Although it sounds like your soil could use some improving, I would not be excessively worried about the soil crusting if your plants are looking healthy. As long as the water will soak in, even if it takes a little bit, the plants will be able to get it. Kisal's suggestion of using mulch is a good way to retain moisture in your soil and is very popular with many people. Below is an example how I created one of my garden spots using extreme measures to improve basically worthless soil.
I had a 30'x30' area that was covered with basement clay subsoil (next of kin to concrete
) from when we built our house. It was a pretty barren spot because even weeds had a hard time gowing there. I got a dump truck load of sawdust from my local sawmill and covered the entire area 8"-10" deep. I scattered 100 pounds of urea fertilizer granuals (46-0-0) over it also to help speed the decomposition process. I then made several passes with my Troybilt tiller to mix it with the subsoil. During that summer, I turned the soil with my tiller every 2 or 3 weeks. The following year I did plant some things, but since the decomposition process was still ongoing, the soil would not release enough nitrogen for the plants to do well. It was after the second year that it really shaped up. It has been many years since I improved that little spot and it is still the best soil I have with the least amount of surface and in depth compaction on my property.
You might think adding as much organic matter as I did was excessive. It takes at least 10 pounds of organic material to decompose to 1 pound of organic matter. Clay subsoil has almost no organic matter in it, so it needed a very large dose to transform it into usable soil. Also adding nitrogen is very important if you add a substantial amount of organic material because the organisms that break down the material use nitrogen as fuel.
There are many references to the fact that you should compost material before adding it to the soil. That is good advice if you want to continue to use your garden every year. Since I have so much garden space, I have the option of just letting an area lay idle while the soil is being improved. As I mentioned above, it took 2 years
for the process to be completed. When you consider that I started with something that was basically worthless for growing anything and compare it to the rich, fertile soil I have now, that was actually a relatively short space of time.
If you want to improve your topsoil
using this method, 2 or 3 inches of sawdust (or other organic material) should be plenty, and the decomposing process should be completed in 1 year.
One note of caution. If you use sawdust you may want to get a soil test after this process because some types of wood are slightly acidic. Also, many plants are severely allergic to walnut sawdust. Walnut sawdust will also kill horses by being absorbed through their hooves. I used poplar sawdust because it is fairly bland for this type of application.