Fruitnut, well, I've never been called on to install fruit trees in a former corn field to I'll defer to your wisdom here. I am called on to establish bearing age fruit trees in all kinds of soil and sometimes on sites where there's hardly any. Establishment of these trees is more problematic than planting one year trees by a long shot. This being my main experience, I tend to error on the side of caution to assure their survival, because replacement is expensive. Dry fruit farming commercially is not done in neglect and if I was installing even whips on a site where the owner wasn't going to be paying much attention, I might include some compost amending as I describe here just to help assure quick establishment, even in the case of neglect and drought. Of course growing quality fruit is a balancing act and too much vigor is the worst thing for producing high quality well colored fruit. When I started my own orchard we were in several years of consecutive or almost consecutive drought summers. I got in the habit of mulching my fruit trees every year because my well was insufficient to spare water for the trees. This is the first year where I've regretted having done that. With all the rain we've had, my enriched soil may be contributing to bland fruit this time. Even if you get the balance right for an average season, it may not be perfect for an exceptional one.

I haven't used the Kellogg Amend, but a quick Googling indicates it's basically compost with some fertilizer added as well as gypsum. You certainly don't need gypsum since it's for improving the texture of clay soil. The fertilizer value could probably be obtained cheaper elsewhere - for example, plain old compost has NPK. If it were me I would get 2 bags of compost instead of one bag of Amend. Peat moss will add organic matter but I'm not real sure if it will do anything special in a sandy soil that compost won't. It's fairly expensive compared to locally made compost. I would also look at their cheaper brands of compost. Sometimes these are real crap and have a lot of soil in them, but sometimes you get lucky and it might look almost as good as the fancy stuff. If there isn't a broken bag to look in, discretly poke a finger-sized hole in one and take a look.

I, too, have sandy soil. The difference being that I get 30-35 inches of rain between July and September. So good drainage is a must! I have amended my soil pretty much like the example BoulderGrower posted, building up the beds some. I did mix the sand back in for some areas. All of my landscaping slopes down to the lake or down to the road, so I worked with that terrain as well. I also have a raised island that is Florida sand and something black, maybe old loam or topsoil, layered in. When I plant anything out there I dig a large hole and fill it with a gritty mix. This has worked well for me. I can't grow some of the nice plants that you can grow due to the soggy summers. Echeveria and Aeonium really struggle. But aloes, agaves, sedums and similar plants do very well with this plan. Good luck!

The first year that I grew onions, I got them in late, slacked off on the weeding, and then decided that they were just doomed and ignored them. (Except for the automatic watering.) I got so many onions that I had to give them away, even though I was rummaging through the weeds to find them. They weren't huge, but they were big enough--I absolutely considered it a success. The second year that I grew onions, I got them in on time, kept them beautifully weeded, and got sad tiny onions. Then I read that onions really, really don't like the root disturbance of weeding. I suspect that the weeding was what caused that failure. The third and fourth years that I grew onions, I planted them on time and grew them through weed barrier fabric (four onions per hole, one hole every eighteen inches--a tremendous excess of space, I realize, but I was deluding myself that maybe onions could be dryfarmed), so that they stayed mostly weed-free without my having to damage their roots. I got nice big healthy onions--despite really lousy soil prep and fertilization, and not enough water. So until I have more data, I think that the key to my onion crop is weed control without actually having to disturb the soil. AND enough sun--the most recent year I grew a pretty long row of onions, going from full-day sun to half-day sun, and the onion size dipped very abruptly when the onions got to the half-day sun. Next time, my plan is on-time planting, good soil prep, full-day sun, weed barrier, and at least twice as much water as last time.