Both leonardite and compost improve soil. Both add organic matter. Both support biological activity. So why would you use one over the other? The answer lies in understanding what each material actually is, and what it does in your soil.
Compost is organic matter in the early stages of decomposition. It's recent—made from plant material that was alive months or years ago. It still contains recognizable components: partially broken down leaves, stems, food scraps. It's rich in nutrients and teeming with active biology.
Leonardite is organic matter at the end of decomposition—the end that took 70 million years to reach. The original plant material is long gone, transformed by geological pressure into stable humic compounds. It doesn't add many nutrients directly, but it dramatically changes how your soil handles the nutrients you do add.
Think of it this way: compost is food for your soil. Leonardite is infrastructure. Compost feeds the biology and adds nutrients that get used up and need to be replaced. Leonardite builds the systems that make your soil function better, and those systems persist for years.
The best approach usually involves both. Compost provides the raw materials—carbon, nitrogen, the full spectrum of nutrients. Leonardite-derived humic substances (like KARA) optimize how those materials are stored, cycled, and made available to plants.
If you had to choose one, compost is more universally useful—it provides both material and function. But if your soil is already reasonably fertile and you want to maximize its potential, or if you're working with poor soil that doesn't seem to respond well to compost alone, humic substances can provide the missing piece.