Liming and fertilization of your pond can increase the fish growth rates and the pounds of fish your pond can produce. Unfertilized ponds in Mississippi will usually have 100-150 pounds of fish per acre. This is the total weight of ALL SIZES OF FISH OF ALL SPECIES IN THE POND. Properly limed and fertilized can support about 300 pounds of fish per acre. Before you begin a liming and fertilization pond you need to consider several things. The effort,expense and labor to lime and fertilize a pond must weighed against the pond size, water exchange rate, water clarity, presence of unwanted aquatic plants and the amount of fishing effort and harvest.
DO NOT FERTILIZE IF YOU HAVE ANY OF FOLLOWING CONDITIONS:
In all areas of Mississippi except the Delta and Loess Bluff (east of the Delta to the Hill region) the soils are acidic. Acidic soils will bind or hold the phosphorus contained in the fertilizer you apply and it will not be dissolve into the water column, where it is needed by the tiny plants (phytoplankton) in your pond that are at the base of the food chain. So, if your soil needs lime and you fertilize, the fertilizer will not work and you will be wasting your money.
The most accurate method is to have a soil sample tested. Call your county cooperative extension service office and ask them to mail you a soil test kit (a box and a form). Take several soil samples from the pond bottom or along the shore line of your pond ---the more samples the better. Mix all the samples together and let the soil dry out. Check fish pond in the "crop grown" section of the form and send it off after filling the box with soil from your pond. The results will be sent back to you indicating how many tons of agricultural limestone you should apply. You really can't overlime a pond.
A less accurate way to determine your lime requirement is to locate your pond location on a the soil-type map located on page 28 of the publication "Managing Mississippi Farm Ponds and Small Lakes" or download it from the link on farm pond publications at the top of this forum. Liming rates range from zero in the Delta to 3 tons per acre in the Lower Coastal Plain along the Gulf Coast.
Another way of determining your lime requirement is to test your water for it's alkalinity. Alkalinity Test kits are inexpensive and easy to use. If your alkalinity is 20 or less, apply 2 tons of lime per surface acre. Waters will alkalinity less than 15 are in desperate need of lime. Waters with alkalinity between 20-30 will have a good response to fertilizer applications. The most you can increase your water's alkalinity is to 35-40 with an proper lime application.
Call your county farm cooperative store or garden supply store and determine if they will deliver and spread the amount of lime you need. Lime is cheap but the transportation of it is not. Expect to pay between $40.00-60.00 per ton. All limestone sold in Mississippi must have a Relative Neutralizing Value (RNV)of at least 63 percent. The higher the RNV number the better the line in terms of purity and fineness of the grind in terms of particle size. Lime with a high RNV value dissolves quickly and changes the soil pH faster so it is worth the money paid for it. Never use liquid lime, quick lime, hydrated lime or other more potent liming agents. If the pH of the water is raised too quickly, you will kill your fish. Lime should be added in the fall and winter, so that it has enough time to react with the soil before you begin fertilizing in March or April. Ideally, limestone should be applied directly to the pond surface. If access is good around a pond, this is not a problem. If the spreader trucks can't get to the pond edge or on the levee, have them apply the lime on land adjacent to the pond where it will wash into the water. If the lime supplier has a minimum quantity you have to purchase which exceeds your lime requirement, don't worry because you overliming will not hurt your pond. All it will do is prolong the time before the next lime application is needed.
Fertilization should begin in the spring when the water temperatures are 60F or higher. This usually means about March 15th in south Mississippi and April 1 in central and north Mississippi. Fertilization rates depend upon your soil type. Again, find your pond location on the Mississippi soil-type map located on page 18 of the publication "Managing Mississippi Farm Ponds and Small Lakes" or download it from the link on farm pond publications at the top of this forum. Rates depend on the type of fertilizer you select to use. Fertilizers are sold containing different levels of Nitrogen, Phosphorus and Potassium. The product will have a number on it like 10-52-4 meaning it contains 10% Nitrogen, 52%Phosphorus and 4% Potassium. Freshwater ponds do not normally need more nitrogen. Phosphorus is the limiting nutrient.
Three types of fertilizer are recommended for Mississippi farm ponds. Liquid fertilizers, which must be stirred or shaken before application with rates ranging from 1/2 to 1 gallon per acre per application. Dilute them with 2 parts water to 1 part fertilizer prior to application. Granular 0-46-0 (Triple Phosphate) fertilizer is the cheapest type but it must placed on a platform to keep it off the bottom where it can slowly dissolve. If you throw 0-46-0 out directly into your pond you are wasting 2/3rds of it. 0-46-0 application rates range from 4-12 pounds per acre per application. Powdered fertilizers (10-52-4) will totally dissolve before they reach the bottom if thrown in water at least 2 feet deep. They are the easiest to use but will cost more than granular fertilizers. Powdered fertilizer rates range from 2-8 pounds per acre per application.
If you have a new pond that has been limed and you use the recommended rate of 0-46-0 for your location and you don't get a plankton bloom (greenish water color), use 20-20-5 at 40 pounds per acre for the first few applications until you get a plankton bloom then switch to one of the 3 recommended types at the appropriate application rates. Older ponds should respond well to the recommended fertilizer formulations (0-46-0 or 10-52-4). The first three fertilizer applications can be made at least every 2 weeks or you can wait to fertilize until your water visibility indicates that you need to.
You can easily check your water clarity by purchasing or making a secchi disc. This is a round plate about 8 inches in diameter. A end of a #10 can works well as does a piece of plywood. Divide the disc into 4 equal sections. Paint 2 of the sections black and 2 white. The colors should alternate so that the same colors should not touch each other. Drill a hole through the center of the disc. Run an eyebolt through the hole and attach some washers or weights to the eyebolt on the underside of the disc to help it sink. Attach a 4 foot or longer section of rope hat has been marked at 6, 12, 18, 24 and 30 inches through the top of the eye bolt.
To check your water clarity, slowly lower the disc into the pond until you see difference between the colored sections. Raise it until you can first see the different colored sections of the disc. Mark the surface of the water on the rope by grabbing it at that location. Measure the distance from the surface of the water to the disc. If the distance is 18 inches or more, it's time to fertilize. If the distance is less than 18 inches, wait a week and check it again. DON'T FERTIILIZE UNTIL YOUR WATER CLARITY IS OVER 18-24 INCHES. DON'T APPLY MORE FERTILIZER THAN THE RECOMMENDED RATE PER ACRE. DON'T FERTILIZE IN AN ATTEMPT TO KILL AQUATIC PLANTS OR ALGAE.
Fertilization can be used to limit the depth to which sunlight penetrates in your pond which may help you limit the establishment of aquatic plants. If sunlight cannot reach the bottom of your pond, then plants can't get established.
If undesirable amounts of aquatic plants develop, STOP FERTILIZING UNTIL YOU TREAT THOSE AQUATIC PLANTS TO REDUCE THEIR COVERAGE.
Don't fertilize ponds in Mississippi from October to the end of February.
MDWFP Fisheries Biologist