Pond Owners-Now is a good time to lime.

Lime is used to increase alkalinity. Common liming material is calcium carbonate (CaCO₃) or agricultural limestone. Other liming materials include calcium hydroxide (Ca(OH)₂)--hydrated lime, slaked lime, builder's lime--and calcium oxide (CaO)--burnt lime, unslaked lime, quick lime. Calcium hydroxide and calcium oxide are not recommended unless you are applying to an empty fish pond because they can drastically change pH. They are also highly caustic which makes them dangerous to handle. You can purchase lime either in bulk which is cheaper or bagged which is easier to handle especially for small ponds.

Alkalinity can be checked with the water test kit, but a soil sample must be taken to determine the amount of lime to be added to your pond to increase the alkalinity. Approximately 10 samples should be taken from around, the pond. To collect soil from the deep areas, use a long pole with a can attached. Mix the samples in a 5-gallon bucket. Allow the sample to dry. Soil samples are sent to NCDA Soil Testing Lab for analysis. Make sure you identify the sample as a pond sample. You can get packing and shipping materials from your local NC Cooperative Extension office. Make sure that you follow the directions for packing, or your sample may not be analyzed.

You can also determine the lime requirement by using the same application rate that people are using for crops in your area. If the rate is correct, the total alkalinity should be above 20 mg/l after 3 to 4 weeks. If not, apply more and check again in 3 to 4 weeks. For a general recommendation, ponds seldom need less than 2 tons/acre and it is not uncommon to apply 5 tons/acre. Check alkalinity in 3 to 4 weeks. If low, apply again.

Typically, lime can be added any time of year, but it is usually added in the late fall and winter to allow the lime time to react with the soil and water before spring. You need to remember that you are treating the pond bottom as well as the water so when applying the lime should be applied over the whole pond as much as possible. Lime can be applied from a boat or a platform attached to a boat, for large applications.