The untethered rock in soil profile is
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The soil profile is an important tool in nutrient management. By examining a soil profile, we can gain valuable insight into soil fertility. As the soil weathers and/or organic matter decomposes, the profile of the soil changes. For instance, a highly weathered, infertile soil usually contains a light-colored layer in the subsurface soil from which nutrients have leached away. On the other hand, a highly fertile soil often has a deep surface layer that contains high amounts of organic matter. With clues provided by soil profile, we can begin to predict how a soil will perform under certain nutrient management conditions.
In the previous section, we looked at how soil is actually an integration of water, air, minerals and organic matter. Now we will view the soil as a vital part of the earth’s physical landscape.
The world’s soils are like blankets that cover most of the earth’s land surfaces. We could not survive without it since most crops would not be able to grow in the dense rock that lies underneath. There is no uniform depth to our earth’s soils. While it can be absent in places of exposed bedrock, soil may extend up to tens of meters into the earth’s surface. Although this may not seem insignificant when compared to the depth to the core of the earth, the soil profile can be very intricate and diverse. In fact, the soil profile is made up of distinct layers, known as horizons. The five most common horizons are collectively known as the master horizons. Figure 5 below depicts a road cut in Maui which shows the multitude of layers that can exist in soil. Though the soil profiles in Figure 6 belong to two very different soils, both contain distinct surface and subsurface soil layers.