I have applied lots of lime and you are correct ag lime can be applied by the ton. Ag lime needs to be applied at least one ton per acre but I recommend more because its difficult to get good coverage at that rate. Usually its more cost effective to just get a full truck delivered (10-20 tons depending on who you call) I usually end up spreading 3-4 tons per acre and get good results. The average pond around here is about 20 ppm hardness. Expect 3 tons per acre to bring up hardness to about 60 ppm for 4-5 years. If you regularly test the water you will see the hardness drop off and then you will know when to lime again. Remember it takes about 3 months for ag lime to change water hardness so dont wait till the last minute to lime. I have had several clients lime early in the spring only to find out the lime wont be working for them until summer. A 3 man crew (with a tractor) can spread 20 tons in about 5 hours. Expect to pay $20 -30 per ton of lime delivered, and about $30 per ton to spread. the most important factor when liming a pond is to make sure the entire pond bottom is covered. You are liming the soil on the bottom of the pond (not the water). Its the same principal as liming a field. Make sure it is evenly distributed.

Hydrated lime changes the hardness on the water, not the hardness of the soil therefore its eaily flushed from the pond. expect a hydrated lime treatment to last 6 weeks at most. Hydrated lime will rapidly change the pH of the water. If it is over applied (more than 50 pounds per acre) the pH change is so rapid it will cause a fish kill. Hydrated lime will work but I recommend ag lime. I have never seen any studies that show how much stress is inflicted on fish by using hydrated lime but I'm sure it is significant. maybe a smarter fish consultant than myself can answer that one.

Shan O'Gorman
Pro Ponds