  We study LDPC codes for the channel with input ${x}\in \mathbb{F}_q^m$ and
output ${y}={x}+{z}\in \mathbb{F}_q^m$. The aim of this paper is to evaluate
decoding performance of $q^m$-ary non-binary LDPC codes for large $m$. We give
density evolution and decoding performance evaluation for regular non-binary
LDPC codes and spatially-coupled (SC) codes. We show the regular codes do not
achieve the capacity of the channel while SC codes do.
