USDA Agricultural Research Service (ARS) scientists at the Water Management Research Unit, Ft. Collins, CO, have developed WeedSite, a software program that you can use to evaluate the effects of site-specific weed management (SSWM) in irrigated corn-cropping systems. You can download WeedSite for free at arsagsoftware.ars.usda.gov.
With the software, you can use your computer's mouse to draw weed maps of your fields on the computer screen. The ARS program uses the maps to calculate the untreated area of the field, herbicide use and cost, yield loss from weed competition, and number of weeds left in the field. ARS reports that, with this information, the program computes the net benefits of using SSWM versus applying herbicide uniformly across the field.
By mounting a digital still camera and a GPS unit on a tractor, you can take photos and match them to GPS coordinates. The ARS software estimates weed cover from the images and then constructs a field map for you. ARS reports that, with the map and a sprayer, you can locate and treat weed-covered sections, detect new invasions and monitor changes in existing patches.