Water Application Methods - Practices of Irrigation and On-farm Water Management - page 58

content may cause foliar damage if sprayed directly on the plants (e.g., sprinkler
irrigation). In this case, consider systems that deliver water directly on or below the
surface such as drip, surface, or LEPA (low energy precision agriculture) systems. In
these methods, less water is applied to the soil (and hence less salt) than with surface
methods. Special consideration is also needed in the placement of drip tubing and
emitters when irrigating with saline water.
Labor Requirement
The labor requirement and skill required for operation and maintenance varies
greatly between systems. Labor availability and cost are prime considerations for
a labor-intensive system. For example, studies have shown that about one-man-hour
per acre is required for a hand-move sprinkler system. Mechanical move systems
require 1/10 to 1/2 as such labor. Automated systems are more expensive but may
be more profitable when the labor costs over the life of the system are considered.
Surface irrigation often requires a much higher labor input - for construction,
operation, and maintenance - than sprinkler or drip irrigation. Surface irrigation
requires accurate land leveling, regular maintenance, and a high level of farmers'
organization to operate the system. Sprinkler and drip irrigation require little land
leveling; system operation and maintenance are also less labor intensive.
Energy Requirement
With surface irrigation, little or no energy is required to distribute the water through-
out the field, but some energy may be needed to bring the water to the field,
especially when water is pumped from the ground. In some instances, these energy
costs can be substantial, particularly with low water use efficiencies. Some labor
and energy will be necessary for land grading and preparation.
Economic Factors
Costs and Benefits
Before choosing an irrigation system, an estimate must be made of the costs and
benefits of the available options. On the cost side, not only the construction and
installation but also the operation and maintenance (per hectare) should be taken
into account. These costs should then be compared with the expected benefits (price
of yields). It is obvious that farmers will only be interested in implementing a certain
method if they consider this economically attractive (higher benefit-cost ratio).
Initial Investment/Development Cost
Although a method is found to be economical, it cannot be implemented due to limi-
tation of fund for initial development cost. Sprinkler and drip systems require higher
initial costs. Among surface irrigation configurations, basin irrigation is generally
expensive to develop and maintain.