Abstract
The field water management system provides “constant water level control,” which manages the water level within a certain range during the post-rice planting period in a paddy field. In the “constant water level control,” the water level in the paddy field rises to a set level due to irrigation, and then it fluctuates periodically, decreasing from the set level to the specified control range. The water requirement rate and irrigation water volume were calculated using the fluctuation range of water level data from the field water management system, and the calculation method and its accuracy were evaluated through comparison with actual measurements. Although the calculated and measured water requirement rates were influenced by the length of observation time, they showed a difference of approximately ±1.5 mm d-1. The irrigation water volume during the post-rice planting period was calculated using the water requirement rate. A difference was found between the calculated and measured daily water volume, and the total water volume for a period of approximately 1 weeks was almost similar to the calculated value. Despite the difference between the calculated and measured daily irrigation water volume, the total irrigation water volume for ~1 weeks was similar. Inconsistent irrigation timing was responsible for the difference observed between the calculated and measured daily irrigation water volume.
