  We analyze the main properties of the Bergman spaces of weak $L_p$- solutions
for a biquaternionic Vekua equation of the form \[
\mathbf{D}w(x)-\mathbf{Q}_Aw(x)=0 \] on bounded domains of $\mathbb{R}^3$,
where the operator $\mathbf{Q}_A$ involves quaternionic conjugation and
multiplications, both left and right, by essentially bounded functions.
Properties such as completeness, separability, and reflexivity are shown. It is
demonstrated that the solutions belonging to the Bergman spaces are locally
H\"older continuous and that the evaluation maps are bounded in the $L_p$-norm.
Consequently, for the case $p=2$, we obtain a reproducing integral kernel and
an explicit formula for the orthogonal projection onto the Bergman space. For
$1<p<\infty$, the explicit form for the annihilator of the Bergman space in the
dual $L_{p'}$ is presented, along with an orthogonal decomposition for $L_2$.
