Our yard is all sand, approximately 5 acres. We plan on adding about 3-5 inches of topsoil, but are unsure of it's success. What is the best grass to seed with for root length, and drought and disease resistance. We need to have a lawn that can survive a lot of activity. Our home is located in Tuscola County.
Tuscola County Michigan
You have a big project ahead of you, but it's achievable! I'd add well rotted organic matter (compost, peat, manure, leaves) and till into the sand which will enable the sand to retain moisture better and provide nutrients to deeper turf roots. Then I'd add the topsoil and till it in too, so there's no boundary between sand and topsoil. If you're up to it, now add more compost and till into the topsoil. Now you should do a soil test to learn what soil type you have (will plant grass seed in), it's fertility, organic content and what recommendations MSU makes for seeding a new lawn. Soil test info here: https://www.canr.msu.edu/uploads/files/Soil_Test9-12RS.pdf
Here is a good site on caring for high, medium and low maintenance lawns (seeding recommendations and fertilizer:
This site also has seed and lawn establishment recommendations:
Root depth is partially determined by grass type but also by mowing height. Read the bulletin on 'mow high for weed & grub control' at this website: https://www.canr.msu.edu/home_gardening/tip_sheets/
Have your yard ready to seed by Sept 1st, seed it (I recommend seeding at the highest recommended ramount), roll lightly (to improve seed to soil contact) and mulch with clean straw. I have done this on smaller plots. Watering 5 acres will be a challenge but you shouldn't have to wait too long for fall rains and cooler temperatures to see your lawn sprout and grow.