Soil is one of the primary sustainers of life on planet earth. It significantly contributes to every aspect of the living world. Fundamentally, soil support producers and primary production. It is also important to understand the concepts of soil properties, soil formation process, and features of productive soils. Importantly, soil productivity entails soil fertility, including the inherent factors that influence the growth of plants. Another aspect of soil that is important to learn is its structure. Soil structure refers to the arrangement and organization of its particles and other constituent substances (Johns, 2015). The structure of the soil in a given area influences the fertility of that region. As mentioned above, there are features and elements of soils that influence their ability to support primary productivity, influenced by their formation process and climatic condition.
Elements of Soils That Contribute to Their Ability to Support Producers and Primary Productivity
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Soil fertility is the foundation on which the growth of plants is sustained. Fertile soils lead to higher yield and healthier plants. For soil to be classified as fertile, several elements must be considered. These components are fundamental elements minerals, moisture content, the potential of hydrogen (pH), bulk density, and clay content. Together, these elements determine the ability of soils to support producers and primary productivity. The mineral composition of soil helps predict soils' capacity to retain vital nutrients required for plant growth. For plants to be healthy, the soil must have nutrients such as nitrogen (N), phosphorous (P), potassium (K), Sulphur (S), calcium, and magnesium (Mg). Other important nutrients include copper (Cu), zinc (Zn), iron (Fe), manganese (Mn), boron (B), and molybdenum (Queensland. Government, 2013). Soil pH is the second element that is a crucial determinant for soils' ability to support producers and primary productivity. For optimum fertility, the soil's pH should be between 5.5 and 7 (Soil Science Society of America, n.d.). Soil pH determines the ability to maintain optimal nutrient availability of soils.
The third element is the moisture content of a given soil. Moisture content determines the accessibility of nutrients to plants. Nutrients are readily available in soils with high moisture content than solid matrix soils. Clay content influences the cation exchange capacity (CEC) of soils (Precision Agronomics, Inc, 2019). Soils with high CEC are more fertile than those with low CEC. Low CEC is an indicator of a high leaching rate of a given soil. Bulk density is the other element that determines soil fertility. The best soil for plant growth should not be compact to ease root penetration, thus aiding plants' ability to reach nutrients. Soils that have these elements well-balanced support the thriving of plants.
Soil Formation Process
The foundation of the soil-forming process is the minerals that are produced from rocks. Rocks are the parent materials in the soil-forming process. Natural erosion and weathering of rocks are the processes that lead to soil formation. Some of the factors that lead to weathering of rock materials include water, gravity, changes in temperature, and wind. Others include living organisms and chemical interactions. Soil formation is a product of four aspects: weathering, structural development of soil, differentiation of the soil structure, and soil movement (Soil-Net.com, n.d.). As mentioned above, weathering is the most important aspect of soil formation. Weathering of parent material can be categorized into two groups: physical and chemical weathering.
Six forms of physical weathering result in soil formation. First, freezing and thawing force the rock structures apart. In this type of weathering, water enters in rock cracks, and when it freezes, it expands, which pushes rocks to break apart. Second, when rocks are heated, they expand and contract when they cool down. Over time, just like freezing and thawing, the rocks will crumble gradually, leading to soil formation. Organisms are the third contributor to the weathering process. Soil is home to organisms, plants, and animals. These organisms can push through rocks, eventually breaking some parts of the rocks. The fourth process is unloading, such as experienced when glaciers move over the earth's surface. When ice melts, the earth's surface is relieved of huge pressure. Repeated unloading of ice also weakens rocks, and eventually, they break into pieces. Grinding is the fifth process under physical weathering. This happens when rocks grind on each other, leading to their disintegration. The last type of physical weathering is wetting and drying, whereby rocks are wetted and become prone to swelling and later dry, evidenced by a reduction in size (Soil-Net.com, n.d.). When the wetting and drying process is repeated over time, they weaken, resulting in their disintegration. These processes together encompass physical weathering.
Apart from physical weathering, rocks can also be disintegrated through a series of chemical reactions. Some of these processes include carbonation, dissolution, and oxidation. Although some minerals may be stable within rocks, they can become unstable when dissolved in water or become exposed to the atmosphere. Consequently, they alter the rocks near the surface resulting in their disintegration (Soil-Net.com, n.d.). For example, oxidation occurs when oxygen in the soil react with other chemicals in the soil, weakening rocks, while carbonation is the reaction of rocks with carbonic acid.
