The Purpose of Fertilizing Your Lake


Lake fertilization provides planktonic algae with nutrients for growth in much the same way fertilizing a pasture increases grass yields. The food chain in a lake or  pond starts with algae (phytoplankton), so the productivity of your pond and lake management program is greatly enhanced through fertilizer application. Proper pond  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 the total alkalinity of the water is below 20 ppm. If this is the case, it’s time to lime your pond. In the eastern half of the United States, check the alkalinity of your pond or lake first before dumping out expensive fertilizer. If alkalinity is below 20 ppm, add agricultural limestone to neutralize acidity in the soils.

Do not use quick or slaked lime because 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. As such, a mud sample should be analyzed to determine the amount of lime to add. To get a good sample, collect mud samples from many places in your pond. 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 a soil testing lab. Often times, if you contact a state agricultural office, they will direct you on how to store and ship the sample. And here is a tip: Place the words “fish pond” on the smaple to ensure the proper tests are run. The analysis will recommend the proper liming rate — and then the work begins!

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