SimRoot modeling data In order to investigate the relationships between changes in root hair phenotypes and N capture under different N and transpiration regimes, a maize root system with the primary root and lateral branches varying in root hair length and density were simulated in the functional-structural plant model SimRoot. SimRoot offers a realistic platform to simulate the effect of the whole root system and/or a specific root traits on plant growth and resource acquisition because it is equipped with both carbon and nutrient models (Lynch et al. 1997; Dathe et al. 2016). Root hair length was modified by varying root hair growth rate. We used a 1*1*1 mm cubic finite element grid for the simulations. Simulations were run for 15 days. Transpiration rate was modified to manipulate the mass flow component. Four levels of nitrate were used in the simulations corresponding to 20.8, 62.4, 104 and 145.6 kg ha-1. All root parameters except for the parameters of interest (root hair length, root hair density) were kept constant. This research was supported by grants from the Howard G. Buffett Foundation and the National Science Foundation-PGRP grant DBI 0820624 to JPL and Mahidol University to PS’s time for developing the manuscript.