Variation in the flow rate of drip emitters in a subsurface irrigation system for different soil types

Abstract

Several studies have shown that irrigation is essential for global agricultural development. However, water is a limited resource and should be used as efficiently as possible, which requires appropriate management. As such, the search for irrigation techniques that are more efficient in terms of water use, such as subsurface drip irrigation, is ongoing. Subsurface drip irrigation systems are highly efficient and can serve as suitable alternatives for the rational management of water. However, these systems also have limitations; specifically, variation in flow rate can occur depending on the soil characteristics. Subsurface drip irrigation systems covered by only a thin soil layer have been used, especially in irrigated coffee crops in Brazil; however, most related studies have investigated the variation in the flow rate at relatively great soil depths. Thus, the objective of the present study was to evaluate two emitters buried at a depth of 5 cm to determine the variation in the flow rate within four different soil types, and assess the wet-bulb. The evaluated soil types were classified as a sandy loam, silty loam, clay loam or clay, and the two emitters evaluated included a pressure-compensating drip emitter (PC) and a non-pressure-compensating model (NPC). With respect to the PC emitter, a flow rate reduction was detected only in the clay loam soil, but with respect to the NPC emitter, a reduction in the flow rate was detected in a sandy loam and clay loam. The flow rate varied even at shallow depths for some soils, and the soil type and emitter flow rate affected this variation, as well as the water distribution in the wet-bulb. Thus, this variation should be considered even for systems installed at shallow depths.