Beginning in 1983, the UW Madison Extension has been conducting yield trials of grass varieties annually to be published in UW Extension Publication A1525. These trials are conducted at several research stations in the state of Wisconsin: Arlington, Lancaster, Marshfield and Spooner Agricultural Stations. Yield is collected for each grass variety at each cutting. The work was started by Dr. Michael Casler and was continued by Dr. Daniel Undersander. In this data set, the individual grass varieties have been aggregated to species level. Yield is recorded as the average annual total for each species at each location planted in a given year, in tons/acre. Grass species included are: bluegrass (Poa pratensis L.), festulolium (Festulolium braunii K.A.), Italian ryegrass (Lolium multiflorum Lam.), meadow bromegrass (Bromus riparius Rehmann), meadow fescue [Schedonorus pratensis (Huds.) P. Beauv], orchardgrass (Dactylis glomerata L.), perennial ryegrass (Lolium perenne L.), quackgrass (Elymus repens L.), reed canarygrass (Phalaris arundinacea L.), smooth bromegrass (Bromus inermis Leyss.), tall fescue [Lolium arundinaceum (Schreb.) Darbysh], and timothy (Phleum pratense L.).