Nursery Techniques - Afforestation, Reforestation and Forest Restoration in Arid and Semi-arid Tropics - page 23

Fig. 2.6 Schematic layout of a pressure-pipe network for water distribution in a central nursery. GI
galvanised iron, OHR overhead water reservoir, HDPE high-density polyethylene
Water conveyance channels (WCCs) are required if irrigation is manual—with the
help of hand-held rose cans. When only a GLR is available and it does not provide
adequate pressure to operate hydrants, this is the only choice left. Water is conveyed
through channels to small underground water reservoirs (UGR). Rose cans are then
used for lifting water manually and spraying it on the plants in beds. WCCs must be
laid out carefully on regular gradient or else these will overflow and water will spill
out. A network of channels will be required to cover the nursery (Fig. 2.7 ). The cost
of all the WCCs and the associated UGRs may add up to that of a pipe-and-hydrant
system, and where the latter is feasible, it should be preferred.
A pressure-pipe network with hydrants (outlet nozzles) suitably distributed in
the nursery will enable manual irrigation with roses attached at the end of flexible
rubber pipes, thus increasing labour productivity as water need not be manually
filled into cans. Sufficient water pressure should be available throughout the network.
Inadequate pressure will slow down flow of water and will take longer to irrigate,
effectively leading to higher labour costs. Given sufficient operating pressure head
(of at least 2 m at all points), this should be a cost-effective and reliable solution. Care
should be taken while designing a network of this type to ensure uniform pressure
throughout the network. A number of hydrants open simultaneously may suddenly
bring down pressure in certain branches of the network and make these inoperative.
Beds are essential elements of a nursery. Beds are used to hold pots in position
(container beds) or to hold soil or potting mix in which seeds germinate (germination
beds or seedbeds). Beds can also be the identified field plots where plants grow to
a height sufficient for preparing cuttings or for transferring to pots (mother beds or
growing beds). Beds for different purposes should be laid out carefully and labelled
systematically by organising these into blocks, sectors, or series so as to make it
easy to identify these for the purposes of recording plant inventories. Layout of beds
should be drawn on a signboard fixed at a prominent place in the nursery.