Soil Forming Factors

Soil Forming Factors

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Introduction

In the natural environment, one of the most important elements that constitute it is soil. It contributes greatly to the sustenance of the living components as well as influencing their distribution on the world’s surface. Being a habitat provider, soil also controls and regulates the circulation of water as well as chemical components present within the atmosphere (Nadimi & Farpoor, 2011). Some of the vital gases within the environment also rely on soil for their circulation. They include oxygen and carbon dioxide, which are crucial to the biological and cellular processes within living organisms. Another role carried out by soil includes recording the human activities that have occurred in the past up until the recent time. Due to this, soil enriches the cultural essence and heritage of various communities.

From the brief detailed discussion on the importance of soil to the low and higher life forms as well as to the environment, it is important to understand its formation and the factors involved in this process. Soil formation is an intricate process that allows for the development of soil based on several factors, which influence it (Nadimi & Farpoor, 2011). The paper delves deeper into understanding the process of soil formation and the role each factor plays in determining the overall soil development process and composition. Comprehension of these factors and soil formation process allows the global community to appreciate the environment and equips the society with information useful in environment conservation and preservation.

Soil Formation

The layering of the soil in horizontal strata is affected by five environmental factors. Each factor changes the overall makeup of the soil and the layer it will be categorized. Additionally, it is imperative to note that a change in one factor results to the formation of a different soil despite the other factors remaining constant. According to geological research, an estimated 95% of the world soil locality does not align with its origin (Tedrow & Cantlon, 1958). This translates to the reality that soil moves aided by the stratified formation and thus only 5% can be termed as residual. While reviewing the soil taxonomy, two determining factors influence the quality of the sol formed. They include the presence of organic material such as animal and plant material or that of mineral material such as clay, silt and sand (Barshad, 1957). These materials encompass the parental material and thus constituting the first stage of soil formation. It. Depending on the material within the soil, the soil fertility is also affected. This also applies to the presence of the five factors outlined. This is primarily because during the soil formation process, there is gradual addition and removal of nutrient depending on which factor is dominant.

1. Biota

Animal and plants are categorized as Biota, another factor that significantly contributes to soil formation. In evaluating the living material that is directly in contact with soil and thus affecting the weathering process, it is obvious to state that vegetation constitute a larger portion as compared to animals and other smaller living forms (Barshad, 1957). With this in mind, it is imperative to consider how the vegetative cover affects soil composition as well as its formation.

One of the factors related to this phenomenon is the variability of roots systems in existing plants. Thus, it implies that the type of plant also affects the soil composition and formation. For instance, when comparing products resulting from organic decomposition from hardwood and conifer trees, there is a substantial difference despite the process being catalyzed by the same factors (Major & Jenny, 1981). Secondly, factors such as the nutrient content, life cycle and the volume of the vegetation come into play thus further the extent to which the soil organic content is reliant on vegetative cover. An illustration of these effects can be observed when analyzing soils derived under grass cover and trees. These two samples of soils vary greatly in terms of organic content and thus exhibiting different levels of weathering owing to the difference is organic decomposition rates.

1. Parent Material

On analyzing the parent material, it is evident to state that it is composed of minerals and rocks. It provides the medium on which the other mentioned factors act on thus degrading the rocks into smaller grains that constitute the soil (Major & Jenny, 1981). When studying the parent material, it is noteworthy to understand that there are various types of parent material as previously mentioned. For instance, mountains are composed of rock, which might have deposits of shale, or obsidian that is eventually degraded over the years to develop different type of soils compared to that derived from the sea bedrock (Barshad, 1957). In Nebraska, various parent soils can be observed ranging from clays from riverbeds in Missouri and sands present in the Hilly regions. Limestone and sandstone soils are likely to be observed in areas such as extensive plains that form part of the ancient seas that existed decades ago (Bockheim, Gennadiyev, Hartemink & Brevik, 2014). Owing to the aforementioned variations of parent material, it is obvious to state that the soil formed following the weathering process will be different in terms of mineral content and fertility. Subsequently, it is also valid to mention that the extent of weathering greatly relies on the type of parent material being degraded as some are more resistant thus taking a longer period to form soil.

The rate of degradation of the parent material is not primarily reliant on the factors that influence soil formation (Nadimi & Farpoor, 2011). Several weathering processes have a greater impact on this process. They include

• Changes in volume and chemical constituents of the soil
• Soil erosion by gravity, water, ice and wind
• Change in temperature which includes thawing and freezing
• Water content change within the parent material
• Living organisms such as burrowing animals, microbes, roots of trees and plants and insects

The aforementioned processes are categorized as either being physical or chemical in nature. The physical effects of these processes include the mechanical breakdown of the rocks into smaller particles (Ubalde, Sort & Poch, 2011). The minerals present within the soils are then chemically degraded to form new compounds, which constitute the composition of the soil formed.

