A dirt pond adds beauty and value to any property. Properly sealed, a farm pond lets you water poultry and livestock, farm fish, irrigate crops, swim, and canoe. A backyard pond becomes a landscaping feature that attracts birds, lets you harbor hobby fish and grow aquatic plants. Because the soil in ponds makes them prone to seepage, you need an impermeable base to prevent leaks. There are several ways to seal a dirt pond, and the one that's best for you will depend upon the size of your pond.
Fence off your pond site and place livestock, such as pigs, cows and goats, in the enclosed space. The animals' movements will compact feces into the soil in a relatively short time and provide a natural seal.This centuries-old method used by farmers is known as "gleying."
Mechanically compact the soil. Mix water with the spare clay dug from the pond and spread it in several 6-inch layers. Drive over each layer repeatedly using the tractor tires to compact the base. Keep the compacted basin moist until rainwater fills the pond.
Mix a natural clay, such as sodium bentonite, with porous soil for small landscaping ponds or for larger ones where clay is unavailable. Bentonite absorbs many times its dry weight when wet to create an impermeable seal, and does not harm wildlife or affect water quality. Apply a layer of the mix evenly to the entire pond basin with a fertilizer spreader or shovel, and rake if the pond is small. Rainfall will swell the mix and seal the basin.