Final answer:
The statement is false; soil samples are not solely from topsoil. The A horizon is considered topsoil and is essential for plant production, while the B horizon is the subsoil, dense with fine materials. For tasks like establishing turf, knowledge of both topsoil and subsoil properties is necessary.
Step-by-step explanation:
The statement that soil samples should only come from topsoil, unless you're attempting to establish turf on exposed or relocated subsoil, is False. The A horizon is considered to be the topsoil, which is the layer where organic material is mixed with inorganic products of weathering, rich in nutrients, and is crucial for plant production. The B horizon refers to the subsoil, which is mostly fine material that has moved downward and can be denser. Depending on the purpose of the soil analysis or project, samples from different horizons may be needed.
For instance, when establishing turf, especially on areas where topsoil has been removed or on construction sites, it is necessary to amend or modify not just the topsoil but potentially the subsoil as well to ensure the grass roots can establish themselves effectively. In such cases, knowing the properties of subsoil becomes just as important as understanding the characteristics of the topsoil. Sampling only the topsoil would not provide the complete picture necessary for these specific situations.