Farmer Brown tet the hypothei that the more alfalfa prout cattle eat, the more milk they produce. He divide hi pature into four field and put twenty cattle in each field. Field 1 cow get no alfalfa prout, field 2 cow get ten pound of prout per day, field 3 cow get twenty pound of prout, and field 4 cow get thirty pound. He feed all group fifty pound of regular hay per day, ue the ame breed of cattle, and give them the ame amount of water. He meaure gallon of milk produced per cow every day. What i the independent (teted) variable in Farmer Brown' experiment?