Runoff and soil loss from bare fallow plots at Inverell, New-South-Wales

Abstract

Three 41 m long bare fallow plots were established on a chocolate soil (Mollisol) at Inverell in late 1976 to determine the soil erodibility (K) factor for use in the Universal Soil Loss Equation (USLE). The K-factor was estimated as 0.018 tonne hectare hour per hectare megajoule millimetre, indicating a soil of low to moderate erodibility. This value was close to that predicted from the soil erodibility nomograph used in the USLE. The average annual soil loss over the eight year period was 51 t/ha, while the largest individual storm soil loss from the plots was 47 t/ha. The two largest soil losses in each year accounted for 60-99% of the annual soil loss. Various erosivity indices were examined for their ability to predict runoff and soil loss from individual erosive storms. Indices which had separate variables for soil particle detachment (energy component) and particle transport (runoff component) were superior, although a large proportion of the variation in runoff and soil loss remained unaccounted for, and the possible reasons for this are examined. The highest correlation was obtained between soil loss and runoff amount.