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Chapter 19

Chapter 19. Urban Soil. Problems With Urban Soils. Problems differ between Rural Growers and Urban Soil Users Urban more severe Extreme variations in soil conditions across a city landscape Complicates landscaping Soil moving often causes very poor soil quality.

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Chapter 19

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  1. Chapter 19 Urban Soil

  2. Problems With Urban Soils • Problems differ between Rural Growers and Urban Soil Users • Urban more severe • Extreme variations in soil conditions across a city landscape • Complicates landscaping • Soil moving often causes very poor soil quality

  3. Problems (Continued) • Urban soils are improved by adding Organic Matter such as: • Leaves • Grass Clippings • Compost • Bagged Manures

  4. Three Traits of Urban Soil • Buried Debris • Compaction • Contamination

  5. Buried Debris • Contractors often bury wood or masonry scraps on the job site • Buried scraps may cause: • Restricted drainage • Excessive drainage • A physical barrier to root growth • Buried masonry, which contains lime, can raise pH to unacceptable levels.

  6. Compaction • Urban Soils are usually moderately to severely compacted • Compaction can be measured by Bulk Density • At a bulk density of 1.7, roots cannot penetrate the soil • Many of our best urban trees hale from floodplains • It is possible to break up compaction if no plants are in the way

  7. Ways 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

  8. Soil Contamination • Deicing Salts • Sodium chloride creates saline or even sodic soil conditions, and chloride may reach toxic levels • Damages plant tissue directly, especially evergreens, by desiccation • Lead Contamination • Lead added to paint and gasoline • Primarily effects children causing permanent brain damage, and even death • Lead found in blood can lower an IQ level by three points • Contributes to high blood pressure in adults • Main source of soil lead is automobile exhaust from cars using leaded gas • Derelict Land • Def- Land severely damaged by human abuse that it is unusable without costly abatement efforts

  9. Urban Erosion • The impact of construction site erosion differs slightly from farmland erosion • Rilled and gullied land must be repaired before a site can be sold • In extreme cases erosion can • Undercut roads • Collapse roads • Collapse foundations • Contributes to off-site problems

  10. Controlling Erosion • Keep disturbed areas small • Protect disturbed areas • On steep slopes, layer of rock (rip-rap) controls erosion • Keep runoff velocities low • Divert runoff away from disturbed areas • Retain sediment on-site • Grass strips filter soil out of runoff water, as do silt fences • Establishing Vegetation • Permanent turf is the best cover, but mowing is a problem on steep hills • Hydroseeding- mixture of water, seed, and chopped hay that is blown on a slope from the side of the road

  11. Calculating Soil Loss • The Universal Soil Loss Equation (USLE) • Used to estimate soil losses • Predicts soil loss only from small rills and sheet erosion • Written As: • A = R K LS C P • R = Rainfall factor • K = Erodability factor – obtained from soil survey data or calculated from USDA Handbook 537 • LS = Slope factor • C = cover and management factor for bare, stripped soil • P = support practice factor (usually 1.0; few applicable)

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