Which of the following is NOT a characteristic of soil horizon 'O'?

The uppermost soil horizon, known as horizon 'O', is primarily characterized by its rich organic material content, which includes decomposed leaves, plant material, and microorganisms. Its composition significantly influences the soil's fertility and structure, making it vital for plant growth. This layer is commonly dark in color, which is a result of the high organic matter concentration, as dark hues generally indicate organic richness.

The characteristic of horizon 'O' being composed primarily of sand is not applicable. Sand is typically found in lower horizons, such as 'A' or 'E', where it contributes to soil texture and drainage properties rather than organic richness. Thus, citing that horizon 'O' is primarily sand is incorrect, highlighting the distinctive role and composition of this upper layer. Understanding this differentiation is crucial in nutrient management, as it emphasizes the importance of organic material in soils for agriculture and environmental health.