Germplasm Supply, Propagation and Nursery Management of Miombo Fruit Trees - Indigenous Fruit Trees in the Tropics: Domestication, Utilization and Commercialization - page 358

two aspects. The first is the genetic quality or the source of the seed and the
second is its physical condition. The characteristics of the parent tree can
greatly influence the characteristics of the seedlings. According to Wightman
(1990), a good-quality seedling has the following characteristics:

● It is healthy, growing vigorously and free of diseases.

● It has a robust and woody single stem that is free of deformities.

● The stem is sturdy and root diameter is large.

● The root system is dense, with many fine roots and fibrous hairs.

● There is a balance between shoot and root mass.

● It is accustomed to short periods of drought and full sunlight.

The physical condition of the seedling can be improved by appropriate
management, which includes nursery site selection, the use of appropriate
media, fertilization and pest management.

19.5.1 Nursery site selection

Selection of the nursery site is an important consideration when seedlings are
raised on seedbeds or in containerized nurseries. Miombo fruit tree seedlings
were exclusively raised in polyester bags by Böhringer et al. (2003). However,
nursery site selection in terms of source of shade and water supply is crucial in
raising planting material of miombo fruit trees. Studies of the effects of shading
showed that seedlings of Sclerocarya birrea raised under 25% shade had better
growth, so that within 12 months the seedlings were big enough for grafting. In
the 1995 grafting session, 100% uptake was recorded for the seedlings that
were raised under 25% shade. Seedlings raised under 50 and 100% shade
were too thin and too short, respectively (Taylor et al. , 1996). Similarly, Uapaca
kirkiana seedlings grew well under partial shade (Ngulube et al. , 1995).
The supply of water to plants in the nursery appears to be an important
determinant of the nursery site in southern Africa. A study conducted in
1998/1999 on nursery location and productivity (Böhringer et al. , 2003)
showed that most tree nurseries are located close to permanent water sources
such as dambos and river banks. The study indicated significant differences
between dambos and riverbanks. A steady supply of water for irrigation is
crucial for an indigenous fruit tree nursery.

19.5.2 Potting mixture

The potting mixture used can have a significant influence on the growth of
seedlings. Normally, forest soil from ordinary miombo woodland or from a
natural forest stand of the species is used for raising indigenous fruit tree
seedlings. Mhango (2000) compared various potting mixtures in southern
Malawi, and recommended a mixture of 75% forest soil and 25% sawdust as the
best for growth of Uapaca kirkiana . Compared with forest soil alone, this mixture
is reported to be lighter and to have higher total porosity, water-holding porosity