Humus soil is rich in plant nutrients, such as nitrogen, potassium and carbon. Humus forms naturally over many years, or it can be manufactured in a compost heap in a much shorter time frame. In addition to numerous organic compounds, humus is also high in bacterial life, which encourage plant growth in many ways. For long-term plant growth, humus is the ideal choice, because it will require less frequent treatments to maintain the level of fertility required for plants. For long or short term planting, humus should either be the primary soil, or be mixed with the existing soil to increase fertility.
Humus and Soil Fungi
Bacteria and different types of fungi are responsible for turning plant waste and debris into nutrients that can be reabsorbed by the plants. Other bacteria act to condition the soil to adapt the soil for absorption by plant roots. Still other forms of bacteria and soil fungi serve to protect plants and the soil by preventing the growth of harmful pathogens, and removing existing ones. Fertile soil requires many different type of microorganisms to remain healthy, and adding humus or compost is the most common method of improving soil quality organically.
Humus is Active Soil
It is important to remember that humus is made up of dead things, but it is very much alive. Experts say that one very reliable test of topsoil fertility is to dig a hole 1 cubic foot in size, and count the earthworms contained in the soil you remove. Soil with 45-60 earthworms is considered highly fertile, and soil with less than 30 is generally given treatments of additional compost before planting. And because healthy soil is very good at keeping itself healthy, humus soils work out well for long term planting, even for trees or bushes that will remain in place indefinitely.
Optimal Top Soil for Plant Growth
Humus makes some of the very best top soil you could hope to have, especially if you are using humus created by composting. To help plants grow strong, humus tends to be lighter than other soil types, making it easier for roots to push their way through the soil as well as allowing air and moisture to permeate the soil evenly. Long-term plant growth demands a viable and active soil, or else the soil will be quickly depleted, and the plants will falter or fail completely.
Treating Other Soils With Humus
Other soil types benefit from having humus mixed into them. Sandy soils are often deficient in nutrients and moisture, for example. Adding humus increases the available nutrients, and adds a certain amount of density to the sand so that it is able to retain more moisture. Clay, while it is rich in inorganic compounds and minerals, is often lacking in carbon, nitrogen, and potassium. Mixing clay with compost infuses these missing nutrients, and has the added benefit of loosening the soil density so that roots are able to grow stronger. For all planting, short and long-term projects alike, adding humus into the topsoil is a great way to help guarantee strong plant growth.