The study of the effect of different plant spacing on runoff, soil erosion and soybean yield was conducted in Yandev, Gboko, Benue State, Nigeria. The site for the experiment was manually cleared of its natural vegetation. The experiment was performed on nine 2m x 1m micro plots of fine tilt and slope 3%. Boundaries of burnt bricks were built round each micro-plot to prevent the entry of runoff from adjacent plots and land. Collecting pits were excavated at the lower end of each micro-plot in the direction of the slope and plastic bucket collectors of 40 litres were installed to catch runoff and soil erosion sediments from the micro plots. The size of each micro plot was 2m2 . The experiment consisted of three treatments replicated three times. Treatment one (T1) with plant spacing of 20cm x 20cm, treatment two (T2) with plant spacing of 30cm x 30cm and treatment three (T3) with plant spacing of 40cm x 40cm. Runoff and soil erosion data were determined after each rain storm by measuring the runoff with a 1000ml measuring cylinder. The soil erosion was determined by measuring the oven dried soil erosion sediment with an electronic weighing balance. The soybean yield was determined by weighing the harvested and sun dried soybean grain at a moisture content of 12.6% using an electronic weighing balance. The values of the runoff from the different treatments are 202.50 m3 /ha for treatment one (T1) with plant spacing 20cm x 2cm, 221.00 m3 /ha for treatment two (T2) with plant spacing 30cmx30cm and 238.50 m3 /ha for treatment three (T3) with plant spacing 40cmx40cm. The mean soil erosion values were 16.87 kg/ha for treatment one (T1), 48.03 kg/ha for treatment two (T2) and 142.20 kg/ha for treatment three (T3).

Keywords : Plant spacing, Runoff, Soil erosion, Soybean yield.