Check with your county agent. This is from the soil and water test links archive. Get about 10 to 12 samples from around the pond using a long piece of small pvc to get samples from pond bottom. Stick it in the bottom , pull up and take out core and put in a box mixed with the other 10 cores. When dry mix and take to county agent. He has the forms to send in.

Miss. -- Extension Soil Testing Laboratory, Box 9610, Mississippi State, MS 39762