[A-GE27] Subsurface Mass Transport and Environmental Assessment

[AGE27-P01] Effect of coupling a crop model with HYDRUS-1D on crop growth prediction

★Invited Papers

*Koki Oikawa¹, Hirotaka Saito¹, Kenichi TATSUMI¹, Yasunori Ichihashi² (1.Graduate School of Agriculture, Tokyo University of Agriculture and Technology, 2.RIKEN)

Keywords:Crop growth model, HYDRUS-1D, Vadose zone

Improved accuracy of crop growth models is required for agronomic management in response to climate change, efficient irrigation and drainage, and appropriate fertilizer management. The crop growth model predicts crop growth, such as dry weight and plant height, based on weather conditions and fertilizer and irrigation management. To improve the accuracy of crop growth models, it is important to accurately predict water and solutes transfer between aboveground and underground areas. In the underground, root water and solute uptake must be reasonably evaluated. HYDRUS-1D is software that simulates the dynamics of water, solutes, and heat in the vadose zone (Simunek et al., 2008). The water flow in the soil is determined by solving the Richards equation using the finite element method. Shelia et al. (2018) estimated crop mass by coupling the DSSAT model with water flow simulations in the subsurface of HYDRUS-1D. However, the dynamics of nitrogen, which is important for crop growth, has not been taken into account. Tatsumi (2021) developed the Integrated Rice Growth Model (iRGM) for rice growth simulations under various meteorological, fertilizer, and water conditions, and simulated dry weight agreed well with the measured values.
The main objective of this study was to investigate the effect of coupling HYUDRUS-1D and iRGM on the crop growth prediction. The two models are coupled with common variables through input and output files. While, in HYDRUS-1D, root water and nitrogen uptake were calculated, root length, potential transpiration, and potential evaporation were calculated in iRGM. These variables are used in both models. Potential transpiration and evaporation are determined by above-ground weather conditions and crop growth conditions. The crop growth rate depends on the root nitrogen uptake and the water stress determined from the root water uptake by HYDRUS-1D.
The differences in results between the iRGM model and the coupled HYDRUS-1D and iRGM are discussed. The iRGM model predicted leaf area index (LAI), plant height, and dry weight. The coupled model was able to calculate detailed volumetric water content and nitrogen concentration profiles of the root zone domain.

References
Shelia, V., 2018, Journal of Hydrology and Hydromechanics, 66(2), 232-245.
Simunek, J., et al., 2008, Vadose Zone Journal, 7, 2, 587–600.
Tatsumi, K., 2021, Transactions of the ASABE, 64(5), 1581-1610.