Transcript Chapter 19
Chapter 19 Urban Soil Problems With Urban Soils Problems differ between Rural Growers and Urban Soil Users Extreme variations in soil conditions across a city landscape Urban more severe Complicates landscaping Soil moving often causes very poor soil quality Problems (Continued) Urban soils are improved by adding Organic Matter such as: Leaves Grass Clippings Compost Bagged Manures Three Traits of Urban Soil Buried Debris Compaction Contamination 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. 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 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 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 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 Controlling Erosion Keep disturbed areas small Protect disturbed areas Keep runoff velocities low Divert runoff away from disturbed areas Retain sediment on-site On steep slopes, layer of rock (rip-rap) controls erosion 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 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)