Humans have stomaches to absorb their food and rely on an innumerable amount of other organisms to make these nutrients available. Plant's stomaches are the soil! Their roots release energy 'exudates' to attract the right biology to make nutrients available around their roots. If these micro organisms are not present in the soil then the plants will be vulnerable to pests and disease and not produce healthy food.
We are on a mission to produce compost full of the biology to green our landscapes and produce abundance as well as offer food waste collection to change the current system. We can cycle these nutrients as nature has done forever.
Soil Food Web
All of these things should be found in a healthy soil.
A spoonful of soil can contain billions of bacteria with thousands of different types. Bacteria eat organic matter and release manure as plant available nutrients. They are also food for protozoa, nematodes and arthropods.
Fungi do an important job in breaking down organic matter like bacteria, but they can also form a beautiful sysmbiosis with plants, creating a secondary root structure exchanging nutrients and water. This fungi is called Mycorrhizae.
Single-celled organisms that feed on bacteria and produce a nitrogen rich maure which is in perfect plant available form. They're one of the favourite foods for nematodes.
There are a few types of nematodes, but what you want are fungal and bacterial feeding nematodes as well as predatory nematodes that will eat protozoa and other nematodes. They are also food themselves for arthropods.