  In this article, we have analysed the behaviour of scalar field and
cosmological constant in $f(R,T)$ theory of gravity. Here, we have considered
the simplest form of $f(R,T)$ i.e. $f(R,T)=R+2f(T)$, where $R$ is the Ricci
scalar and $T$ is the trace of the energy momentum tensor and explored the
spatially homogeneous and anisotropic Locally Rotationally Symmetric (LRS)
Bianchi type-I cosmological model. It is assumed that the Universe is filled
with two non-interacting matter sources namely scalar field (normal or phantom)
with scalar potential and matter contribution due to $f(R,T)$ action. We have
discussed two cosmological models according to power law and exponential law of
the volume expansion along with constant and exponential scalar potential as
sub models. Power law models are compatible with normal (quintessence) and
phantom scalar field whereas exponential volume expansion models are compatible
with only normal (quintessence) scalar field. The values of cosmological
constant in our models are in agreement with the observational results.
Finally, we have discussed some physical and kinematical properties of both the
models.
