Farm Pond Management

Introduction   |   Managing Fish   |    Liming   |   Fertilization   |   Feeding Fish   |   Calendar   |   Drawdown   |   Calculations   |   Balance Key

Click here for a printable version of this publication: Fertilizing Mississippi Farm Ponds

Lime is used to increase the alkalinity of pond waters, which in turn increases the basic productivity in ponds and sets the stage for an effective fertilization program.

The most common method of increasing alkalinity in waters is by adding agricultural limestone (calcium carbonate). Fish managers in Europe and Asia have reported that applications of lime to fish ponds on soils of low calcium content resulted in greater fish production. Fish managers in the United States showed that applications of lime to lakes increased pH and total alkalinity and also cleared water of brown stain from humic substances. Clear water results in deeper light penetration and greater photosynthesis, as well as increased zooplankton production.

Fertilization does not produce adequate phytoplankton (algae bloom) in many ponds with soft waters and acid mud because carbon dioxide is in short supply, and added phosphate adheres tightly to the bottom mud. Addition of lime to these ponds elevates total bicarbonate alkalinity and increases pH in the water. Neutralization of bottom mud with lime prevents phosphate from adhering to it, thereby increasing phosphorus concentrations in the water. As a result of these changes in water quality, phytoplankton blooms develop upon application of inorganic fertilizers. Liming soft water ponds to increase alkalinities to at least 20 ppm is beneficial to fish production.

As a general rule, ponds with alkalinities less than 20 ppm do not respond well to fertilization and should be limed in the fall before springtime fertilization is initiated. Liming ponds with alkalinities greater then 20 ppm typically will not increase the response to fertilizer. It does, however, increase the alkalinity and pH buffer capacity.

Total Alkalinity

Total alkalinity is the total concentration of bases in water expressed as parts per million (ppm) or milligrams per liter (mg/L) of calcium carbonate (CaCO3). These bases are usually bicarbonates (HCO3) and carbonates (CO3), and they act as a buffer system that prevents drastic changes in pH. For example, in waters with low alkalinity, pH might fluctuate from 6 or lower to as high as 10 or above; while in high alkalinity waters, pH might fluctuate from about 7.5 to 8.5.

Total alkalinity is not the same as hardness. Calcium (Ca++) and magnesium (Mg++) are primarily responsible for hardness. However, in most waters, alkalinity and hardness have similar values because the carbonates and bicarbonates responsible for total alkalinity are usually brought into the water in the form of calcium carbonate or magnesium carbonate. Waters with high total alkalinity are not always hard, since the carbonates can be brought into the water in the form of sodium or potassium carbonate.

Sampling Soil Ponds

Do not start a pond fertilization program without first finding out the lime requirement of the soil on the pond bottom. Application of phosphate fertilizers to ponds with acid soils is a waste of money and time. The type of soil in your pond also determines the amount of fertilizer you should apply.

Water pH and alkalinity can be measured by sending a water sample to the Mississippi State Chemical Laboratory (662-325-3324) for analysis, please view their price guide for costs. However the best method of finding out the lime requirement for your pond is to sample the soils on the bottom of the pond. To do so, collect a bottom mud sample from several places around the edge of the pond, mix it together, take one sample from the mixture and air-dry; then place this sample in a soil sample box (your county Extension agent has boxes for collecting and shipping the soil samples) and submit to the Extension Soil Testing Laboratory, Box 9610, Mississippi State, MS 39762 (the laboratory can be contacted by phone at 662-325-3313) for a lime requirement test. Be sure to indicate in the "crop grown?" window on the submission form that this sample is for a farm pond. The sample will be analyzed, and you will receive a report indicating if your pond needs lime and how much to apply. An example of soil test results is available to aid you in your interpretation.

For new ponds or during drawdowns follow these instructions for sample collection (the sample submission process is the same as above).

• If pond is larger than 3 acres, partition the pond into 3-acre blocks and sample each block separately. (If pond is less than 3 acres, collect 3 samples per acre and treat each acre as a block.)
• Collect about a pint of soil from each of 10 locations per block.
• Thoroughly mix the 10 samples together in a bucket.
• Take one sample from the mixture and air-dry; then place this sample in a soil sample box
• Repeat this procedure for each 3-acre block in the pond.

Application of Lime

Ponds in some areas of Mississippi may need as much as 3 tons of agricultural or dolomitic limestone per surface acre (your soil testing results will tell you how much to apply) to bring the soil pH up to the point that phosphorous fertilizers can promote adequate growth of microscopic plants and animals. Spread lime in shallow water in the upper end of the pond, or on land, as close to the water's edge as possible, that drains directly into the pond. In new ponds, lime can be disked into the soil before filling the pond. Apply the lime 2 to 3 months before starting fertilization, and repeat every 3 to 4 years.

The best liming material in Mississippi is agricultural or dolomitic limestone. This is the same form of lime that farmers use on their crop and pasture land and can be purchased in bulk or bag form. Do not use quicklime, hydrated lime, or other more potent liming agents! Lime spreader trucks can be used in new pond sites (and those that have been drained) prior to flooding. On older established ponds, it may be necessary to back the spreader truck to the edge of the water and turn on the spreader. This method works well if there is good vehicular access to the edges of the pond. In some cases, it may be necessary to spread lime evenly along the upper shoreline and allow it to wash by runoff into the pond, or you can spread the lime from boats. Even distribution is preferable since the lime needs to be applied to the bottom mud. In very limited access areas, sometimes a small in-flowing creek is the only way to introduce lime into the pond, but this would be the least beneficial of the methods mentioned. A lime treatment will usually last from 2 to 5 years, depending on the amount of water flowing through the pond and the acidity of the bottom mud. A method that usually works well on ponds with high acid soils is to apply the lime the soil testing report calls for; then apply one-fourth of that amount during each following year to be sure the lime requirement is satisfied.