In the dry year (precipitation less than 280 mm), the lower level
of Grade B of the irrigation amount is chosen for the first three
stages. And the lower level of Grade C of the irrigation amount is
chosen for the last two stages. Taking the year of 1999 as an example,
it has the precipitation of 256 mm. The optimum irrigation demand
calculated is 180 mm and the irrigation demand is 200 mm
stage and maturing stage, the irrigation is small because the