International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 11 Issue: 07 | July 2024 www.irjet.net p-ISSN: 2395-0072 © 2024, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 470 IoT-Based Real-Time Soil Health Monitoring System for Precision Agriculture Kapalik Khanal 1 , Grishma Ojha 2 , Sandeep Chataut 3 , Umesh Kanta Ghimire 4 1 Institute of Engineering, Tribhuvan University, Kathmandu, Nepal 2 Oklahoma State University, Stillwater, OK, 74078 3 University of South Dakota, Vermillion, USA, 57069 4 Head of Department, Institute of Engineering, Thapathali Campus, Kathmandu, Nepal ---------------------------------------------------------------------***--------------------------------------------------------------------- Abstract - Monitoring soil health is a tedious and time- consuming task that requires intensive laboratory testing. Soil testing is a multi-step process that involves sample collection, proper packaging, and sending the soil to the nearest laboratory. The entire process requires a significant amount of time and resources and hence, it is not feasible to get real time soil health data from this approach. With the advancements in sensor technologies and data transmission protocols, it is now possible to monitor, collect, extract, analyze, and store real-time in-situ soil health data. In this article, we propose an IoT-based real-time soil health monitoring system using ESP32S3 that can measure soil moisture, electrical conductivity, pH, ultraviolet radiation, temperature, nitrogen, phosphorus, and potassium content of the soil. The system can choose from three communication protocols, Wi-Fi (IEEE 802.11), Global System for Mobile Communications (GSM) and Long Range (Lo-Ra) mesh networking based on their suitability to ensure real-time data transmission from the sensor units to the centralized server. The server also hosts a user-friendly web application interface for real-time visualization of soil parameters. The system is aimed at helping farmers or other stakeholders to take data-driven informed decisions to enhance crop yields in any cropping system. Key Words: soil-sensors, IoT-based, circuit, real-time, precision-agriculture, soil-health, ESP32, low-power 1. INTRODUCTION Soil is the most important natural resource and the foundation for life on Earth. Soil supports the entire agricultural systems in the world and the health of the soil dictates the availability of food for the global population. Soil is composed of minerals, organic matter, water, and air at different proportions. The weathering of the parent rock into fine particles due to its exposure to atmosphere and activity of different gases and water help in the formation of mineral base for the soil [1]. Additionally, microbial activity and plants and animals provide organic matter to the minerals, forming a soil suitable for plant growth and agricultural production [2]. Depending on the type of mineral or parent material involved in the formation of the soil and the amount of organic matter or nutrient available, the soil properties may vary across different regions and cause changes in yield [3]. The soil parameters including moisture content, light intensity, nutrients content, Cation Exchange Capacity (CEC), salinity, pH, and soil temperature directly influence the growth and development of crops. Hence, monitoring these variable soil parameters and implementing proper management strategies is vital for successful crop production. Chart -1: Soil moisture fluctuation in top 5 mm layer of loam soil on 5 to 7 days after irrigation [4] The parameters such as soil moisture content, lux intensity and temperature can fluctuate significantly within a day because of several reasons such as rainfall, solar radiation, evapotranspiration, and soil drainage. Jackson (1973) measured the evaporation dynamics of soil surface in a loam soil in Arizona by measuring the volumetric water content of the top 5 mm of soil every 30 minutes. The diagram below shows fluctuations in soil moisture content of the top layer of the soil due to daily wetting and drying cycle [4]. The soil nutrient's availability also varies within a growing season due to factors including nutrient mineralization and immobilization, leaching, nutrient uptake by plants, and nutrient inputs and losses. The nutrient demand of the plants is also different at different growth stages [5]. The demand for nitrogen is higher in the plant's vegetative growth stages, whereas the demand for phosphorus and