USE OF MICROLYSIMETERS TO MEASURE EVAPORATION FROM SANDY SOILS

Evaporation from soil can be a major component of crop water balance and land surface energy balance. A number of different applications of the microlysimeter method to measure evaporation from soil have been used in recent studies. Microlysimeters were used extensively in three sandy soils for this study. Measurement of evaporation from microlysimeters with different dimensions and of different ages allows discussion of the sources of error inherent in the method. The evaporation recorded from microlysimeters of diameters 214 mm, 152 mm and 51 mm was not significantly different. A comparison of 100 mm and 200 mm deep microlysimeters showed that depth had no significant influence during the first 2 days after extraction from the soil profile. For periods beginning 2 or more days after rain, significant differences in evaporation owing to depth may not occur for up to 7 days. Soil cores extracted at different times showed significant differences in evaporation immediately following a rain event, and no significant differences 2 or more days thereafter. This period of significant difference was extended to about 4 days when the method was used within a crop (i.e. root extraction of water in the field significant). A protocol for use of microlysimeters is developed from these results.