The Colorado Division of Wildlife recommends whisking an egg and a teaspoon of chicken bouillon in a gallon of water and spraying everything. I use a blender to mix it up, and be sure to run it through a fine strainer before you use it so bits won't clog the spray nozzle.

It works. You do have to repeat it fairly often if it rains.

Pretty much any commercial repellant product is of organic origin. They are typically concoctions made from fermented eggs, hot peppers or other pungent plant extracts or predator urine. Bobex is a brand name for a very good deer repellant and Plantskydd makes both a deer, rabbit and other small mammal repellant.

These also need to be reapplied frequently due to rain/irrigation and because their effectiveness fades over time. It is also suggested to alternate between two or more products or methods as the critters become accustomed to a single product used repeatedly and then begin to ignore it.

Someone did an article that appeared in Fine Gardening magazine a while ago that tested various Deer "repellents" and they concluded they worked kind of, somewhat, for a short while but that the deer apparently became used to them and ignored them.
I don't know if this video from PBS Nature would be of interest or help, but watching the hour long program may provide some insight to the problem.

Here is a link that might be useful: the private life of deer