Earthworms will tell you whether the soil is good or not!

Many farmers complain that today’s soil feels “lifeless”—despite heavy fertilizer use, both yield and quality decline year after year. In fact, you can tell whether the soil is healthy by simply counting the number of earthworms.

         Earthworms are one of the animal groups with the highest biomass among soil organisms and play an irreplaceable role in maintaining the functions of soil ecosystems. It can be said that earthworms are the transformers of soil fertility and serve as bioindicators of soil quality; the absence of earthworms in agricultural fields signals that the soil has already encountered problems.

         In recent years, with the rapid development of industrial and agricultural production, numerous toxic and harmful substances have entered soil ecosystems, inflicting devastating impacts on earthworms and other soil fauna. In contaminated soils, certain sensitive earthworm populations have disappeared, while those capable of tolerating pollutants have persisted, leading to marked changes in their abundance and community structure. This indicates that earthworms serve as sensitive bioindicators of soil pollution.

         Most earthworms can consume each day an amount of soil roughly equal to one-third of their body weight. While this may not sound like much, according to Darwin’s conservative estimates, “in the course of a year, a healthy earthworm population in one acre of soil will move and process more than twenty tons of soil.” After digesting the soil, they excrete castings; their primary function is to grind soil particles into finer fractions and to thoroughly mix humus‑rich organic matter with the mucus lining their gut. The roles of earthworms in the soil are as follows:

         ① Improve soil structure. Earthworm activity improves soil structure, enhances the soil’s water-holding capacity and aeration, and helps protect and maintain soil organic matter.

         ② Decompose soil organic matter and enhance the efficiency of nutrient transformation in the soil. Earthworms decompose and fragment coarse organic matter in the soil, thereby facilitating its breakdown by microorganisms and accelerating nutrient cycling.

         ③ Increase the availability of readily available nutrients in the soil. Earthworm activity can enhance the availability of soil nutrients and accelerate nutrient turnover; it also significantly promotes soil nitrogen mineralization, thereby increasing the content of available nitrogen in the soil.

         ④ It promotes plant growth. Earthworm activity promotes root growth, plant development, and high crop yields. At the same time, it facilitates the dispersal of beneficial plant-associated microorganisms, alters their community structure, and suppresses the abundance and activity of plant pests, parasites, and pathogenic fungi.

         ⑤ Effects on soil microbial communities. Earthworms and vermicompost provide a highly favorable microhabitat for the growth of microorganisms and microsoil animals, as well as for the elongation and development of plant roots.

         ⑥ Effects on soil enzyme activity. Vermicompost is rich in readily available nutrients and promotes microbial growth, while microorganisms secrete a variety of degradative enzymes. Its favorable structure provides an optimal spatial environment for enzymatic reactions. Moreover, the intestinal digestion process in earthworms further enhances enzyme activity.