Design and construction of a portable smart weighing lysimeter for accurate measurement of crop water requirement

Due to increasing evapotranspiration and water resources scarcity, accurate estimation of crop water requirement is quite necessary. The existing improvements and the development of smart and automated devices in the field of agriculture have made lots of progress in agricultural required plant-environment measurements. In this study, design, construction and calibration of a portable small weighing smart lysimeter has been introduced. This device is capable of direct measurement for determination of crop evapotranspiration, crop coefficient and also to find the behavior of chemical compounds at desired soil depth and water. This study was conducted in an experimental farm located in Shahid Bahonar University of Kerman during years 2016-2017. In order to design the device the inner tank dimension was considered as 27 cm in diameter and 30 cm in height with stainless steel cover and outer cylinder with 40 cm diameter. Because of this weighing system, an aluminum alloy single point load cell has been used where it has 60 kg rated capacity. An automatic weather station installed near small lysimeter and recorded weather data such as rainfall, temperature, relative humidity, air pressure, sunshine hours and intensity of radiation. On the other hand for supplying crop water use, an automatic irrigation system with known time distances was installed near lysimeter’s setup. An automatic drainage sensor at the bottom of lysimeter’s cylinder determines excess water amount. Measuring soil moisture and soil temperature at desired depth are possible by their sensors. Load cell calibration was done by applied known weights to the small lysimeter. Then correlation diagram between known weights and lysimeter weight changes resulted in R2=0.9998. Other sensors also were calibrated. Finally, lysimeter gets ready for cultivation surrounding a farm.