Design and evaluation of a plant-controlled atmometer for measuring crop evapotranspiration
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Date
2023-01-03
Authors
Rahman, Mujibur
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Abstract
Irrigation is essential for optimal crop development and yield enhancement. Atmometers measure the evaporation rate through a porous surface to estimate the potential evapotranspiration (ETp), which is used to calculate the actual crop water consumption (ETa) using crop coefficients. When the soil is dry, however, plants transpire at a lower rate due to the increasing difficulty in drawing water from the soil. Therefore, the ET of a plant spans two phases: weather limiting Phase 1 and soil limiting Phase 2. The traditional atmometers presume that the crop is adequately irrigated and do not account for the drop in evapotranspiration caused by drier soils as in Phase 2. The objective of this project was to design and evaluate a plant-controlled atmometer capable of detecting crop water ET under both Phases 1 and 2. An atmometer with a variable evaporation rate determined by weather conditions and soil water status was built and tested. Experiments on the rate of evaporation through porous plates revealed that evaporation could be controlled by imposing a negative pressure on the water supply side to mimic the plants. Evaporation rates through porous ceramic plates were measured under different negative pressures to develop a relationship. This relationship was used to simulate the plant ET under different soil water contents and regulate the evaporation rates through the modified atmometer based on soil water content. In this experiment, an increase in ET rate led to increased negative pressure on the water supply side when the water supply was restricted. Water was released from the reservoir to the porous ceramic plate to match the weather conditions and the soil water content to mimic the plant. The change in water volume in the supply reservoir was used to calculate the ETa of the crop.
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Keywords
Atmometer, Evapotranspiration, Evaporation rate, Soil moisture sensors, Irrigation scheduling