Improving ORYZA2000 for Simulating Rice Growth and Yield with Different Nitrogen and Water Management Options Under Drought Stress.

ORYZA2000, a crop model for rice, has been calibrated and validated across Asia with reliable ability to predict rice growth and yields. It is also used to identify and evaluate the water and nitrogen fertilizer management options in various rice production systems. However, like all crop models, ORYZA2000 has its weaknesses and needs continuous improvement to comply with future applications, particularly for simulations of rice growth and yield under severe abiotic stress. Since 2009, the main progress of the model is its capacity to take into account the effects of severe drought stress on the rice crop. New sub-models to simulate root growth, soil temperature, soil C&N dynamics, and pond nitrogen processes have been developed, and modifications in assimilate allocation, water and nitrogen uptake, drought stress quantification, and irrigation management were made to represent the effects of drought stress on rice growth.  Presented case studies have demonstrated that the improvements on ORYZA2000 have significantly improved rice growth and yield estimation under severe periodic and continuously drought-stressed environments. With these additional capabilities, ORYZA2000 offers a handy tool in assessing the effects of drought tolerance traits on rice production.