Management of Salt-Affected Soils - Practices of Irrigation and On-farm Water Management - page 309

salt-affected soil depending on the practical importance. Chemical amendment neu-
tralizes exchangeable Na and Na carbonate. Leaching followed by amendment is
needed for removal of salts derived from the reaction of the amendments. Gypsum,
sulfur and sulfuric acid are commonly used.
One way to prevent excess salination would be the use of humic acids, especially
in regions where too much irrigation was practiced. In soils with excess salts, humic
acids can fix anions and cations and eliminate them from the root regions of the
plants.
8.6.2.5 Irrigation and Water Management Practices
Water management is the key to successful salinity management. Frequent light
watering, using subsurface drip or sprinklers, can help leach excess salts with-
out allowing excess deep drainage to contribute to water table problems. Irrigation
management also impact on nutrition of saline soil.
Pre-sowing (or Pre-plant) Irrigation
Most crop plants are more susceptible to salt injury during germination or in the
early seedling stages. An early-season application of good quality water, designed
to fill the root zone and leach salts from the upper 15-30 cm of soil, may provide
good enough conditions for the crop to grow through its most injury-prone stages.
Irrigation Frequency Management
Salts are most efficiently leached from the soil profile under higher frequency irri-
gation (shorter irrigation intervals). Keeping soil moisture levels higher between
irrigation events effectively dilutes salt concentrations in the root zone, thereby
reducing the salinity hazard. Most surface irrigation systems (flood or furrow sys-
tems) cannot be controlled to apply less than 3 or 4 in. of water per application
and are not generally suited to this method of salinity control. Sprinkler systems,
particularly center-pivot and linear-move systems configured with low energy pre-
cision application (LEPA) nozzle packages, or properly spaced drop nozzles, and
drip irrigation systems provide the best control to allow this type of irrigation
management.
Drip Irrigation
The drip system provide for opportunities to enhance the use of saline waters in
water scarce areas and even on saline soils. It results in considerable savings in
irrigation water thus reducing the risks of secondary salinization.