Development of a real-time irrigation control system considering transpiration, substrate electrical conductivity, and drainage rate of nutrient solutions in soilless culture of paprika (Capsicum annuum L.)

IoT-Based Smart Irrigation Systems: An Overview on the Recent Trends on Sensors and IoT Systems for Irrigation in Precision Agriculture

“…Among the possibilities for ET monitoring with sensors, the integration of soil moisture changes can offer evaporation data. Nonetheless, the measurement of transpiration is more complex; it can be estimated with the data of sensors that measure radiation, leaf area index, and vapor pressure deficit [109]. Due to the complexity of its measurement, it is not included as a monitored variable in most of the papers of precision agriculture.…”

Irrigation of Greenhouse Crops

“…A more rational approach for irrigation scheduling is the accumulated radiation method, allowing more closely matched water supply to the ET rate, which is primarily a day time phenomenon depending strongly on solar radiation [14,69,89,108,109]. However, Shin et al [110] indicated that the transpiration rate of soilless paprika (Capsicum annuum) plants did not proportionally increase with an increase in light intensity, especially in high light conditions.…”

“…Weighing lysimeters, measuring ET C directly through changes in mass, while drainage lysimeters calculate ET C through water budgets, where excess water removed by drainage or vacuum is subtracted from a known water volume applied to the soil surface [54]. In addition, Shin and Son [69] used load cells for the direct estimation of irrigation and drainage water amounts in soilless systems. Measurement practices, as cited by Sabeh [124], have ranged from weighting lysimeters measuring output every 10 min to calculating a 60 min average of 1 min measurements.…”

“…In addition, the percentage of the drainage amount could be tuned for irrigation control in greenhouses using a trial-end-error approach (e.g., the percentage of drainage should not be higher than 30% of the irrigation applied). Although the irrigation control system considers drainage amount as a single variable, it could not calculate the exact water amount used by the plant [69].…”

“…The different methods of irrigation scheduling in greenhouses is summarized below ( Table 1). Electrical resistance sensor (e.g., gypsum blocks) Irrigation frequency for soil [62] Volumetric water content Dielectric sensor (e.g., time domain reflectometry, frequency domain) Irrigation frequency for soilless and soil cultivations [62][63][64] Electrical conductivity Electrical conductivity sensor Irrigation frequency for soilless cultivation [65][66][67] Physical properties Mathematic formula Irrigation dose/frequency for soilless and soil cultivations [23,51,65,68] Percentage of drainage Mathematic formula, weighting devices Irrigation volume and frequency based on trial and error for soilless [69,70] Phyto-sensing Leaf water potential Pressure chamber Irrigation timing [33] Stomata resistance Diffusion porometer Irrigation timing [33] Canopy temperature Infrared thermometry Irrigation timing [33,71,72] Flow on water in the stem Heat balance sap flow sensor Irrigation timing/detect water shortages [33,73,74] Changes in stem diameter Dentrometer Irrigation timing [33] Crop reflectance…”