One of the most important foundation component of agriculture is the soil. The soil has three main purpose: retain water for the plants, provide nutrients to the plant and give physical support to the plant. Soil contains many minerals in it that is vital for plant growth. Soils differ in different regions because it contains one type of mineral more than other soil in other regions. This kind of mineral can come from volcanic activity as well as weathering activity. Soil has layers (or horizons). At the very top, humus can be found which is rich in organic matter (usually decomposing plant and animal matter). As we go deeper below the surface, the soil particles become bigger until we hit rocks (the parent material of soils).
Soil is made up of sand, silt and clay. All sand, silt and clay are not the same. Sand is bigger in (particle) size than silt and silt is bigger in (particle) size than clay. The perfect soil for agriculture is said to be 40% sand, 40% silt and 20% clay, which is referred to as loamy soil. This creates the best environment for plant growth.
The earth is so filled with soil that we need not fabricate it. All we need to do is understand it and, if necessary, inject the right minerals into it to keep it in perfect balance for plant growth. When we can determine the pH of the soil and maintain it between 3.5 and 9.5 by using the elements of the earth to our advantage, we can grow crops of the best quality consistently. We can engineer the soil to our advantage. We can engineer it for certain crops. Some crops thrive in arid regions; some thrive in wet regions (by the bodies of water). The farmer or horticulturist must give himself to understanding the symbiotic relationship between a particular plant and its environs.
When I attended Denbigh this year, I came across an interesting display that said “Poor Dirt = Dirt Poor” and focused on poor soil management practices. The point was driven home with photo comparisons between fields in California and Jamaica featuring tomatoes, melons, onions and orange trees. The California farms yield more from the same area, not because of different irrigation or fertiliser practices, but because of inadequate soil conservation techniques in Jamaica.
Above quote is from David Mullings in his article, Growing the Jamaican Economy: Agriculture.
Soil pH Range and Classification
Most soils have pH values between 3.5 and 10. In regions with higher rainfall, soil pH typically ranges from 5.0 to 7.0. In contrast, soils in drier areas generally fall between 6.5 and 9.0.
Soils are commonly classified by pH as follows:
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Neutral: pH 6.5 to 7.5
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Alkaline: pH above 7.5
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Acidic: pH below 6.5
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Soils with a pH below 5.5 are considered strongly acidic
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Origins of Soil pH
The natural pH of a soil is primarily influenced by the type of parent rock it was formed from and the environmental factors involved in its weathering—such as climate, vegetation, topography, and time. These processes usually lead to a gradual decrease in pH, making soils more acidic over time.
Rainfall is a major contributor to soil acidification. Additionally, the use of certain fertilizers can alter soil pH, either increasing or decreasing the availability of nutrients to plants.
Effects of Soil pH
Soil pH significantly influences the solubility of nutrients and chemicals in soil water. Some nutrients are more readily available in acidic soils, while others are more accessible in alkaline conditions. However, most mineral nutrients are optimally available to plants when the soil pH is close to neutral.
Strongly acidic soils can hinder plant growth due to toxicity from elements like aluminum and manganese, or from deficiencies in calcium and magnesium. On the other hand, alkaline soils may limit the availability of essential nutrients such as zinc, copper, boron, and manganese.
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