Causes and Concerns
Rooting depth can be physically restricted by compacted soil.
Soil compaction is caused when an external force applies pressure to soil which reduces porosity, destroys structure, limits water infiltration, reduces air circulation and increases resistance to penetration of roots. This condition can diminish crop yield and plant vigor. While many people are aware of the negative effects soil compaction can have, they may underestimate its significance. Soil conditions contribute largely to plant health or disorders in a landscape setting. Overly compact soil can reduce the amount of root growth and consequently limit the ability of plants to uptake water and nutrients. If it has been a dry growing season, compacted soil can increase the symptoms of drought stress. During wet years soil aeration will become difficult, leading to loss of nitrate-nitrogen to the atmosphere (denitrification) which will present as symptoms nutrient deficiency but may require more than just fertilizer to reverse effects. This condition can be very difficulty to correct, so efforts need to be made to prevent compaction from occurring. The most common causes of soil compaction on residential lands are home construction and foot traffic. Fine textured and clay-ey soils can also be affected by rain drops and sprinkler irrigation.
Prevention Practices
There are several cultural practices that can be employed on home landscapes to prevent or minimize soil compaction:
- Addition of Organic Matter- Amending soil with organic matter within the first 6 to 8 inches is ideal, for clay type and compacted soils any less will lead to a shallow root system, reduced growth and vigor and lower stress tolerance. Discuss your options and plan with your arborist to determine timing and composition for amendments.
- Traffic Flow Management- Heavy foot traffic through your gardens and landscapes can be a major contributor to soil compaction. Moist soils can be compacted up to 75% from the first time it is trod upon. Implementing raised garden beds and establishing walkways can prevent this problem. Also limiting foot traffic on clay-ey soils and when soil is wet will aid in preventing compaction.
- Mulching- Using the right type and amount of mulch can reduce the force of compaction. Mulch will also mitigate any compaction caused by rainfall or irrigation by absorbing the shock before it contacts the soil.
- Mechanical Aeration- Aerating your lawn and around trees will reduce soil compaction, consult with your arborist regarding when and where aerating should occur.
- Moderate Moisture- Avoid cultivating overly moist or dry soils. Irrigate the appropriate amount for your landscape, the time of year and your plants. Consult with your arborist for advice specific to your property.
- Equipment Placement- If you have upcoming home construction projects requiring material stockpiling and heavy equipment, carefully plan where these materials will be stored or placed. Avoid placing or storing anything heavy in the root protection zone of your trees; this can comprise an area larger than the dripline. Ask your arborist to evaluate your property prior to construction commencement, together you can develop a plan to ensure the success and health of your trees throughout the project and beyond.
http://www.soils.wisc.edu/extension/pubs/A3367.pdf
http://www.extension.umn.edu/agriculture/Tillage/soil-compaction/index.html#consequences
http://www.ext.colostate.edu/mg/gardennotes/215.html
