Gardening: Soil compaction, a pressing issue
Soil compaction can bring with it serious consequences when trying to grow anything green. In fact it can be almost impossible to establish or maintain plants in compacted soil because it interferes with the movement of water, air, nutrients and roots in the pore spaces between soil particles.
This makes root penetration and growth harder leading to poor shallow rooting, poor plant growth and a greater need for irrigation and fertilizer. As a result soil compaction can result in increased costs for the homeowner for water, fertilizer and in the end plant replacement.
Compaction issues also have a detrimental effect on the environment because of increased erosion and runoff volumes, which in turn increases the delivery of nutrients and other pollutants to nearby water bodies. Since all the fertilizer and water being put on the compacted landscape cannot percolate down through the soil to be used by the root systems to filter out these pollutants they have nowhere to go but into the surrounding ecosystem. Obviously not a “best management practice.”
Compaction can be caused or exacerbated by driving on landscapes with heavy equipment during construction or constant traffic such as using unpaved areas as driveways or for parking. Walking will also cause areas to decline, especially in St. Augustine grass which does not tolerate foot traffic well. This problem can be accelerated if the soil is wet.
The best way to deal with soil compaction in the landscape is to prevent it from happening. You should limit, or eliminate, the amount of traffic over future or existing planting areas. In fact many municipalities have rules pertaining to the protection of existing plants when building on a site.
Marco Island’s article IV, landscaping code states (b) during construction, all reasonable steps necessary to prevent the destruction or damaging of existing vegetation shall be taken. No excess soil, additional fill, equipment, liquids, or construction debris shall be placed within the drip line of any vegetation that is required to be preserved, or that will be credited towards the required landscaping. And also (c) protective barriers shall be installed and maintained beyond the drip line of all retained vegetation unless site improvements prohibit installation of barriers beyond the drip line, and shall remain in place for the duration of the construction process phase.
The location of the protective barriers shall be determined by a landscape architect or design professional. These rules are in place because the constant traffic means the plants will not be a viable part of the landscape once the root system has been compacted.
There are few options for improving compacted soil. Deep tillage or sub-soiling using large machinery to break hardpans and loosen the soil can be impractical in urban areas because of buried utilities and the expense of dealing with those. Obviously it would mean removing all vegetation and beginning again in an existing landscape. The only place this would be considered is at a construction site before installation of utilities or landscaping.
Shallow tillage will break up surface soil but can only reach the first six inches. While it would not damage utilities it could not be used around existing trees or turf due to root damage. Plug aeration is not as effective as shallow tillage but can be used in turf. And air tillage can be used around trees but not turf. Once again it is an expensive proposition to correct soil compaction if it can be corrected at all. So the best course of action is to prevent it from happening in the first place.
Never use your landscape as a parking lot unless you have paved it first. If you find yourself walking on the same path to the boat dock, install some stepping stones. It looks much nicer than the dirt path or area that will eventually result from the constant traffic. In fact I believe Marco Island hands out code violations to property owners who park their cars on unimproved areas of their lawn and will require them to properly pave the area or park elsewhere.
There is nothing attractive about dirt yards or swales. Marco Island is better than that.
Eileen and Peter Ward have owned a landscape and lawn maintenance company for 35 years. Eileen can be reached at Gswdmarco@comcast.net or 239-394-1413.