is good for soil fertility? The unexpected answer is: humus. While for many hummus is the ultimate dip, humus is the ultimate organic soil.
Humus, which literally means “earth” and “ground” in Latin, is made from decomposed plants and other organic materials¹. Because of its high ratio in organic compounds, humus is also very rich in microorganisms which help plants to absorb nutrients or to combat diseases. This makes humus a great solution for soil fertility². In nature, humus is the top layer of dark organic matter that forms in the soil when plant and animal matter decays. However, humus can also be made at home by mixing up primarily coffee grounds and tea leaves; other kitchen waste can also be used such as mouldy bread and vegetable cores. Grass cuttings can also be added. To this mixture, one cubic foot of sand or clay can also be added and the humus is ready to be used.
Humus contains many useful nutrients and minerals for healthy soil, with nitrogen being the most important of all. Nitrogen is particularly important for plant growth because it is primarily responsible for vegetative growth and a building block for protein in the plant. Specifically, humus consists of about 60% carbon, 6% nitrogen, and smaller amounts of phosphorus and sulfur³. Because it acts as a storehouse for essential plant nutrients, it helps determine soil fertility level. But humus also provides further essential benefits to the soil.
One of the most important functions of humus is that it makes the soil more porous, improving soil aeration, infiltration and drainage. Humusless soil can become extremely compacted and airless and form very hard crusts that resist the infiltration of air, rain, or irrigation water and hence also prevent the emergence of seedlings. This function of humus improves the structure of the soil and in conjunction with humus’s capacity to retain important nutrients, humus rich soil helps plant grow more easily.
In addition, humus’s biochemical structure enables it to moderate or buffer excessive acid or alkaline soil conditions. This allows humus to prevent toxic substances from entering the ecosystem as heavy metals as well as excess nutrients that can harm soil fertility, are bound to the complex organic molecules of humus. Humus also holds the equivalent of 80–90% of its weight in moisture, and can increase the soil’s capacity to withstand drought conditions². It is usually black or dark brown and this dark colour attracts the sunlight and helps to warm up cold soils in the spring⁴.
Furthermore, humus supports the growth of an all-important organism called mycorryhzal fungi. This fungi forms a symbiotic relationship with many plants and is an important factor in the soil food web. What is more, this fungi help bind the soil particles to form good soil structure.
Overall, adding humus in the soil will increase soil fertility and enhance the growth of seedlings and other vegetation while also reduce the need for watering to a minimum and help make plants more resilient to disease.