Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/16/2000
Publication Date: 3/1/2001
Interpretive Summary: Water can be applied more efficiently to row crops with subsurface drip irrigation (SDI) than with overhead sprinkler systems. A long term project was designed to evaluate the application of water and resultant yield with peanut crop rotations. A SDI system was installed in Southwest Georgia with thin wall drip tube laterals spaced at 0.91 and 1.83m distance (3'and 6'), three irrigation elvels (100%, 75%, and 50%), and five crop rotations. Th SDI design was different from large farm acreage design to maximize the number of plots while reducing hardware components by using a branching technique. The SDI system was fully automated to calculate runtimes, inject chemical amendments (fertilizers, insecticides, etc.), apply water, and collect irrigation and weather data. Irrigation water was applied daily at 100%, 75% and 50% of estmated crop water use. The branching technique decreased the number of flow meters and injector pumps by half with an estimated savings of $9600. Each field mainline took about six minutes to fully pressurize with slight fluctuations in pressure and flow rate depending on the number of mainlines turned on (maximum of six at any one time). Irrigation plus rainfall supplied just over 100% of the water required for peanut crop use. The other irrigation treatments supplied 75% and 53% of the irrigation water required. Physical problems with the system included lightning damage tot he automatic controller and rodent damage with the thin-wall drip laterals. Overall, this SDI system was used to efficiently supply water to a peanut crop in Southwest Georgia.
Technical Abstract: A subsurface drip irrigation system (SDI) was designed and installed to conduct long term research on peanut crop rotations. The SDI system was designed for maximum number of treatments with minimum amount of equipment. The system includes two thin-wall drip tape lateral spacings (buried at 30 to 35 cm), three irrigation levels, and five crop rotations replicated three times for a total of 90 plots in a randomized block design. Each mai line branches into two field mainlines reducing the number of flow meters and injector pumps by half. Irrigation treatments of 100%, 75% and 50% were based ont he crop water use and crop coefficient curves. Potential evapotranspiration (ETo) was estimated using the modified Jensen-Haise equation adjusted for location conditions. 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 six minutes to pressurize. There were slight fluctuations in pressure and flow rate for short time durations as valves were turned off and on. About $9600 was saved by using a branched design system of one flow meter and injector pump per line. Irrigation plus rainfall supplied just over 100% of the water required forcrop use. 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 peanut crop in southwest Georgia.