Adding pulverized agricultural lime is the leading remedy for soft (low alkalinity, low hardness) acidic water lakes and is the most overlooked lake management activity in this region. Our soils are often naturally acidic, and along with acidic rainfall, the runoff through pine straw and dead leaves contributes to the overall acidity. An acidic lake may take on several different appearances, the water will be very clear, a dark brown or black tannic color, or it may stay muddy after rainfall.
Measuring Lake Soil for Lime Application
Most lakes in the North Carolina region need around 2 – 3 tons of agricultural lime per surface acre if they have never been limed in the past. An additional 1 – 2 tons of lime is often required each 3 – 5 years afterward. Sandy soil does not require lime application as frequently. Lime binds to clay soil more tightly and therefore needs more lime applied less frequently. The best way to determine the appropriate amount of lime to apply is to collect mud samples from the top 4 inches of the lake bottom. Collect mud samples along an “S” shaped route throughout the lake, including shallow and deep areas in a clean bucket. Remove leaves, sticks and rocks and mix the mud samples together. Spread the mud on a piece of clean plastic to dry and then have the sample analyzed for its lime requirement by a soil-testing lab.
The Benefits of Lime Application
"Liming is one of the most cost-effective methods of slowing the effects of acidification and enhancing the abundance and diversity of aquatic life." (Liming Acidified Lakes and Ponds, Department of Fisheries and Wildfire Sciences, Virginia Tech). Proper liming is particularly important if productive fishing is a priority for the lake. Lime helps make the nutrients in the water available for plankton growth and reproduction.
Plankton includes microscopic plants and animals that form the base of the food chain for the fish.
Plankton also give the lake water an attractive deep green color that helps shade the bottom and prevent vegetation growth in deep water. Most importantly, plankton produces most of the dissolved oxygen required for the fish to live. The lime also buffers the water so stressful changes in pH don’t occur between early mornings and late afternoons on sunny days. Adding lime should also reduce any muddy water appearance by encouraging the suspended sediment to settle more quickly. Acidic water is negatively charged and suspended clay sediment particles are generally negatively charged. However, remember that agricultural lime is simply powdered rock and results will often require months to be effective.
Be sure to evenly distribute the sizable amounts of lime evenly over the surface of the water. One method of doing this is using a fiberglass hulled inflatable boat to lime the lakes. It is small and portable and will hold 1 ton of lime at a time. Some companies use small barges. Lime is loaded on the boat and a pump sprays lake water onto the pile washing it into the lake as the boat travels back and forth over the lake in a grid pattern. Another solution is to use a six wheeled ATV with a dump bed to dump small piles of lime along the shoreline of the lake. You may be able to get a lime spreader truck to spread the lime as much as possible around the shoreline. Some people simply have the lime dumped in the head of the lake. The time required for the lime to be effective is directly proportional to how well the lime is spread, so it is important to take the time to evenly distribute the solution.