Vertical plants may require you to place nozzles that pass 1-5 inches on each side of the plant. The exact distance depends on the plant. Generally you should spray vegetables with high pressures and high volumes for disease or insect control. Are all gaskets, pistons, bushings and other parts in working order. Big leaks waste chemicals, cost you more and increase the risk for environmental pollution.
Inaccurate gauges mean inaccurate applications.
Thoroughly go over the sprayer system to be sure that the season doesn't catch you unprepared. Order back-up parts for those that will wear down before the season ends. But that was long ago, and people don't do that anymore. Actually canning food at home isn't a dying tradition. The most commonly canned foods are jams, jellies and vegetables.