Rainworms are divided into three ecological groups based on their digging behaviour and lifestyle. The epigenic species live on the bottom in the litter layer. They stay slow and don’t dig tunnels, their body is usually pigmented. The epigenic species reduce the amount of leaf waste on the bottom. An example is the Lumbricus rubellus species. The endogenous species live in the top layer of the soil. They dig tunnels which are often horizontal and lie just below the surface. Rainworms belonging to this group become medium-sized and don’t have pigmentation, are often pale in colour. Endogenous worms break down leaf waste and provide aeration for the top layer. An example is the Allolobophora chlorotica species. The third group are the anecan species; worms who dig deep, vertical tunnels. The anecan species have pigmentation and become the largest. Through the deep tunnels, the bottom is aerated better and water can be removed better. One example is the ordinary rainworm (Lumbricus terrestris).
Rainworm populations depend on both the physical and chemical properties of the soil, such as soil temperature, humidity, acidity (pH), salts, aeration and texture. In addition, sufficient food must be present and the species must be able to propagate and spread. To achieve this, regular organic material must be added to the soil by inserting it into the ground or sprinkling it on the ground.
Rainworms play a very important role in improving the soil structure. The rainworm digs long tunnels into which atmospheric air can penetrate so that the soil is aerated. As a result, aerobic bacteria can live deeper in the soil, such bacteria accelerate the decomposition of organic substances even more. Because the rainworms move in their corridors, air is being moved in the soil which benefits the aeration. The use of heavy agricultural machinery causes the air to be squeezed out of the soil; thanks to the work of the rainworms, the soil becomes better suited for plants to grow. The tunnels of rainworms are appreciated by plants, it allows their roots to penetrate more easily.
In addition, the water management of the soil is also better if there are rainworms in it. Through the long tunnels, the soil can absorb, drain and hold more water, depending on the circumstances. Another feature of the rainworm that benefits the soil condition is the eating of dead, shed plant parts. The rainworm converts these into minerals that are very important to plants. The organic material is hereby partially digested and the remaining soil is returned well mixed again. Rainworms were described by Charles Darwin as a “natural team”, estimating that every several years, the entire surface layer of the world passes through the stomach of an earthworm.
The rainworm plays such a major role in soil ecology because the species is found in huge numbers. In humus-poor soil, 62 worms per square meter can occur and in humus-rich soil even more than 432 worms per m². According to an estimate, rainworms make up about half of the biomass in the soil. In an area of 1000 square meters, about 125 kilograms of rainworms can be found, in fertile soils this can amount to 3 tons of rainworms, even though it is not just the ordinary rainworm but all kinds of earthworms. In fields where many worms are present, the yield is significantly higher than fields in which no worms live. When weighing the worms’ faeces in a square meter over one year, the animals were shown to produce 4.4 to 8 kilograms, which means an annual processing of 44 to 80 tonnes of soil per hectare.
For soil improvement and composting, we have compiled the compost worm, including the redworm (epigenic species), the eisenia (endogenous species), the dendrobena and the deworm (anecan species). These can be ordered from the web shop. We recommend 50 grams of compost worms per square meter.