The implications of soil classification for agricultural development in Nigeria By OKONJI, NORA ISIOMA
What is soil classification?
Firstly, the soil is an independent natural resource that results from the interaction between factors and processes of soil formation.
Soil classification is an essential aspect of agricultural development in Nigeria. It plays a significant role in determining the appropriate agricultural practices, land use planning, and land management strategies in various regions of the country. Soil classification refers to the process of grouping soils based on their physical, chemical, and biological properties. This classification system is important for understanding soil behavior, identifying soil limitations and potentials, and providing guidance on appropriate land use and management practices.
OSHA (Occupational Safety and Health Administration) uses a measurement called “unconfined compressive strength” to classify each type of soil. This is the amount of pressure that will cause the soil to collapse. This value is usually reported in units of tons per square foot. Soils can be classified as Type A, Type B, or Type C. they state that Type A soil is the most stable soil in which to excavate. Type C is the least stable soil. It’s important to remember that a trench can be cut through more than one type of soil. osha.gov
History of soil classification
Soil classification has a long and complex history, dating back to ancient times when farmers and other agriculturalists first began to observe and document the differences between various types of soil. However, it wasn’t until the modern era that soil classification truly became a science in its own right.
One of the earliest attempts at soil classification was made by the Greek philosopher Theophrastus in the 4th century BCE. He divided soils into six categories based on their fertility and texture, and his work was later expanded upon by the Roman writer Cato the Elder. Another earliest known soil classification system in the world can be found in an ancient Chinese book Yugong (2,500 y.b.p.), where soils of China were classified into three categories and nine classes based on soil color, texture, and hydrologic features; the classification was used for land evaluation (Gong Zitong 1994). iuss.org
In the 18th century, Swedish scientist Carl Linnaeus developed a classification system based on the physical and chemical properties of soils, dividing them into six categories based on their color, texture, and other observable characteristics. This system was later refined by German scientist Christian Ehrenberg, who added additional categories, based on the mineral content of soils, followed by Arthur Casagrande in the 1948, commissioned by the Federal Aviation Administration (FAA), developed the Airfield Classification System which eventually became the Unified Soil Classification System (USCS). Modified versions of the USCS are used across the world today. aashtoresource.org
More recently, advances in soil science and technology have led to the development of more sophisticated and detailed classification systems, such as the World Reference Base for Soil Resources and the Australian Soil Classification. These systems take into account a wide range of factors, including soil texture, mineralogy, organic content, and physical properties, and are used by scientists and agriculturalists around the world to better understand and manage soils.
Classification of Soil in Nigeria
Soil in Nigeria can be classified into three major groups based on their geological origin and physical properties. These groups are:
Sedimentary soils:
These soils are formed from the weathering and erosion of sedimentary rocks such as sandstone, limestone, and shale. They are usually found in areas of low altitude and are characterized by their high fertility and water retention capacity. Sedimentary soils are further classified into the following subgroups:
Coastal plain sands:
These are soils found along the coastal plains of Nigeria, and they are usually sandy with low water retention capacity.
Inland valley soils:
These are soils found in the valleys and lowlands of Nigeria, and they are usually rich in organic matter and nutrients.
Alluvial soils:
These are soils formed from the deposition of sediment by rivers and streams. They are usually rich in nutrients and are good for agriculture.
Igneous soils:
These soils are formed from the weathering and erosion of igneous rocks such as granite, basalt, and gneiss. They are usually found in areas of high altitude and are characterized by their low fertility and poor water retention capacity. Igneous soils are further classified into the following subgroups:
Volcanic soils:
These are soils formed from the weathering of volcanic rocks such as basalt and tuff. They are usually very fertile and are good for agriculture.
Granitic soils:
These are soils formed from the weathering of granite rocks. They are usually poor in nutrients and water retention capacity.
Metamorphic soils:
These soils are formed from the weathering and erosion of metamorphic rocks such as schist, gneiss, and quartzite. They are usually found in areas of moderate altitude and are characterized by their moderate fertility and water retention capacity. Metamorphic soils are further classified into the following subgroups:
Schist soils:
These are soils formed from the weathering of schist rocks. They are usually moderately fertile and have good water retention capacity.
Quartzite soils:
These are soils formed from the weathering of quartzite rocks. They are usually poor in nutrients and water retention capacity.
