Design and performance of a laser-gauging microlysimeter for measuring the water balance of paddy rice

摘要

We introduce a high-precision microlysimeter suitable for measuring the water balance of paddy rice (Oryza sativa L.). The microlysimeter was designed to measure the changes in water level in a rice paddy using a laser displacement sensor as a gauge.The system consists of a plant and soil container paired with a PVC service cylinder. The container and cylinder are connected by a flexible tube that maintains the water surface at the same level in both parts of the system. The container is placed in arice paddy, where it is exposed to wind and rain; therefore its water surface level fluctuates widely. To reduce the influence of this undesirable fluctuation, the laser gauge was mounted in the service cylinder, which was enclosed by a weather shelter.This system successfully minimized the influence of water surface fluctuations and enabled the measurement of water losses or gains at hourly intervals with an error of 0.1 mm or less. The microlysimeter allowed accurate measurements of evapotranspi-ration and is sensitive enough it could potentially detect sap flow taken up by the rice plants at night.