Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/1997
Publication Date: N/A
Citation: Interpretive Summary: More and better information is needed on rates and patterns of soil movement in Palouse watersheds in order to better guide conservation planning. The Cs137 fall out from nuclear testing in the 1960's offers a unique opportunity to track soil movement since that time. The Cs137 attaches to the soil and moves with the particles that are eroded or translocated by tillage. Tillage translocation were ignored and uncertainties in tillage practices for use in the RUSLE calculations were problems, but data from Cs137 movement in a field size watershed were approximately in balance with erosion estimates with the Revised Universal Soil Loss Equation (RUSLE).
Technical Abstract: More complete information is needed on the rates and patterns of soil movement in Palouse watersheds to better guide conservation planning. Water erosion has historically been predicted from rates using the Universal Soil Loss Equation (USLE) or the Revised USLE (RUSLE). These equations, however, do not account for deposition or tillage erosion. This study was conducted to assess patterns of soil movement in an open Palouse watershed over a 27 year period using the Cs137 tracer technique and to statistically compare transect and point based RUSLE soil loss rates with Cs137 based soil loss rates measured at 74 Cs137 sampling points located on 89 landscape profiles. One hundred fifty eight soil samples were collected from a modified grid pattern and analyzed for Cs137 activity. Soil movement rates were interpolated at 8025 points in the sample grid using ordinary point kriging. Hillslopes were classified into geometric and geomorphic components. The kriged mean net soil movement rate for the 27 year period was minus 3.3 kg per square meter per year. Doubly convex landscape positions have experienced the most severe erosion apparently due to tillage erosion. The measured Cs137 and transect based RUSLE median soil loss rates were both significantly higher than the point-based RUSLE median; however, no significant difference existed between the transect-based RUSLE and measured Cs137 median soil loss rates (alpha = 0.05). Meaningful comparisons between Cs137 and RUSLE soil loss rates can only be made if a tillage movement rate, history of crop management, and the accuracy of RUSLE relationships and operating files are known.