1.1 Introduction
Soil properties are critical for understanding patterns of vegetation community composition and primary productivity in arid and semiarid ecosystems globally (McAuliffe et al., 1994). The relationship between incoming precipitation and water availability for plant growth in these water-limited systems is modified by vegetation, topography, and soil properties that affect surface redistribution, infiltration, and water retention (Duniway et al., 2010). Therefore, spatially explicit information for relevant soil properties is needed to understand the mechanisms governing plant species distributions and vegetation dynamics, particularly in efforts to forecast responses to changing climate.
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, Limitations of the Study and Definition of technical terms.
1.2 Background of Study
Soil maps show the distribution of soils across an area but also depict soil science theory and ideas on soil formation and classification at the time the maps were created. The national soil mapping program in the USA was established in 1899. The first nation-wide soil map was published by M. Whitney in 1909 and showed soil provinces that were largely based on geology. In 1912, G.N. Coffey published the first country-wide map based on soil properties. The map showed 5 broad soil units that used parent material, color and drainage as diagnostic criteria. The 1913 national map was produced by C.F. Marbut, H.H. Bennett, J.E. Lapham, and M.H. Lapham and showed broad physiographic units that were further subdivided into soil series, soil classes and soil types. In 1935, Marbut drafted a series of maps based on soil properties, but these maps were replaced as official U.S. soil maps in 1938 with the work of M. Baldwin, C.E. Kellogg, and J. Thorp. A series of soil maps similar to modern USA maps appeared in the 1960s with the 7th Approximation followed by revisions with the 1975 and 1999 editions of Soil Taxonomy (Adsabs, 2021).
Soil surveys have been conducted to meet user needs by creating an inventory of local soil resources, and by educating the public about the role of soils in their environment (Brown and Miller, 1989). The primary objective of soil survey programs is relatively consistent: to delineate uniform management areas (i.e. map unit polygons) across the landscape and provide users with information on soil properties and soil interpretations for these map units to support generalized soil use and management decision making.
The factor approach served as the basis for the development of particular methods of soil mapping in Russia and abroad. In fact, most of the soil maps all over the world have been created on its basis. The main difference between these two approaches consists of the principle of delineation of soil areas: via interpolation between the points in the case of the point-based approach and in agreement with the boundaries of the particular factors of soil formation (topography, vegetation, geological structure, climate, etc.) in the case of the factor-based approach. Note that the point-based approach was suggested for mapping particular soil properties, whereas the factor approach was applied for mapping soils identified in agreement with the accepted soil classification. The methods of point mapping are very laborious. The precise delineation of boundaries requires a great number of points of soil survey. Soil mapping in large areas with the use of this method is very expensive and is often almost impossible. At small-scale work, it can result in great errors of soil-geographical boundaries. At the same time, this method can be more accurate than the factor approach at large-scale work, at mapping individual soil properties in particular. Within the framework of the factor-based method, soil boundaries are determined by the data obtained upon the description of soil pits laid with due consideration for the so-called soil-landscape relations.
There are also the properties that virtually do not depend on the classification position of soils (e.g., some agrochemical characteristics, soil water content during the survey, etc.). The evaluation of soil resources (one of the main aims of soil map) may require the analysis of spatial variation of a greater amount of soil properties. For example, according to the analysis by FAO specialists (Rome, 1983), about 55 soil properties may be used at land evaluation for crop production. The geography (regularities of spatial variation) of many of them cannot be described by expert analysis of the classification position of a soil. This means that the information of traditional soil maps may be insufficient for the assessment of soil resources. In addition, the quality of data on factors of soil formation is very important for the factor mapping. Soil maps based on incorrect data are of poor quality. This is especially the case for soil mapping on the basis of soil classification of 2004 (Shishov et al., 2004). It includes a large number of human-transformed soils, which makes very important the information on the geography of the anthropogenic factor of soil formation. In addition to the modern data, its changes over at least the last century are required. The approaches to the compilation of this kind of maps of the anthropogenic factor have not been elaborated by the present time, which makes it very difficult (and even impossible) to apply the classification system of 2004 for soil mapping (on a large scale, in particular) on the basis of the factor approach.
In addition, the solution of practical problems often requires the analysis of particular soil properties rather that the classification position of soils. Theoretically, there is a need in maps of certain soil properties. In traditional approaches, particular values of soil properties are associated with the soil name in the classification by expert judgment, so that the traditional soil map may be transformed into maps of individual properties. The obtained cartograms of soil properties are used for solution of practical problems (Kiryushina et al., 2017). Nevertheless, the resulting maps of individual soil properties are often very simplified and schematic, because the distribution pattern of particular soil properties often differs from the pattern of mapping units in a conventional map.
Therefore, in Abia State where the research was carried out, the activities that was conducted is to know the Soil Mapping in Umudike Ikwuano LGA Umuahia.
1.3 Statement of Problems
The problem of correct scientific (not statistical) soil mapping appeared with the foundation of soil science. Early in the 20th century, G.F. Nefedov proposed to map soils as individual layers of their properties on the basis of a regular or irregular grid of points of field survey (Nefedov, 1914) (this approach can be referred to as the point-based approach).
However, in the course of scientific discussions, the direction suggested by V.V. Dokuchaev and based on the analysis of the factors of soil formation, received the priority development. In essence, it implies the search for an ecological niche of a particular soil and is based on the idea that a given combination should result in the formation of only one particular soil (Dokuchaev, 1950). In addition to all its advantages, this approach was much less expensive and time-consuming than the point-based approach. It could be used as the basis for the development of small-scale maps, which was impossible within the framework of the point-based approach suggested by G.F. Nefedov (Researchgate, 2021).
1.4 Aim and Objectives of Study
The aim of the study is to carry out Soil Mapping in Umudike Ikwuano LGA Umuahia. In achieving this aim, the following specific objectives were laid out as follows:
- To assess the Spectral and Topographic Input Layers of soil mapping in Umudike Ikwuano LGA Umuahia
- To perform a field assessment of mapped soil in Umudike Ikwuano LGA Umuahia
- To assess the spectral and topographic variables / input layers
- To examine the implications for digital soils mapping
1.5 Significance of Study
The boundary is often determined by an expertise based on the analysis of spatial variation in topography and other factors of soil formation (Kolos, 1973). The object of soil mapping according to this method is represented by soil units of a particular soil classification position. This means that at the use of different classifications, the pattern of soil areas (i.e., the soil map) may be different. Therefore, soil map compiled by this method may be used as a basis for obtaining precise data on the geography of those soil properties, which are significant for the used soil classification (Dokuchaev, 1950).
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.
1.6 Scope of Study
The study focuses on the Soil Mapping in Umudike Ikwuano Local Government Area Umuahia, Abia State.
1.7 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.
- Financial Constraint: Insufficient fund tends to impede the efficiency of the researcher in sourcing for the relevant materials, literature or information and in the process of data collection (internet).
