Mine Rehabilitation Handbook - Mining and Blasting

5.6.2 Planting
Some options available for re-establishing native vegetation are outlined
below. Significant numbers of species can become established from
seed stored in the topsoil if appropriate soil handling methods (section
5.4) are used. The planting method or methods selected will depend on
size and nature of the site and the species being established.
Cover crops can be considered where a quick cover for erosion control
is required. When establishing native plants with a cover crop a
compromise must be reached between the density of the cover crop
needed to provide rapid erosion control and the tendency of the cover
crop to suppress or smother the native species. Dense cover crops may
also pose a fire hazard. Hybrids such as sudax can be useful cover
crops, as they don’t set viable seed and so won’t persist on the site.
Direct Seeding
• Potentially a very economical and reliable method for establishing
species which produce sufficient numbers of easily collected, viable
seed with high germination and seedling survival rates.
• Advantages include low costs, random distribution of plants and no
check on growth rates through planting-out.
• Disadvantages include higher risk of failure through adverse climate
conditions, competition from weeds, loss of seed by insect predation
and low seed germination and survival rates.
• Failure can result in loss of seed stocks and seasonal opportunity
for field work.
• Seed can be broadcast by hand, conventional or modified agricultural
equipment, by air and by hydromulching etc.
• Select the seeding method most appropriate for the site - specialised
direct seeding equipment is now being manufactured but simple
easily manufactured tools can assist e.g. the “Leggate Spear” (refer
figure 5.10). In many cases, broadcasting by hand is still the best
option. Mechanically sowing native seeds is difficult because of the
large range in seed size, which make an even coverage of seed hard
to obtain. In addition, many native seeds have awns or other
appendages that can create problems for mechanical seeding.
• Broadcast seed can be buried after spreading by harrowing etc. or
left on the soil surface. Care must be taken not to bury the seed too
deep for successful establishment.
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Figure 5.10
• Seeding rates will depend on species, site conditions, desired
density of vegetation and viability of seed; seed should be tested to
establish approximate viability percentage.
• Numbers of seeds per unit weight is highly variable (e.g. Eucalyptus
species may vary between 3500/2,500,000 seeds/kg).
• Field establishment rates from direct sowing are typically 1-5% for
fine seed species and 5-10% for coarse seed species. An estimate of
the required sowing rates can be calculated from the number of
seeds per unit weight, estimated field establishment rates and the
desired density of plants.
• Bulking of fine seed with sand, sawdust, etc will assist in even
distribution. Pelleting larger native seed to assist in sowing and
reduce wind blow has been successfully achieved.
Bradysporous Species
In some Australian ecosystems, many species retain their seeds on the
plant in woody capsules that open after fire (Bradysporous species).
Where species with bradysporous seeds are an important part of the
ecosystem, the vegetation can often be harvested using a forage
harvester before clearing and spread on areas being rehabilitated.
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