Arduino-Based Microclimate Monitoring System for Tropical Greenhouse

Greenhouse horticulture is one of the most intensive agricultural systems designed to achieve stability of production year-round and higher efficiency of plant growth resources utilization. However, in low-input greenhouses, like those in Ecuadorian lowlands, the inside microclimate is highly dependent on the daily variations in solar irradiance (IR), triggering effects on air temperature (T), relative humidity (RH) and vapour pressure deficit (VPD). Thus, monitoring the greenhouse microclimate, in real time, is critical for achieving optimal operating conditions, during various periods of plant growth. This paper presents the use of the Arduino Mega 2560 microcontroller, based on the ATmega 2560 chip, linked to sensors, to monitor the spatiotemporal variability of IR, T, and VPD inside of a plastic covered multi-tunnel greenhouse, at the Ecuadorian lowland. The sensors were placed in a three-dimensional network of 18 nodes, at either of 0.5 or 2.5 m heights, recording data at 30minute intervals between, from January to May 2023. Within the greenhouse, air ventilation took place through a fixed width zenithal opening and the small mesh screen on the sidewalls. According to data recorded during cloudless days, the IR reached a maximum of 700 Wm$^{-2}$ at noon, 30% lower than outside. Whereas, noon VPD (3.1 kPa) and T $(37^{\circ}\mathrm{C})$ were higher inside than outside the greenhouse. Overall data pointed towards (a) the feasibility of using Arduino-based microclimate monitoring system, as a reliable data communication module for tropical greenhouses, and (b) the urgent need of improving air ventilation and VPD to decrease T and VPD inside the tropical greenhouse.