The importance of having one (or two if possible) individuals whose only responsibility is to guide the applicator to the correct location in the field is only difficult to understand until one has had to deal with the consequences of an error being made.
Colored flags or tapes can be utilized to help distinguish treatments (but check first to see if any participants are color blind). A tractor entering the plot one row off can cause major problems. The concentration required to operate tractor mounted application equipment can result in treating past the end of a plot and running over into the next plot unless a second person is available to control this.
If you are working in an orchard or vinyard or other situation with an undergound irrigation system, be certain you know the depth of the system and location of lines before taking soil samples, or using equipment to inject products beneath the surface. Punctured irrigation lines can add significantly to the time required to establish a trial, may not be evident until systems are turned on to incorporate products, and do not sit well with growers.
Discuss with the grower or field station manager the cultural operations which will be undertaken following applications in order to plant the crop and how to minimize contamination of the treated area with untreated soil. For some crops, soil may be removed from the center of the beds and thrown into furrows to be later replaced by other soil. For other crops, untreated soil from the furrow may be drawn up onto the treated beds.
Each product and cropping system will lend themselves to various methods of application. Applications in irrigation water include flood, basins, furrows, sprinklers, or drip irrigation systems. Liquids can be applied via hand injection gun, injection equipment, large or small sprayers. Powders or granules can be applied either by hand or by commercial equipment .