1. Time

According to research conducted on weathering processes, time is used to place different soils in various age groups depending on the maturity of the soil. This can be determined through evaluating the formation of horizons and layers and the level at which the soil is almost at equilibrium with its surrounding environs (Barshad, 1957). These two factors are time reliant and thus form the criteria through which soil is categorized in terms of age. Additionally, a crucial aspect that is brought forward in determining age of the soil is that rate at which weathering and soil formation takes place (Bockheim, Gennadiyev, Hartemink & Brevik, 2014). According geologists, soils that are almost in equilibrium with the environment tend to exhibit a slower weathering process. The opposite of this scenario is observed in aged soils, which are yet to balance with the environs. Such soils degraded more easily and consistently thus ensuring continuous soil formation.

1. Topography

In evaluating the effects of climate on weathering, the two climatic conditions outlined as regulating the extent of the process are moisture or water content and temperature. Topography has a direct effect on the aforementioned conditions thus being considered as being an influential factor in soil formation (Tedrow & Cantlon, 1958). Topography can be described as the positioning of the land. The impact on water content is primarily because when it rains, water either moves through the soil into the strata aided by the force of gravity or as surface runoff (Barshad, 1957). The later deprives the deeper soil strata and layers access to water thus slowing the weathering process down. Contrarily, wetter areas that take up water through capillary action assisted by gravity have higher rates of dilution of mineral thus enhancing soil formation. However, the level of wetness should be considered, as wetter soils tend to inhibit plant growth through clogging of roots stems thus also leading to reduced soil formation and development.

Topographical alignment of the slope is a critical factor that determines the infiltration of water into the soil layers. This brings about other factors such as the steepness, length and shape of slope (Bockheim, Gennadiyev, Hartemink & Brevik, 2014). To evaluate the effects of the slope alignment further, it is important to understand the categorization of the slope as outlined in table 1. This is done using the Abney level and levels are categorized as gently sloping, moderately sloping, steep, and very steep. An example to illustrate the effects of topography on soil weathering includes an evaluation of upland depression and the flood plains. Soil that is found is the former have high organic content as these lands serve as collecting reservoirs of surface run off material, which includes plant material (Major & Jenny, 1981). Thus, the weathering process is high owing to the high rates of organic decomposition. To identify these soils, they usually have a characteristic dark color and thicker that other soils found within the slope. Contrary to this, soils found within the flood plains are considered productive owing to the intermittent flooding periods, however, they are not suitable for agriculture as the soil lacks proper aeration as well has a lower rate of weathering.

1. Climate

Climatic conditions are influential to the soil forming process primarily because it determines the types of microorganisms and plants that will be present in the soil. Secondly, the water present within the soil is regulated by the type of climate within the locality (Tedrow & Cantlon, 1958). During the weathering process, water plays a substantial role of diluting the minerals within the rocks to catalyze chemical and physical weathering process that are necessary to ensure soil is the end product. This clearly depicts the importance of climate as a determining factor that controls the extent of weathering and overall soil formation process.

Temperature is considered a climatic condition that directly controls the amount of organic matter within the soil. One of the reasons forwarded to validate this observation is the increase of plant growth and foliage in areas that have higher temperature. Due to this increased proliferation of the plants, there is surety that the organic matter will increase overtime. Contrary to this, cold areas exhibit lower levels of organic matter and less organic content within the soil. Localities, which experience both type of climate, termed as “Seasonal weather”, are more prone to the processes of freezing and thawing (Major & Jenny, 1981). These two processes continue occurring over a period. Eventually, the breaking point of the parent material is reached and it weathers off resulting into soil formation.

In conclusion, soil formation is influenced by the discussed factors that play different role in determining the composition, texture, and rate of soil formation. Understanding the dynamics involved in the weathering processes sets precedence on determining the resulting soil within a particular region. This provides crucial information required during agricultural activities as well as determining whether land is suitable for settlement and other human activities.

References

Barshad, I. (1957). Factors Affecting Clay Formation. Clays and Clay Minerals, 6(1), 110-132. doi:10.1346/ccmn.1957.0060110

Bockheim, J., Gennadiyev, A., Hartemink, A., & Brevik, E. (2014). Soil-forming factors and Soil Taxonomy. Geoderma, 226-227, 231-237. doi:10.1016/j.geoderma.2014.02.016

Major, J., & Jenny, H. (1981). Factors of Soil Formation. Ecology, 62(6), 1693. doi:10.2307/1941533

Nadimi, M., & Farpoor, M. (2011). Genesis and clay mineralogy of soils on different geomorphic surfaces in Mahan-Joupar area, central Iran. Arab J Geosci, 6(3), 825-833. doi:10.1007/s12517-011-0350-3

Tedrow, J., & Cantlon, J. (1958). Concepts of Soil Formation and Classification in Arctic Regions. ARCTIC, 11(3). doi:10.14430/arctic3742

Ubalde, J., Sort, X., & Poch, R. (2011). How Soil Forming Processes Determine Soil-Based Viticultural Zoning. J. Soil Sci. Plant Nutr., 11(1), 100-126. doi:10.4067/s0718-95162011000100009