Care of a New Pond and Its Watershed

Creating a really good pond depends not only on careful planning and good construction, but also on protecting the darn, spillway, diversion terraces, pond basin and watershed from erosion. Erosion and siltation shorten the life of a pond and result in muddy waters of poor quality for fish, other wildlife and livestock. For example, bass 28 months old in five experimental clear ponds weighed almost five times as much as bass of the same age in five muddy ponds.

WATERSHED CARE:

To keep the pond from filling with silt, it is best to have the watershed in good cover before dam building starts. Any drainage from roads should be diverted from the pond or caught in a sediment basin. Particularly after grading, roads are a dangerous source of silt and they can increase the pond watershed more than might be thought. Raw gullies or areas of thin cover in the watershed should be worked down, fertilized and seeded without delay. If there is cultivated land in the watershed, a strip of sod should be left between this and the pond. The uncultivated strip should be wide enough and thick enough (a minimum of 50 to l00 feet) to serve as a filter for the pond.

CARE OF THE DAM, SPILLWAY, DIVERSION TERRACES AND POND BASINS:

Immediately after the pond is built, the darn, spillway, basin and diversion terraces should be limed, fertilized, mulched and seeded to grasses or legumes. Get recommendations for fertilizing and- seeding from the Extension Director in your county. If manure is available, use it in heavy applications along with the fertilizer, but don't spread manure in the pond basin: it may stimulate growth of algae or "pond scum." Use only superphosphate and mulch in the pond basin. Work the lime, manure and fertilizer into the surface of the soil by light disking and harrowing. Mix the fertilizer into the soil, but don't disk so deeply as to cause serious erosion. Use hay, straw or any type of mowed vegetation to mulch the raw soil. In the pond basin, scatter 20% superphosphate over the mulch at the rate of 50 pounds per ton of mulch. In the basin where no grass is sown, mulch should be about 5 inches deep. Mulch on the areas seeded with grass should not be more than 3 inches thick so that the grass can come through.

Along with fertilizing and mulching, seed all the raw areas with a nurse crop of small grain. The following nurse crops are recommended: late summer or fall -rye or wheat, at the rate of 100 pounds per acre; spring or early summer -oats, at 65 pounds per acre; hot and dry mid-summer -Sudan grass, at 25 pounds per acre.

Let the nurse crop in the basin grow to no more than 6 inches high before it is covered with water. If you have to mow it, let the clippings lie. As this covering of vegetation decays, it will release mild acids and nutrients. The acids help clear the water and nutrients stimulate the growth of fish food organisms. Tall, heavy growths of the nurse crop, however, could lower oxygen levels by decomposition at a time when a new fish population is developing. Before selecting the grass for the drainage areas, see your County Extension director. Since conditions vary widely over the state, different grasses should be used in different locations. Sow perennial grasses only on the dam, spillway, diversion terraces and pond edges.

SHORELINE SEEDING:

Reduce bank erosion by planting wild millet, Japanese millet, or Reed canary-grass in a 5-foot-wide strip along the shoreline. If the pond is full, the seed should be sown down to the water's edge. If the pond is not full, sow it far enough down that a narrow margin of millet will be covered when the pond fills. These protective plants help considerably in keeping the water clear. If the watershed and raw soil are well protected from erosion, the pond should clear up within a short time after it fills. If it fails to clear because of the nature of the soil, try using agricultural gypsum. But don't use gypsum until you're sure that erosion on the watershed and around the pond has been stopped.

Missouri Department of Conservation, Jefferson City, Missouri 65102