I've noticed that where I live, rainwater seems to be mother's milk for plants: growth really explodes when the rainy season starts and I always thought it was something to do with the lack of dissolved minerals in rainwater but a mention on a local whatsapp got me googling and I discovered that lightning turns atmospheric Nitrogen into nitrates that the plants can use. If you want all the details, read this: https://biologyinsights.com/how-does-lightning-fixation-convert-air-into-fertilizer/ My city has one of the highest frequencies of lightning flashes in the world, due to the subtropical climate and and the high elevation.
This kind of lightning show is common for us in summer. Image: Derek Keats Creative Commons 2.0
If you live in an area with regular thunderstorms, your Nitrogen needs are taken care of.
The rest of the news about my soil is pretty grim. The area is classified as Sourveld, meaning that soil is acidic and very low in nutrients. It takes a couple of years to develop usable soil for growing food, but it can be done with large amounts of compost. I also use a lot of eggshells. While the use of eggshells can be controversial, it works for me: raises the soil pH and adds calcium. I crush the shells quite finely and sprinkle directly on the soil. While the shells almost never break down in the composter, they disappear within a season in my soil.
The other major drawback to the soil in my area is the prevalence of root knot nematodes, which really wrecks the roots of crops unless the soil has been improved. I read that fungi in the soil control the nematodes so I have dug a lot of bark into the soil over the years. Bark isn't very nutritious for the plants but it encourages fungi and also holds water and slowly my vegetables have had healthier roots. The nematodes aren't entirely gone but it's work in progress. For this reason, I only grow root crops in the winter months, when the nematodes aren't active.
Then there are ahem, cat turds. My furry children aren't into using cat litter and turds are not something you really want in the vegetables, due to the possibility of toxoplasmosis but not something I can do much about. This is why it's better to wash well and cook your vegetables before consuming, folks. Cats peeing in the garden is ok, it adds nitrogen and other minerals to the soil.
For the compost, I use a lot of garden waste. All weeds are left directly on the soil to break down and act as mulch. I eat a lot of bananas and toss the peels directly into the vegetable garden - bananas supply a lot of potassium and the peels and weeds break down pretty quickly and then I have a little compost bin for kitchen scraps that I chuck anything organic into. While it's popular to add coffee grounds to the soil, these should be composted first so that any caffeine residue is broken down because caffeine inhibits plant root growth.
The other less common additive to soil is ash: burning releases the minerals held in plant tissues. Sometimes when there's a lot of garden waste and grass I burn it and dig the ash in.
For succulents, you need very little compost and well broken down garden waste works well for them. I have rainwater tanks and use this to water them so I don't fertilise those either. Recently, I started using rainwater on my house orchids and after a long spell of no flowers, most of them will bloom this year.
Resting soil and rotating crops is also a must. Although I can grow food in winter and summer, I change up the plants in a specific bed every season but I also give entire beds a year off: I cover the bed up with garden waste and compost for a couple of months, then dig it all in and start again after 2 growing seasons. This approach has worked well on a piece of soil with the cards stacked against it: when I first moved here, I couldn't successfully grow any vegetables but 10 years later, my vegetable garden produces well.