You can use both. You can buy compost. Compost has a lot more to offer than just giving nutrients to the soil, like fertilizer does, though. It can help retain moisture and also help keep the soil cool when the weather gets hot in the summer.whether I should be using just fertilizer, just compost, or both? I understand the different between them more now, but I'm still confused which one I should be using or both. Is it possible to buy compost? Or can you only get it from making your own? Because if if I can't buy it then I probably can't use any compost this year as I don't compost.
If your soil has what it needs, there usually isn't any need for fertilizer.