  We study the direct sum of q-matroids by way of their cyclic flats. Using
that the rank function of a q-matroid is fully determined by the cyclic flats
and their ranks, we show that the cyclic flats of the direct sum of two
q-matroids are exactly all the direct sums of the cyclic flats of the two
summands. This simplifies the rank function of the direct sum significantly. A
q-matroid is called irreducible if it cannot be written as a (non-trivial)
direct sum. We provide a characterization of irreducibility in terms of the
cyclic flats and show that every q-matroid can be decomposed into a direct sum
of irreducible q-matroids, which are unique up to equivalence.