The classification of soils in Nigeria is mainly based on their geological origin and physical properties. According to FAO soil taxonomy legends are fluvisols, regosols, gleysols, acrisols, ferrasols, alisols, lixisols, cambisols, luvisols, nitosols, arenosols and vertisols. eco-generation.org
Important of soil classification in Nigeria
Soil classification is an important aspect of soil science in Nigeria. The purpose of a soil classification system is to group together soils with similar properties or attributes. From the engineering standpoint, it is the geotechnical properties such as permeability, shear strength, and compress-ability that are important. Wiley Online Library
It also helps to provide useful information about the characteristics and properties of the soil, which is essential for making informed decisions about land use, crop selection, and soil management practices. The following are some of the key benefits of soil classification in Nigeria:
- Agricultural production: Soil classification provides information about the nutrient content, water retention capacity, and other physical properties of the soil. This information is important for farmers to select the right crops to grow, determine the optimal planting and harvesting times, and apply the right amount of fertilizers and other soil amendments to improve crop yields.
- Land use planning: Soil classification helps to identify areas of the country where different types of soils are found. This information is useful for land use planning and zoning, such as determining the best locations for residential, commercial, and industrial development, as well as for the conservation and protection of natural resources.
- Soil conservation: Soil classification helps to identify soils that are prone to erosion, nutrient depletion, and other forms of degradation. This information can be used to develop appropriate soil conservation measures such as crop rotation, cover crops, terracing, and other techniques that help to improve soil health and prevent erosion.
- Engineering design: Soil classification provides information about the strength, stability, and other physical properties of the soil. This information is useful for designing and constructing buildings, roads, bridges, and other infrastructure projects that are built on or in the soil.
Factors affecting soil classification
There are six groups of factors responsible for the kind, rate, and extent of soil development. They are Climate, organisms, parent material, topography, Human activities, and time. Soil from one place is different from another because of the differences in the influence of these factors.
All of these factors interact to create a complex and diverse array of soil types, which can be classified using various systems and criteria. fao.org
Parent Material: The type of rock or sediment that soil is derived from can affect its characteristics, such as its texture, structure, and mineral composition.
Climate: Climate affects soil formation by controlling the amount and timing of precipitation and temperature, which in turn affect the rate of weathering, erosion, and organic matter decomposition.
Topography: The slope and aspect of the land can affect the amount of water and sunlight the soil receives, as well as its drainage, erosion, and deposition patterns.
Organisms: Soil is inhabited by a wide range of organisms, such as plants, animals, fungi, and microorganisms, which can affect its physical, chemical, and biological properties.
Time: Soil formation is a slow process that can take thousands or millions of years, so the age of the soil can affect its properties and characteristics.
Human activities: Human activities such as agriculture, urbanization, and mining can affect soil properties, such as its texture, structure, and nutrient content.
Implications of soil classification for agricultural development in Nigeria
One of the primary implications of soil classification for agricultural development in Nigeria is the selection of appropriate crops. The classification of soils enables farmers to identify the crops that are best suited to a particular soil type. For example, sandy soils are suitable for growing crops like cassava and maize, while clay soils are better for crops like yams and plantains. Similarly, acid soils are best suited for crops like cocoa and oil palm, while alkaline soils are suitable for crops like groundnuts and cotton. By selecting the right crops, farmers can increase their yields and reduce the risk of crop failure.
Soil classification is also important for determining the most effective fertilization methods. Different soil types have different nutrient requirements, and the classification of soils can help farmers identify the most appropriate fertilizers for their crops. For example, sandy soils are typically low in nutrients, so farmers may need to use fertilizers that are high in nitrogen, phosphorus, and potassium. On the other hand, clay soils are generally high in nutrients, so farmers may need to use fertilizers that are low in these elements.
How do soil types affect agricultural production?
Soil is the primary source of nutrients and water, which are crucial for healthy plant development. The wrong soil can prevent plants from getting the moisture and nutrients they need to grow and flourish. (How Soil Types and Garden Soil Mixtures Impact Your Plants. 16 Jun 2020)
Soil type can have a significant impact on agricultural production. Different soil types have varying levels of nutrients, organic matter, water-holding capacity, and physical structure, which can affect the growth and development of plants.
