Notes on Pond Management
Charles Mitchell & Don Nicholson, NCDA&CS regional agronomists
June 2006
For most ponds in North Carolina, pH and alkalinity are more limiting than fertility. For
this reason, the first step in pond management is soil testing and/or solution analysis.
Never fertilize a pond without checking and properly adjusting its pH and alkalinity first.
—When is it necessary? Acid soils and soft water are not conducive to fish
production. To find out if liming is necessary, submit a sample of pond water for
solution analysis. If the report shows total alkalinity and/or hardness values of less than
20 parts per million (ppm), liming is probably warranted. You will need to collect a soil
sample to find out how much lime to apply.
—What does it do? The addition of lime to a pond increases the concentration of
carbonates. Carbonates bind with the carbon dioxide produced by plants and animals
living in the water. By binding with carbon dioxide, carbonates reduce the acidity of the
water. They increase and buffer the pH.
Increasing the pH of water has other beneficial effects. Phosphorus, which is almost
always the most limiting nutrient in freshwater ponds, becomes more available as pH
increases. In addition, microbial activity improves and helps decrease the amount of
organic debris at the bottom of the pond.
—How do I collect a mud sample and get a lime recommendation? To determine
how much lime to apply, you will need to collect a soil sample (mud from the bottom of
the pond) and submit it for analysis. Be sure to enter the correct “crop code” for fish
ponds (069) on the NCDA&CS Soil Sample Information sheet.
Samples can be collected from a boat by using a long pole with an 8-oz can attached to
the end or by taking small plugs of mud with a length of PVC pipe. Randomly collect
mud from both deep and shallow areas over the entire length and width of the pond.
Collect from at least six locations per acre. Thoroughly mix all the mud collected, and
spread it out on a flat surface to dry. Afterwards, pulverize it and fill a soil sample box.
—What types of liming materials are available? Liquid and powdered lime are
common choices for liming fish ponds. Pay attention to the acid-neutralizing value
when selecting a lime product. This value represents the ability of a liming material to
neutralize acid when compared with standard agricultural lime with a 90% calcium
carbonate equivalency. Hydrated or slaked lime and calcium oxide should not be used
to lime fish ponds. These products could drastically raise water pH, thereby killing fish.
—How should lime be applied? Distribute lime as evenly as possible over the entire
surface of a dry or full pond. For dry ponds, apply lime with a spreader and mix it into
the bottom with a disc-harrow. For small, full ponds, spread bagged lime from a boat or
broadcast it from the shore.
For large ponds, bulk quantities of lime may be necessary. A boat 18-feet long by 6-feet
wide can carry 1500 lb of agricultural limestone. Load the lime onto a ½-inch plywood
platform placed over the bow of a large boat or between two small boats. Shovel the
material or wash it off the platform using a water pump, while moving the boat slowly
across the pond.
—When is it necessary? Fertilization is not the best management practice for every
pond. Although it can triple or quadruple fish yield, it is most beneficial for heavily fished
ponds. It also requires time, money and attention to detail.
As a rule, fertilization will not be beneficial when ponds
! have excessive water flow (outflow over 30-day period exceeds volume of pond),
! have extensive areas less than 2 feet deep (conducive to rooting of vegetation) or
! are already being fed for commercial fish production
! are located in watersheds where animals are grazing
! are seldom fished.
—What does it do? Fertilization can double or triple the productivity of a pond by
stimulating the growth of microscopic plants (phytoplankton) and animals
(zooplankton), which comprise the base of the food chain. These organisms are food
for insects and small fish feed, which, in turn, are food for larger game fish.
—When should it be done? Before beginning a fertilization program, submit a water
sample for solution analysis and a pond mud sample for soil testing. If water alkalinity is
below 20 ppm, there is no point in putting out fertilizer. Pond pH must be adjusted first.
It is best to apply recommended lime several months before fertilization, but two weeks
is an absolute minimum. In some cases, a corrective lime application is all that is
necessary to maintain pond productivity.
Pond fertilization requires a series of applications. Begin early in the year when the water
temperature reaches 60°F. Follow up with an additional application every two to three
weeks (whenever water clarity exceeds 18 inches). The actual number of applications
will vary with each pond situation. Continue fertilizing on a regular schedule until late
summer or fall but no later than October.
Modifications can be useful, however. It may be possible, especially in late spring and
summer, to use liquid fertilizer more efficiently and produce a more stable bloom by
applying it at half the recommended rate, but twice as often as the standard fertilization
schedule calls for. For example, you may choose to apply 5 lb/A at two-week intervals in
summer, instead of 10 lb/A at monthly intervals.
