SCRUM: A simple model for estimating uptake of nitrogen and water by field crops

This paper describes the Simple Crop Resource Uptake Model (SCRUM), a configurable generic crop model implemented in APSIM Next Generation's Plant Modelling Framework. SCRUM simulates crop development using a nine‑phase phenology coupled to a simplified plant module consisting of stover, product, root, and nodule (only in legumes) and a thermal‑time‑driven trajectory for daily potential growth. Water limitation is computed through APSIM's canopy energy balance (MicroClimate). Nitrogen uptake is determined by organ growth and tissue nitrogen targets, constrained by soil mineral nitrogen supply and supplemented by biological fixation when enabled. The generic and simple nature of SCRUM makes it easy for new crops to be configured using expert knowledge, enabling rapid set‑up for species and end‑uses where comprehensive crop models are unavailable. Model evaluation using field data indicated that SCRUM, in the APSIM framework, is a promising a tool that can utilised in the analysis of nitrogen and water management practices of across a range of conditions.•A generic, configurable crop model for rapid parameterization of data‑limited species and end‑uses.•Coupled water stress (canopy energy balance) and nitrogen dynamics (demand targets, supply constraints, optional fixation).•A transparent model description including structure, parameter inputs and assumptions.