De or het veldvulling?

The correct Dutch article is:

de veldvulling

Rule Words ending in -ing: almost always de. See the rule

How to use veldvulling

the veldvullingde veldvulling
this veldvullingdeze veldvulling
that veldvullingdie veldvulling
our veldvullingonze veldvulling
your veldvullingjouw veldvulling
every veldvullingelke veldvulling
which veldvulling?welke veldvulling?
a big veldvulling / the big veldvullingeen grote veldvulling, de grote veldvulling