Purpose There is an imperative to accurately assess the environmental sustainability of crop system interventions in the context
of food security and climate change. Previous studies have indicated that the incorporation of legumes into cereal rotations could
reduce overall environmental burdens from cropping systems. However, most life cycle assessment (LCA) studies focus on
individual crops and miss environmental consequences of inter-annual crop sequence and nutrient cycling effects. This review
investigates state-of-the-art representation of inter-crop rotation effects within legume LCA studies.
Methods A literature review was undertaken, starting with a search for all peer-reviewed articles with combinations of ‘LCA’,
‘legumes’ and ‘rotations’ or synonyms thereof. In total, 3180 articles were obtained. Articles were screened for compliance with
all of the following requirements: (i) reporting results based on LCA or life cycle inventory methodology; (ii) inclusion of (a)
legume(s); (iii) the legume(s) is/are analysed within the context of a wider cropping system (i.e. rotation or intercropping).
Seventy articles satisfying these requirements were analysed.
Results and discussion We identified three broad approaches to legume LCA. Most studies involved simple attributional LCA
disregarding important interactions across years and crops in rotations. N-fertilizer reduction through legume residue N carryover
is either disregarded or the benefit is attributed to the following crop in such studies, whilst N leaching burdens from residues are
usually attributed to the legume crop. Some studies applied robust allocation approaches and/or complex functional units to
enable analysis of entire rotation sequences, accounting for nutrient cycling and break crop effects. Finally, a few studies applied
consequential LCA to identify downstream substitution effects, though these studies did not simultaneously account for agro-
nomic effects of rotational sequence changes.
Conclusions We recommend that LCA studies for legume cropping systems should (i) evaluate entire rotations; (ii) represent
nitrogen and ideally carbon cycling; (iii) for attributional studies, define at least two functional units, where one should encom-
pass the multifunctional outputs of an entire rotation and the other should enable product footprints to be calculated; (iv) for
CLCA studies, account for both agronomic changes in rotations and markets effects; (v) include impact categories that reflect
hotspots for agricultural production.