Strong colour fields and cosmic ray showers at ultra-high energies

We argue that the increase of the ratio baryon/meson due to the presence of strong colour fields and percolation in ultra-high energy hadronic collisions, helps to explain some of the global features of ultra-high energy cosmic ray cascades at E > 1018 eV and, in particular the observed excess in the number of muons with respect to current models of hadronic interactions. A reasonable agreement with the small value and slope of the average depth of shower maximum 〈Xmax〉 vs shower energy – as seen in data collected at the Pierre Auger Observatory – can be obtained with a fast increase of the p-Air production cross-section compatible with the Froissart bound.