Detachment of soil organic carbon by rainfall splash: Experimental assessment on three agricultural soils of Spain

An experiment was undertaken to measure the concentration of soil organic carbon (SOC) in particles mobilized by rainfall splash under natural precipitation and to assess its relationship with soil and precipitation properties. Splash cups were deployed on three agricultural soils typical of the central Ebro Valley in Spain (a Cambisol, a Gypsisol, and a Solonchak), and the rainfall characteristics (intensity, kinetic energy) were measured by means of a disdrometer (optical spectro-pluviometer). Evidences of SOC enrichment, i.e. a significantly higher concentration in the splashed material with respect to the parent material, were found in the three soils under study. Differences were found, too, between two particle size fractions (less than 0.05 mm and between 0.05 and 0.5 mm), with higher SOC enrichment in the coarsest fraction. While the amount of splash was clearly related to the erosivity of each rainfall event, no significant effect was found with respect to the SOC concentration. Between the three soils, the Gypsisol exhibited the highest rates of SOC enrichment, and also the largest difference between size fractions. Splash plays an important role on mobilizing fresh carbon fractions, and under certain conditions it may interrupt the soil carbon cycling by favoring the removal of SOC by other erosive processes such as runoff wash, thus preventing its incorporation into the soil carbon pool.