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Although the root length density (RLD) of crops depends on their root system architecture (RSA), the root growth modules of many 1D field crop models often ignored the RSA in the simulation of the RLD. In this study, two model set-up scenarios were used to simulate the RLD, above-ground biomass (AGB) and grain yield (GY) of water-stressed spring wheat in Germany, aiming to investigate the impact of improved RLD on AGB and GY predictions. In scenario 1, SlimRoot, a root growth sub-model that does not consider the RSA of the crop, was coupled to a Lintul5-SlimNitrogen-SoilCN-Hillflow1D crop model combination. In scenario 2, SlimRoot was replaced with the Somma sub-model which considered the RSA for simulating RLD. The simulated RLD, AGB and GY were compared with observations. Scenario 2 predicted the RLD, AGB and GY with an average root mean square error (RMSE) of 0.43 cm/cm(3), 0.59 t/ha and 1.03 t/ha, respectively, against 1.03 cm/cm(3), 1.20 t/ha and 2.64 t/ha for scenario 1. The lower RMSE under scenario 2 shows that, even under water-stress conditions, predictions of GY and AGB can be improved by considering the RSA of the crop for simulating the RLD.