Does Horse Manure Cause Soil Compaction? Understanding Organic Matter Breakdown

A gardener noticed soil compaction under horse manure and asked if the manure was the cause.

How Organic Matter Behaves

• Coarse soils: As manure decomposes into fine particles, it can slow water movement.
• Clay soils: Organic matter initially improves structure and reduces compaction, but the effect is temporary—after a couple of years the organic matter is gone and soil reverts.

Best Practice

Incorporate no more than 30% fresh organic matter into existing soil. This balances improvement with stability.