Management Of Recreational Fish Ponds In Alabama

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Fertilization And Liming

Fertilization provides planktonic algae with nutrients for growth much the same as fertilizing pasture increases grass yields. Proper fertilization increases available food throughout the food chain, thus increasing the amount of fish the pond supports.

Fertilization, however, will not stimulate a good algae bloom if total alkalinity of the water is below 20 ppm. Check alkalinity first. If alkalinity is below 20 ppm, add agricultural limestone to neutralize acidity in the soils. Do not use quick or slaked lime; these will cause a rapid pH change that may kill fish. The amount of lime necessary depends on the characteristics of mud in the pond bottom. A mud sample should be analyzed to determine the amount of lime.

Take mud samples from many places in the pond (see Extension Circular ANR-232, "Liming Fish Ponds"). Combine these samples and spread them out to dry. After samples are dry, mix them together thoroughly and take one sample for analysis. Send this sample to the Auburn University Soil Testing Lab in a soil-test box (available from your county Extension office). Mark the sample "fish pond" so that the proper tests can be run. The analysis will recommend the proper liming rate.

(Photo right) Lime application using a pontoon barge and water pump to evenly distribute the line.

Lime must be applied evenly over the entire pond so that it can react with the bottom mud. If the pond is thoroughly dry, a spreader truck could distribute the lime. If the pond is full, however, the lime will have to be shoveled or washed into the pond from a boat. Several pond management consultants in Alabama will lime ponds at a modest cost. Ask your county Extension office for a list of Alabama Fisheries Consultants.

Lime slowly dissolves into the pond water and is washed out with overflow water. This means that ponds usually need to be relimed every 2 to 4 years. Many pond managers find it practical to increase the liming rate by one and a half or two times the amount recommended. This increases the length of time between lime applications. Some managers reapply half the recommended lime every 2 years to maintain alkalinity. Adding more than the recommended lime (agricultural lime only) will not harm the pond. A typical liming rate in Alabama is around 2 tons per surface acre of pond. Remember: if a pond needs lime it will not respond well to fertilizer.

Fertilizing ponds will increase fish production two- to threefold. Infertile ponds will seldom produce more than 100 pounds of fish per acre. Well-managed fertile ponds can maintain 300 to 400 pounds of fish per acre. If, however, the pond is naturally fertile and is not going to receive much fishing pressure, it may not require fertilizer. If the pond receives only minor fishing (or harvest) pressure, do not fertilize or fertilize at only half the recommended rate.

Once fertilization is started it should be continued. If fertilization is stopped the fish will stunt because of the reduced food supply, and they become more susceptible to disease.

Not all fertilizers work well in ponds. Phosphorus is the nutrient most needed in ponds. Given time, the phosphorus will be absorbed and trapped in the mud of the pond through chemical processes. Once trapped, it is not available to planktonic algae but can promote the growth of weeds and filamentous algae. Nitrogen is seldom needed in older ponds. Occasionally, new ponds need nitrogen but once a pond is established nitrogen usually is abundant.

Fertilizers are labeled with N-P-K ratios or percents of nitrogen (N), phosphorus (P205), and potassium (K2O). The equivalent of 8 pounds of granular -- 4 pounds of liquid -- phosphorous per acre per application is the commonly recommended rate. Liquid fertilizers can be easier to apply and may produce blooms quicker than granular fertilizers. Table 2 lists recommended rates for commonly available fertilizers. For additional information on fertilization, see Extension Circular ANR-249, "Fertilizing Fish Ponds."

The optimum algae bloom is one that allows light to penetrate to a depth between 18 and 24 inches. Submerge the Secchi disk into the pond until it just disappears and note that depth. Follow Table 3 as a guide to fertilization.

A Secchi disk reading of 12 inches or less means the pond is too nutrient rich. At that point you need to determine where excess nutrients are coming from. Have you over-fertilized? Are livestock manures or crop fertilizers entering into the pond? If you are feeding the fish, are you overfeeding? Try to discover the source of the problem. Dense blooms can consume most of the pond's oxygen at night. Be prepared to aerate at night if the visibility is low and there are consecutive days of cloudy weather.

(Photo left) . A secchi disk can be used to determine when to fertilize.

Granular or liquid fertilizers can be used in ponds. Granular fertilizers must not be broadcast into the pond. Granules will sink to the bottom, and the phosphate will be absorbed directly into the mud and be lost. Granules should be placed on a platform that is submerged about 12 inches underwater. Usually one platform is needed for every 25 surface acres of pond. Place the platform in an area of the pond that has wave action. Granules placed on the platform dissolve slowly, spread throughout the pond by water currents, and stimulate a bloom.

Liquid fertilizers are dense and must be diluted with water before applying, or they will sink to the bottom and be absorbed into the mud. Dilute liquid fertilizers about 10 to 1 (water to fertilizer) and spray, splash, or mix into the pond. Apply fertilizer mixture as evenly as possible over the pond surface.

Fertilization should begin in late February or early March, depending on the pond's location in Alabama. This first fertilizer application does not always stimulate a bloom. Continue to fertilize at 2- to 3-week intervals until the pond blooms green. Once a bloom is established, fertilize as necessary to maintain it. Use the Secchi disk guide in Table 3 to help make management decisions. Continue fertilizing until late October.

Some pond managers continue to fertilize through the winter. Although research suggests that winter fertilization does not increase the growth of fish, many managers feel that maintaining the bloom provides some extra food and reduces filamentous algae problems.

One important word of caution: do not fertilize ponds that are infested with aquatic weeds. The fertilizer will only stimulate growth of the weeds. Control weeds before fertilizing (see Weed Control). Establishing a good fertilization program before weeds appear is one of the best methods of weed prevention.

Ponds that are flushed by large volumes of water will lose fertilizer more rapidly and may not sustain a bloom. In this case fertilization is usually ineffective and should be discontinued unless the excess water can be diverted (see Pond Construction). Many ponds will flush repeatedly in winter and early spring but respond well to fertilization in late spring, summer, and fall.

Muddy ponds (12 inches or less visibility) usually will not respond to fertilization. Several methods have been used to clear muddy ponds; however, in most cases, the addition of lime to reduce acidity will settle a muddy pond. If liming does not settle the mud, contact your county Extension agent for advice.

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