Soil Quality Information Sheet

Soil Quality Resource Concerns: Salinization

USDA Natural Resources Conservation Service January 1998

What is salinization?

Salinization is the process by which water-soluble salts

accumulate in the soil. Salinization is a resource concern

because excess salts hinder the growth of crops by limiting

their ability to take up water. Salinization may occur naturally

or because of conditions resulting from management practices.

Any process that affects the soil-water balance may affect the

movement and accumulation of salts in the soil. These

processes include:

• hydrology

• climate

• irrigation

• drainage

• plant cover and rooting characteristics

• farming practices

What causes salinization?

Salinization on the soil surface occurs where the following

conditions occur together:

• the presence of soluble salts, such as sulfates of sodium,

calcium, and magnesium in the soil

• a high water table

• a high rate of evaporation

• low annual rainfall

In semiarid areas, salinization often occurs on the rims of

depressions and edges of drainageways, at the base of

hillslopes, and in flat, low-lying areas surrounding sloughs and

shallow bodies of water. These areas receive additional water

from below the surface, which evaporates, and the salts are left

behind on the soil surface.

Summer fallow management practices may cause increased

salinization by increasing the soil moisture content to the point

that water moves to seeps on hillslopes. Salts accumulate as

the water evaporates from these seeps.

What are some indicators

of soil salinity?

Early signs:

• increased soil wetness in semiarid and arid areas to the point

that the soil does not support equipment

• the growth of salt-tolerant weeds

• irregular patterns of crop growth and lack of plant vigor

Advanced signs:

• white crusting on the surface

• a broken ring pattern of salts adjacent to a body of water

• white spots and streaks in the soil, even where no surface

crusting is visible

• the presence of naturally growing, salt-tolerant vegetation

Soil salinity can be estimated by measuring the electrical

conductivity of the soil solution. Electrical conductivity

increases in a solution in direct proportion to the total concentration of dissolved salts.

What are some effects

of salinization?

Salts in the soil increase the efforts by plant roots to take in

water. High levels of salt in the soil have a similar effect as

droughtiness by making water less available for uptake by plant

roots.
(Prepared by the National Soil Survey Center in cooperation with the

Soil Quality Institute, NRCS, USDA, and the National Soil Tilth Laboratory,

Agricultural Research Service, USDA).

________________________________________________________________________________________________

The U. S. Department of Agriculture (USDA) prohibits discrimination in its programs on the basis of race, color, national origin, gender, religion, age,

disability, political beliefs, sexual orientation, and marital or family status. (Not all prohibited bases apply to all programs.) Persons with disabilities who

require alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA’s TARGET Center at (202)

720-2600 (voice and TDD).

To file a complaint of discrimination, write USDA, Director, Office of Civil Rights, Room 326W, Whitten Building, 14th and Independence Avenue, SW,

Washington, DC 20250-9410 or call (202) 720-5964 (voice or TDD). USDA is an equal opportunityprovider and employer.

Few plants grow well on saline soils; therefore, salinization

often restricts options for cropping in a given land area.

Salinization degrades the quality of shallow ground water and

surface water resources, such as ponds, sloughs, and dugouts.

How can salinity problems be managed?

Reducing the severity and extent of soil salinity is primarily a

problem of water management. Water management can be

addressed in two ways: (1) by managing the area contributing

excess water to the soil (recharge area) or (2) by managing the

area where the excess water comes to the surface (discharge

area).

Recharge management:

• Decrease excess water from infiltrating into the soil in

recharge areas of seeps by diverting surface water to

downslope ponds.

• Maintain the water table at a low, safe level. Do not over

irrigate. In some areas, over irrigation and the lack of natural

drainage has raised the water tables, which may require the

use of an artificial drainage system. Discharge of salty

waters from these drains may contribute to other offsite

problems.

• Irrigate to maintain salts at a level below the root zone in the

soil.

• Use cropping and tillage systems that promote adequate

infiltration and permeability. This includes building organic

matter for soil aggregation and avoiding compaction.

• Plant crops that use the available soil moisture. Shallowrooted crops may not extract excess subsoil moisture that can

lead to salinity.

• Remove excess water from recharge areas of seeps by using

actively growing, deep-rooted plants. Perennial plants and

forages, especially alfalfa, are useful for this purpose because

they have a longer growing season and take up more water

from a greater depth in the soil than annual plants. Forages

may also increase organic matter in the soil and improve soil

structure.

• Return manure and crop residue to the soil to increase soilwater retention.

• Reduce summer fallow by continuous cropping.

• Manage snow so that it is evenly distributed and does not

pond on thawing.

Discharge management:

• Grow salt-tolerant crops.

• Convert to permanent soil cover with salt-tolerant crops in

high risk areas.

• Reduce deep tillage, which may bring up salts from deeper

soil horizons.

• Plant forage crops or trees next to bodies of water to increase

water use.

• Install artificial drainage systems in severely affected areas

only.

• Eliminate seepage from irrigation canals, dugouts, and ponds.

Generally, control measures should take an integrated approach

involving cropping, structural methods, and tillage systems.

Visit our Web site:

 http://soils.usda.gov