SPLASH TRANSPORT OF ORGANIC-CARBON AND ASSOCIATED CONCENTRATION AND MASS ENRICHMENT RATIOS FOR AN OXISOL, HAWAII

Rainsplash is an important component of interrill erosion. To date, fe w studies have critically examined the linkages between aggregate entr ainment by splash and associated nutrient flux. An Oxisol was used in laboratory rainfall experiments with two different antecedent moisture contents (AMC) and ten different rainfall energy flux densities (EFD) . Splash and soil organic carbon (SOC) flux increased with increased E FD regardless of initial AMC. Aggregates were not transported in propo rtion to their content in the original soil matrix, those of 2000-4000 mu m and < 105 mu m were found to be the most resistant to splash. En ergy required to detach 1 gC varied from a median of 1870 J for the 20 00-4000 mu m fraction to 120 J for the 425-850 mu m fraction. Temporal variation in cumulative splash flux and carbon flux for various combi nations of AMC and EFD indicated distinct patterns. Under dry AMC, spl ash increased during 1 h duration storms and this was explained by inc reased aggregate breakdown by air-slaking, decreased soil strength and increased erodibility as soil moisture increased. Wet soil runs exhib ited the opposite pattern of decreased flux with time, probably indica ting a complex response to limited aggregate availability, increased s eal development by raindrop compaction, and transient water layer effe cts in drop impact craters. The formulation of mass-based SOC enrichme nt ratios CER) clearly indicated preferential detachment and transport of splashed aggregates between 250 and 2000 mu m. A reliance of chemi cal transport models on concentration-based ER values can be misleadin g, because it is the balance between nutrient concentration and sedime nt quantity that is important for soil quality and non-point source mo delling.