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 Printable version |
Variations in irrigated rice water requirements according to transplanting dates (Burkina Faso, central zone) |
Cahiers Agricultures. Volume 8, Number 2, 93-9, Mars - Avril 1999, Étude originale
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 Résumé
Article gratuit
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Author(s) : Youssouf Dembélé, Jean Duchesne, Sibiri Ouattara, Zacharie Zida |
Summary : Irrigated rice water requirements were determined using lysimeters at the Mogtedo irrigation scheme in central Burkina Faso (Figure 2). Measurements were obtained through three seasons (1991, 1992 and 1993). Evapotranspiration (ET) and percolation rates were determined, and crop coefficients for different growth stages were calibrated for rice transplanted at the beginning of August (Table 1). Figure 3 shows the daily evapo-transpiration rate trends. The peak value was 7.2 mm/day, with the seasonal mean estimated at 6.0 mm/day. Total evapotranspiration was also calculated for several transplanting dates. ET values were higher for later transplanting dates (Figure 4). The high variability in the percolation values obtained (Figure 5) could be due to the actual soil heterogeneity and to variations in subsurface hydraulic conditions. This seasonal mean percolation value was about 3 mm/day. Irrigation water requirements were then simulated for several transplanting dates (Figure 7). For these simulations, evapotranspiration was computed using the calibrated crop coefficients and modified reference evapotranspiration (FAO). Measured 10-day percolation values were used and 90% of the rainfall level was considered effective. The soil moisture level for each transplanting date was considered when computing the amount of water to be used for soil saturation and preparation (Figure 6, Table 3). The results were compared to the actual amounts of water used for irrigation in 1992 and 1993 (Table 4), which was assessed at about 2,500,000 m3. This was much higher than actual rice irrigation water requirements during the wet season at Mogtedo (1,100,000 m3 to 1,500,000 m3). It should be possible to increase the area under irrigation by improving water management and the irrigation scheme. |
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