I MISS my clay soils! I've just moved to another state, Oregon, smack in the middle of cinder cones and my new soil is pumice and sand. Easy to work but watering is going to be every day until I can get my 'slaves' (micro and macro organisms) to find my garden, eat, make babies, do lots of pooping. I could use a tiller but I've gotten use to doing the work myself as I'll never use a tiller in clay, even dry. I don't think clay ever gets dry unless baked into bricks, sigh.
Tilling clay is like rotating the concrete drum. How is concrete made? It is made with gypsum, lime, gravels, clay (portland cement), water and mixing. Clay is a bit different than sand and silt particles. Very small and FLAT particles of rock. These rock faces have charges that attract other clay particles and the flat sides get together and stay together. These charges are amplified by movement; tilling moist clay increases these charges. A couple of decades ago, people routinely added gypsum, river gravels, to their clay soils (spraying them with water to 'soften' the clods) and with tiller in hand made...their new concrete patio! Or should have. This would be a bummer for someone new to gardening. They probably never tried again.
But clay has great properties; holds moisture, nutrients don't wash away each time you water and a little goes a long way. I manually (arghhh) mixed compost as I double dug my beds...half-heartedly...remember the less you manipulate clay, the better. And I never add gravel or sand or any other mineral (unless my soil tests show a deficiency). Double digging is the most work I do in my garden, I do it ONE TIME the first year. Depending on the subsurface layers, I try to go down 18" to 2' and if there are layers of blue clay, shale, old lumber, roots, garbage, rocks I'll pull them out or punch holes through them for better drainage. The top 6" usually has all the organic material so be careful you don't turn all that over and bury it 18" below.
Plant roots, something like 95% of all the roots in the world are within the top 6" of soil. When adding mulch (hopefully decomposed mulch) to the top of your beds, after the plants are in the soil, be careful not to add more than 2-3". Too much will bury the plant's feeder roots and they won't get enough air and water. Careful with shallow rooted plants such as Daphne, Rhododendrons and Azaleas. Only use an 1" of mulch for these plants. And keep the mulch (and soil) away from the base of woody plants. Mulch keeps moisture trapped in the bark and microorganisms will girdle (kill the vascular system just beneath the bark) and will slowly but surely kill the plant.
My new garden soil has very little organic material, probably 1" of the top soil otherwise it is 3' of uniform pumice and sand, blown from cinder cones 50 miles away. I haven't dug any deeper. In fact, I am only double digging down 1 foot so I don't lose any organic matter. Sure doesn't fluff up like clay did. If this soil were clay, I'd have 3' high beds which would reduce to 1' within a month or two. The beds won't be compacted from being walked on and should last forever, IF you continually top dress with decomposed organic mulch. I also love green cover crops for the winter. Keeps the weeds down, the roots keep the soil friable and when the plants turned over and chopped up in the spring before going to seed, these cover crops add a lot of food for your soil.
I was able to find the local power company in need of places to dump their chips and had 40 yards or more dumped on our property. I won't use any of it in my soil until it is decomposed. Maybe for the walkways in my new greenhouse. It will take years to break down. Our climate is cold and the decomposers are sluggish, I guess. I'll keep 5 or 10 yards to decompose, the rest for my horse's paddocks and the rest we've covered our driveway with 4" to keep the dust down. Works great.
And no, I won't use my horse manure. I spray my horses poo with pyrethrins to reduce flies. I want insects, worms, bacteria to thrive in my soil and my horse poo won't be decomposing properly and the pesticide I certainly don't want in my soil. I till my paddocks and plant pasture seed in the fall. Grass seems to do just fine in yucky soils as long as they get fertilized and watered. One of my neighbors has decomposed horse manure (3 years old) but I need to find out what she gives her horses and what her pesticide practices are before I use any of it in my beds.
I won't double dig again unless I enlarge my beds or move again! The most important thing I do besides watering is watching for nutrient deficiencies and keeping insect/rabbit/deer/fungus/virus/bacterial/mice/rats damage to a minimum. Feed the good guys and the bad get fed too. But a healthy ecosystem albeit made by me, takes both. The good eat the bad. If no bad guys what will the good guys eat? I always top dress my beds with decomposed organic mulch. This keeps the good guys good, grin. The good guys are your 'slaves' doing most of the work for you as they did in a natural ecosystem. Checks and balances. Humans love to control everything. As a gardener, a lazy one to boot, knowledge is power. A good manager delegates!
The first year is the most difficult until you get the soil pH stabilized and full of organic matter. I'll be sending in soil samples to our Cooperative Extension Service for testing once per year to help me figure out a fertilizer program. The products for plant nutrients or fertilizers are quite high tech...grin. They are mostly organic, more slowly taken up than the big blast of inorganic fertilizers and they now come infused with bacteria and mychorrizae! You can make compost 'teas' out of some of these products and water life back into the soil.
In my 'sandy' soil I am going to need to be vigilant with nutrients as they are leached out with every watering. In clay soils you will need to be more careful about how much and what kind of nutrients to add. Clay holds onto nutrients, some more than others. Too much of one nutrient can cause deficiencies in others. Too much fertilizer can kill plants, especially if the fertilizer is inorganic. Once as a new nursery employee I was asked to fertilize. Unfortunately some of the plants had already been fertilized the month before and someone had forgotten. The next day, toast. Big shrubs, expensive trees gone. I tried removing the soil, washing of plant roots and replanting but still casualties occurred. I felt awful. But even worse than that was when I led crews for landscape maintenance.
I had a few landscape maintenance clients that thought if a little works, more is better! Maybe they were talked into it by the chemical company..."Hey how about a 'deep root feeding'?" Remember what I said about most plant roots? Deep roots are for stabilizers, not for uptake of nutrients. The chemical company SAW the signs we put up saying what and when was fertilized. My client's entire landscape was killed, lawn, trees, shrubs, hanging baskets! Guess who got sued...not me! Or my company. Fertilizer is NOT PLANT FOOD. Plants make their own food. Nutrients in the soil are usually part of an elaborate ecosystem. We have to add nutrients because we've 'mined' the original ecosystem...taken trees, indigenous plants, topsoil away leaving a sterile site to build a home or a parking lot.
Can't plant trees to replace a forest. Sometimes I wonder just how educated our 'leaders' are!
So us gardeners have to understand ecosystems, soils, geology, water, chemistry, climate, weather just to grow a tomato plant. Otherwise, you are just lucky. A 'green thumb' is earned through study and experience. No one is born with one...