Esshup -- I have no experience to help with a fertilization plan for a sand pit. I also have never seen any technical information or a study on such an effort. I did see some calculations one time on one pit, and it had about a 3-week turnover time, meaning the entire water volume was exchanged once per 3 weeks by groundwater flow. That's probably about the minimum time to get the fertilize in, and see a response from the algae to get some energy moving up your food web.
Let's see if any of our good field folks can help. N8ly, Greg Grimes, Bill Cody, and Bob Lusk come to mind. Don't want to offend anyone by not mentioning names, so please chime in if there is any experience at all out there. Meanwhile, I'll send Jeff Slipke an email (Southeastern Pond Management) and see if they have ever done this.
