Abstract
A tractor mounted variable rate herbicide applicator with an 800 mm width of application was developed for spraying herbicides in a sugarcane field with a row spacing of 1,500 mm. The system components included a web camera to capture picture of field entries, a ground speed sensor, a PWM circuit to control a 12-volt DC electrical pump and application software that was programmed by Borland C++ builder for processing and controlling the system. The applicator was tested in constant application mode and the variable rate mode. It was observed that working speed, field capacity, field efficiency during constant application mode was higher than that its use as a variable rate applicator. The amount of herbicide used depended on application rate, working speed and field capacity. Application rate with the constant application system was maximum e.g. 2.78 L/min or 407.07 L/ha at 0.41 ha/h field capacity and 1.13 m/s working speed. With a variable rate system, at 0.33 ha/h field capacity and 0.77 m/s working speed, the application rates were varied to 2.00, 1.90, 1.80, 1.70 and 1.60 L/min. At these application rates, herbicide use was 363.64, 345.45, 327.27, 309.09 and 290.91 L/ha, thus herbicide saving, compared to constant application system, was 10.67, 15.14, 19.6, 24.07 and 28.54% respectively. As the working speed of the variable application rate system was slower than constant application system, it affected to field capacity and field efficiency but its less use of herbicide was not only economical but good for reducing harmful effects on the environment. An economic analysis conducted showed the area required for breakeven is 81.86 ha.
