1. Computation of irrigation frequencies required for the upland sugarcane field revealed that the amount of irrigation water, calculated from the amounts of water absorbed by pot plants and soil-surface evaporation, was higher than that of actually measured.
2. For practical applications of the formulas, correction factors were proposed. An applicable estimation of the amount of irrigation water for the upland field can be performed by correcting Tamai's or Sun's formula with 0.6071 or 0.4857.
3. Based on the above corrected values, the amount of effective rainfall also can be determined. Total rainfall corrected by 0.5482 (for Tamai's formula) or 0.5774 (for Sun's formula) gave a reasonable estimation of the amount of water which should be supplemented.
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