Water Application Methods - Practices of Irrigation and On-farm Water Management - page 57

can be used, but surface irrigation is more commonly used. Clay soils with low
infiltration rates are ideally suited to surface irrigation.
When a variety of soil types exists within one irrigation scheme, sprinkler or
drip irrigation is recommended as they will ensure a more even water distribution.
Sprinkler or drip irrigation are preferred to surface irrigation on steeper or unevenly
sloping lands, as they require little or no land leveling. An exception is rice grown
on terraces on sloping lands.
Field Shape/Geometry and Topography
Topography of a field is a decision-making aid in the selection of the type of irri-
gation system, or in determination of size of the irrigation system to be installed.
Sprinklers fit rolling topography, but surface irrigation systems require graded fields.
Odd-shaped fields cannot be easily irrigated with certain types of sprinkler systems
such as center pivots. Rolling topography prohibits the use of furrow or surface sys-
tems because water cannot run uphill. Basins can be adopted in irrigating fields with
irregular shapes and small sizes.
Climate
Local climate greatly influences the choice of an irrigation system. In a very hot,
dry climate, a significant amount of water is evaporated during irrigation through
sprinklers. Strong wind can disturb the uniform distribution of water from sprin-
klers. Under very windy conditions, drip or surface irrigation methods are preferred.
In areas of supplementary irrigation, sprinkler or drip irrigation may be more suit-
able than surface irrigation because of their flexibility and adaptability to varying
irrigation demands on the farm.
Water Availability
An adequate water supply to meet crop demand is important for ease of opera-
tion and for management of an irrigation system. With low probability of rainfall,
a water supply should be large enough to meet crop demand. Location of water
source, quantity, and quality of water should be determined before any type of irri-
gation system is selected. No assumptions should be made with the water supply.
The amount of water available and the cost of the water (due to pumping or direct
purchase) will determine the type of system you should use. If the supply is suffi-
cient, assured and low cost, labor and/or energy saving irrigation method may be
employed. On the other hand, if the supply is scarce/limited and very expensive,
then consider only the most efficient type of irrigation system (e.g., sprinkler, drip).
Water Quality
Surface irrigation is preferred if the irrigation water contains much sediment. The
sediments may clog the drip or sprinkler irrigation systems. Water having high salt