The use of caesium-137 to estimate agricultural erosion on steep slopes in a tropical watershed
✍ Scribed by Gregory N. Nagle; James P. Lassoie; Timothy J. Fahey; Sherwood C. McIntyre
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 154 KB
- Volume
- 14
- Category
- Article
- ISSN
- 0885-6087
No coin nor oath required. For personal study only.
✦ Synopsis
The estimation of erosion and sediment delivery rates in tropical mountain watersheds is dicult and most of the methods widely used for estimating soil erosion over large areas have serious limitations. The 137 Cs approach has potential for quantifying soil erosion because it can provide retrospective estimates of long-term (since 1963) net sediment redistribution relatively quickly. Despite its great potential, 137 Cs has not yet been used in an extensive, reconnaissance level survey of erosion in complex tropical mountain environments. The objective of this study was to examine the applicability of the 137 Cs method to estimate erosion on steep tropical agricultural lands (23 to 80% slopes) in the Nizao watershed, a humid, tropical mountain area of the Dominican Republic. In this study we (i) examine the variation of 137 Cs in ten reference sites Ð eight coee groves and two forested sites Ð and (ii) estimate erosion from 14 cultivated ®elds.
The soil pool of 137 Cs ranged from to 150 to 192 mBq cm À2 on reference sites with minimal erosion. Variability among reference sites was less than expected for such complex mountain terrain. The variability within coee and forested reference (average CV 28%) sites was similar to the variability found on grassland and forested reference sites in the temperate zone.
The estimated annual soil loss from 14 sampled ®elds ranged from 6 to 61 t ha À1 year À1 with an overall mean of 26 t ha À1 year À1 . Overall, the soil erosion estimates found using the 137 Cs method were much lower than those often assumed for such steep tropical hillsides. These erosion estimates account for soil loss since 1963 only and it seems likely that soil losses may have been much higher in earlier decades immediately after initial forest clearing earlier in the 20th century.