  We calculate the ${\alpha'}^4$ corrections to the non-Abelian DBI action on
the D8-brane in the holographic dual of large N_c QCD proposed by Sakai and
Sugimoto. These give rise to higher derivative terms, in particular, four
derivative contact terms for the pion field with the coupling uniquely
determined. We calculate the pion-pion scattering amplitude near threshold. The
results respecting unitarity are in qualitative agreement with the experimental
curves.
