Chapter 19Chapter 19Urban SoilUrban Soil

Problems With Urban SoilsProblems With Urban Soils

Problems differ between Rural Growers Problems differ between Rural Growers and Urban Soil Usersand Urban Soil Users Urban more severeUrban more severe

Extreme variations in soil conditions across a city Extreme variations in soil conditions across a city landscapelandscape Complicates landscapingComplicates landscaping

Soil moving often causes very poor soil qualitySoil moving often causes very poor soil quality

Problems (Continued)Problems (Continued)

Urban soils are improved by adding Organic Urban soils are improved by adding Organic Matter such as:Matter such as: LeavesLeaves Grass ClippingsGrass Clippings CompostCompost Bagged ManuresBagged Manures

Three Traits of Urban SoilThree Traits of Urban Soil

Buried DebrisBuried Debris

CompactionCompaction

ContaminationContamination

Buried DebrisBuried Debris

Contractors often bury wood or masonry scraps on Contractors often bury wood or masonry scraps on the job sitethe job site

Buried scraps may cause:Buried scraps may cause: Restricted drainage Restricted drainage Excessive drainageExcessive drainage A physical barrier to root growthA physical barrier to root growth

Buried masonry, which contains lime, can raise pH Buried masonry, which contains lime, can raise pH to unacceptable levels. to unacceptable levels.

CompactionCompaction Urban Soils are usually moderately to severely Urban Soils are usually moderately to severely

compacted compacted

Compaction can be measured by Compaction can be measured by Bulk DensityBulk Density At a bulk density of 1.7, roots cannot penetrate the soilAt a bulk density of 1.7, roots cannot penetrate the soil

Many of our best urban trees hale from floodplainsMany of our best urban trees hale from floodplains

It is possible to break up compaction if no plants It is possible to break up compaction if no plants

are in the wayare in the way

Ways to Get Rid Of CompactionWays to Get Rid Of Compaction

Deep Tillage

Digging large solid particles into soil

Large amounts of Organic Matter Wood Chips

Leaf Mold

Pave the soil with special pavers and grids that have large

holes built into them Use Of Aerators- machines that remove vertical cores from the soil

For turf, vertical coring to six inches breaks up the soil and

makes passages for air and water movement

Soil ContaminationSoil Contamination Deicing SaltsDeicing Salts

Sodium chloride creates saline or even sodic soil conditions, and Sodium chloride creates saline or even sodic soil conditions, and chloride may reach toxic levelschloride may reach toxic levels

Damages plant tissue directly, especially evergreens, by Damages plant tissue directly, especially evergreens, by desiccationdesiccation

Lead ContaminationLead Contamination Lead added to paint and gasolineLead added to paint and gasoline

Primarily effects children causing permanent brain damage, and even deathPrimarily effects children causing permanent brain damage, and even death Lead found in blood can lower an IQ level by three pointsLead found in blood can lower an IQ level by three points Contributes to high blood pressure in adultsContributes to high blood pressure in adults

Main source of soil lead is automobile exhaust from cars using leaded Main source of soil lead is automobile exhaust from cars using leaded gasgas

Derelict LandDerelict Land DefDef- Land severely damaged by human abuse that it is unusable - Land severely damaged by human abuse that it is unusable

without costly abatement effortswithout costly abatement efforts

Urban ErosionUrban Erosion The impact of construction site erosion differs The impact of construction site erosion differs

slightly from farmland erosionslightly from farmland erosion

Rilled and gullied land must be repaired before a site Rilled and gullied land must be repaired before a site can be soldcan be sold

In extreme cases erosion can In extreme cases erosion can Undercut roadsUndercut roads Collapse roads Collapse roads Collapse foundations Collapse foundations

Contributes to off-site problemsContributes to off-site problems

Controlling ErosionControlling Erosion Keep disturbed areas smallKeep disturbed areas small Protect disturbed areasProtect disturbed areas

On steep slopes, layer of rock (rip-rap) controls erosionOn steep slopes, layer of rock (rip-rap) controls erosion

Keep runoff velocities lowKeep runoff velocities low Divert runoff away from disturbed areasDivert runoff away from disturbed areas Retain sediment on-siteRetain sediment on-site

Grass strips filter soil out of runoff water, as do Grass strips filter soil out of runoff water, as do silt fencessilt fences Establishing VegetationEstablishing Vegetation

Permanent turf is the best cover, but mowing is a problem on steep hillsPermanent turf is the best cover, but mowing is a problem on steep hills HydroseedingHydroseeding- - mixture of water, seed, and chopped hay that is blown on mixture of water, seed, and chopped hay that is blown on

a slope from the side of the roada slope from the side of the road

Calculating Soil LossCalculating Soil Loss The Universal Soil Loss Equation (USLE) The Universal Soil Loss Equation (USLE)

Used to estimate soil lossesUsed to estimate soil losses Predicts soil loss only from small rills and sheet erosionPredicts soil loss only from small rills and sheet erosion

Written As:Written As: A = R K LS C PA = R K LS C P

R = Rainfall factorR = Rainfall factor K = Erodability factorK = Erodability factor – – obtained from soil survey data or obtained from soil survey data or

calculated from USDA Handbook calculated from USDA Handbook 537537

LS = Slope factorLS = Slope factor C = cover and management factor for bare, stripped soilC = cover and management factor for bare, stripped soil

P = support practice factor (usually 1.0; few applicable)P = support practice factor (usually 1.0; few applicable)