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Native Plant Synoptic Garden
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significant amounts of potassium available in the soil is desirable, and has not been found to be
limiting in the Puget Sound region (Chalker-Scott, 2004).
At high levels, aluminum can be detrimental to plants. Aluminum can hinder calcium
and magnesium uptake and cause subsequent deficiencies (Marschner, 1995). “Aluminum
sensitivity varies greatly with plant type; for instance, rhododendrons can tolerate very high levels
of aluminum” (UMass, 2004). The level of aluminum in the soil analysis was found to be 68
ppm, which is in the low to medium range. Typical soils range from 10 to 300ppm, so the soils in
the proposed areas are at a tolerable level (UMASS, 2004). If aluminum levels should reach
levels that would begin to cause problems, liming can lower the level of aluminum (UMASS,
2004).
“Phosphorus aids plants in using the energy from photosynthesis to power the plants
metabolism” (UMASS, 2004). A phosphorus deficiency can limit healthy plant growth and result
in weak root systems; signs of a deficiency can be abnormal size and number of leaves.
Represented by blue in figure six, phosphorus levels on site were low but do not mean that there
is a deficiency problem (Umass, 2004). Phosphorus deficiency does not tend to be a factor
affecting plant health in Western Washington (Chalker-Scott, 2004). Most phosphorus tends to
accumulate near the soil surface and does not move readily in soil because it is tightly adsorbed to
soil particles (Harris et la., Umass, 2004). Since phosphorus tends to be at or near the surface, too
much disturbance of the soil surface can lower phosphorus levels (Harris, 2004). Since the soils
located at the Graham Visitors Center site are low in phosphorus, it may be necessary to fertilize
with a phosphorus enriching fertilizer to help newly planted trees and shrubs grow. Remember
though that phosphorous is generally not limiting in Puget Sound soils, so it would be advisable
to first monitor shrubs for phosphorous deficiencies symptoms before application. Symptoms
would include “distorted, dark green leaves with abaxial reddening or purpling with the
symptoms being more common with younger plants that have less developed root systems”
(Chalker-Scott, 2004). If necessary a soil analysis of soil immediately within the plant’s root
zone coupled with simultaneous tissue analysis could be helpful in detecting a true phosphorous
deficiency.
Nitrate and ammonium were both found at low levels within the soil sample; they are
represented by light blue in Figure six. Nitrate is a soluble nutrient that is made available to
plants by mass flow of water within the soil (Harris, 2004). Because of mass flow, nitrate can
also be leached through the soil too quickly or to depths that do not allow for roots to absorb it
(Harris, 2004). “In contrast ammonium ions do not move freely with soil water, the positively
charged ammonium ions are adsorbed onto soil particles” (Harris, 2004). So instead, ammonium
is converted into more readily available nitrate by soil organisms. This process is called