For example, sandy soils tend to drain quickly and have a low water-holding capacity, which can make it difficult for plants to access enough water during dry periods. In contrast, clay soils have a high water-holding capacity but can become compacted, which can make it difficult for plant roots to penetrate and access nutrients. Loamy soils, which have a balanced mixture of sand, silt, and clay, are generally considered the most ideal soil type for agricultural production, as they provide good drainage and water-holding capacity while also being rich in nutrients.
The pH of the soil also plays a significant role in agricultural production. Some crops prefer acidic soil, while others prefer alkaline soil. In addition, certain soil types can be more susceptible to erosion or nutrient leaching, which can negatively impact crop yields.
Farmers can work to improve soil quality through practices such as adding organic matter, using cover crops, and rotating crops to reduce nutrient depletion. By understanding the characteristics of different soil types and taking steps to improve soil health, farmers can optimize agricultural production and increase crop yields.
Other Factors That Impact Soil Conditions
Local Climate
Climatic characteristics, such as temperature and precipitation, influence soil formation. Soils in the regions that receive high rainfalls tend to be more acidic than ones in dry areas.
Relief of the Area
Hilly areas may experience soil erosion, and the soils are thin with minimal nutrients. Soils in flat areas tend to be deep and have high levels of nutrients as soils from hilly areas are deposited here.
Determining the type of soil in your garden is very helpful. It guides you on the types of plants you should grow and what you might add to the soil to make it suitable for plant growth.
Effects of soil characteristics on crop production
As soils undergo cycles of farming and tillage, the soil organic carbon content decreases, and the soil structures gradually worsen, which, when unmitigated, leads to a decline in soil and harvest quality (Xu et al., 2019; Giannitsopoulos et al., 2019). Soil structural and physical properties affect water availability, the nutrient uptake of crops (Giannitsopoulos et al., 2019), and soil ecology. Improved soil structure can increase soil porosity and enhance nutrient and water recycling, water availability, and biodiversity while reducing water and wind erosion (Alaoui et al., 2011). These improvements in soil quality lead to better soil conditions for crop growth and yields.
Here are some of the effects of soil characteristics on crop production:
Soil Texture: Soil texture refers to the size of mineral particles in the soil. Soil texture affects the water-holding capacity of the soil, as well as the ease with which roots can penetrate the soil. Fine-textured soils (e.g., clay) tend to hold more water than coarse-textured soils (e.g., sand). Crops that require good drainage and aeration, such as tomatoes, do better in sandy soils, while crops that require high moisture, such as rice, grow better in clay soils.
Soil pH: Soil pH is a measure of the soil’s acidity or alkalinity. Most crops prefer slightly acidic soil with a pH between 6.0 and 7.0. However, some crops, such as blueberries, require more acidic soil with a pH between 4.0 and 5.0. Soil pH affects nutrient availability, as some nutrients are more available to plants at certain pH levels.
Soil Nutrients: Soil nutrients, such as nitrogen, phosphorus, and potassium, are essential for plant growth. Different crops require different levels of these nutrients, and the availability of these nutrients in the soil can affect crop yields. Soil fertility can be improved through the use of fertilizers or organic matter.
Soil Structure: Soil structure refers to the arrangement of soil particles. A well-structured soil has good drainage, aeration, and water-holding capacity. Soil structure can be improved through the addition of organic matter, which helps to bind soil particles together.
Soil Moisture: Soil moisture refers to the amount of water in the soil. Most crops require a consistent supply of moisture to grow and produce optimal yields. However, too much moisture can lead to waterlogging and root damage, while too little moisture can result in drought stress.
Inherent Factors Affecting Soil Organic Matter
Inherent factors affecting soil organic matter include climate, soil texture and clay mineralogy. Climatic conditions, such as rainfall and temperature, and soil moisture and aeration (oxygen levels) affect the rate of organic matter decomposition. Organic matter decomposes faster in warm, humid climates and slower in cool, dry climates. It also decomposes faster when the soil is well aerated (higher oxygen level) and much slower when the soil is saturated (lower oxygen level). Decomposition is maximized when the soil is tilled, providing optimal oxygen for microbial activity.
Soils that support grass vegetation (prairie) commonly have at least twice as much organic matter as those that support forest vegetation. Both the top growth and roots of grass vegetation die continually each growing season, adding organic matter to the upper part of the soil. Soils that support forest vegetation commonly have relatively low organic matter content as a result of the following:
- Trees produce a much smaller root mass per acre than grasses.
