What is the primary force causing soil particle aggregation?

The primary force causing soil particle aggregation is electrostatic attraction, particularly through cations. Soil particles, such as clay and silt, possess negative charges, while certain positively charged ions or cations (like calcium, magnesium, and potassium) can bridge these particles together. This attraction helps to form larger soil aggregates, which is crucial for soil structure.

The presence of these aggregates enhances soil health by improving aeration, water retention, and root penetration, ultimately leading to better plant growth. The process of aggregation plays a vital role in the soil's ability to function as a reservoir for nutrients and water, facilitating the overall soil ecosystem.

Other options may relate to soil characteristics but do not address the specific mechanism of aggregation as effectively. Soil moisture retention influences the physical state and behavior of soil but is not the primary driver of how particles bond together. Soil compaction can disrupt aggregation rather than facilitate it, leading to denser soils with reduced pore space. Nutrient cycling is essential for soil fertility but does not directly contribute to the physical process of soil particle aggregation.