This study investigates the development and application of an automatic irrigation system based on hourly cumulative evapotranspiration (ET) to optimize cabbage growth while reducing agricultural water usage. Traditional irrigation methods often result in inefficient water use due to reliance on human judgment or fixed schedules. To address this issue, the proposed system utilizes environmental data collected from a field sensor (FS), the Korea meteorological administration (KMA), and a virtual sensor based on a machine learning model (ML) to calculate the hourly ET and automate irrigation. The ET was calculated using the FAO 56 Penman–Monteith (P-M) ET_o. Experiments were conducted to compare the effectiveness of different irrigation levels, ranging from 40, 60, 80, and 100% crop evapotranspiration (ET_c), on plant growth and the irrigation water productivity (WP_I). During the 46-day experimental period, cabbage growth and WP_I were higher in the FS and KMA 60% ET_c levels compared to other irrigation levels, with water usage of 8.90 and 9.07 L/plant, respectively. In the ML treatment, cabbage growth and WP_I were higher in the 80% ET_c level compared to other irrigation levels, with water usage of 8.93 L/plant. These results demonstrated that irrigation amounts of approximately 9 L/plant provided the optimal balance between plant growth and water conservation over 46 days. This system presents a promising solution for improving crop yield while conserving water resources in agricultural environments.

In recent years, the government has strongly promoted multipurpose utilization of paddy field. However, poor drainage causes waterlogging stress in upland crops, requiring subsurface drainage technology, resulting in high installation and management costs. To address this issue, a low-cost and high-efficiency technique was developed that utilizes wasted coir substrates which have characteristics of high porosity and good drainage, for upland crop cultivation in paddy fields. Soybeans were grown in both paddy soil and wasted coir slab with two planting densities (80×20 cm and 60×20 cm). The results showed that the coir substrates had better performance than the paddy soil in terms of soil physical and chemical properties and the growth and yield of upland crops are improved. The treatments using wasted coir substrate showed a 41.4% increase in yield and a 21.3% increase in protein content compared to PS treatment. Our findings demonstrate that recycling waste coir substrates to grow upland crops is a positive cultivation strategy to solve some drainage problems in paddy fields. This approach offers a sustainable solution for upland crop production while also addressing the issue of waste management in agriculture.

This study developed an efficient cultivation strategy for cabbage production in paddy fields. To address poor drainage, discarded coir substrates (CS) were reused and compared with conventional paddy soil (PS). Four irrigation levels (ETc140, ETc100, ETc60, and ETc0) were applied to both CS and PS to evaluate their interactive effects. An automated irrigation system was deployed, integrating a weather sensor and solenoid valves via a LoRa-based IoT network. Hourly ET₀ was calculated based on Penman–Monteith in real time, and an irrigation event was triggered when cumulative ET₀ reached 1 mm (CS) or 3 mm (PS). The automated irrigation system showed stable performance. Hourly ET₀ estimates were 97% consistent with Korea Meteorological Administration data. The actual total irrigation depth (ID_actual) remained within 2% of the calculated depth (ID). Under moderate irrigation depths (ETc60 and ETc100), the reuse of CS significantly improved cabbage photosynthetic efficiency. Both CS-ETc60 and CS-ETc100 treatments maintained superior yield performance compared with other treatments. This integrated strategy not only offers a practical solution for improving water use efficiency but also enhances the multifunctional utilization of paddy fields, supporting the transition toward more sustainable agricultural practices.