If you’re used to fertilizing fields for bigger crop yields, you may have already heard of fertilizing ponds as well. For others, it’s likely an unfamiliar topic that is often overlooked by the first-time lake owner. While it’s not strictly required, it is a recommended practice for anyone who wants to build a natural cycle of reproduction in their lake. Without routine and carefully calibrated fertilization, you’ll end up with age classes in your lake that are distinct enough it’s hard to keep fry and fingerlings steadily supplied for the next generation. Fertilizing is often a far more useful step than just feeding the fish on their own, for both natural restocking and individual fish growth. Here’s what you need to know to do it correctly for a healthy fishing lake.
What’s the Point?
Fertilizer, in general, is something you want to keep out of lake water because it triggers the growth of plankton and other tiny water plants. When you add fertilizer on purpose to the fishing lake, you’re intentionally growing a crop of these plants for your fish to eat. Tiny fry and fingerlings often eat the plants themselves or the tiny water creatures that eat them. Larger fish feed on the complex chain of life fed by the plankton. Either way, the fish are eventually fed by the fertilization, although they don’t directly consume the nutrients you add to the water.
When to Begin?
Fertilizing when temperatures are below 60 degrees F is a bad idea because the nutrients will only build up in the water rather than triggering a bloom. Winter fertilization is wasteful or downright damaging to the fish, especially since they’ll be dormant and already struggling to get enough oxygen. Continue fertilizing regularly on the schedule recommended below as long as temperatures remain above 60 degrees F. In the warmest climates, this means that fertilization can continue year-round for rapid fish growth.
What Fertilizer to Use?
Nitrogen isn’t the most important nutrient when it comes to algae and phytoplankton growth. In fact, using a high nitrogen fertilizer is likely to trigger the growth of cyanobacteria instead, that aren’t the same kind of plankton and therefore not as helpful in a fishing pond. Look for fertilizers high in phosphorous instead. Liquid corn fertilizers around 10-34-0 are widely recommended for this task. The liquid formulation helps it spread quickly and evenly through the water. Powdered lake and pond fertilizers are also available that work well and require the smallest amount of fertilizer possible. Either option will work if one is more readily available to you than the other.
Soil Fertility
If the soil is highly fertile and the lake isn’t lined, there’s likely little benefit to fertilization. However, all new fishing lakes should be lined for better seepage control and to reduce unnecessary water losses. So, this means that the contact with the mineral-rich soil will be broken. These lakes should definitely receive routine fertilization to keep their nutrient levels high and the chain of plankton growth steady.
When to Fertilize
There’s no need for constant water testing just to decide when it’s time to add some fertilizer. Try using your eyes instead and take a good look at the clarity of the water in your pond or lake. When you can see deeper than 24 inches into the lake, apply a new coating of fertilizer to trigger the plankton bloom to thicken again near the surface. Don’t add any more fertilizer until the bloom clears to this depth again. This will create just the right cycle to encourage good development of food sources for growing fish without triggering algae growth that uses up valuable oxygen supplies.
