Fitting infiltration equations to centre-pivot irrigation data in a Mediterranean soil

Centre-pivot irrigation systems often lead to runoff problems, due to the difficulty in adapting high-water application rates to soil infiltrability. To avoid such problems, a good understanding of soil infiltration characteristics and the factors that influence infiltration rate is necessary. Field tests were carried out, for 2 years, in a Mediterranean soil with different antecedent soil surface conditions and variable water application rates under a centre-pivot irrigation system. The soil infiltration rate was found to decrease not only with an increase in soil water content but also with soil surface compaction. Centre-pivot sprinklers equipped with medium grooved deflectors produced lower infiltration rate values compared to sprinklers with smooth deflectors. The increase in water application rates leads to an increase in soil infiltration rate, especially for durations of less than 25–30 min. Infiltration equations obtained from infiltration tests following previous water application events account for the effect of soil surface compaction and are recommended for design and management of centre-pivot systems. Infiltration tests data was used to fit to different infiltration equations. The Kostiakov-type equation showed the best adjustment to the field data.