Zero flux plane method and hydraulic conductivity method for measuring the drainage component of water balance equation on sandy loam soil
1992
Tarafder, L.H.
The drainage component of the water balance was measured in a sandy loam soil using both the hydraulic conductivity method and the zero flux plane method. The calculated conductivity decreased by a factor of 1000 at 62.80 and 100 cm depths as suction increased from 20 to 60 cm. Drainage calculated using the hydraulic conductivity method at 36 days after sowing of maize (52 mmd-1) was clearly too high. On the other hand the calculated drainange fluxes at 50 and 64 days after sowing (0.73 and 0.064 mmd-1) were low. The zero flux plane method failed to work in this experiment due to continuous rainfall. The failure of both the methods for measuring drainage was due to very steep hydraulic conductivity versus suction curve. In soil with this characteristic, rapid drainage occurs within 1 or 2 days of rain then falls sharply to a very slow rate. Hence estimates of drainage based on measurements at weekly intervals was unrealistic. ET was calculated for maize crop by assuming that before 57 DAS (Days after sowing) and after 64 DAS the drainage component was negligible, hence ET+D = ET.
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