Influence of Climate on Soils
Climate changes significantly impact soils and their functions. Soils are important for modern human society because they influence global food security. There are well documented hot and cold cycles in the universe's history, which affect the various soil processes, especially those related to soil fertility. For example, climatic changes alter soil moisture content and increase soil temperature and carbon II oxide. As the current climate change trends continue to vary across the globe, it is expected to significantly impact soil processes such as weathering, oxidation, dissolution, and hydrolysis. Due to resultant alteration in soil processes, soil properties are also affected, affecting soil fertility. Fundamentally, climatic conditions such as temperature and precipitation influence soil formation. For instance, these parameters provide biomass and conditions for weathering ( Pareek, 2017 ). Climatic conditions determine the rate of energy consumption during the process of soil formation. Other ways through which climatic conditions affect soil determine the moisture level in the soil, movement of soil solutions, and interactions between organic and soil minerals. One acknowledges how climatic conditions and their changes significantly affect soils, their processes, and functions.
Soil Food Web
The soil food web consists of diverse organisms with varying sizes and uses to the soil ecosystem. These organisms eat, thrive, and move through the soil, making it possible to have soil aeration, water percolation, and soil-forming processes. The soil food web constituents include bacteria, fungi, protozoa, nematodes, microarthropods, and the bigger plants and animals found in the soil and around the soil. There is a positive relationship between organisms living below and above the ground known as multitrophic interactions. Scientific literature shows that soil organisms such as arbuscular mycorrhizal fungi and soil pathogens that are part of the ground soil community depend on the above the ground autotroph biomass for food. The reverse is also true where the above the ground autotroph biomass benefit from the ground soil community ( Eisenhauer, 2018 ). Plants support soil food webs through the accrual of dead organic matter, thus increasing soil organisms' diversity, such as decomposer microorganisms.
Similarly, studies have shown a positive association between living organisms below the ground, such as fungi, and the high diversity of plants. For example, below ground communities influence nutrient availability and debris accumulation important for the plants above the ground. Consequently, a healthy community of soil organisms is beneficial for the entire ecology. Principally, the microorganisms that sustain the symbiotic relationships with plant roots promote the availability of minerals, produce hormones important for plant growth, and are antagonists of various disease-causing microorganisms (Food and Agriculture Organization of the United Nations, n.d.). They are responsible for driving the cycling of nutrients and organic matter, enhancing soil productivity, soil restoration, and enhancing plant health. Herbivores will feed on the plants, while carnivorous animals will feed on herbivores. Omnivorous animals such as human beings will feed on both herbivores and plants.
Conclusion
Soil plays an important life support system for plants, animals, and other microorganisms living in it. Importantly, soil fertility influences plant growth through the various functions of microorganisms found in the soil, such as facilitating organic materials' decaying. The soil fertility elements include fundamental elements and minerals, moisture content, pH, bulk density, and clay content. Soil is formed through weathering of rocks, which are termed as parent materials. The two types of weathering are chemical and physical weathering. The weathering process is affected by climatic changes through variations of water and temperature in the soil, the two leading weathering factors. The soil food web is another determinant and contributor to soil fertility. There is a symbiotic relationship between above ground autotrophs and below ground soil community.
References
Eisenhauer, N. (2018). Aboveground-Belowground Interactions Drive the Relationship Between Plant Diversity and Ecosystem Function. Research Ideas and Outcomes , 4, e23688.
Food and Agriculture Organization of the United Nations. (n.d.). Successful Soil Biological Management with Beneficial Microorganisms. http://www.fao.org/agriculture/crops/thematic-sitemap/theme/spi/soil-biodiversity/case-studies/soil-biological-management-with-beneficial-microorganisms/en/
Johns, C. (2015). Soil Structure and the Physical Fertility of Soil. https://www.futuredirections.org.au/publication/soil-structure-and-the-physical-fertility-of-soil/
Pareek, N. (2017). Climate Change Impact on Soils: Adaptation and Mitigation. MOJ Eco environ. Sci , 26 (3).
Precision Agronomics, Inc. (2019). What are the Factors that Influence Soil Fertility ? http://sstinfolab.com/influence-soil-fertility.html
Queensland. Government. (2013). Soil fertility https://www.qld.gov.au/environment/land/management/soil/soil-properties/fertility
Soil Science Society of America. (n.d.). Soil Fertility . https://Www.Soils4teachers.Org/Fertility#:~:Text=Usually%20a%20fertile%20soil%20will,Ph%20between%206%20and%207 .
Soil-Net.com. (n.d.). Soil Formation – Introduction . https://www.soil-net.com/legacy/advanced/soil_formation2.htm
Soil-Net.com. (n.d.). Weathering Processes . https://www.soil-net.com/legacy/advanced/soil_formation3.htm
