Another challenge for proper representation of agricultural reality is
the consideration of crop rotations in LCA. “If an LCA study focuses on
just one crop […], it fails to account for the interactions between this
crop and preceding and subsequent crops” (Cowell et al., 1995). Agricultural
systems are highly complex, and their functional principles are
quite well understood, but not all underlying material flows can be
easily quantified. To have a complete picture of involved substances
and material flows, it is essential to find system boundaries that are
equally valid, both in agricultural practice and in the LCA model. This
is relevant, because the quality of this representation affects the quality
and meaningfulness of the overall LCA results. Finding appropriate
system boundaries might be relatively easy for chemical reactions – if
they take place in test tubes or systems with clear physical borders –
but such clear borders do not exist for agricultural systems.