# Influence of _Eisenia fetida_ on the Nematode Populations during Vermicomposting Process
## 1 Introduction  
Composing is a natural and controlled decomposition process that transforms organic materials into a nutrient-rich soil conditioner. This process involves the mineralization and partial humification of organic matter, in controlled aerobic conditions, to a stable, pathogen-free product with the properties of humans [1]. Composting occurs in two distinct phases--mineralization and humification--each further divided into two respective stages: meso- and thermophilic stages during the mineralization phase, and cooling and maturation stages during the humification phase. The energy produced during mineralization is accumulated in the form of heat, which increases the temperature of the compost and is a characteristic feature of the process. During cooling, humic substances are synthesized, which leads to the production of mature compost.  
Earthworms play a pivotal role as crucial biological factors in the soil ecosystem. These organisms are central to the decomposition and mineralization of organic matter within the soil. The agricultural significance of earthworms has been recognized for an extended period, as they contribute significantly to soil fertilization processes and exert influence on the physicochemical properties of the soil [2]. Vermicompost is produced with the participation of earthworms. They feed on organic residues [3], promote the colonization of the soil by beneficial bacteria and fungi, and break down pathogens and pests [4]. Earthworms have been observed to enhance the mobility and accessibility of heavy metals. They achieve this by stimulating microbial activity and accelerating the decomposition of organic matter. Additionally, they contribute to soil pH acidification, diminish the dissolved organic carbon responsible for metal transportation, and directly uptake these metals [5; 6].  
The most popular earthworm breeding species among earthworms is _Eisenia fetida_[7; 8]. This species is distinguished by a high activity in processing the substrate and the ability to manifest this activity all year round, with the shortest period of development and the highest rate of reproduction. _Eisenia fetida_ is used throughout the world for this purpose as it is ubiquitous, can tolerate a wide range of temperature and can live in wastes with good moisture content.  
Nematodes are small organisms abundant in soil, they present a high species diversity. Nematodes span various trophic levels within soil ecosystems, functioning as bacteriores, fungivores, plant feeders, predators, and omnivores. This diverse spectrum allows them to consume a broad array of food sources [9]. The number, species diversity, and trophic structure of nematode communities are significantly influenced by biotic (humidity, temperature, pH, abundance of organic matter), abiotic (interspecific competition, relationships with other organisms) and anthropogenic (soil, pollution) factors. Hence, nematodes possess several characteristics that make them excellent bioniticators [10; 11; 12; 13; 14; 15]. Nematodes are closely related to plants, microorganisms, and other groups of soil fauna. They take part in the circulation of nutrients [16]. Their high nutritional activity and rapid metabolism play an important role in processing microbial biomass and releasing mineral nitrogen compounds into the soil [17]. Nematodes have the capacity to stimulate and facilitate the growth and proliferation of microorganisms, particularly those engaged in decomposing organic matter [18]. Conversely, controlling plant feeder nematodes is essential in agriculture due to their direct impact as pests or vectors of different plant diseases [19].  
This study aimed to investigate the influence of _Eisenia fetida_ presence on nematode communities during the compost process, specifically focusing on the potential changes in nematode density and structure within sites introduced with _Eisenia fetida_. It was hypothesized that certain nematode types would exhibit greater dominance in _Eisenia fetida_-inhabited sites compared to the control sites.