How to Fertilize Your Lake


Fertilizing your lake or pond will help promote phytoplankton, zooplankton, and keep your fish healthy, but how exactly does one fertilize a lake? Well, granules will sink to the bottom and the phosphate will be absorbed directly into the mud and lost. To promote the best use of expensive granular fertilizer, granules should be placed on a platform or in a permeable sack that is submerged about 12 inches underwater.

Usually one platform is needed for every 10 surface acres of lake. Place the platform in an area of the pond that has good wave action and this will serve to mix the fertilizer with the water in  your lake. Granules placed on the platform dissolve slowly, spread throughout the pond by water currents, and stimulate a bloom.

Liquid fertilizers are verydense and must be diluted with water before applying them or the liquid will sink to the bottom and be absorbed into the mud. This will not help your lake management program, so dilute liquid fertilizers about 10 to 1 (water to fertilizer) and spray, splash, or mix them into the pond. In addition, try to apply the fertilizer mixture as evenly as possible over the pond surface.

One important word of caution regarding the management of your lake: Do not fertilize ponds that are infested with aquatic weeds. Much like a lawn or crop, the fertilizer will only stimulate growth of the weeds. Make a good attempt to control weeds before fertilizing and you will save yourself both time and trouble. With that said, establishing a good fertilization program before weeds appear is one of the best methods of weed prevention.

Small lakes and 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 in the watershed, upstream of the water body. Many ponds will flush repeatedly in winter and early spring but respond well to fertilization in late spring, summer, and fall. The only way to know for sure is try, monitor, and see what happens. 

Muddy ponds, those with 12 inches or less visibility, usually will not respond to fertilization. This happens because like other plants, algae (phytoplankton) needs sunlight to grow.  Several methods have been used to clear muddy ponds, but in  most cases the addition of lime (to reduce acidity) will settle a muddy pond.

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