Roadside Revegetation

PLANNING PHASE TWO: ASSESS SITE
Irrigation
Applying irrigation water is another method of reducing soil pH by leaching out bases.
However, the amount of water needed to lower pH levels can be very high; in most cases,
using irrigation is not a viable mitigating measure. It is also difficult to find irrigation water in
arid environments that is low in bases and salts. Applying irrigation water high in bases will
raise pH and salt levels in the soil, compounding the problem.
Apply Organic Matter
Incorporated composts or other types of organic matter can lower soil pH as the organic
matter decomposes (Havlin and others 1999). For arid sites, however, the pH and conductivity
of the organic matter must be tested prior to purchase to avoid the possibility of introducing
organic matter high in salts.
Add Nutrients
To compensate for the tie-up of certain nutrients, the addition of nutrients through fertilization
might be considered. The benefits of using fertilizers on arid soil must be offset by the possibility
of creating fertilizer salt problems.
Mitigating for Salts
Since high levels of soluble salts are usually caused by poor soil management, the key to
mitigating high salinity is to avoid creating the conditions that could cause those levels.
In soils where internal drainage is poor, prevention may be the only feasible approach for
reducing salt problems.
Avoid Mulch or Soil Amendments with High Salinity
Testing all materials to be applied to the site will aid in the prevention of increased salt levels
in the soil. Amendment materials with electrical conductivity readings in excess of 1,000 mS/
cm should be avoided.
Reduce Commercial Fertilizers
Some commercial fertilizers, control-release fertilizers (CRF) in particular, can significantly
increase the soluble salts found in the soil. This can be a major problem when using CRF in
arid conditions. The fertilizer will begin to release following wet, warm spring conditions, but
will not be leached through the soil without significant rainfall through the summer. Salts can
build up to damaging levels, both on the surface and in the plant root zone.
Apply Gypsum with Irrigation
Incorporation of gypsum (calcium sulfate) followed by leaching can be effective in situations
where sodium is the cause of high soluble salts (e.g., de-icing materials have been applied
to roads). The calcium in gypsum will displace sodium, and the sodium will then leach out of
the soil profile with irrigation or rainfall (UMES 2004).
Irrigation
Application of irrigation water could leach salts from the soil. The amount of water depends
on the soil type. In arid soils, application of 6 inches of water can reduce salinity levels by 50
percent; 12 inches can reduce salinity levels by 80 percent; and 24 inches can reduce salinity
levels by 90 percent (UMES 2004). Application of irrigation water would need to occur over
several days. However, for most sites, this is not practical due to high costs.
5.6 SURFACE STABILITY
Surface stability is the tendency of the soil to remain in place under the erosive forces of rain,
wind, and gravity. Good surface stability is essential for establishing plants, reducing erosion,
and maintaining high water and air quality. When seeds are applied to unstable surfaces, they
Roadside Revegetation: An Integrated Approach to Establishing Native Plants and Pollinator Habitat
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