SUBSURFACE DRIP IRRIGATION SYSTEM DESIGNED FOR RESEARCH IN ROW CROP ROTATIONS

Abstract

A subsurface drip irrigation (SDI) system was designed and installed to conduct longterm research on peanut(Arachis hypogaea) and associated cotton (Gossypium hirsutum) and corn (Zea mays) crop rotations. The objectives wereto design a subsurface drip irrigation system for a longterm irrigation research project, describe potential versus actualexpenses of the designed system, and to show SDI system performance for irrigation scheduling in row crop (peanut)production. The system includes two thinwall drip tape lateral spacings buried 30 to 35 cm below the soil surface, threeirrigation levels, and five crop rotations replicated three times in a randomized block design. Each mainline branches intotwo field mainlines reducing the number of flow meters and injector pumps by half. Potential evapotranspiration (ETo ) wasestimated using the modified JensenHaise equation adjusted for location conditions. Irrigation treatments of 100, 75, and50% were based on the crop water use and crop coefficient curves. Irrigation water was applied on a daily basis. Aprogrammable logic controller (PLC) acquired hourly weather parameters, flow data, and controlled the total system. A wellwater source was used with a separate pump to supply water to the drip irrigation system. The SDI system operated anddelivered water to the field crops within the design constraints. Each field mainline took about 6 min to pressurize. There wereslight fluctuations in pressure and flow rate for short time durations as valves turned off and on. About $9600 was saved byusing a branched design of one flow meter and injector pump per line when compared with a nonbranched system. Irrigationplus 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 southwestGeorgia.