generating a digital management map using gps for herbicide application by vra spraying

this paper presents a method for generating a digital management map to apply cyanazine pre-emergence herbicide. the main objective was to develop a precision method to generate management maps for the variable rate application of herbicide to reduce the amount of herbicide applied and its adverse impact on the environment. first, local and utm coordinates of a field were determined using total station and four static gps receivers. data processing was performed using a pc with compass software. a 14.8 m grid was created using land software and laid out on the field. grid point sampling was done at the center of each cell at a depth of 20 cm and analyzed in a laboratory. the laboratory results showed that the range of, maximum, and minimum soil organic matter content (omc) was 0.82, 1.25 and 0.43, respectively. omc had a normal distribution with an average of 0.86% and a standard deviation of 0.18%. soil texture varied between loam, sandy loam and loamy sand. the kriging interpolation method was then used to determine the make-up at other points in the grid. by considering manufacturer recommendations for herbicide application based on omc and soil texture, four zones were determined for herbicide application rates of 1.4, 1.7, 2.9 and 3.5 l/ha. a digital map was then generated and used to determine that the total required herbicide was 1.61 l/ha. it was determined from the map that herbicide application could be decreased up to 13% using an application rate of 1.6 l/ha instead of 2.9 l/ha over 67.9% of the field area. the map can be utilized to determine desired input for an electronic controller of a vra boom sprayer.