Start / Water and irrigation / Crop water demand
How much water the soil holds for the plant, how much needs to be replaced, and when it is time to irrigate.
Pre-sizing and estimating tool: the results do not replace a design, calculation, or report signed by a qualified professional, nor verification against the applicable standards.
Water the soil holds at each root depth, with the same difference between FC and WP.
The three main values, in millimeters of water.
Drag the controls to simulate data different from what you entered (from 30% less to 30% more) and watch the result change instantly.
Approximate values from FAO-56 (Table 19), for comparison only. They do not replace the physical analysis of your soil.
The calculation done in steps, with the values you entered.
The calculation memo gathers this page's inputs, results, equations, assumptions, and references, with fields for project, responsible person, and review. The full report also includes the charts and interpretations, in color. In the print window, choose Save as PDF.
Enter the soil moisture at field capacity (CC) and at wilting point (PMP), the root depth, and the current moisture. The calculator shows the available water, the part that can be used before stress, and the depth to replace.
CC of 30%, PMP of 12%, roots at 60 cm, current moisture of 22%, p of 0.5 and efficiency of 85%.
AD = (30 − 12) ÷ 100 × 600 mm = 108 mm. AFD = 0.5 × 108 = 54 mm. Depth to replace = (30 − 22) ÷ 100 × 600 = 48 mm; gross depth = 48 ÷ 0.85 = 56.5 mm.
From the soil water retention curve, measured in the laboratory or estimated from physical analysis. Data from your own area are the best source.
Because not all the applied water is available to the plant: drift, evaporation and percolation reduce system efficiency.
Important notice: the Agrocalcs tools make estimates and preliminary sizing based on the data entered and on published engineering methods. They do not replace a design, a calculation report or a report signed by a qualified professional (CREA/ART), nor verification against the applicable technical standards and legislation, such as the Regulatory Standards of the Ministry of Labor. Material and fuel properties vary: check with the manufacturer or with analyses of your process before deciding. By using the site, you agree to the Terms of Use.
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