Ans. Topsoil is best for crop cultivation. Topsoil that is the A horizon is the layer of soil that is located just below the O Horizon. This layer consists of minerals and decomposed organic matter. Due to this, the soil is very dark in colour. This layer helps many plants to grow their roots firmly. The topsoil is the topmost layer of the soil which is usually 5 to 10 inches (that is 13–25 cm). This layer has the highest concentration of organic matter and microorganisms and thus it is most suitable for crops to grow. This soil layer is where most of the Earth's biological soil activity takes place. Topsoil is made up of mineral particles and organic matter, water, and air.