The Model inputs are at the top of the diagram. Every day there is always a weather input and very ocassionally there is a fertilizer input. The plant dry weight at the beginning of the day may also be considered to be an input.
The Model's output for the day is the increment in plant weight at the bottom of the diagram.
At the end of the day, the weight increment is added to the plant dry weight and then the processing for the next day begins.