A TRACTOR-MOUNTED IRRIGATION SYSTEM SIMULATOR FOR CHEMIGATION RESEARCH

An improved system for the application of chemicals in irrigation water to small research plots was designed, constructed and evaluated. The system was tractor-mounted with a three-point hitch for easy removal from the tractor. It had application booms on both sides of the tractor with full jet nozzles spaced 51 cm (20 in.) apart for chemigation and microsprinklers spaced 1.8 m (6 ft) apart for a pivot-attached sprayer system (PASS). The operator’s platform, located behind the tractor and in front of the spray booms, carried the injection system, injection pumps and chemical tanks. Water was supplied to the system from a 38-mm (1.5-in.) diameter drag hose or from a nurse tank towed behind the tractor. The injection pumps were powered by an auxiliary generator attached to the tractor. Research plots treated by the system were 5.5 m (18 ft) wide by the desired length. The system had the capacity to apply 2.5 to 6.3 mm (0.1-0.5 in.) of irrigation water or 1900 to 2800 L/ha (200-300 g/a) of chemical mixture for the PASS. The water application depth was controlled by varying the velocity of the tractor and/or the pressure of the irrigation or PASS nozzles. The system was calibrated for water application depth and coefficient of uniformity (CU) and subsequently evaluated for the application of insecticides on whorl-stage corn (Zea mays) during 1995. Chemigation water depth and CU increased linearly with system pressure but was not significantly influenced by nozzle height above catch cups.