SoilSoil ecology can differ due to: Underlying geology Geographic location Climate What types of plants grow there
Physical Properties Soils are the result of the weathering of parent material over a long period of time. Geology influences soil. Weathered rock–Sediment from waterways.
Physical Properties An ideal soil consists of: 50% pore space (water & air) 50% solid (45% mineral and 5% organic matter) Bryan Kotwica, Bugwood.org
Physical PropertiesSoil ProfileWeathering events over time, such as: Leaching Temperature fluctuations Chemical reactions Biological activity Accumulation of different elements and materialsCause the soil to develop horizontal layers called horizons
Physical PropertiesSoil ProfileSoil horizons are: O-Decomposing organic matter (great amount of biological activity) A-Rich in organic matter and biological activity. Fine roots of trees B-Accumulates leached nutrients (few to no fine roots) C-Partially weathered parent material http://soils.usda.gov/education/resources/le ssons/profile/
Physical PropertiesSoil Texture is the fineness or coarseness of a soil determined by relative amounts of minerals. Sand>Silt>Clay Coarse FineLoam- “Ideal” mineral mix of sand silt and clay.
Physical Properties Soil Structure is the arrangement, shape and size of clumps of soil particles, called aggregates. Determined by physical soil properties, chemical changes and biological activity Modified by root growth, temperature fluctuations, burrowing insects and animal activity. Organic matter improves soil structure and increases pore space.
Physical Properties Soil structure helps determine the amount of macropores (air movement or gas exchange) and micropores (water retention) a soil contains because pore space occurs within and between aggregates. Soil Texture influences pore space due to particle size. Sandy soils tend to have more macropores and less micropores than soils with more clay. Bulk Density measures the mass of the soil per unit of dried soil volume. Bulk density can be used as an indicator of pore space and soil compaction. Greater bulk density=more micropores than macropores Different soil textures have different ranges of bulk density
Physical Properties Soil Compaction is the disruption and destruction of soil aggregates. It can be caused by foot and vehicle traffic, high levels of sodium in the soil and watering.
Physical PropertiesSoil compaction Reduces water infiltration and availability Root growth Gas exchange Biological activity
Chemical PropertiesSoil pH Measure of soil acidity or alkalinity Many effects on soil ecology and soil chemistry Greatly affects the availability of soil mineral nutrients to plants Difficult to alter due to soil buffering capacity
Chemical Properties Soil particles have varying negative charges which attract soil mineral nutrients that exist as ions in the soil solution. Positively charged ions are called cations. Cation Exchange Capacity (CEC) measures the soil’s ability to hold on to cations. Soils high in clay and/or organic matter have higher CECs. Soil texture, soil structure and CEC should be considered when determining fertilizer needs. Bryan Kotwica, Bugwood.org
Chemical Properties Saline soils occur when a soil have excess levels of soluble salts which can be toxic to plants Sodic soils have excess levels of sodium which raises the soil pH and destroys the soil structure.
Biological Activity Animals, insects, bacteria, fungi and other organisms help cycle nutrients through the soil and help decompose organic matter. The rhizosphere is a microzone of intense biological activity surrounding actively elongating roots. This environment can be very different from the surrounding soil. Mycorrhizae-certain fungi can form beneficial symbiotic relationships with tree roots Actinomycetes are soil-dwelling bacteria that play a critical role in the decomposition of organic matter Certain atmospheric nitrogen-fixing soil bacteria form beneficial relationships with certain tree roots
Soil Moisture and Plant Growth Soil pore space helps determine the water holding capacity of a soil. A greater amount of micropores means a higher water holding capacity. Well-aggregated soil structure aids aeration and drainage. Tree roots need adequateAndrew Koeser, International Society of Arboriculture, Bugwood.org gas exchange as well as adequate water to thrive.
Urban Soils Urban soils are often altered in such a way as to inhibit tree growth and development. Highly compacted soils Little to no organic matter Little biological activity Suffer greater temperature fluctuationsCraul, Urban Soils, 1985 can contain pollutants
Urban Soil ImprovementBefore planting: Site contains existing trees: Till compacted soils Use air excavation to Remove soil and replace break up compacted soil with better soil around root zone (radial Improve drainage trenching) and (French drains, drain incorporate organic tile) matter. Incorporate organic matter
Water and Trees Water is vital to trees. Large trees can absorb hundreds of gallons of water from soil in a day. Up to 95% of the water taken up by trees can be lost through transpiration. Water use varies due to tree species, size, soil, air temperature, humidity, light and wind. Inadequate soil moisture can lead to root loss, leaf abscission, twig dieback and tree death. Too much water can result in poor nutrient uptake, poor root development, disease and death.
Irrigation Trees generally need less water than turf Proper tree selection and planting may reduce irrigation needs. Irrigation is most important for newly transplanted trees, which can need frequent irrigation
Irrigation If irrigation is needed, water trees infrequently and deeply. Promotes well developed roots Promotes better soil structure Reduces development of pathogens
Irrigation Shallow, frequent watering can lead to poor root development, soil compaction and disease.
Irrigation Systems Sprinklers-When properly used they can be very efficient and economical. Higher potential for water loss due to evaporation. Drip-Delivers water to plant more precisely than sprinklers with less potential for runoff. Drip systems can plug so they need to be monitored. Other systems include soil injection, soaker hose, basin irrigation and temporary, portable drip systems.
