CSLB C-27 Landscaping ContractorSite Preparation and DrainageMedium
A landscape contractor is preparing a site for a new lawn installation where the existing soil has been heavily compacted by construction equipment. To alleviate this compaction and improve root penetration, which mechanical soil preparation technique would be most effective?
- ASurface raking to remove debris
- BLight rototilling to a depth of 2 inches
- CApplying gypsum as a surface amendment
- DDeep ripping or subsoiling to a depth of 12-18 inches
Show answer & explanationAnswer & explanation
Correct answer: D. Deep ripping or subsoiling to a depth of 12-18 inches
Deep ripping or subsoiling is a mechanical technique that uses a heavy-duty implement to break up compacted soil layers deep below the surface (typically 12-18 inches or more) without inverting the soil. This significantly improves aeration, water infiltration, and root penetration, which is crucial for new lawn establishment on compacted sites.
Why the other options are wrong
- A. Surface raking only addresses superficial debris and does nothing to alleviate deep compaction.
- B. Light rototilling only addresses the very top layer and can create a 'hardpan' just below the tilled depth, worsening deep compaction.
- C. Applying gypsum can help improve soil structure in some clay soils by flocculating particles, but it is not a mechanical method and is generally ineffective against severe mechanical compaction.
Deep Ripping/Subsoiling
A mechanical soil preparation technique that uses heavy equipment to break up compacted soil layers deep below the surface (12-18+ inches) to improve root penetration and drainage.
- Effective for severe compaction from construction.
- Increases aeration and water infiltration.
- Does not invert soil layers.
Memory trick: Deep rip the compaction, let roots expand their station.