Nursery Techniques - Afforestation, Reforestation and Forest Restoration in Arid and Semi-arid Tropics - page 39

2.10 Transplanting and Potting

Plants sown in seedbeds are transplanted into polypots. Transplanting age and time
will vary, but on the average, it will be seen that earlier transplants are more success-
ful. Very big plants in seedbeds will have their roots entangled, and disentangling
them will cause seedlings to die. As a general guide to transplanting age, it can be
said that 20-30 days (excluding germination period) is adequate for most species.
For transplanting, a scoop may be used to lift a group of plants along with root
zone soil. From this soil, the individual plantlets can be separated and inserted into
holes made in the polypot potting mix by thrusting a sharp punch. After inserting the
plantlet roots, the hole is closed over up to the collar of the plantlet. A bed of polypot
is gently irrigated after all the pots have received plantlets. If transplanting is done
in hot weather, proper shade should be provided over the beds to prevent the tender
plantlets from getting scorched to death.
Potting of plants is required when tall plants are to be shifted into pots from mother
beds. A plant can be of any age, up to 3 years, before it is potted. However, the older
the plant is, the more is the labour and care required to pot it. Plants should be given a
thorough irrigation and allowed some time for drainage before being potted. To pot a
plant, the soil around its roots is dug as a lump and the soil lump is lifted undisturbed
and placed carefully inside the pot. Some soil should already have been kept in the
pot. After potting the plant, the pot should be filled with potting mix of good quality
and given gentle irrigation. To pot very large plants, plant extractors should be used.
Sometimes repotting or changing pots (transpotting) is required because the ex-
isting pot is too small or its soil has lost all nutrients. Normally, repotting should be
done from a smaller pot to a larger pot. Repotting is similar to potting from ground,
except that the lump of soil is to be obtained by tearing away the old polypot rather
than by digging into ground.

2.11 Irrigating Plants in Pots and Beds

Irrigation in nursery can be carried out in various ways. Flood irrigation should be
applied only in exceptional cases: when no cost can be justified on pipes and sprin-
klers, when cost of labour is too high for irrigating with rose cans, or in temporary
nurseries where water is available in abundance. Flooding will not show any adverse
effect initially but will later lead to lateral expansion of roots, or roots coming out
of pots, and because excess water collected in the beds may not drain, the beds may
become waterlogged and plants may die of asphyxiation. Irrigation with rose cans
and sprinklers has the advantage of being economical in water use and avoids all
the problems just mentioned. However, care should be exercised to apply uniform
quantity of water throughout the bed. Uneven irrigation will result in uneven growth,
or growth clines, making culling and selection an inherently erroneous exercise.
Irrigation schedule should be worked out with care. While excessive irrigation may
have many adverse effects upon the plants, underirrigation will limit plant growth.