Water Application Methods - Practices of Irrigation and On-farm Water Management - page 55

by means of a container or bucket. In the present age of automation, people do
not consider hand watering a viable alternative. However, many horticultural enter-
prises, such as nurseries and fruit trees, cannot use the automated fixed irrigation
system efficiently due to the random location of the plants and therefore use hand
watering.
Capillary Irrigation
Water is applied beneath the root zone in such a manner that it wets the root zone
by capillary rise. Buried pipes or deep surface canals are used for this purpose.
Localized Irrigation
Water is applied around each plant or a group of plants so as to wet locally and the
root zone only. The application rate is adjusted to meet evapotranspiration needs so
that percolation losses are minimized.
Trickle Irrigation
The term trickle irrigation is general and includes several more specific methods.
Trickle irrigation is the slow, frequent application of water to the soil through
emitters placed along a water delivery line. It includes drip irrigation, subsurface
irrigation, and bubbler irrigation.
Trickle irrigation is best suited for tree, vine, and row crops. The main lim-
itation is the cost of the system, which can be quite high for closely spaced
crops. Complete cover crops, such as grains or pasture cannot be economically
irrigated with trickle systems. Trickle irrigation is suitable for most soils, with
only the extremes causing any special concern. With proper design, using pres-
sure compensating emitters and pressure regulators if required, trickle irrigation
can be adapted to virtually any topography. In some areas, trickle irrigation is
successfully practiced on such steep slopes that cultivation becomes the limiting
factor.
Trickle irrigation uses a slower rate of water application over a longer period of
time than other irrigation methods. The most economical design would have water
flowing into the farm area throughout most of the day and every day during peak
use periods. If water is not available on a continuous basis, on-farm water storage
may be necessary. Trickle irrigation can be used successfully with waters of some
salinity, although some special caution is needed. Salts will tend to concentrate at
the perimeter of the wetted soil volume.
Subsurface Irrigation
Applying irrigation water below the ground surface either by raising the water table
within or near the root zone or by using a buried perforated or porous pipe system
that discharges directly into the root zone is termed subsurface irrigation.