Water Conservation Drought tolerant landscaping (Xeriscaping) Minimum irrigation-provides just enough water to maintain plant health, growth and appearance. Group plants with the same water requirements together on the same irrigation schedule (hydrozones). Requires an understanding of water budgets, soil and plant water loss, water-holding capacity, application rates, infiltration rate and irrigation system efficiency. Water needs can also be determined using soil probes, tensiometers and electronic moisture sensors.
Water ConservationRecycled water used in irrigation can be effective but salinity, phytotoxicity and increases in soil pH are potential problems.
Water ConservationThe use of mulch around the base of trees can reduce soil moisture evaporation, as well as: Improve soil structure Improve water infiltration Moderate soil temperature Reduce weed competition Reduce soil compaction and erosion Organic mulches increase soil organic matter as they decompose
Water Conservation Soil amendments to increase water hold capacity Limit turf plantings Reduce or eliminate fertilizer applications during drought conditions Antitranspirants-for temporary use only. Long term use can be toxic to some plants
Flooding and Drainage For some tree species only a short period of flooding can be harmful as photosynthesis shuts down.Drainage Best to establish proper drainage before planting. Improving the soil structure works best French drains, drain pipe/tiles will remove gravitational water, but do not make up for poor soil structure. With after planting drainage improvements care must be taken not to damage the root system. When irrigating, water application rate should not exceed the infiltration rate of the soil. Soil aeration can relieve some drainage problems caused by soil compaction.
Flooding and Drainage Water flow over impervious surfaces (parking lots, roads) can cause flooding and carry pollutants. “Rain gardens” to catch drainage from impervious surfaces can reduce storm water runoff. However plantings must be tolerant of flooding, pollutants and drought conditions.
Introduction Trees require certain essential elements to function and grow. An essential element (or nutrient) is a chemical constituent that is involved in the metabolism of the tree or that is necessary for the tree to complete its life cycle. In nature these elements are present, replenished and recycled by the decomposition of organic matter.
IntroductionIn urban setting, the soil may be different because of: Removal of soil Removal of fallen leaves or other potential organic matter Lack of beneficial soil-dwelling organisms
Tree Requirements Trees take up essential elements dissolved in water through their roots. Each element plays a specific role and cannot be substituted by another element. Essential elements are divided into: Macroelements-needed in larger amounts Microelements-needed in smaller amounts Trees and other plants can only utilize essential nutrients in the form of specific ions.
Essential ElementsC Hopkins Café Managed by My Clever Cousin Mo.C HOPKNS CaFe Mg Ni B Mn Cl Cu Zn Mo
Tree Requirements Growth and development of trees is dependant on the most limiting of nutrients. Nitrogen is often the most limiting of the macronutrients due to leaching, volatilization and, in urban environments, due to lack of nutrient cycling. P,K and S are mostly in adequate amounts in soil.
Tree Requirements Fe, Mn and Zn are usually the most limiting micronutrients in urban soils Micronutrients can be phytotoxic at higher levels
Tree Requirements Soil pH is important because nutrients may be present in the soil but not available to the tree or present in toxic amounts.
Fertilizer Available in many forms Complete fertilizer contains N, P and K. Fertilizer analysis on the label- composition as a % by weight of total N, available P (P2O5) phosphoric acid and K (K2O) soluble potash Always in the order of N- http://www.butlerswcd.org/Homeowner/Soils.html P-K
Fertilizer Because phosphoric acid contains 44% P and soluble potash contains 83% K, the percent P and K on the label must be multiplied by .44 and .83, respectively to calculate the percent amount of P and K. For example: A 50 lbs. bag of 10-6-4 fertilizer contains 5 lbs. N 3 lbs. P 2 lbs K Complete fertilizers are not always needed
Fertilizer May be organic or inorganic Inorganic fertilizers release their elements quickly so they are available to plants quickly They may “burn” the plants and are susceptible to leaching and volatilization. Organic fertilizers are composed of naturally occurring or synthetic carbon-based molecules that must decompose in the soil to release their elements.
FertilizerSlow release fertilizers are a preferred choice for fertilizing trees, either with organic fertilizers or coated inorganic fertilizers.
FertilizerApplication ratesDepends on age, health, species, form of fertilizer, application method, site conditions and desired goal.
FertilizerPrescription fertilization Based on soil tests and foliar analysis Determines the amount and availability of essential nutrients in the soil and how deficient the tree is in specific nutrients.
FertilizerTimingTiming of fertilizer applications depend on the tree, fertilizer type, soil conditions and CEC.
FertilizerApplication techniquesBeneficial to apply fertilizer beyond the drip line.Surface application Requires less time Doesn’t require sophisticated equipment Can deliver nutrients to upper soil, closer to feeder roots Susceptible to volatilization and runoff
FertilizerSubsurface application Drill hole Soil injectionFoliar, implants and injection can be used to correct minor deficiencies, but do not provide long-term impact
FertilizerOver application of fertilizer can result in Burning-higher solute content in soil than in root draws water out of the root Runoff and leaching-nutrients can pollute waterways and ground water Fertilizer salts can raise soil pH affecting the availability of nutrients