A multi-year study of tillage and amendment effects on compacted soils

Area of Science:

• Soil Science
• Environmental Science
• Horticulture

Background:

• Construction activities like grading and heavy machinery traffic compact subsoils.
• Compacted subsoils exhibit low infiltration rates (IR), hindering vegetation and increasing runoff.
• Restoring soil structure is crucial for post-construction ecological recovery.

Purpose of the Study:

• To evaluate the effectiveness of tillage and soil amendments in improving compacted subsoil density and perviousness.
• To assess the impact on soil compaction, infiltration rate, and vegetative growth over time.
• To compare tillage alone versus tillage with amendments (compost, cross-linked polyacrylamide (xPAM), gypsum).

Main Methods:

• Field experiments conducted at five North Carolina sites with varying soil conditions.
• Soil physical properties measured: bulk density (BD) and soil penetration resistance (PR).
• Infiltration rate (IR) assessed using a Cornell Sprinkle Infiltrometer; vegetative growth quantified by shoot mass, cover, and root density.

Main Results:

• Tillage reduced BD and PR at four of five sites within 24-32 months.
• Tilled plots showed IR 3-10 times higher than compacted soil.
• Amendments generally did not improve IR over tillage alone, except for compost and xPAM at one site.
• Vegetative responses to treatments were inconsistent across sites.

Conclusions:

• Tillage is a viable strategy for reducing subsoil compaction and enhancing infiltration for vegetation establishment.
• The positive effects of tillage on soil properties persisted for at least several years.
• While amendments showed limited additional benefit for IR, tillage alone significantly improved soil conditions.