The Internet of Things (IoT) is transforming agriculture by delivering real-time data and control systems, which optimize resource utilization and efficiency. Conventional irrigation techniques frequently struggle with inefficiencies in maximizing crop yield and water use efficiency (WUE), resulting in reduced crop growth and unnecessary resource waste. However, IoT-based smart irrigation systems make data-driven decisions, which can optimize crop yield and WUE; therefore, improving crop output and water conservation in agriculture. This study focuses on integrating IoT-based smart irrigation against traditional techniques that consider red amaranth cultivation. We developed the irrigation system using a microcontroller (ESP32) and various sensors (soil moisture, humidity, and temperature sensors). The impact of irrigation techniques on red amaranth growth and overall crop output was assessed using key characteristics like plant height, leaf count, area, fresh and dry weight, and water use efficiency. Results show that the IoT-based smart irrigation boosts crop yield by approximately 12% while decreasing water usage by around 58%.