Soil Amendment Advice

I'm starting a few new garden beds and could use some advice on what to amend them with and what kinds of ratios to go for. The current soil is approximately 40% sand, 50% silt, and 10% clay with little to no organic matter and 6.0 pH. I'm planting all edible perennials, so the amendments must be food safe. I need a soil mix that's acidic, rich, and moist, but well drained for camellia, vaccinium, Ilex, and gaultheria; One that's the same, but less acidic for osmanthus, elaeagnus, fragaria, and viola; and one that's dry and fast draining for thymus and chamomile. So far I've tilled the beds to a depth of 12" and would like to build them up a minimum of 6" more.

P.S. I'm planning on doing gravel paths between the beds and would appreciate any advice on how to create a tidy well compacted path.

I've never actually created soil mixtures, but I'm sure others can give you advice on soil mixtures they've had success with. But I have done a lot of amending of my garden beds. In fact, I believe when you're using natural materials like compost, amending on a regular basis can only help your soil no matter what type of soil you have.

When I'm making a new bed I mix in a lot of compost and dry leaves. My soil is alkaline so I may also use peat moss.

Because we have a lot of trees, dry leaves are a regular amendment I use. We crush or shred them first so they don't pack down and then either mix them in to the soil or spread them on top as a mulch. They'll break down adding nutrients and texture to the soil.

I also add compost several times a year. Again, you can mix it in or spread it on top around your plants. It will work it's way into the soil and add a lot of nutrients. Many people like composted manure, but I've never used it.

One of my favorites is used coffee grounds. I collect my used coffee, filters and all, and add them to my compost bin. You can also sometimes find a coffee store, like Starbucks, that will give you large amounts of used grounds. Worms absolutely love coffee grounds, by-the-way and you can also add it directly to the soil.

Your gravel paths depend a lot on how much work you want to do. They'll be a lot neater if you dig down some and fill the area with the gravel rather than just pouring gravel on top of the dirt or grass.

Compost, compost and then more compost. That will also neutralize the soil PH.

My two bits... I find gravel paths are rather more work to maintain than mulch paths. Seeds fall down between the stones and have the perfect spot to germinate, even if there is some very plant-unfriendly material under the path (e.g. landscape fabric). The gravel is hard to manipulate a dandelion weeder in. Our mulch paths are relatively maintenance-free by comparison - the fine fibres of the cedar and fir bark mulch mats together and seems to work better to prevent seeds finding a moist crevice to germinate in.

There's another potential problem with gravel paths if you're using it where you have lawn. Stray gravel is not what you particularly want to run the lawn mower over, whereas the mower will just chop up stray mulch with no damage done.

Hi SilverFox!

You are very lucky. You have great soil for gardening/farming. It is right on the boundary of "loam" and "silty loam". This is the kind soil farmers dream of. However we don't know about your organic content, or pH. But I agree with the above people that adding compost is probably all you need to do!
I also agree about the gravel being difficult, especially if under-laid by a "weed blocker". My Mom did this, and the weeds sprouted great, then the roots would be entangled in the fabric and impossible to pull cleanly. Unless you are willing to use Roundup on the path (which it sounds like you don't want to do for good reason), I also suggest some other path material.

Here is a link to the calculator for soil type:

http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/survey/?cid=nrcs142p2_054167

And here is a link to the University of MD Extension Website, where they talk about soil amendments and soil tests etc. I guess since you want plants that desire different pH, this might be useful to know, but if all these plants can be seen in your neighborhood, probably you don't need to worry about using lime etc to change pH.
http://extension.umd.edu/hgic/soils/soil-testing

Very useful information. Thanks everyone! I'm still a bit confused about organic material though. I've seen advice all over the map: some say optimal is around 10-25%; others say the more the better, pile it on 50% or more. Can anyone get specific about the pros and cons?

Well there are some plants that prefer a "mineral soil", these are plants from regions where there isn't much organic matter. Think of a cactus. The desert is sand and rocks. They might stay too soggy if you heap on compost. Plants from moist forests often are adapted to have a layer of organic matter settle on them every year. Also for regular plants if you bury them in compost, this will not go well. Trees can have the surface roots damaged if too deep mulch is applied, as they are there to get oxygen. Also or trees and shrubs mulch on the bark can allow it to stay wet, and rot can set in.
You seem to want pretty ordinary plants, so they like an "ordinary" amount of organic matter. But I agree thyme generally does not particularly appreciate an "organic" soil (organic here means one with lots of organic matter in it, nothing to do with lack of chemicals).
So put some compost there, you might order a truck to deliver it if you want it 6" deeper. But I don't think it "needs" to be 6". Then mix it in a bit. I personally would save some of the pile, then use it for mulch about 1-2" deep, after planting. This will prevent light from hitting the soil, which is a potent trigger for (weed) seeds to sprout.
If you actually don't care if the planting area is 6" higher, you might save yourself some money and just plant directly in it, just using 2" compost as mulch. The worms and other creatures will mix it in for you.

Oh I just noticed you did say pH 6. This is great, just mildly acidic, so most everything should be fine.
I also had decided to grow a few things listed as wanting an alkaline soil. I bought a bag of lime chips, and put some around the plants, in the hopes they will slowly dissolve over time, and release me from the need to put lime on every year. So far so good. Just an experiment, though.
You might save one bed without any amendments, for the things like thyme and chamomile (many of the classic Mediterranean herbs like rosemary, thyme, etc are from hot dry places, and don't appreciate organic matter).

I think you will regret the gravel paths. As you plant, transplant, and do all the other garden tasks through the months and years, the gravel will get kicked into the beds and all kinds of material will fall on the gravel. Furthermore, since the underlying truism about good gardening is to focus on nurturing the soil, it would be advisable to mulch the paths with some kind of organic material such as shredded tree leaves or hardwood chips.

My paths through my large flower garden are made of two types of materials. A few "primary" paths are made of old street bricks. Other "service paths" are made of 8" x 16" pavers which the original owner of the house had procured, and they are laid about 30" apart as stepping stones. The pavers are not slippery when wet, and they are easy to lift and rejigger as needed. I apply homemade compost topped with shredded leaves in these paths, including under the pavers (as well as in the beds themselves).

Our house was built in the mid 1970s, and the original owner had quite a number of beds mulched with stones over plastic. Some were lava stones, others were river stones. Through the years, debris falls on the stones, decays, and the stone beds become rich with humus, and weeds. . . Furthermore, the lava stones are so lightweight that you can't really clean them with a blower. (You would have similar difficulty with gravel.)

In our out-of-sight service area where we have our compost piles, we have for many years thrown down our own homemade wood mulch: We pick up all fallen branches and use our hands to break them up into 3-4" pieces, if possible. (Some are too big to break up by hand, so they go into the shredder or alternatively get put out for the spring municipal pickup.) All these little pieces have been thrown down in the service area, which we call our "twiggy area". After so many years, the soil under the woody material is fluffy. The few weeds that grow there pull right out.

Again, I recommend mulched paths. Feed your worms and soil microbes.