Omaha , NEProbably depends on what part of the country you are in. I would recommend brick dust if you are lucky enough to live near a brick factory. You may also want to ask your local parks and rec field maintenance guys what they top dress their fields with.
thanks for the information , I will let you know how it goesClear out a 10x3 rectangle about 8 inches deep. Put a 2 inch layer of gravel and then layer moundmaster or promound unfired clay bricks. Alternativly you can use mound clay instead of bricks layering 2 inches at a time and tamping, moistening, and adding the next layer. Place the rubber and bring the clay to about 3/4" beneath the top of the rubber using bagged mound clay. Tamp, and then cover with about 1/4"-1/2" of infield fines mixture.
You can get all that stuff from most material/dirt suppliers. Go to Promound or Moundmasters website and look for retailers in your area. Most will let you take as many 5 gallon buckets full of infield cover as you can carry for about $20 once you purchase the clay.
That's how I made mine, and it's held up for the last 5 years with regular maintenance.
-W