The development of a wall-less plug for planting stock of forest trees.
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Date
2011
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Abstract
High output commercial nurseries that cater for the forestry industry are continuously
challenged to efficiently and cost effectively produce good quality planting stock to establish
large plantations. Currently, South African commercial nurseries produce planting stock in
solid compartmentalized trays. One of the major drawbacks of these containers is the
susceptibility of trees to root deformation following outplanting, combined with the need for
the return of empty containers to the nursery. A potential solution to these challenges is the
introduction of wall-less plugs for the production of planting stock. Wall-less plugs are
volumes of growing medium, usually cylindrical in shape, devoid of an impenetrable wall in
which a plant can grow and establish itself. Such plugs may enable the production of planting
stock with improved root systems, without the need for the return of empty containers after
outplanting. In this research four prototypes of wall-less plugs were developed, produced on a
small scale and tested. These were: 1) Paper-maché plugs made using the original WRIBLOK
protocol whereby composted pine bark was bound together with repulped newspaper, 2)
Sponge blocks, 3) Hessian bags and 4) Covetan bags. The performance of these prototype
wall-less plugs was compared with the performance of four tray types used commercially by
the forestry industry: 1) Poly 128 shallow, 2) Poly 98 deep, 3) Unigro 128 and 4) Sappi 49.
These are polystyrene and polypropylene-based containers. Of these containers the Unigro
128 and Sappi 49 containers were of similar performance. Performance in terms of height and
root collar diameter increase over ten weeks from the time of sowing of the paper-maché
plugs was similar to that of the Unigro and Sappi 49 containers. The sponge block, Hessian
bags and Covetan bags produced inferior quality planting stock compared to the other
treatments tested.
Although little progress was made in the ability to describe how one root system differs from
another in terms of their branching patterns, a technique was developed to determine root
surface area by image analysis software that is freely available. This method may prove useful
for further research and for determining seedling quality in commercial nurseries.
Description
Thesis (M.Sc.Agric.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.
Keywords
Forests and forestry--South Africa., Trees--Seedlings., Plant plugs., Forest nurseries., Tree planting., Trees--Propagation., Roots (Botany)--Development., Theses--Forestry.