I did some Pawnee flying years ago, and have fielded a bunch of complaints about ag applicators from people. Here's my experience:
- The FSDO will probably not care. Ag application is a different set of rules, and there is wide latitude on min safe alt. You can talk to them, but in my experience, they yawn.
- New guys aren't always sensitive to the community.
- Personal visits, and if you can nicely talking with the pilot almost always works, but certainly talking with the boss works.
- In the states I am most familiar with, there are right to farm legislation, and that makes life easier for farmers (and ag applicators).
- Contacting the farmer who is working the land, and having him get you in touch with the applicator is also a good strategy, because farmers care more about their neighbors than applicators.
Having said all that, if you are having livestock issues, then you are being harmed, and there is greater risk. Personally, I would write a letter and send it to the farmer, applicator (if you know who) and the FSDO. Ultimately, in my experience, these matters are resolved only by persuading the applicator to do his field differently.
Sorry, no regurgitation of regulations here, because from your description, the regulations are not going to fix things.
I changed my mind. I need to cite 14 CFR 137.49, which states that an aircraft may be operated closer than 500 feet to persons, buildings and the ground. This is essential for effective ag application, and I can say that 50 foot clearances over buildings are quite common. 100 foot clearances over houses are as well. How low is too low? Where will you go when the fan quits, and if you can clear the structure or person and make a suitable off airport landing (or at least argue that you could) then you are fine. The rules are different for congested areas, and the FAA changes their interpretation of congested areas as they wish, but in all my years in aviation, I have never heard of a ag applicator being violated for unsafe altitude, when performing ag operations. So to summarize, over an uncongested area, there is no regulatory figure of X number of feet. It's not 500, it's not 200. Period.
Finally, if you are aggrieved by the operation, then you may have a tort action, not a regulatory action. In all fairness, there have been successful tort actions where disturbance of livestock and race horses have been involved.