This paper proposes a knowledge-based expert system
called SAS as a solution for fertilizer application problem
faced by palm oil smallholder. Normally, rule-based, casebased,
or condition-based system is sufficient. However, palm
oil fertilizer properties are uncertain and varied that based on
external and internal conditions of the palm tree environment.
Rule-based, case-based, or condition-based alone cannot implicitly
justify the suitability of the fertilizer recommended
entirely. However, SAS supports any inference process with
a suitable justification obtained from a human expert. As
such, SAS that uses combination of knowledge-based and
expert system approaches through a web-based application,
is the best solution to solve the problem. This opportunity is
seen as a chance to implement SAS in agriculture domain,
specifically on the suitability recommendation of fertilizer,
which in turn, helps RISDA and MPOA in disseminating
knowledge on fertilizer.