Aftermarket planter modifications to control row unit down pressure have been well promoted into the Ontario marketplace, and are advertised for their ability to improve planter function, and final yields. The basic principles behind the modifications have merit, but the relative yield impacts of the different modifications, and their ability to respond above and beyond what is currently available in the marketplace is unknown, and has generally not been well investigated beyond anecdotal evidence. As a result, it is difficult to predict the returns these modifications can provide, making it difficult to make recommendations of when or where the use of these modifications may be most warranted.