Adding Amendments
Our soil is sand about 8" under the topsoil. Previously the land had corn and soybeans, alternating every year. This really depleted the soil.
Over the past year we put down 252,000 lbs. of Topsoil, Compost and Manure and rototilled it into the soil.
In winter we use a cover crop to add more nutrients into the soil
Worm Castings
After all of the addition of compost, topsoil and manure we sometimes will add worm castings to the soil for some of our special plants, just to give them a bit more nutrients.
There are a number of amendments you can add to the soil, but worm castings are one of the best of them for our purposes.
Check with where you buy your plants for their recommendations.
Fertilizer Injector System
After we put in our automated watering system, we also invested in a fertilizer injector system. The first year we went with a cheap injector that really didn't work.
Last year we added a Dosatron Injector and love it. You can dial it down to the exact mixture, and it is operated by water pressure no electricity required.