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How irrigators can estimate effective rainfall, and use that estimate to schedule irrigations properly. Scheduling irrigation based on crop demand (see NebGuide G85-753 Irrigation Scheduling Using Crop Water Use Data, on the checkbook method) requires an estimate of effective precipitation or rainfall. Effective rainfall estimates are also important for planning cropping sequences in both dryland and irrigationd crop production. Effective rainfall is the amount of rainfall stored in the crop root zone. Rainfall that runs off the soil surface or passes through the root zone does not contribute to crop growth and yield. There are two steps to estimating effective rainfall accurately. First, the total rainfall amount must be measured accurately. Second, the amount stored in the root zone must be determined.