Jeffry Hill is a consultant who has a degree in plant science.
Today organic amendments are becoming more and more popular, but to buy the right amendments you first need to find out as much as you can from the sellers and manufacturers of the products. If you are buying compost, inquire about the materials used and the length of time it took to create the compost. You also want to know the maximum temperature that the compost reached, storage conditions and whether it was sterilized or not. This can give you an idea about the carbon-to-nitrogen (C:N) ratio and the concentration of toxins and other substances.
Straw, wood chips, and bark are examples of low-quality amendments. They dissolve very slowly, have a high C:N ratio and can actually decrease the amount of nitrogen contained in the soil. Composts and rotten leaves are intermediate-quality amendments. While they also take a long time to decompose, they do release some nutrients and help increase the amount of organic matter in the soil.
Fresh manures, young legumes, and fresh grass clippings are some of the highest-quality materials that you can find. They have a low C:N ratio, decompose extremely quickly and provide a boost full of nutrients to the soil.
In addition to collecting as much information about a commercial product before buying it, also use your senses and intuition. If you want an alive, messy, complex and fertile soil, then you need alive, messy and complex combination of amendments for it. Touch and smell compost before buying it. If it has a synthetic smell and feels dead, it probably is. Good compost is rich black in color. It also has an earthy smell to it and a consistent size equal to that of fine particles.
You also need to be sure that you are not bringing any seeds of weeds or undesired pests when adding new amendments to your soil. Symphylans, also known as garden centipedes or pseudo centipedes, live in the western states. They are white in color and look like centipedes, even though biologically they are only distantly related. Garden centipedes can bring considerable harm to the soil by consuming roots and seeds. To make sure that the compost you are about to buy is symphylan-free, spread it on a black sheet of paper or plastic and make sure that no white centipedes start crawling out of it. Manures and composts can contain seeds of weeds if they were not heated enough. To check for weed seeds you can take a small sample, wet it, wrap it in a wet paper towel and place the towel with the sample in an open Ziploc bag. Keep the matter wet for a few days and see if any weeds start to grow. That’s how experts like Jeffry Hill check manures and composts for weed seeds.