It’s that time of year when water temperatures are reaching 60-65° F, and pond owners are hearing now is the optimal time for pond fertilization. Fertilizing a pond is different than fertilizing a field and requires using a fertilizer that is high in phosphorus rather than nitrogen. When done correctly, pond fertilization can provide many benefits including enhancing the overall food chain by providing food for phytoplankton which in turn allows the pond to produce more pounds of fish. Additionally, fertilization can reduce the presence of submerged aquatic vegetation by decreasing water clarity and limiting the amount of light that reaches the pond bottom.
In terms of water chemistry, alkalinity, hardness, and calcium are recommended to be tested prior to fertilizing to ensure an efficient fertilization program. A pond with very low alkalinity or hardness (< 20 mg/L) will require the addition of agriculture lime before beginning the fertilization process. The amount of fertilizer required for a pond will be dependent on its hardness and calcium concentrations. Ponds with low, moderate, and high concentrations of hardness will require low, moderate and high rates of fertilizer, respectively.
Not all ponds need to be fertilized. In fact, fertilization is discouraged for ponds with existing populations of aquatic vegetation or water clarity of less than 18” of visibility. But, if you are considering fertilizing your pond this spring start by having your water chemistry checked first. Send your water sample to The Texas AgriLife Extension Service Aquatic Diagnostic Laboratory.
For more information on fertilizing ponds, please read Fertilization of Fish Ponds.