Which term describes a dense structure in soil?

The term that best describes a dense structure in soil is "a dense structure." This phrase directly indicates the compactness and solidity of the soil arrangement, which can significantly influence properties such as water retention, aeration, and root penetration. A dense soil structure usually has smaller pore spaces between particles, resulting in less air and water movement, which can affect plant growth and microbial activity.

In contrast, the other terms suggest characteristics that do not align with describing density specifically. "Softly packed" implies a less compact soil, "loose structure" suggests greater airflow and space between soil particles, and "high density" may describe a condition but does not encapsulate the concept of a dense structure as effectively as the phrase chosen. Hence, "a dense structure" accurately portrays the state of soil that is tightly compacted and cohesive.