Lateral transfer of organic carbon and phosphorus by water erosion at hillslope scale can be a key component in understanding their budget in agricultural areas, particularly those located in areas where erosion rates are high. In this study dissolved organic carbon (DOC) and dissolved reactive phosphorus (DRP) in runoff, and organic carbon (OC) and total phosphorus (TP) in sediment were measured in three olive orchards. These measurements were carried out in a three year runoff plots trial under two different soil management systems (temporary cover crop in the lanes, CC, and conventional tillage, CT). DOC losses (7.8–13.6 kg ha-1 yr-1) were equivalent, and OC losses (101–432 kg ha-1 yr-1) were higher than those measured in other agricultural and forest systems. Thus, both sources of OC, dissolved in runoff and in sediment, should not be neglected as a relevant flux to water bodies in the region and in the soil organic carbon (SOC) balance at hillslope scale. Losses of DRP (0.03–0.21 kg ha-1 yr-1) were in the lower to medium range of published values in agricultural areas, while losses of TP in sediment (2–39 kg ha-1 yr-1) were in the higher range of those reported form agricultural areas in the Mediterranean region, as the combined result of enrichment in sediment and high sediment losses. There is the scope for a large reduction of TP by reducing sediment losses through appropriate CC management. Average annual concentration of DOC in runoff and OC and TP in sediment was correlated with that of the top 5 cm of the soil in the lanes of the orchards. When analyzed at event scale, in DOC, OC and DRP presented a moderated trend towards a larger concentration for runoff events of low magnitude, below 10 to 20% runoff coefficient approximately. However, these trends at event scale presented a large scattering that precludes the determination of robust correlations for prediction and model calibration purposes.

Project P08-AGR-03643, P12-AGR-931 (Andalusian Government) and FEDER funds (European Unión). The long term experiment at Benacazón was also supported by Syngenta through project BIOSUELO.

Postprint de la versión final de manuscrito aceptado en revista.

Peer reviewed