Many farm ponds in Kentucky serve the dual purpose of a place to relax and catch a few fish or swim. They also may be used for irrigation or rural fire control. Managing ponds for multiple purposes can be difficult. Pond volume, watershed size and number of animals kept in the watershed, will affect nutrient run-off into the pond. When properly applied, to the watershed, little of the nitrogen and phosphorus contained in inorganic fertilizers should be lost in runoff into the pond.
Fish populations may benefit from the minimal nutrient runoff of well managed pastures. However, excessive nutrients from livestock waste will create water quality problems. Aquatic plants and algae will thrive on excessive nutrients and may become difficult to control.
The weedy appearance can be unattractive as well as cause largemouth bass to have a more difficult time preying on bluegill. This may result in an overpopulation of bluegill. Chemical controls can be time consuming and costly and in some instances, may not be legal, safe or practical in livestock watering ponds.
Ponds used for fishing must be stocked properly, limed and harvested correctly. For Kentuckians interested in maintaining fish ponds, a monthly management calendar is available from http://ces.ca.uky.edu/westkentuckyaquaculture. Before using any fertilizers or chemicals, be sure to check that they are safe for livestock if the pond is serving this dual purpose.
Weed control is an essential part of pond management. Preventive measures include proper design. Banks should be sloped steeply so that very little water is less than two to three feet deep. To help prevent serious weed infestations you can do the following things:
*Most waters in Kentucky are sufficiently rich in plankton and other food organisms to support large fish without the need for supplemental fertilization.
*Maintain a good sod and grass cover around your pond. This will help prevent runoff and erosion. Do not fertilize the turf directly around the pond.
* If the water is used for livestock, fence the pond and water the animals from a stock tank below the dam and outside the fence. Animals will increase turbidity and fertility and erode the banks. Do not allow livestock access to a pond unless a gravity flow tank cannot be installed. In this case, fence the pond to allow limited access to a few locations around the shoreline. Consider providing a source of shade in pastures so animals can avoid extreme heat.
* Check septic tanks for possible leaching into the pond. Locate new septic drainage fields so that the nutrient-rich effluent will not reach your pond.
* Do not permit runoff from chicken coops, feedlots and other areas to enter your pond.
If you have a weed problem mechanical controls can be used. Mechanical controls include hand removal, dredging of shallow pond areas or winter draw down may be effective in freezing and killing shoreline vegetation. Using rakes with ropes attached can work for removing some floating plants. But these methods can be impractical or uneconomical.
A biological control that can be used is triploid grass carp to control soft-stemmed vascular plants and branched algae. These fish are plant eaters and can help control pond vegetation. They need to be stocked at a rate of 5 to 20 fish or more per surface acre of water depending on the severity of the plant problem.
Chemical control methods also can be used. Weed identification is essential in determining which herbicide to use. When used properly, aquatic herbicides are effective in controlling vegetation without harming fish. There may be restrictions on water usage for a period of time after treating with a particular herbicide. Always check the herbicide label for possible restrictions.
For more information on pond construction and maintenance, contact me at the Lincoln County Cooperative Extension Service Office at 365-2447.