—What fertilizer materials are appropriate? Liquid, granular and powdered fertilizers
are available for pond fertilization. The fertilizer grade listed on the container consists of
three numbers: % nitrogen (N), % phosphate (P2O5) and % potash (K2O). In general,
phosphorus is more important to fish production than either nitrogen or potassium.
—How should fertilizer be applied?
Liquid fertilizers are heavier than water. They will sink to the bottom of a pond unless
they are mixed well at the time of application. They must be applied into turbulence or
diluted with water. Possible methods of application for liquid fertilizers include
! dripping it into the water from the bow of a boat driven by an outboard motor so
that the wake of the boat and the action of the propeller mixes the fertilizer into
the water;
! pouring it directly into the turbulence caused by the outboard motor;
! pouring it into a wash tub, or similar container, at the pond's edge; diluting it
with more than 10 parts of water; and sloshing the mixture onto the pond
surface;
! using a small pump to dilute the fertilizer with water and then pumping the
solution out onto the pond [best method for ponds smaller than 2 acres];
! applying it full strength with a garden sprayer by directing the spray onto the
pond surface while walking around the pond [Note: With some sprayers, it is
necessary to dilute the fertilizer with water so that it will pass through the nozzle.]
Granular fertilizers should not be placed in direct contact with pond mud. Mud traps
the phosphorus in the fertilizer and makes it unavailable. For this reason, applying
granular fertilizer from a platform is preferable to broadcasting it onto the water surface.
Never broadcast fertilizer granules into deep water.
The preferred method of application for granular fertilizers involves positioning a
platform one foot under water to hold granular fertilizer off the bottom. Pour fertilizer or
place open bags of it on the platform where it will slowly dissolve and be distributed by
water currents. A platform measuring 45 square feet is adequate for a 5- to 10-acre
pond. Smaller platforms can be used in smaller ponds. More than one platform should
be used in ponds larger than 15 acres.
—Remember
! If water outflow during any spring or summer month is more than the total pond
volume, fertilization will be pointless. If heavy outflow occurs only during winter
and early spring, you may be able to get response to fertilizer during a drier part
of the year. You can reduce excessive outflow by constructing diversion ditches,
enlarging the pond and/or constructing another pond above the existing one.
! Adopt a routine fertilization schedule and stick to it. Fish do not have a
consistent food source when ponds are randomly fertilized once or twice a year.
! If phytoplankton do not grow after fertilization, investigate possible problems with
the lime requirement, excessive water outflow, weeds or muddy water. Growth
may be difficult to initiate or re-establish after potential problems are eliminated.
Temperature, clouds and other weather-related factors can be influential.
Deal C, Edwards J, Pellmann N, Tuttle RW, Woodward D. 2000. Ponds—planning,
design, construction (revised). Washington (DC): United States Department of
Agriculture, Natural Resources Conservation Service. Agriculture Handbook 590. 85 p.
Available online: fairfaxcounty.gov/nvswcd/aghandbook.pdf
Jensen JW. 1990. Fertilizing fish ponds. Auburn (AL): Alabama Cooperative Extension
System. Publication ANR-249. 4 p.
Available online: www.aces.edu/pubs/docs/A/ANR-0249/
Lazur AM, Cichra CE, Watson C. 2002. The use of lime in fish ponds (revised).
Gainesville (FL): Florida Cooperative Extension Service, Institute of Food and
Agricultural Sciences, University of Florida. Fact Sheet FA38. 5 p.
Available online: edis.ifas.ufl.edu/BODY_FA028
Lewis GW. 1999. Pond fertilization & liming. Athens (GA): University of Georgia College
of Agriculture and Environmental Sciences and Cooperative Extension Service. Bulletin
867. 8 p.
Available online: pubs.caes.uga.edu/caespubs/pubs/pdf/b867.pdf
Rice JA, Noble RL, Curry RL, editors. 1999. Pond management guide (revised). Raleigh
(NC): N.C. Cooperative Extension Service in cooperation with N.C. Wildlife Resources
Commission. Publication AG-424. 30 p.
Available online: www.ces.ncsu.edu/nreos/wild/pdf/pond/mgt_guide.pdf
Wright RA. 2001. Liming fishponds (revised). Auburn (AL): Alabama Cooperative
Extension System. Publication ANR-232. 3 p.
Available online: www.aces.edu/waterquality/articles/0109001/0109001.pdf
Wynne F. 2002. The use of agricultural limestone and gypsum in ponds (revised).
Mayfield (KY): Kentucky State University Cooperative Extension. 3 p.
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