Diagnosis of soil hydrophobicity linked to pig slurry use in a calcareous soil

Pig slurry fertilization in dryland agriculture of semiarid areas is a matter of concern because of the increasing intensity of livestock farming. Slurry is a nutrient source but if it triggers soil water repellency (SWR), this could constrain its application over the surface in the crop cycle. In SWR tests, choice of a suitable drying soil temperature is a key point, as temperature affects its expression. Its determination must also be easily integrated with the different standard analytical procedures in laboratories. In this study we evaluated the persistence and the severity of the SWR in undisturbed soil samples dried at 40 °C. Soil samples came from a long-term fertilization experiment where five slurry treatments plus a control were implemented. Soil samples were taken seven times during a 51 days (d) period, starting 4 d before slurry application and up to 47 d after. The maximum recorded SWR persistence and severity was classified as moderate and severe, respectively. As soil dried at 40 °C was able to express hydrophobicity after pig slurry fertilization, the SWR tests can be easily included in the framework of routine procedures for soil sample analysis where this effluent has been applied. Further research is needed in slurry rainfed fertilized areas to evaluate SWR variability (annual and between cropping seasons) and its additional impacts in these agricultural systems.