I think a more important question would be do you need weight and if so how much, What is the purpose of the weight, Are you losing traction, Do you just have a MMM or do you have additional attachments such as a front plow that require you to add additional weight to the rear, I think you tractor has either 23x8.50-12 or 23x10.50-12 rear tires, The 23x8.50-12 has a 6 gallon capacity for ballast and the 23x10.50-12 has a 7 gallon capacity, If you used liquid calcium ballast you would add 64 lbs each tire to the 8.50's and 75 lbs each tire to the 10.50's, Using a less corrosive substance like antii freeze or windshield wiper fluid would give you around 50 lbs each tire for the 8.50's and 58 lbs for the 10.50's.
What is the weight of your tractor and the weight rating on your tires, adding liquid ballast to your tires will not increase the weight the tractor on the tires but will add to the overall weight of the tractor and provide additional traction, Adding wheel weights will increase the weight of the tractor on the tires and provide additional traction.