What does soil compaction primarily affect in plant health?

Soil compaction primarily affects air space in the soil, which is crucial for plant health. Compacted soil has reduced pore spaces, leading to decreased air circulation. Adequate air space is essential for root respiration; without it, roots struggle to take in oxygen, which can stunt plant growth and make plants more susceptible to disease.

When soil is compacted, it not only restricts airflow but also impacts water movement and drainage, though the primary concern is the air availability for roots. This decreased air space can lead to poor root development and can hinder the plant's ability to absorb nutrients effectively, although those processes are secondary.

In contrast, while water retention, nutrient absorption, and soil temperature may also be affected by compaction, the most immediate and critical impact is the reduction of air space necessary for healthy root function, underscoring the significance of air availability in supporting overall plant health.