- Trees do not die back and decompose annually. Much of the organic matter in a forest is tied up in the wood of the trees and thus is not returned to the soil.
As we already know that soil organic matter (SOM) is the material derived from the decomposition of plant and animal residues and plays a crucial role in maintaining soil fertility, structure, and water-holding capacity. umn.edu
There are several inherent factors that can affect the quantity and quality of SOM in soil, including:
Climate: Soil organic matter accumulation is favored by a warm and moist climate, as it promotes microbial activity and enhances the rate of decomposition of organic matter. Conversely, cold and dry climates tend to reduce SOM levels due to slower microbial activity and lower rates of decomposition.
Parent material: The type of rock or mineral from which soil is derived can affect the amount and quality of SOM. For example, soils derived from limestone tend to have higher levels of SOM because the mineral is rich in calcium, which promotes microbial activity and the decomposition of organic matter.
Topography: The slope of the land can affect the accumulation of SOM in soil. Steep slopes tend to have lower SOM levels because the soil is more prone to erosion, while flat or gently sloping land can accumulate organic matter more easily.
Soil texture: The texture of the soil, or the relative proportions of sand, silt, and clay, can affect the amount and quality of SOM. Clay soils tend to have higher SOM levels because they have a higher capacity to hold water and nutrients, which promotes microbial activity and organic matter decomposition.
Vegetation: The type and density of vegetation can affect the amount and quality of SOM in soil. For example, grassland soils tend to have higher SOM levels than forest soils because grasses have a more extensive root system, which contributes to the buildup of organic matter.
Soil properties that affect crop growth and development
There are several soil properties that can affect crop growth and development. Here are some important ones:
Soil pH: The pH level of soil can have a significant impact on crop growth. Most plants grow best in a pH range of 6.0 to 7.5. If the pH level is too low or too high, it can affect the availability of essential nutrients, making it difficult for the plant to grow and develop properly.
Soil texture: Soil texture refers to the size of soil particles. Soil with a high percentage of clay particles tends to hold water and nutrients well, but can also become compacted, making it difficult for plant roots to penetrate. Soil with a high percentage of sand particles is well-draining but may not hold nutrients well. Loamy soils, which are a mixture of sand, silt, and clay particles, are generally considered ideal for plant growth.
Soil structure: Soil structure refers to the arrangement of soil particles into aggregates. Soil with good structure allows for good drainage and air circulation, which are essential for plant root development. Compacted soils, on the other hand, can restrict root growth and reduce plant productivity.
Soil fertility: Soil fertility is the ability of soil to provide essential nutrients to plants. Soil that is rich in organic matter and has a good balance of nutrients can support healthy plant growth. However, if the soil lacks essential nutrients, it can result in stunted growth and poor crop yields.
Soil moisture: The availability of soil moisture is critical for plant growth. Soil that is too dry can limit plant growth, while soil that is too wet can cause root damage and reduce plant productivity. The ideal moisture level for most plants is between 50% and 75% of the soil’s water-holding capacity.
Soil temperature: temperature can also impact crop growth. Different crops have different optimal temperatures for growth, and if the soil is too cold or too hot, it can affect germination, root growth, and nutrient uptake. There are other four important factors that influence crop yield; are
- Soil fertility,
- Availability of water,
- Climate, and
- Diseases or pests.
These factors can pose a significant risk to farms when they are not monitored and managed correctly. Overall, healthy and productive soil with good physical, chemical, and biological properties is essential for optimal crop growth and development. Omnia Nutriology, Oct. 2016
Conclusion
Understanding the implications of soil classification for agricultural development in Nigeria is obviously of pivotal importance to agricultural development. In the tropics, as elsewhere, the prospects for institutionalizing sustainable development strategies are not encouraging. Matching farming systems to soil properties should become one of the objectives of the research component of sustainable agriculture. A good detailed soil map is the tool for targeting soil conservation measures, and recommending farming systems. Soil nomenclature, particularly as employed by the different kinds of classification systems in existence around the world, has contributed to some of the myths and misconceptions and, in some instances, even confused the issue. Basic differences in soil-forming conditions are related to geology, paleoclimate, geomorphology, and factors of soil formation. The application of advanced technologies to deal with agricultural development in Nigeria will offer many opportunities.
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