Here is a video of someone using a Mini Mantra Plus ULV Sprayer (model 100300) in Argentina:

http://www.youtube.com/watch?v=7VGAqsSAvj8

Note the high speed of application - you are able to adjust the rate to match your walking speed.  With a glyphosate product you are able to spray 2500 square meters (about 0.62 acres) per 500 ml (17 oz.) tank as seen in the video.