What is meant by the term "compaction" in relation to soil?

The term "compaction" in relation to soil refers to the hardening of the soil, which leads to a reduction in both aeration and water penetration. When soil becomes compacted, the particles are pushed closer together, reducing the pore spaces that allow air and water to move through the soil. This can significantly hinder plant growth as roots require both oxygen and water to thrive. Compact soil can lead to poor drainage, making it difficult for water to reach the root zone, and limit the availability of nutrients due to the restricted movement of water.

In contrast, choices related to raising soil temperature, enhancing moisture retention, or increasing organic matter focus on different aspects of soil health and do not accurately describe the negative impacts of compaction. These processes either benefit soil structure or are unrelated to compaction effects, illustrating why the focus on hardening and its consequences for aeration and water infiltration is critical in understanding soil health in the context of landscape horticulture.