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Soil Quality Soil Quality Soil is an important, but often overlooked compo- nent of water management. Soil quality refers to the ability of soil to perform its functions. Soil is espe- cially important in regulating runoff of storm water and in supporting trees, shrubs, lawns and gardens. Urban activities, such as construction grading, often result in erosion, sedimentation and soil compaction. Management practices are often needed to restore soil quality after development. Erosion Erosion on construction sites is one of the most seri- ous problems facing urban soil quality. Erosion, which produces sediment, is accelerated when soil is disturbed or left bare and exposed to wind and water. Although erosion on construction sites often affects only a small percentage of a watershed, it can be a major source of sediment. The potential for ero- sion can be 100 times greater than on agricultural land and the delivery rate to receiving waters is much higher. Compaction Compaction is the other serious issue facing urban soil quality. It occurs when soil particles are pressed together. As soil particles are squeezed together, soil Soil Quality 2005 . . . key to absorbing and infiltrating rainfall A healthy topsoil has high organic matter content with 50 percent pore space in the soil profile. High organic matter content allows water to be absorbed and infiltrated. density increases and pore space for air and water are reduced. Lack of pore space in the soil reduces water intake and movement throughout its layers. Compaction also limits root growth and the biological diversity of the soil. T h e s e problems are compounded when organic matter content is lost by topsoil removal. For homeowners, compacted soil with low organic matter makes it difficult to establish and maintain lawns and land- scaping. In urban communities, soil com- paction can lead to low infiltration rates, increased erosion and storm water runoff, decreased water quality due to more pol- luted runoff, and increased flooding. It is essential that exposed land and com- paction be minimized during urban con- struction. Communities need to work with developers and contractors to limit com- paction and soil loss during construction operations. Construction grading compacts the soil and exposes land to erosive rain and wind.

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Soil Quality

Soil QualitySoil is an important, but often overlooked compo-nent of water management. Soil quality refers to theability of soil to perform its functions. Soil is espe-cially important in regulating runoff of storm waterand in supporting trees, shrubs, lawns and gardens.Urban activities, such as construction grading, oftenresult in erosion, sedimentation and soil compaction.Management practices are often needed to restoresoil quality after development.

ErosionErosion on construction sites is one of the most seri-ous problems facing urban soil quality. Erosion,which produces sediment, is accelerated when soil isdisturbed or left bare and exposed to wind andw a t e r. Although erosion on construction sites oftena ffects only a small percentage of a watershed, it canbe a major source of sediment. The potential for ero-sion can be 100 times greater than on agriculturalland and the delivery rate to receiving waters ismuch higher.

CompactionCompaction is the other serious issue facing urbansoil quality. It occurs when soil particles are pressedt o g e t h e r. As soil particles are squeezed together, soil

Soil Quality2 0 0 5. . . key to absorbing and infiltrating rainfall

A healthy topsoil has high organic matter content with 50percent pore space in the soil profile. High organic mattercontent allows water to be absorbed and infiltra t e d .

density increases and pore space for airand water are reduced. Lack of pore spacein the soil reduces water intake andmovement throughout its layers.Compaction also limits root growth andthe biological diversity of the soil. T h e s eproblems are compounded when org a n i cmatter content is lost by topsoil removal.For homeowners, compacted soil withlow organic matter makes it difficult toestablish and maintain lawns and land-scaping. In urban communities, soil com-paction can lead to low infiltration rates,increased erosion and storm water runoff ,decreased water quality due to more pol-luted runoff, and increased flooding.

It is essential that exposed land and com-paction be minimized during urban con-struction. Communities need to work withdevelopers and contractors to limit com-paction and soil loss during constructiono p e r a t i o n s .

Construction grading compacts the soil and exposes land to erosiverain and wind.

Soil Quality

Soil Quality

The USDA is an equal opportunity provider and employer.

Restoring Soil QualityOrganic MatterIncreasing organic matter content increases biological life, thenumber of soil pores, and soil permeability. Compost, or decom-posed organic material, is a great source of organic matter.Compost improves soil structure, aeration, water retention,drainage, and nutrient quality.

Deep TillageDeep tillage can be performed withm a c h i n e r y. Always have underg r o u n dutilities and other underground plumbingor wires located and marked. It is best toperform deep tillage when moisture con-tent is about 40 percent.

More Information on Soil QualityFind additional information about soil quali-ty by visiting the following websites:

• www.iowasudas.org• http://soils.usda.gov/sqi/• www.lowimpactdevelopment.org• www.cwp.org• www.stormwatercenter.net

Undisturbed Soil Compacted Soil

Composition of undisturbed soil,by volume

Composition of compacted soil,by volume

Soil ComponentsAll soil is made up of air, water, decayed plant materials, numer-ous kinds of living and/or dead organisms (organic matter), andmineral matter (sand, silt, clay). The soil composition, however,can be dramatically changed by pedestrian and vehicular traff i c ,especially when the soil is wet. Soil components most easilychanged are the amounts of soil air and water.

VegetationEstablishing vegetation to cover bare soil iscritical. A seeded lawn with a mixture of grassseed and compost is best for new lawns. It isoften less expensive and establishes fasterthan sod. The higher organic matter contentand improved soil structure in compost-seed-ed lawns can retain 80 percent more rainfall,resulting in less watering and fertilizer thansod lawns and less storm water runoff .

Native LandscapingNative plants have a tremendous root struc-ture. This deep root structure adds org a n i cmatter to the soil and increases infiltration.Use native landscaping strategically to man-age rainfall and diversify urban landscapes.

40%-45%

25%

25% 74%

18%

6% 2%5%-10%

Mineral Matter Soil Water Soil Air Organic Matter

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OM OMSA

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