1.1 Introduction
The earthworm is considered the critical environmental mediator capable of affecting earth functions and microbial activities by generating priming effects. Energy-rich mucus stimulates microorganisms and signals hormone-like molecules that affect plant genes’ expression. The effect of this, however, may rely on your food choice, range, dietary intake, assimilation, and digestion, helping earthworms digest microorganisms by reducing microbial biomass, particularly fungal biomass (Hoang et al., 2016; Lipiec et al., 2016; Drake et al., 2007). It could also be used to pick or stimulate soil microbes that help them in soil digestion, as the earthworm bottom frequently lacks adequate enzymes.
As a prelude to other parts of this study, this chapter will discuss the background upon which this study was initiated, the statement of problems that led to this study, the Aim and Objectives of the study. Others are Significance of the study, Scope of work, Research hypothesis and questions, Limitations of the Study and Definition of technical terms.
1.2 Background of Study
Earthworms are one of the most common soil animals in terrestrial ecosystems. They can accelerate the decomposition of returned straw by a series of activities, including crushing, feeding, digesting, and burrowing, and thus promote the transformation of fresh straw residues into humus (Six et al., 2004). In particular, the elevated degradative enzymatic activities in earthworm intestines can convert some difficult-to- decompose substances into easy-to-use organic materials, which are then excreted in the wormcasts to facilitate utilization by microorganisms (Hedde et al., 2013). Earthworms can thus significantly increase the rate of decomposition of low-quality straw (high C/N, high lignin and polyphenol content) (Lubbers et al., 2017).
In addition, the organic matter and soil are fully mixed during the ingestion–excretion process, which promotes the transfer of surface straw carbon to the deeper layers of the soil and finally enhances soil fertility by increasing the rates of soil nutrient cycling and turnover (Verhulst et al., 2011).
Many studies have revealed direct or indirect effects of earthworms on soil microbes (Groffman et al., 2004; Suarez et al., 2004). Some studies suggest that earthworm activities (Curry and Schmidt, 2007) have changed the numbers and the activities of microorganisms (Blouina et al., 2013), which can promote their propagation and growth. The studies by Singer et al. (2001) and Cao et al. (2015) have also shown increases in the numbers of fungal propagules in wormcasts. Other studies have suggested that fungi provided food for earthworms, which reduced the soil fungal populations by eating, dispersing, and killing soil fungal spores and hyphae.
Recent research on the influence of invasive earthworms on forest soil microbial communities (Price-Christenson et al., 2020) shows that carbon in the leaf litter layer is homogenized between the organic and the mineral horizons by invasive earthworms (Amynthas spp.) consuming and eliminating the leaf litter layer. The homogenization and the partial digestion of this carbon shift the soil microbial community from a fungal-dominated to a bacterial-dominated community. These results demonstrate that earthworm activity has a large impact on soil microorganisms, which may alter their functions and services to the ecosystem.
Although there are many reports on the effects of earthworms on microbial communities (Curry and Schmidt, 2007; Blouina et al., 2013), previous studies have mainly focused on forests and grasslands (Groffman et al., 2004; Suarez et al., 2004; Hale et al., 2006; Dempsey et al., 2011). There are few reports on farmland and, in particular, on the effects of earthworms on fungal population diversity and ecosystem function when straw is returned. Therefore, the mechanisms whereby earthworms change the structure and the function of fungal communities in farmlands are not clear.
Therefore, in Nigeria where the research was carried out, the activities that was conducted is to determine the Effect of Earthworm Density on Decomposition Or Reduction of Surface Residues.
1.3 Statement of Problems
Investigation revealed that recent research shows that straw return leads to significant changes in the structure and diversity of the soil bacterial ecosystem (Fu et al., 2012; Sun et al., 2013). Soil fungi excrete a comprehensive set of enzymes that allow them to degrade returned straw and thus play an important role in its recycling (Mitchell and Zuccaro, 2006).
Earthworms are one of the most common soil animals in terrestrial ecosystems. They can accelerate the decomposition of returned straw by a series of activities, including crushing, feeding, digesting, and burrowing, and thus promote the transformation of fresh straw residues into humus (Six et al., 2004).
Therefore, if excessive amounts of straw are returned to the field, its slow rate of decomposition will lead to poor germination, poor seedling growth, and increased incidence of soil-borne diseases (Prasad et al., 2016). These problems have greatly reduced the benefits of straw return.
1.4 Aim and Objectives of Study
The aim of the study is to determine the Effect of Earthworm Density on Decomposition or Reduction of Surface Residues. In achieving this aim, the following specific objectives were laid out as follows:
- To assess the earthworm density on the reduction of surface residues
- To examine the factors influencing the Earthworm population Density on Decomposition of Surface Residues
- To discuss the impact of earthworms on soil fertility, microbial population, and earthworm interaction among agriculture practices.
1.5 Research Questions
The study came up with research questions so as to be able to ascertain the above stated objectives. The specific research questions for the study are stated below as follows:
- Are there factors influencing the Earthworm population Density on Decomposition of Surface Residues?
- What is the earthworm density on the reduction of surface residues?
- What is the impact of earthworms on soil fertility, microbial population, and earthworm interaction among agriculture practices?
1.6 Research Hypothesis
In order to pursue the objective of this study, the following generalized statements have been designed to guide and aids in obtaining the result for the experiment to be conducted. For this work, the null hypothesis will be represented with H0 while the alternative hypothesis will be represented with hypothesis H1.
Hypothesis One
- H0: There are no significant factors influencing the Earthworm population Density on Decomposition of Surface Residues
- H1: There are significant factors influencing the Earthworm population Density on Decomposition of Surface Residues
1.7 Significance of Study
This study will be of immense benefit to researchers who intend to know more on this study and can also be used by non-researchers to build more on their research work. This study contributes to knowledge and could serve as a guide for other study.
1.8 Scope of Study
The scope of the research is focused on Determination of the Effect of Earthworm Density on Decomposition or Reduction of Surface Residues in Nigeria.
1.9 Limitations of the Study
During the course of this study, many things militated against its completion, some of which are:
- Time Constraint: The time frame given to accomplish this project was very short due to school academic calendar and it was carried out under pressure which made the researcher not to implement some necessary features.
- Research material: availability of research material is a major setback to the scope of the study.
- Frequent power failure: This made the researcher append more money on fuel to ensure sustainable power.
