)<BR>E_r=0.000212 I₃₀^2.50 (r=0.844)<BR>E_r=0.0125 R₆₀^1.45 (r=0.894)<BR>E_r=0.00833 R₃₀^1.42 (r=0.909)<BR>E_r=0.00127 I_602.25 (r=0.798)<BR>E_r=0.000628 I₃₀^2.17 (r=0.797)<BR>6. As a result of the existence of volcanic ash soil like Kuroboku soil which contained a large amount of humus, gully erosion rarely occured, but sheet erosion, for which the surface of the soil is stripped off in thin layers, did occur.