Indian Journal of Agricultural Sciences 90 (10): 1980–7, October 2020/Article https://doi.org/10.56093/ijas.v90i10.107978 Development of an IoT based weighing type micro-lysimeter for soilless cultivation POOJA GOYAL 1 , RAKESH SHARDA 2 , MUKESH SIAG 3 and K G SINGH 4 Punjab Agricultural University, Ludhiana 141 004, India Received: 30 January 2020; Accepted: 20 October 2020 ABSTRACT In the present study, an attempt has been made to apply Internet of Things (IoT) for precise irrigation management. A weighing type micro-lysimeter based on IoT was developed to measure the amount of water consumed by the cucumber crop grown in soilless media under naturally ventilated greenhouse conditions at the Research Farm of Punjab Agricultural University, India. The developed system consisted of two components, i.e. hardware assembly and web-based application. The hardware assembly consists of load cells, a weight sensing module, i.e. HX711 module and a micro controller, i.e. arduino assembled in the control box of the weighing balance. A modular code was written in arduino to record the weight readings. The stored data in the microcontroller was sent to a web based application via wif. The weight changes at the lysimeters due to irrigation, drainage and evapotranspiration were monitored in real time through an IoT platform, i.e. Thingspeak. Three lysimeters were placed at different locations to account for the slight variations in micro-climate within the greenhouse. The positive fux i.e. irrigation and negative fux, i.e. (leachate+ actual evapotranspiration (ET c )) from the lysimeter were derived from the IoT platform. Irrigation and leachate from the lysimeter was also measured manually to verify the accuracy of the readings obtained from the IoT platform. The study showed that IoT based lysimeters presents a reliable and convenient way to measure ET c as there was a good agreement (R 2 > 0.98) between irrigation component derived from IoT and actual irrigation applied. Key words: Evapotranspiration, Greenhouse, IoT, Lysimeter, Soilless Water has always been a limiting resource, both in terms of quantity and quality. Therefore, optimum irrigation is necessary, in terms of proftable agriculture to attain best level of production. As 80% of the available water is utilized in agriculture (Dhawan 2017), proper irrigation scheduling of the crops is required for effcient utilization of these scarce water resources. Calculations of irrigation scheduling are based on the estimations of crop water requirements (CWR). As 99% of the water used by the crop is in the form of evapotranspiration (ET) (Rana and Katerji 2000), it is important to measure ET accurately for all the crops. There are many direct and indirect methods by which ET can be calculated or estimated but the use of lysimeters have long been considered as a standard method for actual measurement of ET and for validation of reference ET equations (Jensen 1974; Doorenbos and Pruitt 1977, Allen et al. 1989). A more detailed information on the use of lysimeters for ET can be found in Harrold (1966); Aboukhaled et al. (1982); Howell et al. (1985); Marek et al. (1988). Lysimeter is a device which essentially works 1,2,3,4 (email- poojagoyal1605@gmail.com, rakeshsharda@ pau.edu, siagmukesh@pau.edu, kamalgurmit@pau.edu), Department of Soil and Water Engineering, on the principle of soil-water-balance approach. The daily weight changes at the lysimeters are monitored regularly with the load cells or weighing balances to measure actual crop ET (Howell et al. 1985). Weighing lysimeters presents the most accurate data and ET can be determined accurately over periods as short as 30 min. (Allen et al. 2011). Lysimeters of many different designs, sizes, shapes, and measurement systems have been built over the years. Boast and Robertson (1982) introduced a new concept of micro-lysimeter and deviations were quantifed with the traditional bigger lysimeters. Tyagi et al. (2000) used rectangular lysimeters for crops like rice, maize, sorghum, wheat, berseem and sunfower using water balance approach to compute the crop ET from the lysimeters. Abedi-Koupai et al. (2011) measured and modelled the water requirement for cucumber, tomato, and pepper using micro-lysimeter inside the greenhouse. The ET c for cucumber crop was found to be 202 mm for a period of 3.5 months. The concept of precise irrigation is already being used in agriculture to improve the water-use effciency of the crops. Wireless Sensor Networks (WSN) are slowly being adopted to improve the effciency in agriculture (Mendez et al. 2012; Liu et al. 2007). The WSN comprises various sensors that monitor physical and environmental conditions like temperature, relative humidity, solar radiation, soil 144