Here's what I'd do. Cut a couple strips of 3/4" plywood, say four inches wide and not quite as long as the shower sides. Using clamps, glue, and corrosion resistant deck screws, fasten the strips to the underside of the edges of the plywood subfloor, where you cut it. This creates a "lip" on either side. Cut the new piece of subfloor plywood to fit and drop it in. Fasten it to the new plywood lip on either side with glue or construction adhesive and more screws, and of course screw it securely to the floor joists. Frankly I don't think the support of the walls is compromised enough to be an issue, if at all, but the above steps will enable the load to be distributed much as it was before you cut out the rotted portion. I doubt they're load bearing walls. Good luck. This post was edited by airqual_guy on Mon, Jul 28, 14 at 0:08

Those walls are not load bearing - they only have to hold themselves up. If you want to feel secure, and especially if you are tiling and need a rigid floor, add some blocking across from joist to joist, using nail-on hangars where you can't get to the ends of the blocking. then put the subfloor back. http://www.diydeckplans.com/sites/default/files/image/building-guide/blocking/blocking-2.jpg

Two long beds sounds like a good plan. They can be any width less, but don't make them wider than 4'. If you have short arms, make them less wide. Just test your reach from both sides of a 4' space. You want to be able to reach 2' into the bed if you can. This way, with paths all the way around, you'll never be walking in the beds. When you make paths, consider your body size and agility lol. It seems silly, but paths that are too skinny can be tough to maneuver. I like my paths to be - AT LEAST - 18", but many people like them wider. In your case, if you make the center path 2', that should give you 2 - 4' X 12' beds. That's a very good start for a first time gardener. As for amendments... since you don't yet have a soil test (depending where you are, contacting your local agricultural agent if you're in the U.S. will help you get a cheap test, and they will explain what you need to do,) and you removed the original soil, it is a little tough for us to advise on amendments. Again, I'm not judging, but as others have discussed, often native soil is as good, or better than anything you can buy. But, what's done is done, and we can't see what you were working with, so it's tough to say what the best choice was in your case. However, at this point, you might want to consider mixing some of that clay back in. Clay, when properly amended, is very nutritious, and offers some good qualities. You've already eliminated its major downside... compaction. So, before you spend more money, I'd consider adding back some clay. This offers another positive... see, with soil you brought in without a soil test, it's tough to advise what to amend with because we don't know how much organic matter, manures, fertilizers, etc... are in your loam. If you add back some clay, you'll probably be safe adding some compost and manure. If you have to buy them (unless you live on, or near a farm, most first time gardeners do have to purchase them,) get both compost and manure. Compost does offer decent nutrient value, but its real benefit is to the life it brings to a soil. Manure (if you do live near a farm, make sure it's fairly well composted) brings fertility. The 2 working together will get you off to a good start, but don't add 'too much' of either. To get a feel for your conditions, do the tests that kimmq describes. If you no longer have the clay, you can buy soil, but as others mentioned above, it is always a gamble. You just never know what's in soil from somewhere else. All the other advice above looks good, keep posting so that we know what your thinking. The good thing about gardening is that there are many ways to accomplish good results. Some things may not be available in your area, but others are... Also, its good to put at least basic info in you user name. In your question you can offer more info, like what part of your State - N, S, E, W,. etc... A word on organics... you can do a web search and learn about organic gardening. Basically, you can begin to think of it as using 'natural' methods and ingredients. A compost pile is a very good start. Every gardener will need to make these decisions, and your first 2 'tests' that challenge your feelings in this regard will be about fertilizers and pest control. Some ferts are synthetic. Some are 'organic'. Pest control can consist of organic methods and products, it can be chemical poisons, and like with ferts, it can be anything in between... You have to decide what you are comfortable with, and your tolerance levels. When it comes to pest control though, there is an axiom... always use the least toxic choice that solves the problem.

Atantis got a hair cut. I trimmed all the lower leaves because I've been thinking of heeling in small pots underneath Atlantis. Atlantis is in a pot so I won't be damaging any roots. I've been seriously looking for room in my garden to dig some pots in for the winter! Clear Fork River Valley (on the left) gets better each year. Love the corrugation.