Subsurface drip irrigation system designed for research in row crop rotations

A subsurface drip irrigation (SDI) system was designed and installed to conduct long-term research on peanut (Arachis hypogaea) and associated cotton (Gossypium hirsutum) and corn (Zea mays) crop rotations. The objectives were to design a subsurface drip irrigation system for a long-term irrigation research project, describe potential versus actual expenses of the designed system, and to show SDI system performance for irrigation scheduling in row crop (peanut) production. The system includes two thin-wall drip tape lateral spacings buried 30 to 35 cm below the soil surface, three irrigation levels, and five crop rotations replicated three times in a randomized block design. Each mainline branches into two field mainlines reducing the number of flow meters and injector pumps by half. Potential evapotranspiration (ET(o)) was estimated using the modified Jensen-Haise equation adjusted for location conditions. Irrigation treatments of 100, 75, and 50% were based on the crop water use and crop coefficient curves. Irrigation water was applied on a daily basis. A programmable logic controller (PLC) acquired hourly weather parameters, flow data, and controlled the total system. A well water source was used with a separate pump to supply water to the drip irrigation system. The SDI system operated and delivered water to the field crops within the design constraints. Each field mainline took about 6 min to pressurize. There were slight fluctuations in pressure and flow rate for short time durations as valves turned off and on. About $9600 was saved by using a branched design of one flow meter and injector pump per line when compared with a non-branched system. Irrigation plus rainfall supplied just over 100% of the water required for peanut. The other irrigation treatments supplied 75 and 53% of the irrigation water required. Overall, this SDI system was used to efficiently supply water to a row crops in southwest Georgia.