Liming Ponds and Lakes

Most lakes and ponds in the southeast, except those built in Blackbelt soils or those receiving water from limestone aquifers, will benefit from the addition of agricultural limestone. If crop or pastureland surrounding your lake site requires the addition of lime, your pond may also need lime.

How to check for lime.

“Can I check the pH of my pond to see if it needs lime?” is a question we frequently receive. According to Dr. Claude Boyd, world-renowned water quality expert from Auburn University Department of Fisheries, pH is not a reliable indicator of whether your pond needs lime. “Most pond owners are not aware that the pH normally fluctuates in a pond as a result of photosynthesis. Values are usually lower in the morning and higher in the afternoon,” says Boyd. “Total hardness and alkalinity are much better indicators of your pond’s requirement for lime. These tests can be performed from a sample of pond water. To determine the amount of lime required in your pond, a composite mud sample is often required, and a standard test can be conducted by most labs that analyze farm soil samples.”

The application of agricultural limestone has been used to increase fish production in acid soils in Europe for more than a century. Research during the 1940s and 1950s in recreational ponds in the southeast showed significant increases in bluegill production by applying lime to ponds with acid soils. Ponds with hardness and alkalinity values of less than 20 parts per million (ppm) benefited the most.

Why Lime?

Liming lakes and ponds is very similar to liming a pasture or food plot. If the pH of the soil is low, plants are unable to absorb the components of the fertilizer. Once the acid soil is neutralized, crop production can increase without increasing fertilization. In ponds, phosphorus is a key ingredient in the production of phytoplankton. Liming increases the amount of soluble phosphorus in the water, increasing the efficiency of pond fertilization and the production of food for fish.

The application of finely ground agricultural limestone over the entire pond surface neutralizes the acidity of the bottom muds and immediately increases the concentration of calcium and magnesium in the water column, providing a buffer against high swings in pH. Soft waters with low hardness values may experience high pH swings with values exceeding 10.0. These can often be toxic, resulting in fish kills.

How much to apply?

Dr. Marty Brunson, a pond expert from Mississippi State, says, “Apply agricultural limestone to the bottom of newly constructed ponds when possible. I like my clients to disc this in the bottom, as it seems to react quicker than applying it just on the surface. Use the finest-ground limestone available for best results. In the early days we used 1 to 2 tons per acre, but now 4 to 5 tons is a common rate. The effects of the lime last longer at the higher rate.

“In ponds and lakes that are full,” says Brunson, “applying lime by washing it off specially constructed barges is the best method of application. Agricultural limestone is heavy and does not go into solution quickly, so most of it goes to the bottom.
Dumping piles of lime around the shore or at the upper end of a pond is not very effective, as the limestone does not move very far from where it is deposited.”

Large watersheds or high flow ponds.

Larry Clay, retired fisheries biologist with the US Forest Service and living in Euphora, Miss., has had considerable experience with lakes that have a high water flow throughout most of the year. “Early in my career, we tried to fertilize many of our forest service lakes in Mississippi. These were lakes with acid-soil watersheds that produced typical brown, tannic acid water and where fertilizers would not create a plankton bloom. We applied agricultural limestone to many of these lakes and were successful in creating plankton blooms. The limestone lasted two to four years in the lakes with watersheds of 10:1, but in larger watersheds, with high flows during the winter or spring, the limestone lasted only a year,” says Clay.

“Knowing that our treatment was only effective for approximately a year, we began to look at more cost effective methods of liming. We began to use hydrated lime at low rates in the early summer and found that these treatments would often last through August or September. We would make the same treatment again the following year. This would allow us to fertilize and increase our fish production, but our annual material costs for lime were less than $20 per acre.” Clay advises, “Don’t try this at home, hydrated lime, if improperly applied, can kill fish.” Not only that, he warns, it is very caustic and can be dangerous to the inexperienced applicator. If your lake has high winter or spring flows, this may be an alternative method of increasing your plankton and food production.

Time of application.

Agricultural limestone requires some time to react with the pond bottom and should be applied well before beginning a fertilization program. Most applications are made during the fall, winter or early spring. Bulk lime is the most economical source of limestone and can be delivered in quantities of up to 28 tons per truckload. Bagged lime is available and could be used in small ponds.

There are many individuals and consulting companies who specialize in applying agricultural limestone in lakes and ponds. These professionals can coordinate delivery and application of one to many truckloads of agricultural limestone. If you want to increase the efficiency of your fertilization program and produce more fish in your lake, applying lime may be just the ticket.